University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Analytical Letters

  • Publisher: Taylor and Francis
  • FAD Code: ANLE
  • CODEN: ANALBP
  • ISSN: 0003-2719
  • Abbreviation: Anal. Lett.
  • DOI Prefix: 10.1080/0003271,10.1081/AL
  • Language: English
  • Comments: Fulltext from 1968 V1

Citations 481

"Fast Fourier Transform Continuous Cyclic Voltammetry Development As A Highly Sensitive Detection System For Ultra Trace Monitoring Of Thiamine"
Anal. Lett. 2007 Volume 40, Issue 3 Pages 547-559
P. Norouzi; M. R. Ganjali; P. Daneshgar; A. Mohammadi

Abstract: In this work, a highly sensitive method for the fast monitoring of thiamine hydrochloride in flow-injection systems has been developed. The fast Fourier transform continuous cyclic voltammetry (FFCV) in flowing solution as a detection system was applied for the very fast monitoring of thiamine in its pharmaceutical formulations. This technique is very simple, precise, accurate, time-saving and economical, compared to all previous reported methods. The effects of various parameters on the sensitivity of the detection system were considered. The best condition was obtained within the pH value of 2, and scan rate value of 25 V s-1, accumulation potential of -400 mV, and accumulation time of 0.6 s. The proposed method has some advantages over other reported methods such as, there is no need for the removal of oxygen from the test solution, has a sub-nanomolar detection limit, and finally the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. This research also introduces a special computer-based numerical method, for the calculation of the analyte signal and noise reduction. The electrode response was calculated based on partial and total charge exchanges on the electrode surface after subtracting the background current from that of noise. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation and potential ramp of analyte, was applied on an Au disk microelectrode (12.5 µm in radius) in a continuous way. The detection limit of the method for thiamine was 1.0 x 10^-12 M. The relative standard deviation of the method at 1.0 x 10^-8 M was 2.2% for 8 runs.

"The Successful Use Of Cellulose Acetate Membrane For Very Low Density Lipoprotein Isolation And Cholesterol Quantitation"
Anal. Lett. 2007 Volume 40, Issue 1 Pages 77-84
M. Anwar

Abstract: The lipoproteins have been successfully isolated electrophoretically from the blood samples of patients having suffered from hyperlipoproteinemia type III but having survived myocardial infarction. The VLDL fraction from the cellulose acetate membrane is cut out and the total cholesterol and cholesterol of the VLDL extracted. The cholesterol is determined using an immobilized cholesterol esterase/oxidase column using a flow injection analysis system. Copyright © Taylor & Francis Group, LLC.

"Improved Performance Of The Potentiometric Biosensor For The Determination Of Creatinine"
Anal. Lett. 2007 Volume 40, Issue 1 Pages 39-52
Claus Dallerup Rasmussen; Jens E. T. Andersen; Birgit Zachau-Christiansen

Abstract: Contemporary methods of analyzing creatinine engage chemicals harmful to the environment and generate large volumes of waste disposals. By introducing a membrane-based potentiometric biosensor with immobilized creatinine deaminase, the measurements can be performed by miniaturized portable devices that are easy to handle and allow rapid analysis with minimum consumption of chemicals. Thus, the enzymatic creatinine biosensors were revisited and optimized with respect to repeatability, sensitivity, limit of detection (LOD), and response time. A detection limit of 0.3 ?M and a sensitivity of 58.78 ±0.03 mV (23.5°C) were obtained in tris buffer at pH=7.4 after introduction of shielding of all electronics and software filtering. Measurements performed by flow injection analysis (FIA) showed that the response time could be lowered to approximately 30 sec using sample volumes of 30 µL. Interferences were corrected for by application of the Nicolsky-Eisenman equation, thus allowing determination of creatinine in matrices resembling those of clinical measurements. Investigations of sandwich structures showed that the sensitivity decreased as a function of the number of membranes on top of the immobilized layer of active creatinine deaminase. It was thus shown that the sensitivity depends on the distance of diffusion of species from the sample solution through the membranes to the enzyme. Copyright © Taylor & Francis Group, LLC.

"The Use Of Boron-doped Diamond Electrodes For The Amperometric Determination Of Flavonoids In A Flow Injection System"
Anal. Lett. 2006 Volume 39, Issue 14 Pages 2737-2748
Valber A. Pedrosa; Andréa R. Malagutti; Luiz H. Mazo; Luis A. Avaca

Abstract: This paper describes the use of boron-doped diamond electrode for the amperometric detection and quantification of flavonoids in tea samples using a flow injection system. Flavonoids are phenol derivates widely distributed in fruits, nuts, seeds, flowers, vegetable peels, and beverages; they are known to exhibit high antioxidative activities. After optimization, the experiments were performed at a fixed potential of 0.42 V vs Ag/AgCl with a flow rate of 2.5 mL min-1 in a Britton-Robinson buffer at pH 5.0. The results revealed that the peak current increases linearly with rutin concentration in the interval 0.1-2.5 x 10^-4 mol L-1 and the detection limit was 7.7 x 10^-6 mol L-1. The method was used for the determination of rutin in three different green tea (Camellia sinensis) infusions by the direct addition of 150 µL of untreated sample. The repeatability of current responses for injections of 150 µL rutin was evaluated to be 2.1% (n=20) and the analytical frequency was 100 Hz h -1. The results were compared with the results obtained by high-performance liquid chromatrography-diode ray detector. Copyright © Taylor & Francis Group, LLC.

"Indirect Mercury Speciation In Biological Tissues By Closed-vessel Microwave-assisted Digestion And Flow-injection Cold-vapor Atomic Fluorescence Detection"
Anal. Lett. 2006 Volume 39, Issue 14 Pages 2657-2669
J. J. Berzas Nevado; R. C. Rodríguez Martín-Doimeadios; F. J. Guzmán Bernardo; M. Jiménez Moreno

Abstract: A simple and rapid method based on closed vessel microwave-assisted extraction was developed to determine total, inorganic mercury and organomercury in biological tissues. Total mercury was extracted using HNO3:H 2O2 (4:1) mixture. In a separate subsample, extraction of mercury species was carried out with tetramethylammonium hydroxide (TMAH). The total and inorganic mercury analyzes were carried out by flow-injection cold-vapor atomic fluorescence spectrometry (FI-CV-AFS). The organomercury concentration was calculated by difference. Considering a sample amount of 0.2 g, the detection limits were 4 and 26 ng/g for total and inorganic mercury, respectively. The accuracy of the procedures was checked by analyzing certified reference materials and recovery studies of spiked fish tissues. Copyright © Taylor & Francis Group, LLC.

"Spectrophotometric Determination Of Furosemide Based On Its Complexation With Fe(III) In Ethanolic Medium Using A Flow Injection Procedure"
Anal. Lett. 2006 Volume 39, Issue 13 Pages 2557-2567
Felipe Silva Semaan; Éder Tadeu Gomes Cavalheiro

Abstract: A fast flow injection procedure with spectrophotometric detection based on the furosemide complexation with Fe(III) ions in ethanolic media is described. As carrier the flow single line system configuration used an ethanolic 10 -2 mol L-1 Fe(III) solution flowing at 1.0 mL min -1, a 50 cm sample loop (250 µL total sample injection), and a 50 cm long reactor coil, at room temperature. The detection at 513 nm presented a linear dynamic range from 1.00 x 10^-4 to 1.00 x 10 -2 mol L-1, obeying the linear equation Abs = 8.9 x 10^-3 + 22.3 x [furosemide] (r = 0.998, n = 7). The limit of detection (3?/slope) was 3.00 x 10^-5 mol L-1. The proposed method was applied to four commercial samples from different suppliers, as tablets and ampoules, and a synthetic urine sample spiked with the analyte without an effect from the other substances present in the formulation. The proposed procedure presented an analytical frequency of 95 measurements per hour. The results agreed with those from both the label and those determined by a spectrophotometric comparative procedure. Recoveries close to 100% were found in the commercial formulations and synthetic urine matrixes. Copyright © Taylor & Francis Group, LLC.

"Flow-injection Chemiluminescence Analysis Of Cloperastione Hydrochloride"
Anal. Lett. 2006 Volume 39, Issue 12 Pages 2475-2481
Shuwen Sun; Jiuru Lu

Abstract: A new chemiluminescence (CL) reaction was observed when cloperastine hydrochloride was injected into the reaction mixture after the CL reaction of Ce(IV) and sodium sulfite finished. A new flow injection CL method for the determination of cloperastine hydrochloride was established based on the CL reaction. The relative standard deviation (RSD) for the determination of cloperastine hydrochloride was 1.3% (n = 11, c = 1.0 x 10^-6 g/mL). The CL intensity responded linearly to the concentration of cloperastine hydrochloride in the range 2.0 x 10^-7 ? 2.0 x 10 -5 g/mL (r = 0.9962). The detection limit was 5 x 10 -8 g/mL cloperastine hydrochloride. The method had been applied to the determination of cloperastine hydrochloride in tablets with satisfactory results. Copyright © Taylor & Francis Group, LLC.

"A Sensitive Flow Injection Fluorimetry For The Determination Of Carbamazepine In Human Plasma"
Anal. Lett. 2006 Volume 39, Issue 12 Pages 2417-2428
Zhi-Qi Zhang; Guo-Xi Liang; Jian Ma; Ying Lei; Yue-Mei Lu

Abstract: A simple, sensitive, and specific flow injection fluorimetric method has been developed for the determination of carbamazepine (CBZ). The proposed method is based on use of a solid-phase reactor containing lead dioxide for on-line oxidization of CBZ into a strongly fluorescent compound in a medium of phosphoric acid. The product has a green-yellow fluorescence at a maximum excitation wavelength of 355 nm and an emission wavelength of 478 nm. Under the optimum conditions, the fluorescence intensity is proportional to the concentration of CBZ ranging from 0.0005 to 4.000 ?g mL-1. The detection limit is 5.7 x 10^-5 ?g mL-1 (2.4 x 10^-10 mol L-1) and the relative standard deviation is 1.4% at the sampling rate of 45 h-1. The proposed method has been applied to clinical estimation of CBZ in real patients' plasma samples with the results compared with those obtained by HPLC method. Copyright © Taylor & Francis Group, LLC.

"Electroanalytical Study Of The Pesticide Ethiofencarb"
Anal. Lett. 2006 Volume 39, Issue 12 Pages 2387-2403
M. Fátima Barroso; M. Carmo; V. F. Vaz; M. Goreti; F. Sales; Paula Paíga; Cristina Delerue-Matos

Abstract: A detailed study of voltammetric behavior of ethiofencarb (ETF) is reported using glassy carbon electrode (GCE) and hanging mercury drop electrode (HMDE). With GCE, it is possible to verify that the oxidative mechanism is irreversible, independent of pH, and the maximum intensity current was observed at +1.20 V vs. AgCl/Ag at pH 1.9. A linear calibration line was obtained from 1.0 x 10^-4 to 8.0 x 10^-4 mol L-1 with SWV method. To complete the electrochemical knowledge of ETF pesticide, the reduction was also explored with HMDE. A well-defined peak was observed at -1.00 V vs. AgCl/Ag in a large range of pH with higher signal at pH 7.0. Linearity was obtained in 4.2 x 10^-6 and 9.4 x 10^-6 mol L-1 ETF concentration range. An immediate alkaline hydrolysis of ETF was executed, producing a phenolic compound (2-ethylthiomethylphenol) (EMP), and the electrochemical activity of the product was examined. It was deduced that it is oxidized on GCE at +0.75 V vs. AgCl/Ag with a maximum peak intensity current at pH 3.2, but the compound had no reduction activity on HMDE. Using the decrease of potential peak, a flow injection analysis (FIA) system was developed connected to an amperometric detector, enabling the determination of EMP over concentration range of 1.0 x 10^-7 and 1.0 x 10^-5 mol L-1 at a sampling rate of 60 h-1. The results provided by FIA methodology were performed by comparison with results from high-performance liquid chromatography (HPLC) technique and demonstrated good agreement with relative deviations lower than 4%. Recovery trials were performed and the obtained values were between 98 and 104%. Copyright © Taylor & Francis Group, LLC.

"Multi-walled Carbon Nanotubes As Sorbent For Flow Injection On-line Microcolumn Preconcentration Coupled With Flame Atomic Absorption Spectrometry For Determination Of Cadmium And Copper"
Anal. Lett. 2006 Volume 39, Issue 11 Pages 2285-2295
Hua-Ding Liang; De-Man Han

Abstract: Multi-walled carbon nanotubes (MWNTs) were used as sorbent for flow injection (FI) on-line microcolumn pre-concentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace cadmium and copper in environmental and biological samples. Effective pre-concentration of trace cadmium and copper was achieved in a pH range of 4.5-6.5 and 5.0-7.5, respectively. The retained cadmium and copper were efficiently eluted with 0.5 mol L-1 HCl for on-line FAAS determination. The MWNTs packed microcolumn exhibited fairly fast kinetics for the adsorption of cadmium and copper, permitting the use of high sample flow rates up to at least 7.8 mL min-1 for the FI on-line microcolumn pre-concentration system without loss of the retention efficiency. With a pre-concentration time of 60 sec at a sample loading flow rate of 4.3 mL min -1 , the enhancement factor was 24 for cadmium and 25 for copper at a sample throughput of 45 h-1. The detection limits (3?) were 0.30 and 0.11 ?g L-1 for Cd and Cu, respectively. The precision (RSD) for 11 replicate measurements was 2.1% at the 10-?g L-1 Cd level and 2.4% at the 10-?g L-1 Cu level. The developed method was successfully applied to the determination of trace Cd and Cu in a variety of environmental and biological samples. Copyright © Taylor & Francis Group, LLC.

"Fully Automated Spectrophotometric Method For The Determination Of Buspirone In Pharmaceutical Preparations"
Anal. Lett. 2006 Volume 39, Issue 11 Pages 2243-2253
Marta F. T. Ribeiro; João L. M. Santos; José L. F. C. Lima; Ana C. B. Dias; Elias A. G. Zagatto

Abstract: A fully automated kinetic method for the spectrophotometric determination of buspirone in pharmaceutical preparations is proposed. The analytical system was implemented by using multiple solenoid micropumps for sample and reagents insertion, which led to improved operational simplicity and low reagent consumption. A three-way solenoid valve enabled the establishment of two parallel reactors and the exploitation of the fixed time approach for differential kinetics. Linear calibration plots for buspirone concentrations of up to 60 mg L-1 were obtained, with a detection limit of 2.8 mg L-1. The sampling rate was about 55 samples per hour. Copyright © Taylor & Francis Group, LLC.

"Investigation Of Chemiluminescence Behavior Of Flavonoids With Cerium (IV)-rhodamine B System"
Anal. Lett. 2006 Volume 39, Issue 9 Pages 2007-2024
Hanchun Yao; Xiaofeng Yang; Hua Li

Abstract: The chemiluminescence (CL) behavior of five major flavonoid types in cerium (IV)-rhodamine B system was investigated by flow-injection. Strong CL was observed when cerium (IV) reacted with rhodamine B in sulfuric acid medium in the presence of flavonoids. This reaction system has been established as a simple, rapid, and highly sensitive flow injection CL analysis for quercetin and kaempferol, and their detection limit (3?) was 2.7 and 0.22 nmol/L, respectively. The relative standard deviation (n=8) was 1.2% for 1.0 ?mol/L quercetin and 1.9% for 0.5 ?mol/L kaempferol. This method was successfully applied to the determination of quercetin in the hydrolysate of rutin and compared well with the high performance liquid chromatography (HPLC) method. From a comparison of several related flavonoids, it was concluded that only flavonoids that contain a free 3-hydroxyl and 2, 3-double bond in conjugation with 4-oxo function could produce a relatively strong CL emission. Copyright © Taylor & Francis Group, LLC.

"Fast Monitoring Of Nano-molar Level Of Gentamycin By Fast Fourier Transform Continuous Cyclic Voltammetry In Flowing Solution"
Anal. Lett. 2006 Volume 39, Issue 9 Pages 1941-1953
Parviz Norouzi; Mohammad Reza Ganjali; Leila Hajiaghababaei

Abstract: A novel method for the determination of gentamycin in flow-injection systems has been developed in this work. The principal advantages of this method are that it is rapid, simple, and possesses low detection limit. Some investigations were also done to find the effects of various parameters on the sensitivity of the proposed method. The conditions producing the performance were the pH value of 2, the scan rate value of 350 V/s, accumulation potential of (100 mV), and accumulation time of 0.9 s. Some of the advantages of the proposed method are: the removal of oxygen from the test solution is not required anymore, the detection limit of the method is sub-nanomolar, and finally, the method is fast enough for determination of such compounds, in a wide variety of chromatographic methods. We also introduce a special computer-based numerical method for calculation of the analyte signal and noise reduction. After subtracting the background current from noise, the electrode response was calculated, based on partial and total charge exchanges at the electrode surface. The integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, to obtain a sensitive determination. The waveform potential was continuously applied on an Au disk microelectrode (12.5 ?m in radius). Detention limit of the method for gentamycin was found to be 1.0 x 10 -9 M. For 10 runs, the relative standard deviation of the method at 1.0 x 10 -7 M was 2.1%. Copyright © Taylor & Francis Group, LLC.

"Improved Multianalyte Determination Of The Intense Sweeteners Aspartame And Acesulfame-K With A Solid Sensing Zone Implemented In An FIA Scheme"
Anal. Lett. 2006 Volume 39, Issue 7 Pages 1333-1347
J. F. García-Jiménez; M. C. Valencia; L. F. Capitán-Vallve

Abstract: A multianalyte flow-through sensor is proposed for the simultaneous determination of aspartame (AS) and acesulfame-K (AK) in tabletop sweeteners. The procedure is based on the transient retention of AK in the ion exchanger Sephadex DEAE A-25 placed in the flow-through cell of a monochannel flow injection analysis (FIA) set-up using pH 2.70 ortophosphoric acid/sodium dihydrogen phosphate buffer 0.06 M as carrier. In these conditions AS is very weakly retained, which makes it possible to measure the intrinsic ultraviolet (UV) absorbance of first AS and then AK after desorption by the carrier itself. The applicable concentration range, the detection limit, and the relative standard deviation were the following: for AS, from 10 to 100 ?g mL -1 ; 5.65 ?g mL -1 ; 3.4% (at 50 ?g mL -1 ); and for AK, between 40 and 100 ?g mL -1 ; 11.9 ?g mL -1 and 1.61% (at 50 ?g mL -1 ). The method was applied and validated satisfactorily for the determination of AS and AK blends in tabletop sweeteners. The results were compared against an HPLC reference method. Copyright © Taylor & Francis Group, LLC.

"Recent Developments In Automated Determinations Of Trace Level Concentrations Of Elements And On-line Fractionation Schemes Exploting The Micro-sequential Injection - Lab-on-valve Approach"
Anal. Lett. 2006 Volume 39, Issue 7 Pages 1243-1259
Elo Harald Hansen; Manuel Miró; Xiangbao Long; Roongrat Petersen

Abstract: The determination of trace level concentrations of elements, such as metal species, in complex matrices by atomic absorption or emission spectrometric methods often requires appropriate pretreatments comprising separation of the analyte from interfering constituents and analyte pre-concentration. In this context sequential injection (SI) and lab-on-valve (LOV) schemes have proven themselves as superb vehicles to act as front-end microanalytical methodologies, particularly when employing solid-phase extraction (SPE) procedures. In this communication, selected SPE-procedures in the bead-renewable fashion are presented as based on the exploitation of micro-sequential injection (?SI-LOV) using hydrophobic as well as hydrophilic bead materials. The examples given comprise the presentation of a universal approach for SPE-assays, front-end speciation of Cr(III) and Cr(VI) in a fully automated and enclosed setup, and the combination of SPE with fractionation schemes of environmentally interesting solid samples (such as soils or sediments) in order to conduct ecotoxicological studies. Copyright © Taylor & Francis Group, LLC.

"A Multi-element Flow Injection System For Heavy Metals Determination"
Anal. Lett. 2006 Volume 39, Issue 6 Pages 1211-1228
María S. Di Nezio; Miriam E. Palomeque; Beatriz S. Fernández Band

Abstract: A multi-element flow injection (FI) system with spectrophotometric detection was developed for sequential determination of Zn(II), Cu(II), Cd(II), Pb(II), and Hg(II). Dithizone reagent was used for the previously mentioned analytes and it was prepared on line by using a solid reagent column (SRC). Bear in mind that the most hazardous elements for environmental contamination are lead, cadmium, and mercury; a multi-element FI system with pre-concentration steps is proposed to determine their trace levels in natural waters. Results obtained for different samples agreed satisfactorily with those obtained by the reference method inductively coupled plasma-atomic emission spectrometry (ICP-AES). Detection limits were 5.4, 5.0 and 14 ?g L-1 for Cd(II), Pb(II), and Hg(II), respectively. The percent of relative standard deviation (RSD) was better than 4.5% for each one. Copyright © Taylor & Francis Group, LLC.

"Online Flow Injection Preconcentration And Flame Atomic Absorption Spectrometric Determination Of Palladium(II) Using Inorganic And Inorganic-organic Hybrid Materials-packed Microcolumns"
Anal. Lett. 2006 Volume 39, Issue 6 Pages 1187-1199
Ramachandran Sarojam Praveen; Sobhi Daniel; Talasila Prasada Rao

Abstract: Various inorganic and inorganic-organic hybrid materials-packed columns, including commercially available C18 bonded silica gel and alumina columns, were tested for the on-line pre-concentration of palladium(II) and subsequent determination by flame atomic absorption spectrometry (AAS). Several thioligands were investigated for complexing palladium(II) and subsequent sorption, elution, and determination by flame atomic absorption spectrometer. Among them, diethyl ammonium dithiocarbamate was found to give the highest enrichment factor for a given concentration of palladium(II) under optimized conditions. After testing the accuracy of the developed method by analyzing certified reference material (SARM 7), it was applied for the analysis of street and domestic fan blade dust samples. Copyright © Taylor & Francis Group, LLC.

"Highly Selective And Sensitive Preconcentration Of Mercury Ion And Determination By Cold Vapor Atomic Absorption Spectroscopy"
Anal. Lett. 2006 Volume 39, Issue 6 Pages 1171-1185
Mehrorang Ghaedi; Mohammad Reza Fathi; Ardeshir Shokrollahi; Fahimeh Shajarat

Abstract: A simple and selective method based on a sodium dodecyl sulfate (SDS)-coated chromosorb P modified by 2-mercaptobenzoxazole (MBO) has been developed to selectively separate and concentrate ultra trace amounts of mercury(II) ions for its highly sensitive measurement by cold vapor atomic absorption spectrometry (CVAAS). The mercury ions were adsorbed quantitatively on SDS-coated chromosorb due to its complexation with MBO, while the retained Hg2+ ions were then stripped from the column with minimal amounts of 2 M nitric acid in acetone. The eluting solution was sent to CV-AAS for evaluating Hg2+ ion content and results indicate that the calibration curve was linear for Hg2+ ion in the range of 0.05-85.6 ng mL-1 and 0.09-9.6 ?g mL-1 of Hg2+ ions. Maximum capacity of the SDS-coated chromosorb modified with 40 mg of the ligand was found to be 498 ± 30 ?g of mercury(II), the limit of detection was 0.01 ng mL-1, and enrichment factors were about 300, which make it suitable it for dilute solution analysis. The method was successfully applied to the determination of Hg2+ ion content in real samples. Copyright © Taylor & Francis Group, LLC.

"In Vitro Monitoring Of Picogram Levels Of Captopril In Human Urine Using Flow Injection Chemiluminescence With Immobilized Reagent Technique"
Anal. Lett. 2006 Volume 39, Issue 6 Pages 1115-1127
Zhenghua Song; Shuang Hou; Xiangyang Yu; Xiaofeng Xie; Xiaodong Shao

Abstract: A flow-injection procedure for detection of captopril using a Co2+-captopril complex formed on line based enhancement of luminol and dissolved oxygen chemiluminescence is described. The chemiluminescence reagents, luminol and Co2+, were both immobilized on ion exchange resin in the flow injection system. When captopril solution flowed through the immobilized Co2+ column, the Co2+-captopril (1:2) complex formed on line could greatly enhanced the chemiluminescence intensity generated from the reaction between luminol and dissolved oxygen. The increment of chemiluminescence emission was correlated with the captopril concentration in the range from 7 to 1000 pg mL-1, and the detection limit was 2 pg mL-1 (3?). One analysis cycle, including sampling and washing, could be accomplished in 0.5 min with relative standard deviations of less than 3.0% (n = 11). The proposed method was applied directly in the assay of human urine without any pretreatment and it was found that the captopril concentration reached its maximum after being administrated orally for 1.5 hours, with the mean excretion ratio in 6.5 hours of 54.3% in the body of volunteers. The possible chemiluminescence mechanism was discussed. Copyright © Taylor & Francis Group, LLC.

"A New Flow-injection Chemiluminescence Method For The Determination Of Acyclovir And Gancyclovir"
Anal. Lett. 2006 Volume 39, Issue 5 Pages 973-983
Nannan Wang; Yuhai Tang; Xunyu Xiong; Xiaonian Han; Chunling Yu

Abstract: A rapid and sensitive flow-injection chemiluminescence (FI-CL) method, which is based on the CL intensity that generated from the redox reaction of Ce(IV)-rhodamine B in H2SO4 medium, for the determination of acyclovir and gancyclovir is described. For acyclovir, the determination range is 3 x 10^-8 g mL-1-7 x 10^-5 g mL-1, with 1.56 x 10^-8 g mL-1 as its determination limit. During 11 repeated measurements for 1 x 10^-6 g mL-1 acyclovir, the relative standard deviation was 2.08%. For gancyclovir, the determination range was 5 x 10^-8 g mL-1-7 x 10^-5 g mL-1, with 2.35 x 10^-8 g mL-1 as its determination limit. The relative standard deviation is 2.83% with 11 repeated measurements of 1 x 10^-6 g mL-1 gancyclovir. This method can be successfully used to determine the content of acyclovir and gancyclovir in injections, acyclovir in eye drops, and, maybe, also for other ciclovirs. Copyright © Taylor & Francis Group, LLC.

"Speciation Of Chromium In Water Samples By Cloud Point Extraction Combined With Low Temperature Electrothermal Vaporization ICP-OES"
Anal. Lett. 2006 Volume 39, Issue 4 Pages 809-822
Yingjie Li; Bin Hu; Zucheng Jiang; Yiwei Wu

Abstract: A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma optical emission spectrometry (ETV-ICP-OES) detection was proposed for the determination of chromium species. Thenoyltrifluoroacetone (TTA) was used as both an extractant for CPE of Cr(III) and a chemical modifier for ETV-ICP-OES determination. When the system temperature is higher than the cloud point temperature (CPT) of the selected surfactant, Triton X-114, the complex of Cr(III) with TTA could enter the surfactant-rich phase, whereas the Cr(VI) remained in aqueous solutions. Thus, an in-situ separation of Cr(III) and Cr(VI) could be realized. The concentrated analyte was introduced into ETV-ICP-OES for determination of Cr(III) after proper disposal. Cr(VI) is reduced to Cr(III) prior to determining total Cr, and its assay is based on substracting of Cr(III) from total chromium. The main factors affecting cloud point extraction and the vaporization behavior of the analyte were investigated in detail. Under the optimized conditions, the limit of detection (LOD) for Cr(III) was 0.22 ?g/L by pre-concentration of a 10 mL sample solution, and the relative standard deviation (RSD) was 3.8% ([Cr(III)] = 0.5 µg/mL, n = 5). The proposed method was applied to the speciation of chromium in different water samples. In order to verify the accuracy of the method, a certified reference water sample was analyzed, and the results obtained were in good agreement with certified values.

"Flow Injection Spectrophotometric Determination Of The Antibacterial Levofloxacin In Tablets And Human Urine"
Anal. Lett. 2006 Volume 39, Issue 4 Pages 741-750
I. F. Al-Momani

Abstract: A sensitive and fast flow-injection (FI) spectrophotometric method for the determination of levofloxacin based on the formation of a colored product upon oxidation with N-bromosuccinimide (NBS) in acidic medium is proposed. Optimization of chemical and FI variables has been made. Under the optimized conditions, the sampling rate was over 90 h-1, the calibration curve obtained was linear over the range 10^-300 µg mL-1, and the detection limit was 3 µg mL-1. The proposed method was successfully applied to the determination of levofloxacin in pharmaceuticals and human urine samples. It was also found that the excipients in the commercial tablet preparation did not interfere with the assay. Results are precise (RSD < 2.7%; n = 10) and in agreement with those found by the reference high pressure liquid chromatography (HPLC) procedure. Copyright © Taylor & Francis Group, LLC.

"Determination Of Sb(III) And Total Sb In Antileishmanial Drugs By Spectrophotometric Flow-injection Hydride Generation"
Anal. Lett. 2006 Volume 39, Issue 3 Pages 543-554
Eduardo Costa de Figueiredo; Pedro Orival Luccas; Marco Aur&eacute;lio Zezzi Arruda

Abstract: A spectrophotometric procedure based on hydride generation and flow analysis is proposed for determination of antimony (III) [Sb(III)] and total antimony (Sb) in pharmaceutical samples. Firstly, Sb(III) reacts with hydrogen species generated in the system, forming antimony hydride. The reaction leads to a decrease in the permanganate concentration and, hence, in the intensity of the color of this specie, which is spectrophotometrically measured at 528 nm. Total Sb is determined as Sb(III) after Sb(V) reduction using 0.02% (m/v) KI. Some parameters, such as the number of channels of the gas phase separator, injection volume, coil length, and KBH4 concentration, are investigated. The system presents a frequency of ~100 h-1 and precision <3.0% [expressed as relative standard deviation (RSD) of 30 measurements using a 3.0 mg L-1 Sb(III) solution]. The analytical curve ranging from 0.5 mg L-1 to 5.0 mg L-1 (r > 0.998; n = 5) permits limit of detection (LOD) and limit of quantification (LOQ) of 83 and 250 ?g L-1. For total Sb, the accuracy is checked by atomic absorption spectrometry applying the t test and the results are in accordance at the 95% confidence level. Recovery tests are used to check the accuracy for Sb(III) determination, and the recoveries are between 95% and 105%. Copyright © Taylor & Francis Group, LLC.

"Effect Of Mercury(II) Traces On Catalytic Activity Of Peanut And Horseradish Peroxidases"
Anal. Lett. 2006 Volume 39, Issue 3 Pages 521-541
Nailya A. Bagirova; Svetlana V. Muginova; Tatyana N. Shekhovtsova; Irina G. Gazaryan; Robert B. van Huystee

Abstract: Mercury(II) in the range of 0.1-1 ?g L-1 concentrations was found to be a much more efficient inhibitor of native peanut peroxidase (PNP) than of horseradish peroxidase (HRP) in the reaction of o-dianisidine oxidation with hydrogen peroxide. The possible reason for the different degree of mercury(II) effects on the catalytic activity of both enzymes was studied. It was shown that the different number of glycans in PNP and HRP molecules (three and eight, respectively), or their absence in the molecule of wild-type recombinant horseradish peroxidase refolded from E. coli inclusion bodies (recHRP), does not play a significant role in the effects caused by mercury(II). The efficient inhibition of PNP by mercury(II) in the absence of any other additives (for example, thiourea) originates from a greater mobility of the distal calcium ion in the enzyme molecule. A model scheme for the interaction of the studied plant peroxidases with mercury(II) was proposed. The PNP-based enzymatic method for mercury(II) determination with cmin = 0.04 ?g L-1 (0.2 nmol L-1) was developed and the possibility of PNP application for analysis of different samples was demonstrated. Copyright © Taylor & Francis Group, LLC.

"Flow Injection Photoamperometric Investigation Of Ascorbic Acid Using Methylene Blue Immobilized On Titanium Phosphate"
Anal. Lett. 2006 Volume 39, Issue 3 Pages 451-465
Yusuf Dilgin; G&uuml;rel Niscedilli

Abstract: Methylene blue (MB) was incorporated into titanium phosphate (TiP) after pretreatment of TiP with the gas, n-butyl amine. The dye is strongly retained and not easily leached from the layered host matrix. The adsorbed MB on TiP was used to prepare modified carbon paste electrodes (MCPE), which were studied voltammetrically and in amperometric flow injection (FI) mode for the electrocatalytic oxidation of ascorbic acid (AA). The electrochemical behavior of the immobilized dye was investigated with cyclic voltammetry, at a pH 7.0 phosphate buffer containing 0.5 M KCl, at different potential scan rates. The MB immobilized on the support underwent a quasireversible electrochemical redox reaction. A homemade flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimized for sensitivity and reproducibility at a flow rate of 1.5 mL/min, a transmission tubing length of 25 cm, a sample injection volume of 100 µL, and a constant applied potential of +100 mV vs. SCE. The calibration curve for AA was linear over the concentration range from 1.0 x 10^-6 to 2.5 x 10^-5 mol L-1 for both amperometric and photoamperometric studies. But the slope of the photoelectrocatalytic FIA procedure was improved about 52% compared with those obtained without irradiation. The results obtained for AA determination in some pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA. Copyright © Taylor & Francis Group, LLC.

"Automated Method For The Total Creatinine Determination In Dehydrated Broths"
Anal. Lett. 2006 Volume 39, Issue 2 Pages 387-394
Carolina C. Acebal; Mar&iacute;a Eugenia Centuri&oacute;n; Adriana G. Lista; Beatriz S. Fern&aacute;ndez Band

Abstract: In order to improve the quality control of dehydrated broth, a new automated method was developed to determine total creatinine in dehydrated broths. The sample pretreatment was coupled on-line with the Flow Injection Analysis (FIA) system for analyte determination by the classical Jaffe reaction, stopped flow methodology, and spectrophotometric detection. The time consumed was reduced from 7h, which is necessary with the official method, to 25 min. The calibration graph is linear between 0.342-1.368 mg creatinine/ 100 mL. The relative standard deviation (RSD%) was 1.7%, the sample throughput was 7 h -1, and the detection limit was 0.185 mg creatinine/100 mL. The validation of the proposed method was carried out with real samples. The obtained results were compared with those obtained from the Association of Official Analytical Chemists (AOAC) reference method. Copyright © Taylor & Francis Group, LLC.

"Flow Injection Analysis Spectrophotometric Determination Of Platinum"
Anal. Lett. 2005 Volume 39, Issue 1 Pages 197-205
Khageshwar Singh Patel, Nitin Kumar Jaiswal, Paresh Chandra Sharma, Peter Hoffmann

Abstract: A new, simple, rapid, and selective procedure for the flow injection analysis (FIA) spectrophotometric determination of platinum (Pt) is described. The method is based on the color reaction of Pt(IV) with SnCl2 in the HCl medium. The mixed surfactants, i.e., cetylpyridinium chloride (CPC)+Triton X-100 (TX-100) are used to enhance sensitivity of the method. The value of apparent molar absorptivity in the term of Pt is 3.00 x 10^3 L mol-1 cm-1 at absorption maximum, 405 nm. The detection limit (causing absorbance greater than 3SD) of the method is 150 ng/mL. The optimum concentration range for the determination of Pt is 0.5-18 µg mL-1 with slope, intercept and correlation coefficient 0.0086, -0.001, and +0.99, respectively. The sample throughput of the method is 120 samples/h at the flow rate of 3.7 mL/min. The composition of the complex, and the reaction mechanism involved are discussed. The effect of FIA and analytical variables on the determination of the metal is optimized. The method has been tested for the analysis of Pt to the catalytic materials.

"Sample Injection For Capillary Electrophoresis On A Micro Fabricated Device/On Chip CE Injection"
Anal. Lett. 2005 Volume 39, Issue 1 Pages 3-16
Bernd W. Wenclawiak and Ren&eacute; J. P&uuml;schl

Abstract: Reproducible injection for capillary electrophoresis on a µdevice/Lab on chip is not an easy task. Different injection designs (e.g., T-type, double T-type, cross) and different injection modes have been applied (pinched injection, gated injection, optically gated injection, pressure/pneumatic injection, double L injection) with various analytes. Problems and properties of the different modes are described.
Microfluidic Injector Review

"Flow Injection Determination Of Humic Acid With Chemiluminescence Detection"
Anal. Lett. 2005 Volume 38, Issue 14 Pages 2439-2447
Yuhong Tian, Qi Jun Song, Zhaozhe Hua

Abstract: A very sensitive and fast flow injection chemiluminescence method, based on the oxidation of humic acid (HA) by 1,3-dibromine-5,5-dimethylhydantion in the presence of glycine in alkaline medium, was developed for the determination of trace humic acids in water. A wide calibration range from 0.001 to 1.0 µg mL-;1 was obtained at the optimized conditions and the detection limit was as low as 0.5 ng mL-;1 of humic acids. Most of the foreign substances tested showed relatively high tolerance levels and the proposed method was successfully applied to the determination of humic acid in river water and tap water.
Acids, humic River Water Chemiluminescence Interferences Optimization

"Flow‐Injection Spectrophotometric Determination Of Dipyrone In Pharmaceutical Formulations Using Ammonium Molybdate As Chromogenic Reagent"
Anal. Lett. 2005 Volume 38, Issue 14 Pages 2315-2326
Luiz H. Marcolino&#8208;J&uacute;nior, Rog&eacute;rio A. Sousa, Orlando Fatibello&#8208;Filho, Fernando C. Moraes, Marcos F.S. Teixeira

Abstract: A simple and rapid flow-injection spectrophotometric method is reported for the determination of dipyrone in pharmaceutical formulations. The method is based on the reaction of dipyrone with ammonium molybdate in acidic medium to produce blue molybdenum, which was detected spectrophotometrically at 620 nm. The analyte was determined in a single-line flow system. The calibration curve obtained was linear in the range of 5 x 10^-4 to 8 x 10^-3 mol L-1 for dipyrone concentration and the precision (sr=1.7%) was satisfactory. The method proved to be selective and adequately sensitive. Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 95.3%-101% and relative errors less than 5.0% for five pharmaceutical formulations were found.

"Separation And Removal Of Mercury(II) From Water Samples Using (Acetylacetone)-2-thiol-phenyleneimine Immobilized On Anion-exchamge Resin Prior To Determination By Cold Vapor Inductively Coupled Plasma Atomic Emission Spectroscopy"
Anal. Lett. 2005 Volume 38, Issue 13 Pages 2217-2230
Derya Kara

Abstract: (Acetylacetone)-2-thiol-phenyleneimine (H2L) immobilized on an anion-exchange resin (Dowex) was used for separation and removal of mercury from natural water samples and for pre-concentration prior to its determination by cold vapor inductively coupled plasma atomic emission spectroscopy. The metal was eluted from the column using a solution of 10% thiourea in 0.1 M HCl. The modified resin is higly selective with an exchange capacity of 1.60 mmol g -1. Various parameters like pH, column flow rate, and desorbing agents are optimized. The proposed method has a linear calibration range of 15-1000 ng/ml Hg(II), with a relative standard deviation at the 15 ng/ml level of 3.5%. The precision of the method (evaluated as the relative standard deviation obtained after analyzing six series of five replicates) was ±4.2% at the 50 ng/ml level of Hg(II). The method has been used for routine determination of trace levels of mercury species in natural waters. The potential application of modified resin for the removal of mercury(II) from two natural water samples (top water and lake water) spiked with 50 ng/ml of mercury (II) was studied by ICP-AES, and the results proved that excellent percent extraction of mercury(II) from both natural water samples was obtained by column method using modified resin. Copyright © Taylor & Francis, Inc.

"Validated Flow Injection Spectrophotometric Assay For The Quality And Stability Control Of Gemfibrozil Tablets"
Anal. Lett. 2005 Volume 38, Issue 13 Pages 2165-2173
Paraskevas D. Tzanavaras and Demetrius G. Themelis

Abstract: A validated flow injection spectrophotometric assay has been developed and optimized for the determination of gemfibrozil in pharmaceutical formulations. The method is based on the direct measurement of the absorbance of the analyte-under flow conditions-in basic medium, at 276 nm. The assay was optimized in terms of sample injection volume and flow rate and validated in terms of linearity, repeatability, detection limit, accuracy, and selectivity. Linear calibration curve was obtained in the range of 20-100 mg l-;1, while the detection limit (1.4 mg l-;1), the repeatability (sr <1.0%, n=12) and the sampling rate (30 h-;1) were satisfactory. The method was applied successfully to the quality control of one batch (batch number 052) and the stability control of three batches (batches number 049-051) of a gemfibrozil-containing formulation (Prelisin®, Cosmopharm Ltd, Greece).

"Determination Of Aluminum Traces In Hemodialysis And Tap Water Using Standard Method's Procedure Modified And Flow Injection Ionic Exchange Preconcentration"
Anal. Lett. 2005 Volume 38, Issue 13 Pages 2089-2101
Edson Luiz da Silva, Edgard Moreira Ganzarolli, Rold&atilde;o R. U. de Queir&oacute;z

Abstract: A procedure for the spectrophotometric determination of aluminum traces in water using a flow injection (FI) pre-concentration system has been proposed. The flow system was made up of a peristaltic pump, an injector-commutator, and a minicolumn filled with 300.0 mg of Amberlite IR-120 cationic exchange resin. After the pre-concentration step, aluminum was eluted by a 4.0 mol l-;1 HCl solution. In a second stage, out of the flow system, the eluate was neutralized with a 4.0 mol l-;1 NaOH solution. The aluminum was submitted to the reaction with eriochrome cyanine to form a chelate in solution buffered to pH 5.85, according to the Standard Method's procedure with some modifications, and this was followed by spectrophotometric detection. Chemical and flow variables were studied in the pre-concentration system. The precision of the proposed method was calculated for a solution containing 46.8 µg l-;1 of Al(III), when 40.0 mL of solution were pre-concentrated (n=7), and their respective relative standard deviation (RSD) was 1.8%. The detection limit obtained was 1.7 µg l-;1 of Al(III) (sample volume=40.0 ml). The proposed method was successful in determining aluminum in water certified reference material.

"The Determination Of Perphenazine By A New Simple Flow‐Injection Chemiluminescence Method"
Anal. Lett. 2005 Volume 38, Issue 12 Pages 1933-1941
Xiaonian Han, Yuhai Tang, Chunling Yu, Xiaohui Zheng, Qingju Jin

Abstract: A rapid and simple flow-injection chemiluminescence (CL) method is described for the determination of perphenazine, which is based on the CL intensity that generated from the redox reaction of Ce (IV)-perphenazine in HNO3 medium is proportional to the perphenazine concentration without any sensitizers. The proposed method allows the determination range within 1.0 x 10^-7-7.0 x 10^-5 g mL-;1 with a detection limit of 8.0 x 10^-8 g mL-;1, and it has been successfully applied to the determination of the perphenazine in pharmaceutical tablet compared well with the official method.

"Evaluation Of An FIA Operated Amperometric Bacterial Biosensor, Based On Pseudomonas Putida F1 For The Detection Of Benzene, Toluene, Ethylbenzene, And Xylenes (BTEX)"
Anal. Lett. 2005 Volume 38, Issue 10 Pages 1531-1547
Josef D. Rasinger; Giovanna Marrazza; Fabrizio Briganti; Andrea Scozzafava; Marco Mascini; A. P. F. Turner

Abstract: Recently, the development and optimization of a flow injection analysis (FIA) operated bacterial biosensor based on the aerobic catabolism of Pseudomonas putida ML2 was reported in the literature (Lanyon et al. 2004, 2005). By adapting information from these reports, we investigated whether operating parameters and procedures of the benzene biosensor could be directly applied to a new system based on a different bacterial strain for the detection of the whole benzene, toluene, ethylbenzene, and xylenes range. Cells of the investigated bacterial strain, Pseudomonas putida F1, were immobilized between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. The P. putida F1 aerobically degrades benzene, toluene, and ethylbenzene (BTE) (Cho et al. 2000). The BTE biosensor in kinetic mode FIA displayed a linear range of 0.02-0.14 mM benzene (response time: 5 min, baseline recovery time: 15 min), 0.05-0.2 mM toluene (response time: 8 min, baseline recovery time: 20 min), and 0.1-0.2 mM ethylbenzene (response time: 12 min, baseline recovery time: 30 min), respectively. Due to the differences in sensitivity, response, and baseline recovery times for BTE, it was possible to differentiate each compound in mixtures of these volatile organic compounds (VOCs). No response for xylenes could be obtained since they cannot be completely metabolized by this bacterial strain. However, it was reported that the range of compounds degradable by P. putida F1 can possibly be expanded by cultivating the cells on different carbon sources (Choi et al. 2003). The sensor showed good intra- and interassay reproducibility, and all obtained results were comparable with those reported in the literature. The demonstrated reproducibility and the simplicity and ease of use as well as the portability for in situ measurements indicates that the biosensor could be suitable as a reliable initial warning device for elevated BTE levels in indoor and outdoor environments. Copyright © Taylor & Francis, Inc.

"OnLine Coupling Of A Flow Injection System To TS‐FF‐AAS For Preconcentration And Determination Of Lead In Water And Vegetables"
Anal. Lett. 2005 Volume 38, Issue 9 Pages 1427-1443
C&eacute;sar Ricardo Teixeira Tarley and Marco Aur&eacute;lio Zezzi Arruda

Abstract: An online solid phase pre-concentration system coupled to thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for Pb(II) ions determination is described. In the pre-concentration system, Pb(II) ions complexed with ammonium O,O-diethyl-dithiophosphate (DDTP) in an acidic medium are pre-concentrated as a neutral complex onto 20 mg of polyurethane foam (PUF) packed into a mini-column. The complex retained in the PUF is then released to TS-FF-AAS by using an 80% (v/v) ethanol solution. Chemical and flow variables associated with the pre-concentration, such as the pH dependence of the Pb-DDTP complex, the DDTP concentration, and pre-concentration and elution flow rates were optimized by the univariate method. The best sample pH value and DDTP concentration achieved are 2.0 and 0.5% (w/v), respectively, while the best pre-concentration and elution flow rates are 2.4 and 1.0 mL min-;1, respectively. Under the optimized conditions, the present method, which is operated in volume mode (only 2 mL), makes possible the determination of Pb(II) ions within a linear range from 5.2 to 300.0 µg L-;1 with a detection limit of 1.5 µg L-;1 and analytical frequency of 16 h-;1. The precision (n=10) assessed as relative standard deviation (RSD) is, respectively, 7.3 and 4.8% for 6 and 200 µg L-;1 solutions of Pb(II). The pre-concentration system provides an enrichment factor of 6.4 and consumption index of 310 µL. Hence, the coupling of the pre-concentration system to TS-FF-AAS is proven to be an efficient strategy to enhance TS-FF-AAS detectability. The applicability of the method was verified by analyzes of spiked water samples as well as with certified and reference vegetable materials.
Lead(2+) Environmental Vegetable Spectrophotometry Preconcentration Column Polyurethane foam Optimization

"Reactions Of Orthophthalaldehyde And Related Compounds With Amino Acids"
Anal. Lett. 2005 Volume 38, Issue 8 Pages 1213-1220
Petr Zuman

Abstract: Reaction of orthophthalaldehyde with thiols and of the product of this reaction with amino acids is commonly used for determination of amino acids. This reaction is often utilized in pre-column and post-column derivatization in chromatography and forms the basis of procedures applied in commercial amino acid analyzers. The product of this reaction is known to be an isoindole derivative, but the reaction paths of its formation are not understood. Better knowledge of chemical processes involved seems essential for development of more reliable procedures for determination of amino acids.

"Determination Of Hydrogen Peroxide, Glucose And Hypoxanthine Using (bio)sensors Based On Ruthenium Dioxide-modified Screen-printed Electrodes"
Anal. Lett. 2005 Volume 38, Issue 7 Pages 1099-1113
Petr Kotzian; Petra Br&aacute;zdilov&aacute;; Kurt Kalcher; Karel Vytrcaronas

Abstract: Screen-printed electrodes modified with ruthenium dioxide were investigated as amperometric sensors for the determination of hydrogen peroxide using flow injection analysis (FIA). With additions of enzymes (glucose oxidase or xanthine oxidase) immobilized onto the electrode surface, via Nafion films, corresponding biosensors for the quantification of glucose or hypoxanthine were developed. Factors influencing their amperometric responses (operational potential, flow rate, pH of the phosphate buffer carrier) were studied in detail. Applications in food analysis were also examined. Copyright © Taylor & Francis, Inc.

"Microbial Biosensor For The Analysis Of 2,4‐Dichlorophenol"
Anal. Lett. 2005 Volume 38, Issue 7 Pages 1071-1083
Jongjit Jantra, Hamid Zilouei, Jing Liu, Benoit Guieysse, Panote Thavarungkul, Proespichaya Kanatharana, Bo Mattiasson

Abstract: A flow injection cell-based biosensor was constructed for 2,4-dichlorophenol (DCP) analysis by using a Clark-type oxygen electrode as a transducer. A mixed bacterial culture capable to biodegrade DCP was immobilized between a Teflon membrane and a dialysis membrane and attached to the oxygen electrode. Optimization of the flow rate, the injection volume, the carrier buffer concentration, and pH was carried out. Under optimum conditions (100 mM phosphate buffer, pH 7.50; flow rate 0.10 mL min-1; sample volume 100 µL), the sensor response was linear between 0.01 and 0.30 mM DCP. The detection limit was 0.02 mM DCP, and the sensor was quite stable during 5 days of operation.
2,4-Dichlorophenol Electrode Electrode Sensor Detector Optimization

"Europium Sensitized Chemiluminescence Determination Of Pazufloxacin Mesylate In Urine And Serum"
Anal. Lett. 2005 Volume 38, Issue 6 Pages 971-979
X. -L. Wang; S. -L. Chen; H. -C. Zhao; L. -P. Jin; Xia Li

Abstract: A novel chemiluminescence (CL) flow injection method for the determination of pazufloxacin mesylate (PZFX) is described. It is based on CL of a KMnO 4-Na2S2O4 system sensitized by the complex [Eu(PZFX)2]3+, and shows the intensive characteristic bands of Eu3+. The optimum conditions for CL emission were investigated. Under the optimum experimental condition, the linear range is 1.0 x 10^-8-1.0 x 10^-6 mol/L and the detection limit is 2.6 x 10^-9 mol/L. The method was successfully applied to the determination of PZFX in serum and urine samples. The possible mechanism for this CL system is discussed. Copyright © Taylor & Francis, Inc.

"A Sample Introduction Method Based On Negative Pressure In Flow Injection‐Capillary Electrophoresis System And Its Application To The Alkaline‐Earth Metal Cation Separation"
Anal. Lett. 2005 Volume 38, Issue 5 Pages 857-867
Jianwei Wang, Zuanguang Chen, Peixiang Cai, Jinyuan Mo

Abstract: A new sample introduction method based on negative pressure has been developed in the flow injection (FI)-capillary electrophoresis (CE) system with contactless conductivity detection (CCD). In the system, the sample was carried to the interface by background electrolyte (BGE), which was carried by a dual-channel peristaltic pump. Sample introduction into capillary was performed through the negative pressure at the outlet of capillary. Duration of the injection was controlled by a precise homemade time circuit connected to the voltage supply of vacuum pump. When the sample was transported to the inlet of capillary, the vacuum pump was started and a small volume sample was injected within 1.0-2.0 s. Negative pressures from 20 to 25 kPa are appropriate and other important injection parameters were studied. The RSD values (n=8) of the negatively pressurized injections, within the range of 0.8-1.1% for migration time, are comparable with those of gravity injection. The performance of the whole system was further demonstrated with satisfactory results in the separation of four alkaline-earth metal cations (Mg2+, Ca2+, Sr2+, Ba2+) with CCD.
Magnesium(II) Calcium(2+) Strontium(II) Barium(2+) Conductometry Electrophoresis Injection technique

"Chemiluminescence Microflow Injection Analysis System On A Chip For The Determination Of Sulfite In Food"
Anal. Lett. 2005 Volume 38, Issue 4 Pages 563-571
Deyong He; Zhujun Zhang; Ying Huang

Abstract: Based on the chemiluminescence (CL) reaction between Ce (IV) and sulfite sensed by Rh6G and Tween 80 in acid medium, a new microflow injection analysis (?FIA) system on a chip for the determination of sulfite with chemiluminescence method was described in this paper. The channels of the ?FIA system etched by CO2 laser were 200 ?m wide and 150 ?m deep and the volume of reaction area was 1.80 µL. All reagents, including sample, were monitored by the injection pump with the rate of 50 µL/min. The linear range of sulfite concentration was 1.0-60 ?g/mL with the detection limit of 0.5 ?g/mL. The proposed method had good reproducibility with the relative standard deviation 3.0% (n = 7) for 20 ?g/mL of sulfite and was very sensitive and simple. It had been successfully applied to the determination of sulfite in food.

"Flow-Injection Turbidimetric Determination Of Tannins In Tea Samples Using Copper(II)/Acetate As Precipitant Reagent"
Anal. Lett. 2005 Volume 38, Issue 3 Pages 511-522
Evandro Piccin, Heberth Juliano Vieira, Orlando Fatibello-Filho

Abstract: A flow-injection (FI) turbidimetric method for determination of tannins content in tea samples based on the precipitation reaction with copper(II) in acetate medium is proposed. In this method, 350 µL of 0.05 mol L-1 copper(II) and 350 µL of sample were injected simultaneously in two water carrier streams of a merging zones system. After mixing at a 50 cm coiled reactor, the mixture converged with a flow stream of 0.10 mol L-1 ammonium acetate solution producing a precipitate in a 100 cm coiled reactor that was monitored at 500 nm. Under the optimized experimental conditions, the calibration graph for tannic acid was linear in the concentration range from 18.0 to 725 mg L-1 with a detection limit of 6.49 mg L-1. The relative standard deviations (RSD) were smaller than 1.2% (n=10) for solutions containing 110 and 365 mg L-1 of tannic acid, and the analytical frequency was 90 determinations per hour. The results obtained in the analysis of tea samples (green, black, and brown) were compared with those provided by the Folin-Ciocalteu method.
Tannins Plant Turbidimetry Method comparison Precipitation Optimization Merging zones

"Determination Of Phenol By Preconcentration-Direct Chemiluminescence In A FIA Assembly"
Anal. Lett. 2005 Volume 38, Issue 3 Pages 499-510
B. G&oacute;mez-Taylor Corominas, J. V. Garc&iacute;a Mateo, L. Lahuerta Zamora, J. Mart&iacute;nez Calatayud

Abstract: The determination of phenol in water samples is proposed with the aid of a flow-injection system. The analytical procedure is based on the direct chemiluminometric emission by oxidation of the analyte with potassium permanganate in acidic medium. The flow assembly is provided with a solid-phase reactor filled with a resin type XAD-4 for analyte pre-concentration. A large study of potential interferences, namely, amino acids reaching water through degradation of organic matter; metals and inorganic metal ions typically present in water interfering with the CL emission of the parent compound, was performed. The calibration graph was linear over the phenol concentration range 1.0-20.0 ng mL-1; the LOD was 5.0 ng mL-1. Finally, the method was applied to the determination of phenol in waste- and groundwater.
Phenol Ground Chemiluminescence Resin Preconcentration Interferences

"Determination Of Heparin Using Azure B By Flow Injection Analysis-resonance Light Scattering Coupled Technique"
Anal. Lett. 2005 Volume 38, Issue 2 Pages 317-330
Cheng Zhi Huang; Xiao Bing Pang; Yuan Fang Li

Abstract: A flow injection analysis-resonance light scattering (FIA-RLS) coupled technique was developed originally to determine hepanrin in the presence of Azure B (AB). The FIA-RLS coupled technique overcomes the drawbacks of RLS technique such as poor reproducibility and tedious operation without sacrificing sensitivity and simplicity. The method is based on the enhanced weak RLS intensity of AB by the addition of a trace of heparin (HP) with ?max located at 340.0 nm at pH 7.96. In time scanning mode, a linear relationship between FIA-RLS intensity and heparin concentration in the range of 0.01-6.0 ?g mL-1 was established with the limit of detection (LOD) of 6.4 ng mL-1 (3?) with a relative standard deviation (RSD) of 2.1% (n = 20, S/B > 3), and the LOQ of 10 ng mL -1. Owing to the introduction of FIA automation, the throughput of FIA-RLS coupled technique could be more than 120 samples per hour.

"Flow Injection Spectrofluorimetric Method For Determination Of Chromium(VI) Using Stopped-flow Technique"
Anal. Lett. 2005 Volume 38, Issue 2 Pages 303-315
Bo Tang; Taixing Yue; Xifeng Shi; Junsen Wu; Yan Wang

Abstract: A novel fluorescent reagent, pyridine-2-aldehyde benzothiazoline, was synthesized. The reaction between pyridine-2-aldehyde benzothiazoline and Cr(VI) was studied in detail. Based on the oxidation reaction, a highly sensitive and selective flow injection spectrofluorimetric method (using stopped-flow technique) was developed for online determination of Cr(VI). Under the optimum experimental conditions, the oxidized product of pyridine-2-aldehyde benzothiazoline had excitation and emission maxima at 310 and 398 nm, respectively. The linear range was 7.6 x 10^-3 ? 5.0 ?g mL-1 of Cr(VI), the detection limit was 2.3 ng mL-1, and the maximum sampling rate was 40 h-1. The effect of interferences was studied. This proposed method was successfully applied to the determination of chromium in sludge.

"A Fully Automated Assembly Using Solenoid Valves For The Photodegradation And Chemiluminometric Determination Of The Herbicide Chlorsulfuron"
Anal. Lett. 2005 Volume 38, Issue 1 Pages 179-184
K. Mervartov&aacute;, J. Mart&iacute;nez Calatayud, M. Catal&aacute; Icardo

Abstract: This paper presents a new photochemiluminescent system for the determination of chlorsulfuron in water samples. The light from a low-pressure mercury lamp is used as a clean, reproducible, and inexpensive "reagent" for the derivation of the pesticide, performed in glycine buffer at pH 9.5. Then, the photo-products from irradiation are oxidized by permanganate in sulfuric acid solution. The oxidation reaction was favored by using high temperatures. A comparative study and discussion about the use of polyphosphoric acid instead of sulfuric acid in the oxidation reaction is also presented. The use of solenoid valves allows for the easy, complete automation of the process with low sample and reagent consumption. The calibration graph was linear over the range 0.1-1.3 mg L-1 of chlorsulfuron, the limit of detection was 0.06 mg L-1, and the throughput was 25 h-1. The proposed method was applied to the determination of the pesticide in spiked mineral water samples.
Chlorsulfuron Mineral Chemiluminescence Heated reaction Valve UV reactor

"Potentiometric Flow Injection Analysis Of Drotaverine Hydrochloride In Pharmaceutical Preparations"
Anal. Lett. 2005 Volume 38, Issue 1 Pages 111-132
Hosny Ibrahim, Yousry M. Issa, Hazem M. Abu-Shawish

Abstract: Five poly (vinyl chloride) (PVC) membrane electrodes for the determination of drotaverine hydrochloride (DvCl) were constructed and fully characterized in terms of composition, life span, response time, usable pH range, working concentration range, and temperature. The membranes of these electrodes consist of drotaverinium-silicotungstate (Dv-ST), silicomolybdate (Dv-SM), phosphotungstate (Dv-PT), phosphomolybdate (Dv-PM), or tetraphenylborate (Dv-TPB) ion associations dispersed in PVC matrix with dibutyl phthalate plasticizer. The electrodes showed near-Nernstian response over the concentration range of 2.0 x 10^-6 to 1.0 x 10^-2 M DvCl and were applied to the potentiometric determination of drotaverinium ion in pharmaceutical preparations in steady-state and flow injection (FI) conditions with average recoveries of 98.1-102.2% and relative standard deviation of 0.308-1.310%. The electrodes exhibit good selectivity for DvCl with respect to a large number of inorganic cations, organic cations, sugars, and amino acids. The sensitivities of these electrodes are high enough to measure as low as 0.87 µg/mL of DvCl which permits the determination of the Ksp values of the ion associates used.
Drotaverin Pharmaceutical Electrode Interferences Selectivity Solubility product constant

"Flow Injection Potentiometric Determination Of Dothiepin Hydrochloride"
Anal. Lett. 2004 Volume 37, Issue 15 Pages 3237-3254
N. T. Abdel Ghani, R. M. El-Nashar, A. A. Bioumy

Abstract: New plastic membrane electrodes for dothiepin hydrochloride (DpCl) based on dothiepin phosphotungstate (Dp-PTA), dothiepin phosphomolybdate (Dp-PMA), and a mixture of both (Dp-PTA/PMA) were prepared. The electrodes were fully characterized in terms of their composition, life span, pH, and temperature, and then were applied to the potentiometric determination of the dothiepinium ion in its pure state and pharmaceutical preparations in batch and flow injection conditions. The selectivity of the electrodes toward many inorganic cations, sugars, and amino acids was also tested.

"Flow‐Injection Chemiluminescent Determination Of Thiamine In Pharmaceutical Samples By On‐line Photodegradation"
Anal. Lett. 2004 Volume 37, Issue 15 Pages 3205-3218
A. Wasielczuk, M. Catal&aacute; Icardo, J. V. Garc&iacute;a Mateo, J. Mart&iacute;nez Calatayud

Abstract: A simple, sensitive, and precise method for the determination of thiamine hydrochloride in a flow-injection system is described. The method is based on the UV irradiation of thiamine in acid medium. Then, the photo-fragments are oxidized by permanganate in acid medium, and the resultant chemiluminescent intensity is measured. The optimum conditions for the photoreaction and for the chemiluminescence emission were investigated. The method allows the determination of thiamine, over the range 0.05(LOD)-84 mg L-1, with a throughput of 30 h-1, and a RSD (n, 20) at 20 and 0.5 mg L-1 of the thiamine level of 2.5 and 1.3%, respectively. The method was applied to pharmaceutical preparations.

"Batch And FIA Spectrophotometric Determination Of Sodium And Potassium Ions Via Reaction With Sulfophthalein Derivatized Crown Ethers"
Anal. Lett. 2004 Volume 37, Issue 13 Pages 2721-2738
Irena Nemcova; Simon Ciheln&iacute;k; Petr Rychlovsk&yacute;; Lenka Antalova

Abstract: The mono- and bis-monoaza-15-crown-5-ethers and monoaza-18-crown-6-ethers, bound to the sulphophthalein dyes phenol and bromophenol red, were synthesized. Their complexing properties were studied and, on this basis, these substances were found to be suitable spectrophotometric reagents for nonextraction batch and flow-through (FIA) determination of Na+ and K+ ions in ethanol medium. The optimal reaction and flow conditions were found and a method was developed for determination of both ions. Although the reactions are not fully selective toward both ions, it is possible to carry out the determination of both ions in sample by using a suitably selected reagent at certain concentration ratios. The results are comparable for both dyes and for the mono- and bis-compounds; the size of the cavity in the crown ether is decisive.

"Graphite Furnace Atomic Absorption Spectrometric Determination Of Rhodium After Online Ion-Exchange Preconcentration"
Anal. Lett. 2004 Volume 37, Issue 13 Pages 2685-2700
Fuensanta S&aacute;nchez Rojas, Catalina Bosch Ojeda, Jos&eacute; M. Cano Pav&oacute;n

Abstract: A method for the determination of rhodium in different samples at trace levels is presented. The investigated metal is pre-concentrated on a chelating resin microcolumn [1,5-Bis(2-pyridyl)-3-sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion-exchange resin (Dowex 1x 8-200)] placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 4 M HNO 3, which acts as the elution agent, pass through the microcolumn eluting Rh(III), which is directly deposited in the graphite tube as a drop of a precisely defined volume. The detection limit is 0.3 ng mL -;1. Linearity is maintained in the concentration range 0-50 ng mL -;1 for rhodium, with correlation factor of 0.999 and relative standard deviation of 1.8% for 10 ng mL -;1 of Rh. The effects of various parameters such as pH, concentration and volume of eluent, sample loading time, sample flow rate, and interference of a large number of metal ions and anions on the determination of this metal was studied in detail to optimize the conditions for their determination in various samples. The method is found to be highly selective, fairly sensitive, simple, rapid and economical, and may be safely applied to their determination in different complex materials, such as environmental samples and catalysts.
Rhodium Environmental Industrial Spectrophotometry Preconcentration Column Dowex Optimization Interferences

"Kinetic Spectrophotometric Determination Of Formaldehyde In Fabric And Air By Sequential Injection Analysis"
Anal. Lett. 2004 Volume 37, Issue 12 Pages 2545-2555
Suling Feng, Jing Fan, Aijun Wang, Xingguo Chen, Zhide Hu

Abstract: A kinetic method for measuring formaldehyde by sequential injection analysis (SIA) with spectrophotometric detection was developed for the first time. The method was based on the inhibitory effect of formaldehyde on the ethyl green (EG)-sulfite reaction. The linear range for formaldehyde was 1.0-20.0 µg mL -;1; the detection limit was 0.020 µg mL -;1. The measurement rate was 130 sec, thus allowing to analyze 27 samples per hour, the total reagent consumption in a cyclical procedure is only 240 µL. The method was applied to the determination of formaldehyde in fabric and air, and compared with acetyl acetone spectrophotometric method.
Formaldehyde Commercial product Environmental Spectrophotometry Sequential injection Method comparison Kinetic

"Determination Of Catecholamines By Flow Injection Chemiluminescence Method Based On Their Restraining Effects On The Luminol–Potassium Chlorate System"
Anal. Lett. 2004 Volume 37, Issue 12 Pages 2445-2458
Yuanyuan Sun, Yuhai Tang, Xiaohui Zheng, Hong Yao, Zhao Xu

Abstract: A rapid and precise continuous flow method was described for the determination of catecholamines based on the catecholamines great inhibitory effects on the chemiluminescence reaction of luminol-potassium chlorate in basic solutions. The optimum chemical conditions for the chemiluminescence reaction were investigated. Under the optimized conditions, four catecholamines: adrenaline, noradrenaline, isoprenaline, and dopamine were determined. The detection limits are 0.2 ng mL-;1 for adrenaline, 0.4 ng mL-;1 for noradrenaline, 0.7 ng mL-;1 for isoprenaline, and 0.4 ng mL-;1 for dopamine. The method was successfully applied to the determination of the four catecholamines in pharmaceutical injections. A brief discussion on the possible chemiluminescence reaction mechanism is presented.

"Flow-injection Analysis Spectrophotometric Determination Of Bismuth In Environmental And Pharmaceutical Samples"
Anal. Lett. 2004 Volume 37, Issue 10 Pages 2163-2174
Kavita Agrawal; Girdhar Lal Mundhara; Khageshwar Singh Patel; Peter Hoffmann

Abstract: A new, simple, rapid, selective, and sensitive flow-injection analysis (FIA) method for the spectrophotometric determination of Bi is described. It is based on reaction of Bi (III) with I- ions in the presence of cationic surfactants (CS), i.e., cetylpyridinium chloride, cetyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, dodecyltrimethylammonium bromide in sulfuric media to give a violet-colored complex. The apparent value of molar absorpitivity of the complex in the terms of Bi with four CSs lie in the range of (1.00-1.20) x 104 L mol-1 cm-1 at ?max 490 nm. Among them, the most sensitive CSs, i.e., cetylpyridinium chloride (CPC) has been selected for the detailed studies. The detection limit (causing absorbance >3 sec) of the method is 65 ?gL-1 Bi. The sample throughput of the method is >120 samples hr-1. The effect of diverse ions and surfactants in the FIA determination of Bi is examined. The composition of the complex is discussed. The analytical and FIA variables in the determination of Bi are optimized. The method has been applied for analysis of Bi in the environmental and pharmaceutical materials.

"Flow Injection Spectrophotometric Determination Of Isoproterenol With An On-line Solid-phase Reactor Containing Immobilized Manganese Dioxide"
Anal. Lett. 2004 Volume 37, Issue 10 Pages 2111-2124
Viviane G. Bonif&aacute;cio; Luiz H. Marcolino-J&uacute;nior; Orlando Fatibello-Filho

Abstract: This work reports the application of a simple, sensitive, and rapid flow injection system for the spectrophotometric determination of isoproterenol by using a solid-phase reactor containing MnO2(s) immobilized in a polyester resin. The method is based on the oxidation of isoproterenol to produce isoproterochrome, which was monitored at 492 nm. The analytical curve was linear in the isoproterenol concentration range from 1.0 x 10 -5-2.0 x 10^-4 mol L-1, with a detection limit of 1.7 x 10^-6 mol L-1. The relative standard deviation (RSD) was 0.9%, and an analytical frequency of 60 hr-1 was obtained. The average recoveries varied from 101.0% to 104.2%, evidencing the absence of matrix effect on the flow injection procedure. The effect of excipient substances frequently found with isoproterenol in pharmaceutical formulations, such as lactose, sucrose, starch, poly(ethylene glycol), and sodium chlorine was evaluated by using the proposed flow procedure. None of these substances caused significant interference in the proposed method. The procedure was successfully applied to the determination of isoproterenol in pharmaceutical preparations, and the results were compared with those results obtained by using an ultraviolet (UV)-spectrophotometric method.

"Flow-Injection Spectrophotometric Determination Of Amoxcillin, Cephalexin, Ampicillin, And Cephradine In Pharmaceutical Formulations"
Anal. Lett. 2004 Volume 37, Issue 10 Pages 2099-2110
I. F. Al&#8208;Momani

Abstract: Amoxcillin, cephalexin, ampicillin, and cephradine were determined spectrophotometrically in the pure form and in the pharmaceutical formulations by using flow-injection analysis (FIA). The method is based upon the hydrolysis of the drug under investigation in basic medium and then the reduction of the formed hydrolyzed product by the on-line generated I 2 in acidic medium. The decrease in the intensity of the I 2 color was monitored at 460 nm and found to be proportional to the concentration of the compound under investigation. Variables such as acidity, reagent concentrations, flow rate of reagents, and other FI parameters were optimized to produce the most sensitive and reproducible results. The method was successfully applied to the analysis of pharmaceutical preparations.

"Determination Of Trace Metals In Fuel Alcohol By FAAS Using Nb 2O 5–SiO 2 As Sorbent Material In A Flow Injection On-Line Preconcentration System"
Anal. Lett. 2004 Volume 37, Issue 9 Pages 1909-1924
Edson Luiz da Silva, Dilma Budziak, Eduardo Carasek

Abstract: This paper describes an on-line pre-concentration system for the determination of copper(II), cadmium(II), cobalt(II), and zinc(II) in samples of fuel alcohol. The analytes were enriched in a minicolumn containing with silica gel chemically modified with niobium(V) oxide (Nb 2O 5-SiO 2). The metals were desorbed from the minicolumn with a solution of nitric acid and determined on-line by flame atomic absorption spectrometry (FAAS). Enrichment factors for copper(II), cadmium(II), cobalt(II), and zinc(II) were 21.3, 23.1, 16.6, and 27.5, respectively, using a pre-concentration time of 2 min. Detection limits for copper(II), cadmium(II), cobalt(II), and zinc(II) were 1.4, 0.2, 1.4, and 1.0 µg L -;1, respectively. Method precision was evaluated by analyzing an alcoholic solution containing 30 µg L -;1 of Cu(II), 15 µg L -;1 of Cd(II), 45 µg L -;1 of Co(II), and 15 µg L -;1 of Zn(II), and their respective relative standard deviation (RSD) were 1.3%, 4.2%, 1.7%, and 1.7% (n = 7). The accuracy of the method was assessed by testing analyte recovery in the fuel alcohol samples.

"A Novel Flow-injection Analysis Method Of Glucose Based On Template-synthesized Sol-gel Nanotube Array Enzyme Membrane Reactor"
Anal. Lett. 2004 Volume 37, Issue 9 Pages 1793-1809
Wei Yang; Hui-Ying Qu; Huang-Hao Yang; Jin-Gou Xu

Abstract: A synthetic enzyme-loading nanotube membrane was developed and used in flow-injection analysis (FIA) for the first time. The membrane was based on an anodic alumina oxide (AAO) film that has cylindrical pores with monodisperse nanoscopic diameters, and silica nanotubes (SNTs) were chemically synthesized within the pores of this film through sol-gel chemistry. Horseradish peroxidase (HRP) was immobilized on the inner walls of the SNTs. The fabrication and initial testing of a flow-through membrane reactor design for heterogeneous enzyme reactions were presented and applied to the determination of glucose in real samples. This novel immobilized enzyme membrane reactor possesses some advantages over both open-tubular and packed-bed reactors often used in FIA. The present work shows that the membrane containing SNTs offers considerable potential and new perspectives for the use of such nanomaterials.

"Flow Injection Analysis Of Benzene Using An Amperometric Bacterial Biosensor"
Anal. Lett. 2004 Volume 37, Issue 8 Pages 1515-1528
Yvonne H. Lanyon, Giovanna Marrazza, Ibtisam E. Tothill, Marco Mascini

Abstract: A bacterial biosensor integrated within a flow injection analysis (FIA) system has been developed for the detection of benzene, based on its aerobic catabolism by Pseudomonas putida ML2. P. putida ML2 cells were immobilized between two cellulose acetate membranes and fixed onto a Clark dissolved oxygen electrode. Biosensor responses were investigated with the FIA system, resulting in a linear detection range between 0.01-0.1 mM benzene. A response and baseline recovery time of 6 and 10^-15 min, respectively, was obtained. A stable and reproducible sensor response has been found up to 28 days of use based on the same bacterial membrane, and the sensor has shown a high specificity to benzene, with a negligible response to other benzene-related compounds. Its ease of operation, rapid and sensitive response, and cost-effective production, demonstrate that the P. putida ML2 biosensor has potential applications for the analysis of samples containing benzene. The optimization of the biosensor-flow injection system is described.

"Development Of A Laccase-modified Electrode For Amperometric Detection Of Mono- And Diphenols. The Influence Of Enzyme Storage Method"
Anal. Lett. 2004 Volume 37, Issue 8 Pages 1497-1513
Anna Jarosz-Wilkolstrokazka; Grzegorz Janusz; Tautgirdas Ruzgas; Lo Gorton; Elzbieta Malarczyk; Andrzej Leonowicz

Abstract: Results are reported for biosensors based oh two different preparations of the same enzyme, laccase from Cerrena unicolor, one lyophilized and one stored frozen at -18°C, for monitoring phenolic compounds. The enzyme was adsorbed on graphite electrodes and these were used in a flow through wall jet cell connected to a flow injection set-up. The electrodes were used at -50 mV vs. Ag|AgCl. The effect of Ph, flow rate of the carrier buffer was investigated as well as the operational and storage stability. Biosensors based on the frozen enzyme preparation were shown to be superior for biosensor construction.

"Factorial Design And Doehlert Matrix In Optimization Of Flow System For Preconcentration Of Copper On Polyurethane Foam Loaded With 4-(2-Pyridylazo)-resorcinol"
Anal. Lett. 2004 Volume 37, Issue 7 Pages 1437-1455
C&eacute;sar Ricardo Teixeira Tarley, Walter Nei Lopes dos Santos, Carla Moreira dos Santos, Marco Aur&eacute;lio Zezzi Arruda, S&eacute;rgio Luis Costa Ferreira

Abstract: The present paper describes a flow pre-concentration system for copper determination by flame atomic absorption spectrometry (FAAS) based on the sorption of Cu(II) ions onto a mini-column of polyurethane foam (PUF) loaded with a chromogenic reagent [4-(2-pyridylazo)-resorcinol (PAR)]. The variables associated with flow pre-concentration system performance, such as pH, buffer concentration (BC), and sampling flow rate (SF), were optimized using a full factorial (2 3) design plus a central point and Doehlert matrix. The results obtained, based on the Pareto chart and analysis of variance (ANOVA), demonstrated that pH and BC, as well as the interaction (pH x BC) are statistically significant at the 95% confidence level. By using 20 mL of sampling volume the proposed method, under conditions optimized by the Doehlert matrix (formation of Cu(II)-PAR (1:2) complex at pH 6.4, 0.017 mol L -;1 phosphate BC, and 10 mL min -;1 SF), allows to determine Cu(II) ions with a detection limit of 0.35 µg L -;1 and precision (n = 8) as relative standard deviation (RSD) of 3.2 and 1.1 for copper solutions containing 10 and 30 µg L -;1, respectively. Also, a satisfactory linear range (1.2-40 µg L -;1), an enrichment factor of 105 and a sample throughput of 28 hr -;1 were achieved. Interference studies showed that the PUF-PAR mini-column retains Cu(II) ions in the presence of several transition and alkali metals without presenting interferences. The method was applied for copper determination in water samples (mineral and tap water) and high salt aqueous samples (physiological serum containing 0.9% (m/v) NaCl). The validation of the method was checked by analyzing the Cu(II) content in the samples, as well as from analyte addition. The recoveries ranged from 91.0% to 101.1%.

"A Microchip With Air Sampling And Chemiluminescence Detection For Analyzing Iron In Nature Water And In Whole Blood"
Anal. Lett. 2004 Volume 37, Issue 7 Pages 1401-1410
Jiagen Lv and Zhujun Zhang

Abstract: A mircrofluidic chip, based on using an air stream for fluidic controlling and coupled with chemiluminescence (CL) detection, was presented. The reported design promised a simple, low cost chip fabrication, and an easy operation. With each assay time less than 3 min, the described microfluidic chip was applied in determination of iron(II) content in nature water and total iron content in whole blood. Experiment results showed the potential for a multitude of applications of the presented chip. The calibration graph of chemiluminescent intensity (I CL) vs. iron(II) concentration was linear in the range 1.0 x 10 -;6-5.0 x 10 -;5 mol L -;1, and the detection limit (DL) was 3.0 x 10 -;7 mol L -;1 (3s).

"Effect Of Exhaustion Hood Flow Rate In Flow Injection Cold Vapor And Hydride Generation Atomic Absorption Spectrometry"
Anal. Lett. 2004 Volume 37, Issue 5 Pages 1025-1034
Oktay Cankur; O. Yavuz Ataman

Abstract: The effect of exhaustion hood flow rate in the laboratory was investigated. It has been observed that this parameter significantly affects the analytical signal. This effect was more evident in cold vapor (CV) atomic absorption spectrometry (AAS) signal when unheated quartz T-tube atomizer (QTA) was used as atom cell. At maximum exhaustion hood flow rate, the peak height and peak area values for Cd decreased to 36% and 35%, respectively, of those obtained under no exhaustion. When CV cell with both ends covered with quartz plates was used, exhaustion hood flow rate did not affect the analytical signal significantly. The exhaustion hood flow rate effect was less pronounced in case of heated QTA as compared to unheated QTA. In addition to exhaustion hood flow rate, the air movements around the atom cell also influenced the analytical signal and precision of the measurement.

"Flow Injection Analysis Spectrophotometric Determination Of Palladium"
Anal. Lett. 2004 Volume 37, Issue 3 Pages 507-516
Kamlesh Shrivas, Khageshwar Singh Patel, Peter Hoffmann

Abstract: A simple and specific method for flow injection analysis (FIA) spectrophotometric determination of Pd is described. The method is based on color reaction of Pd(II) with organic reagent, i.e., N-phenylbenzimidoylthiourea (PBITU) over acidity range, 0.2-2.0 M HCl in the 10% (v/v) ethanolic solution. The value of apparent molar absorptivity of the yellow colored complex in the term of Pd is 1.20 x 10 4 L mol -;1 cm -;1 at λ max 345 nm. The detection limit (causing more absorbance than 3s) of the method is 80 ng mL -;1 of Pd. The optimum working range was 0.25-10.0 µg mL -;1 of Pd with slope, intercept, and correlation coefficient of 0.059, 0.006, and +0.99, respectively. The RSD of the method was ±1.1% for six replicate measurements at level of 2.0 µg mL -;1 of Pd. The sample throughput of the method is 120 samples hr -;1. The composition of the complex is discussed. The method is specific for the determination of Pd as none of the tested ions interfered. The method has been applied for the determination of Pd in the catalytic materials.

"The Three Generations Of Flow Injection Analysis"
Anal. Lett. 2004 Volume 37, Issue 3 Pages 345-359
Elo Harald Hansen and Jianhua Wang

Abstract: The characteristics of the three generations of flow injection analysis (FIA), that is, FIA, sequential injection analysis (SIA), and bead injection-lab-on-valve (BI-LOV), are briefly outlined, their individual advantages and shortcomings are discussed, and selected practical applications are presented.

"Flow-Injection Chemiluminescence Determination Of Papaverine Using Cerium(IV)-Sulfite System"
Anal. Lett. 2004 Volume 37, Issue 1 Pages 143-155
Sichun Zhang; Yafeng Zhuang; Huangxian Ju

Abstract: A sensitizing effect of papaverine on the weak chemiluminescence (CL) reaction of sulfite with acidic cerium(IV) is studied. In papaverine and cerium(IV) solution, the increase in the fluorescent intensity of cerium(III) at 360 nm with an increasing time indicates a slow oxidation of papaverine by acidic cerium(IV). This reaction results in the formation of intermediate radical of papaverine, which enhanced the CL emission of sulfite-cerium(IV) system. Based on this finding, a flow injection (CL) method is proposed for the determination of papaverine. The CL intensity is proportional to the concentration of papaverine from 1.0 x 10^-7 to 1.0 x 10^-5 M with a correlation coefficient of 0.9991. The detection limit is 8.7 x 10^-8 M (3?). The relative standard deviation for seven independent determinations of 1.0 x 10^-6 M papaverine is 2.0%. The proposed method has been satisfactorily used for the determination of papaverine in pharmaceutical preparations and biological fluids.

"Voltammetric Behavior And Determination By Flow Injection With Amperometric Detection Of Benzimidazoles"
Anal. Lett. 2004 Volume 37, Issue 1 Pages 65-79
A. Guzm&aacute;n-V&aacute;zquez de Prada; M. L. Mena; A. J. Reviejo; J. M. Pingarr&oacute;n

Abstract: The voltammetric behavior of fenbendazole, albendazole, thiabendazole, and mebendazole at a glassy carbon electrode in different aqueous (Britton-Robinson buffer, KOH solutions) and predominantly nonaqueous (acetonitrile: water and methanol: water mixtures) working media is reported. 0.1 M KOH and 70:30 acetonitrile or methanol: water mixtures were selected as most appropriate, the sensitivity achieved for the square wave voltammetric determination of fenbendazole in 0.1 M KOH being much higher than in the predominantly nonaqueous media. Flow-injection with amperometric detection of the benzimidazoles was evaluated in the three working media. The electrode responded rapidly and the response was constant over sets of 30 measurements at the selected potentials in all cases, RSD values ranging between 1.6% and 4.4%. No significant electrode surface fouling was observed under the hydrodynamic conditions. Detection limits in the 1.0 x 10^-8 - 1.0 x 10^-7 M concentration range were achieved. As an application, fenbendazole was determined by flow injection with amperometric detection in spiked feed samples at the 30 and 180 ?g g-1 concentration levels, which correspond to the lower and upper concentration for fenbendazole administration to treated poultry. Recoveries of 97 ± 5% and 94 ± 8% were obtained.

"A Multicommuted Flow Procedure For The Determination Of Cholesterol In Animal Blood Serum By Chemiluminescence"
Anal. Lett. 2003 Volume 36, Issue 14 Pages 3011-3024
Cherrine K. Pires, Boaventura F. Reis, Cristiane X. Galhardo, Patr&iacute;cia B. Martelli

Abstract: An automatic flow procedure for cholesterol determination in animal blood serum using enzymatic reaction and detection by chemiluminescence is described. Cholesterol esterase and cholesterol oxidase were immobilized on glass beads packed into two mini-columns (15 mm x 5 mm), which were coupled to flow system. Produced H 2O 2 reacted with luminol produced chemiluminescence that was detected using a solid-state detector. The flow system comprised a set of three-way solenoid valves assembled to implement multicommutation. A microcomputer with an electronic interface controlled the solenoid valves and performed data acquisition. Profitable features such as a sampling throughput of 40 determinations per hour, linear response ranging from 25 to 125 mg L -;1 cholesterol (r = 0.998), detection limit of 3.7 mg L -;1 cholesterol, relative standard deviation of 2.3% (n = 20), and low reagents consumption 0.22 mg luminol and 2.7 mg hexacyanoferrate(III) per determination were achieved. Comparing the results with those obtained using the conventional spectrophotometric method no significant difference at the 95% confidence level was observed.

"Flow Injection Chemiluminescence Determination Of Cephalosporin Antibiotics By Their Enhancing Effects On Luminol–Potassium Periodate System"
Anal. Lett. 2003 Volume 36, Issue 14 Pages 2975-2983
Hong Yao, Yuhai Tang, Yinhuan Li, Yuanyuan Sun

Abstract: It was found that the chemiluminescence arising from the reaction of luminol with KIO 4 in alkaline solution could be strongly enhanced by cephalosporin antibiotics. Based on these observations, a new flow injection chemiluminescence method is proposed for the determination of four cephalosporin antibiotics: cefalexin, cefaclor, cefradine, and cefadroxil. The detection limits of the method are 0.9 ng mL -;1 cefalexin, 0.4 ng mL -;1 cefaclor, 10 ng mL -;1 cefradine, and 10 ng mL -;1 cefadroxil. The method was successfully applied to the determination of four cephalosprin antibiotics in pharmaceutical preparations.

"Construction And Evaluation Of Cysteine Selective Electrodes For FIA Analysis Of Pharmaceuticals"
Anal. Lett. 2003 Volume 36, Issue 14 Pages 2925-2940
M. Goreti F. Sales, Annouschka Pille, Paula C. B. Pa&iacute;ga

Abstract: A flow injection analysis (FIA) system comprising a cysteine selective electrode as detection system was developed for determination of this amino acid in pharmaceuticals. Several electrodes were constructed for this purpose, having PVC membranes with different ionic exchangers and mediator solvents. Better working characteristics were attained with membranes comprising o-nitrophenyl octyl ether as mediator solvent and a tetraphenylborate based ionic-sensor. Injection of 500 µL standard solutions into an ionic strength adjuster carrier (3 x 10 -;3 M) of barium chloride flowing at 2.4 mL min -;1, showed linearity ranges from 5.0 x 10 -;5 to 5.0 x 10 -;3 M, with slopes of 76.4 ± 0.6 mV decade -;1 and R 2>0.9935. Slope decreased significantly under the requirement of a pH adjustment, selected at 4.5. Interference of several compounds (sodium, potassium, magnesium, barium, glucose, fructose, and sucrose) was estimated by potentiometric selectivity coefficients and considered negligible. Analysis of real samples were performed and considered accurate, with a relative error to an independent method of +2.7%.

"Chemiluminescence Flow-Through Sensor For The Determination Of Ascorbic Acid With An Immobilized Reagent"
Anal. Lett. 2003 Volume 36, Issue 13 Pages 2783-2792
Yuming Huang and Zhujun Zhang

Abstract: A chemiluminescence (CL) flow-through sensor for ascorbic acid, based on permanganate electrostatically immobilized on an anion exchange column is described. Ascorbic acid can be measured by the CL reaction directly with the immobilized reagent. The sensors response was linear in the range 0.05-10 µg/mL with a detection limit of 5 ng/mL. The analysis could be performed within 30 s including sampling and washing, giving a throughout of about 120 samples per hour with RSD of 1.6% for 2 µg/mL ascorbic acid. The sensor was stable for over 500 determinations and has been successfully applied to the determination of ascorbic acid in tablets and vegetables.

"Sensitive Flow-injection Chemiluminescence Determination Of Metformin Based On N-bromosuccinimide-fluorescein System"
Anal. Lett. 2003 Volume 36, Issue 12 Pages 2683-2697
Zhouping Wang; Zhujun Zhang; Zhifeng Fu; Wanfen Luo; Xiao Zhang

Abstract: A novel and sensitive flow-injection chemiluminescence (CL) method for the determination of metformin in pharmaceutical formulations over the range of 7 x 10^-9 -3 x 10^-5 g mL-1 is proposed in this article. The method is based on the CL produced during the oxidation of N-bromosuccinimide (NBS) in alkaline medium in the presence of fluorescein as an effective energy transfer agent. Use of cetyltrimethylammonium bromide (CTAB) as a sensitizer enhances the signal magnitude about 100 times. The detection limit is 2.3 x 10^-9 g mL-1 (3?) with a relative standard deviation of 2.7% (n = 11) at 1 x 10^-7 g mL-1 metformin. Ninety samples can be determined per hour. The method was evaluated by carrying out a recovery study and by the analysis of commercial formulations. The results obtained compared well with those obtained by pharmacopoeia method and demonstrated good accuracy and precision. The possible reaction mechanism of the CL in the system is also discussed briefly.

"Determination Of Nitrites, Nitrates, And Their Mixtures Using Flow Injection Analysis With Spectrophotometric Detection"
Anal. Lett. 2003 Volume 36, Issue 10 Pages 2303-2316
M. Brabcov&aacute;, P. Rychlovsk&yacute;, I. N&#277;mcov&aacute;

Abstract: A new flow injection analysis (FIA) method has been developed for determination of nitrites, nitrates, and their mixtures, based on the reaction of nitrites with rivanol (2-ethoxy-6,9-diaminoacridinium lactate) in HCl medium; the concentration of the diazonium salt formed is evaluated spectrophotometrically (λ = 520 nm). Flow-through determination of nitrates can be carried out by using the same reaction following prior reduction in a flow-through reductor filled with copperised cadmium included in the apparatus. The determination of both ions in a mixture is enabled by the use of a switching solenoid valve, which either excludes the reductor (determination of only nitrites) or connects the reductor in the flow-through system (determination of the sum of nitrites and nitrates). The reaction and flow conditions with the full experimental design were optimized and detection limits for nitrite (0.14 mg L -;1) and nitrate (1.2 mg L -;1) determination were obtained. Both anions were determined in soil samples and it was found that excellent correlation exists between the proposed method and the standard methods (Griess reaction and ion-selective nitrate electrode).

"FAAS Determination Of Platinum Using An On-Line Separation And Preconcentration System With A Polymelamine Dendrimer Immobilized Silica Gel"
Anal. Lett. 2003 Volume 36, Issue 10 Pages 2229-2241
Xiongzhi Wu, Peng Liu, Qiaosheng Pu, Zhixing Su

Abstract: A G4.0 polymelamine dendrimer based on silica gel (PMDSG) was fabricated via a divergent approach via repetitive reaction of 2,4,6-trichloro-1,3,5-triazine and 1,6-hexylenediamine from a γ-aminopropyl silica gel (APSG) core for the first time. It was then used as the microcolumn packings for the flow injection (FI) pre-concentration and separation of trace or ultra trace Pt(IV) for the flame atomic absorption spectrometry determination. A limit of detection (LOD) of 0.065 µg mL -;1 was achieved when a 0.500 µg mL -;1 Pt(IV) was pre-concentrated at pH 3.0 with a sampling flow rate of 5.0 mL min -;1 for 60 s and the relative standard deviation (RSD) was no more than 5.0%. The proposed method was successfully used for the determination of Pt in two metallurgical samples.

"Fluorimetric Determination Of Free Cyanide By Flow-Injection Analysis"
Anal. Lett. 2003 Volume 36, Issue 10 Pages 2211-2228
H. P. Beck, Bin Zhang, Adela Bordeanu

Abstract: A flow-injection analysis system for the rapid and sensitive fluorimetric determination of free cyanide is developed. The determination is based on oxidation of nonfluorescent thiamine to highly fluorescent thiochrome (λ ex/λ em = 370/440 nm) in alkaline medium by Cu 2+ when CN -; is present. After designing an appropriate manifold, the effects of chemical variables, FIA system parameters and temperature on the determination of CN -; were studied in detail. Under optimum experimental conditions the working range was linear from 0.02 to 2.5 mg L -;1 with a high sampling throughput of 120 h -;1 at room temperature. The precision, in terms of relative standard deviations for ten replicates of analysis of 1.0 mg L -;1 CN -;, was 1.9%. Interference studies were performed with typical cations and anions in natural waters. CN -; spiked in synthetic water samples was determined by this proposed FI method with good results. The composition of the reduced product [Cu +(CN -;) n] 1-; n was determined using an indirect method. In addition, results of cyclovoltammetric measurements of thiamine are reported which throw light on the electrochemical process.

"Flow Injection Electrochemical Determination Of Apomorphine"
Anal. Lett. 2003 Volume 36, Issue 10 Pages 2199-2210
Jorge M. P. J. Garrido, Cristina Delerue-Matos, Fernanda Borges, Tice R. A. Macedo, Ana M. Oliveira-Brett

Abstract: Few analytical methods are currently available for determination of apomorphine, the active substance of a new oral formulation used in the treatment of erectile dysfunction. In this way a flow injection electrochemical method (FIA-EC) was developed for its quantification and applied to pharmaceutical dosage forms. Based in previous findings regarding the stability of apomorphine in borate buffer and after optimization of several analytical parameters a single channel flow injection manifold was set up that enables the determination of this drug over the concentration range of 3 to 16 µmol L -;1 with a detection limit of 0.5 µmol L -;1 at a sampling rate of 90 h -;1. The simplicity and rapidity of the FIA-EC method used, its reproducibility and sensitivity make it suitable for quality control of pharmaceutical preparations of apomorphine intended for clinical use and research.

"A Reagentless Amperometric Alcohol Biosensor Based On Carbon-Nanotube/Teflon Composite Electrodes"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 2041-2048
Joseph Wang and Mustafa Musameh

Abstract: We report on a multiwall carbon-nanotube (MWCNT)-based alcohol biosensor, based on the incorporation of alcohol-dehydrogenase/NAD + within a three-dimensional MWCNT/Teflon matrix. The MWCNT component offers a marked decrease in the overvoltage for the oxidation of the liberated NADH along with minimal surface fouling effects, hence allowing convenient low-potential stable detection of the ethanol. The electrocatalytic detection is characterized, the biosensor composition and operation are optimized, and the analytical performance is illustrated.

"Flow Injection Amperometric Detection Of Phenolic Compounds At Enzyme Composite Biosensors Application To Their Monitoring During Industrial Waste Waters Purification Processes"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 1965-1986
B. Serra, A. J. Reviejo, J. M. Pingarr&oacute;n

Abstract: Flow amperometric detection of phenolic compounds at graphite"teflon"tyrosinase and graphite"teflon"glucose oxidase"peroxidase composite electrodes is discussed. In this later design, the H2O2 needed for the enzyme reaction with the phenolic compound is generated "in situ" by the enzyme reaction of glucose oxidase with glucose added to the carrier. Flow injection amperometric responses at -0.15 V for the tyrosinase biosensor and at 0.00 V for the bienzyme electrode exhibited a good repeatability and stability of the baseline. The stability of such responses with time was evaluated when the carrier was continuously flowing and the detection potential was continuously applied. FI calibration plots for phenol, 2-chlorophenol, 4-chlorophenol, 4-chloro-2-methylphenol, and 3,4-dimethylphenol were constructed with the tyrosinase electrode, whereas calibration curves for the same compounds and 2,4,6-trichlorophenol were made at the bienzyme electrode. Dual detection was also performed with both electrodes in a parallel configuration and with a multichannel detector. Monitoring of phenolic compounds in waste waters from a refinery was carried out at two different stages in the water purification process. This monitoring needed the insertion of a styrene(divinylbenzene) copolymer cartridge in the FI system to remove the phenolic compounds from the sample, and the further use of this solution as the carrier. The results obtained were compared with those achieved using the colorimetric official method based on the reaction with 4-aminoantipyrine.

"Flow Injection Analysis System For L-Lysine Estimation In Foodstuffs Using A Biosensor Based On Lysine Oxidase Immobilization On A Gold-Poly(m-Phenylenediamine) Electrode"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 1939-1963
Maria H. Divritsioti, Ioannis D. Karalemas, Constantinos A. Georgiou, Demetrius S. Papastathopoulos

Abstract: The development and the evaluation of an amperometric FIA biosensing system for l-lysine determination in foodstuffs is described. The system employs a home-made flow-cell with an amperometric biosensor, prepared by immobilization of lysine oxidase on a gold-poly(m-phenylenediamine) electrode. A peristaltic pump is connected to the flow-cell via a 2-position 6-port sample injector/switching valve for the on-line transfer of the samples. The analytical procedure is based on the oxidation of l-lysine by l-lysine α-oxidase. The produced H2O2 is monitored amperometrically at 650 mV in FIA set-up. The lysine biosensor construction procedure comprises: a) the electropolymerization of m-phenylenediamine on a Si-gold strip electrode and b) the immobilization of l-lysine α-oxidase on the poly(m-phenylenediamine) membrane with glutaraldehyde in the presence of bovine serum albumin. Parameters, such as, flow rate, enzyme amount, monomer concentration, matrix effect, effect of interference's, etc., were studied. The flow-cell biosensor system provides a linear response from 1 x 10-3 to 5 x 10-5 M of lysine, with excellent characteristics of reproducibility, stability, and life-time. The system was further applied and evaluated for the estimation of lysine in various hydrolysate food samples (e.g., pasta, milk, wheat flour, etc.) without any pretreatment with an average recovery of 97.3%.

"Improvement Of A CL-FIA System Using Maltose Phosphorylase For The Determination Of Phosphate-Ion In Freshwater"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 1805-1817
Hideaki Nakamura, Mami Hasegawa, Yoko Nomura, Kazunori Ikebukuro, Yoshiko Arikawa, Isao Karube

Abstract: In a previous study, a phosphate ion (Pi) biosensor consisting of a system of chemiluminescence flow-injection analysis (CL-FIA) combined with a reaction system of maltose phosphorylase, mutarotase, and glucose-oxidase (MP-MUT-GOD) was developed without a detailed investigation of the measurements of real samples. Therefore, in this study, after characterization of the measuring conditions in the CL-FIA system for freshwater samples, we investigated the influences of dissolved substances, such as metal ions, heavy metal ions, inorganic ions, and organic substances, in freshwater on the sensor response. The results of the study indicated that there were no substances giving irreversible effects to the enzyme activities of MP, MUT, or GOD used in this sensor; however, some cations or organic substances influenced the sensor response. We then compared the effects of the elimination of the dissolved substances by a chelate reagent, ion exchange resin, or combination of ion exchange resin and UV irradiation on the sensor response. Consequently, a cation-exchange resin (sulfonated), which improved most effectively the sensor response, was chosen as a pre-treatment method. By utilizing this pre-treatment method, the sensor system could determine the Pi concentrations in 31 samples of river or pond waters in Japan. The results obtained by this sensor system and the molybdenum-blue method were compared, and a regression curve (y=2.78x) with good correlation (r=0.958) was obtained between them. The reason of the slope at the regression curve was discussed. Finally, we introduce a trial type of an automatic CL-FIA biosensor system for future Pi determination.

"Glycerol Dehydrogenase Based Amperometric Biosensor For Monitoring Of Glycerol In Alcoholic Beverages"
Anal. Lett. 2003 Volume 36, Issue 9 Pages 1721-1737
Mihaela Niculescu; Svetlana Sigina; Elisabeth Cs&ouml;regi

Abstract: Biosensors for measurement of glycerol in FIA were constructed using NAD+-dependent glycerol dehydrogenase (G1DH) either co-immobilized with phenazine methosulphate (PMS) or cross-linked to an Os-complex-modified poly(vinylimidazole) redox polymer (PVI13dmeOs) using poly(ethyleneglycole) diglycidilether (PEGDGE). The GIDH/PMS sensor was characterized by a linear range of 0.01-1 mM glycerol, a sensitivity of 1.83 mA/Mcm2, a detection limit (calculated as three times the signal-to-noise ratio) of 0.9 ?M, and with 50% residual activity kept after 15 h of continuous operation at a sample throughput of 30 injections/h. The redox hydrogel-based biosensors showed the same dynamic range, but improved biosensors characteristics, i.e., a sensitivity of 4.79 mA/Mcm2, a detection limit of 0.1 ?M, and a signal loss of only 20% after 15 h of operation in the same conditions. The optimized biosensor configurations were further used for analysis of glycerol in wine and the obtained results were compared with the ones obtained by spectrophotometrical experiments.

"Flow Injection Chemiluminescence Method For Determination Of Ribavirin Based On Enhancement Of Luminol-Persulfate Reaction"
Anal. Lett. 2003 Volume 36, Issue 8 Pages 1587-1595
Yi Lu, Zhujun Zhang, Deyong He, Yufei Hu

Abstract: A novel flow injection chemiluminescence (FI-CL) method for the determination of ribavirin is developed based on the enhancing effect of the analyte on CL emission of luminol oxidized by sodium persulfate in alkaline solution. The CL emission is correlated with the ribavirin concentration in the range from 0.01 to 1.0 µg mL-;1, and the detection limit (3s) is 0.004 µg mL-;1. The relative standard deviation is 2.8% (n = 11, 0.1 µg mL-;1 ribavirin). The method was successfully applied to the determination of ribavirin in pharmaceutical preparations.

"A Bioassay To Detect Contaminant-induced Messenger RNA Using A Transcriptomic Approach: Detection Of RT-PCR-amplified Single-stranded DNA Based On The SPR Sensor In Cyanobacteria"
Anal. Lett. 2003 Volume 36, Issue 8 Pages 1475-1491
Ryoichi Asai; Chikashi Nakamura; Kazunori Ikebukuro; Isao Karube; Jun Miyake

Abstract: We describe a novel sensor system to detect toxic chemicals based on measurement of the RT-PCR-amplified single-stranded DNA (ssDNA) of induced mRNA in Anabaena variabilis. Detection was conducted using a flow-injection type of sensor system based on surface plasmon resonance (SPR). The oligonucleotide probe containing the complementary sequence to a part of ribonuclease P RNA B (rnpB) and cyp110 mRNA was immobilized on the sensor chip. We succeeded in detecting 10 ng of amplified ssDNA using oligonucleotide probes. Using this sensor system, we were able to detect hexadecane using transcriptomic analysis of induced mRNA in A. variabilis treated with 0.2% (vol/vol) n-hexadecane. This method allows for rapid and simple detection of chemicals.

"Immunoaffinity Column Based On Electrostatic Self-Assembly For Flow Immunoassay"
Anal. Lett. 2003 Volume 36, Issue 6 Pages 1131-1145
Shun-Qin Hu, Cun-Xi Lei, Guo-Li Shen, Ru-Qin Yu

Abstract: We reported a new approach to fabricate an immunoaffinity column by enhanced electrostatic self-assembly (ESA) layers of proteins on beads packed in the column. The lambda-carrageenan (LC) was employed to link with IgG Ab or RS IgG Ab. As a result, the strongly negatively charged sulphonate groups of LC were introduced into the backbone of proteins. The adsorption performances of LC-IgG Ab and IgG Ab on beads were investigated by studying changes of fluorescence intensity of solution containing LC-IgG Ab or IgG Ab. The LC-IgG Ab showed preferable adsorption on beads comparing to IgG Ab under the same experimental conditions. The LC-IgG Ab was self-assembled on beads by electrostatic force and formed firmly ESAs on beads in the PBS of 0.01 M pH 7.4 or pH 4.5. The characteristics of ESAs of LC-IgG Ab on beads were investigated and were found to be easily removed from surfaces of beads by recycling the flowing solution of 0.01 M NaOH containing 0.5 M NaCl with a flow rate of 1 mL/min. Thus, ESAs of LC-IgG Ab on beads can be re-fabricated and the immunoaffinity column can be reused. The flow immunoassay system was used to detect the concentration of NH IgG in the range of 0.1-1000 µg/mL.

"On-Line Separation And Determination Of Trace Amounts Of Manganese In Biological Samples By Flow Injection Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Lett. 2003 Volume 36, Issue 6 Pages 1115-1130
Mohammed Zougagh, Amparo Garc&iacute;a de Torres, Jos&eacute; M. Cano Pav&oacute;n

Abstract: A procedure is developed for the determination of Mn in biological samples by FI-ICP-AES acid eluates after pre-concentration of the samples. The pre-concentration step is performed on a 3 cm x 3 mm column packed with silica gel functionalized with 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide (DPTH-gel) and placed in the injection valve of a simple flow manifold. The sorbed element is subsequently eluted with nitric acid. The acid eluate is analyzed by ICP-AES. Five variables (sample flow rate, eluent flow rate, eluent concentration, pH, and buffer concentration) were considered as factors in the optimization process. Interactions between analytical factors and their optimal levels were investigated using Response Surface Methodology (RSM) and based on sequential experimental Doehlert designs. The performance characteristics of the determination of manganese with DPTH-gel was: detection limits, 1.5 ng mL -;1, precision (RSD) 0.5% for 100 ng mL -;1, and enrichment factors, 26 using 60 s pre-concentration time. The sampling frequency was 40 h -;1. The accuracy of the method was demonstrated by the analysis of certified reference biological samples. The results showed good agreement with the certified values.

"FIA-Chemiluminescence Determination Of Acridine Yellow"
Anal. Lett. 2003 Volume 36, Issue 5 Pages 1039-1049
R. O. Segarra Guerrero; M. Catal&aacute; Icardo; C. G&oacute;mez Benito; J. Mart&iacute;nez Calatayud

Abstract: The direct determination of yellow acridine is performed by a FIA assembly on the basis of the oxidation of the acridine. The acridine solution is injected into a pure water stream. This solution merges with the oxidant solution (KMnO4 in sulfuric acid medium) and the resulting chemiluminescence allows the method to be applied over the range 0.01-100 mg L-1 of acridine with a correlation coefficient of 0.9997. The relative standard deviation (%) is 1.6 and the sample throughput 60 h-1. The influence of foreign substances is also tested. The new method is applied to the determination of yellow acridine in waste waters.

"Determination Of Monocrotophos Pesticide By Flow Injection Chemiluminescence Method Using Luminol-Hydrogen Peroxide System"
Anal. Lett. 2003 Volume 36, Issue 5 Pages 1029-1038
Jianxiu Du, Xiaoyu Liu, Jiuru Lu

Abstract: A simple flow injection chemiluminescence method is described for the determination of monocrotophos pesticide, based upon the direct reaction of monocrotophos with luminol and hydrogen peroxide in alkaline medium in the presence of an enhancer of sodium chloride. The CL intensity was linear related to monocrotophos concentration in the range of 2.0 x 10 -;8-1.0 x 10 -;6 g/mL with a detection limit of 7 x 10 -;9 g/mL. The relative standard deviation was less than 3% for 1.0 x 10 -;7 g/mL monocrotophos in eleven repeated measurements. This method was successfully applied to the determination of monocrotophos in water samples. The possible reaction mechanism was also discussed briefly.

"Determination Of Chromium(VI) By Batch Injection Analysis And Adsorptive Stripping Voltammetry"
Anal. Lett. 2003 Volume 36, Issue 5 Pages 955-969
Christopher M. A. Brett, Olga M. S. Filipe, C. Susanna Neves

Abstract: A new sensitive voltammetric method is presented for the determination of trace levels of Cr(VI). The method is based on square wave adsorptive stripping voltammetry (AdSV) in conjunction with the electrochemical batch injection analysis technique at mercury thin-film electrodes. The determination of chromium is made in the presence of cupferron as ligand. Relevant experimental parameters are explored and optimized, such as injection mode, cupferron concentration, accumulation potential and time, and square wave parameters. A pre-concentration time of 20 s at -;0.8 V vs. SCE results in a detection limit of 32 nM. The relative standard deviation for 12 measurements of 0.12 µM was 6.5%. Possible interferences by other trace metals are considered.

"Flow Injection Chemiluminescence Determination Of Thiol-Containing Drugs Based On A Quinine-Sensitized Permanganate Reaction"
Anal. Lett. 2003 Volume 36, Issue 4 Pages 871-879
Yinhuan Li, Ahui Zhang, Jianxiu Du, Jiuru Lu

Abstract: A new flow injection chemiluminescence method is presented for the determination of four thiol-containing drugs, cysteine, N-acetylcysteine, glutathione, and captopril. It was found that the oxidation of these drugs with potassium permanganate accompanied by weak chemiluminescence in acidic condition. The presence of quinine sulfate enhanced chemiluminescence signal greatly. The method allows to determine 0.02-2 µg mL -;1 cysteine, 0.05-2 µg mL -;1 N-acetylcysteine, 0.05-2 µg mL -;1 glutathione, and 0.02-1 µg mL -;1 captopril with limits of detection of 0.01 µg mL -;1, 0.02 µg mL -;1, 0.02 µg mL -;1, and 0.006 µg mL -;1, respectively. The relative standard deviations were less than 2% (n = 11) and the sample measurement frequency was about 120 samples h -;1. The application of this method was demonstrated by the analysis of cysteine and captopril in some pharmaceutical preparations.

"Determination Of Methanol By 4-[N-Methyl, N-(1-naphthylmethyl)]-amino-4-oxo-butanoic Acid In Presence Of 4-Dimethylaminopyridine And 1-Ethyl-3-(3-dimethylaminopropyl) Carbodiimide Hydrochloride As Catalysts"
Anal. Lett. 2003 Volume 36, Issue 4 Pages 813-825
Chia-Chi Kuo, Yen-Hsia Wen, Shihn-Sheng Wu, Hsin-Lung Wu

Abstract: High performance liquid chromatography (HPLC) with chemically removable derivatizing reagents for the analysis of methanol has been developed. Methanol was derivatized with 4-[N-methyl, N-(1-naphthylmethyl)]-amino-4-oxo-butanoic acid (NAOB), using 4-dimethylaminopyridine (DMAP) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) as activators. NAOB and the activators are chemically removable and can be removed by aqueous base and acid treatment after derivatization to minimize reagent interference in chromatography. The method can simultaneously determine methanol, ethanol and 1-propanol. The proposed HPLC method was validated for linearity, specificity, accuracy and reproducibility. The method was applied to the analysis of methanol spiked in Ipecac fluid extract with a satisfactory recovery (>95%).

"A Flow-Injection-ICP System Sequential Multielemental Analysis With Simultaneously Mercury(II) Preconcentration Step"
Anal. Lett. 2003 Volume 36, Issue 4 Pages 781-795
Luiz Fabricio Zara; Julio Cesar Rocha; M&aacute;rcio Raimundo Milani; Andr&eacute; Henrique Rosa; Ademir dos Santos; Ricardo Lima Serudo

Abstract: A flow-injection system for multielemental analysis with a mercury(II) pre-concentration step using a resin Chelite-S® (Serva Feinbiochemica Heidelberg, Part No. 41709) packed minicolumn by inductively coupled plasma atomic emission spectroscopy is described. A mercury reductive elution procedure with a mixture of SnCl2/HCl was used, which allows use of 6 mol/L HCl solution instead of concentrated hydrochoric acid. The main parameters related to ICP operation, such as radio frequency power (950-1750 W), auxiliary argon flow (0.0-1.5 L/min) and spray chamber nebulizer pressure (15-35 psi), were studied. Optimization of the FIA system was reached by defining the best eluent carrier stream (1.4-2.8 mL/min), Hg(0) carrier stream (10-40 mL min-1), loading time (0.5-4.0 min), sample flow rate (1.25-10.0 mL/min), temperature of reactor gas-liquid separator (GLS) (25-75°C) and eluent volume (50-350 µL). Throughput is around 30 samples per hour for analytical solutions within the range 50-2500 ng Hg(II)/L. Results from certified material showed good precision (RSD <3%, n = 12) and no statistical difference was observed for real samples analyzed by AAS and by the proposed system.

"Flow Injection Analysis For Monitoring Antioxidant Effects On Luminol Chemiluminescence Of Reactive Oxygen Species"
Anal. Lett. 2003 Volume 36, Issue 4 Pages 749-765
Meltem Sarinodotahmetogbrevelu; R. Alan Wheatley; Idotclal &Ccedil;akinodotcinodot; Idotlker Kanzinodotk; Alan Townshend

Abstract: Knowledge of the antioxidant capacity of specific chemicals is essential to understanding the susceptibility to oxidative stress. Various assays have been developed for measuring the scavenging capacity of molecules. In the present study we used a continuous flow system for monitoring chemiluminescence (CL) reactions initiated by superoxide (O2-) derived from xanthine-xanthine oxidase reaction), hydrogen peroxide (H2O2, hypochlorite anion (-OCl) (derived from NaOCl), hydroxyl (.OH) (generated from O2-FeSO4-buffer), or peroxynitrite (ONOO-) (freshly synthesized). By adapting the flow injection analysis (FIA) method, inhibition of luminol-CL responses of these reactive oxygen species (ROS) by ascorbic acid (well-characterized, chain-breaking antioxidant) and other antioxidants were also investigated. Data showed that to monitor the antioxidant sensitivity of CL responses initiated by ROS is possible by using FIA method.

"Electrochemical Determination Of Dihydrocodeine In Pharmaceuticals"
Anal. Lett. 2003 Volume 36, Issue 3 Pages 577-590
J. M. P. J. Garrido, C. Delerue-Matos, F. Borges, T. R. A. Macedo, A. M. Oliveira-Brett

Abstract: Two analytical methods for the quality control of dihydrocodeine in commercial pharmaceutical formulations have been developed and compared with reference methods: a square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC). The electrochemical methods proposed were successfully applied to the determination of dihydrocodeine in pharmaceutical tablets and in oral solutions. These methods do not require any pretreatment of the samples, the formulation only being dissolved in a suitable electrolyte. Validation of the methods showed it to be precise, accurate and linear over the concentration range of analysis. The automatic procedure based on a flow injection analysis manifold allows a sampling rate of 115 determinations per hour.

"Development Of A Reactor Type Bio-sensor For Trichloroethylene"
Anal. Lett. 2003 Volume 36, Issue 3 Pages 539-547
Tae-Sung Han, Satoshi Sasaki, Kazuyoshi Yano, Kazunori Ikebukuro, Kitayama Atsushi, Teruyuki Nagamune, Isao Karube

Abstract: This paper describes a microbial sensor for the determination of trichloroethylene (TCE) with flow injection analysis (FIA) based on the microbial degradation of TCE. The sensor consists of two parts, namely, immobilized microbial beads in the column and a chloride-ion electrode as the sensing part. The sensor responds when a change in the concentration of chloride ion is detected as a result of microbial degradation of the TCE in the sample solution. The sensor responded linearly to the TCE in the range of 0.03"2 ppm. The lifetime of a reactor-type TCE sensor is twice that of a membrane-type (microbes immobilized on a membrane) TCE sensor. To avoid the influence of chloride ion in the environment, a dual electrode system was introduced. The reference electrode (chloride-ion electrode 1) measures chloride ion in ground water, while the working electrode (chloride-ion electrode 2) detects chloride ion produced from TCE (as a result of microbial degradation) and that already present in ground water. The difference in the responses of these two electrodes corresponds to the chloride-ion concentration from TCE degradation alone. Two advantages of this sensing system are its simplicity for taking measurements and its ability to avoid influence from any chloride ion already present in the sample solution. This system is more applicable to in situ environmental monitoring than other methods, such as the chromatographic method and a system that we previously constructed in our laboratories.

"Flow Injection Analysis Of Sulfide By Gas Phase Molecular Absorption UV/Vis Spectrometry"
Anal. Lett. 2003 Volume 36, Issue 2 Pages 479-492
Afsaneh Safavi, B. Haghighi, F. Peiravian

Abstract: A simple FIA method is described for the determination of sulfide in aqueous solution. Two hundred and thirty microliters of sulfide sample solution is injected into the water stream. The stream is then mixed and reacted with a carrier solution containing sulfuric acid. The hydrogen sulfide evolved is separated from liquid stream by the use of a gas-liquid separator and then is swept into a flow-through cell using N 2 carrier gas. The absorbance of the gaseous phase is measured at 195 nm by the use of an UV/Vis spectrophotometer. Under optimum conditions, the limit of detection was 0.07 µg S2-. The relative standard deviation of repeated measurement of 23 µg of S2- was 0.4%. Up to 60 samples h-1 can be analyzed. The effects of several anions and cations on the determination of sulfide were studied. The proposed method was successfully applied to the determination of sulfide in sulfurous spring water samples and the results obtained were in good agreement with the results of stabilized iodine titration procedure.

"Spectrophotometric Determination Of Organophosphoric Insecticides In A FIA System Based On AChE Inhibition"
Anal. Lett. 2003 Volume 36, Issue 1 Pages 59-73
Andrei F. Danet; Bogdan Bucur; Mihaela-Carmen Cheregi; Mihaela Badea; Simona Serban

Abstract: This work presents a FIA system for pesticide analysis in water based on irreversible inhibition of acetylcholine esterase by organophosphoric insecticides with spectrometric determination of thiocholine with Ellman's reagent. The enzyme was immobilized on amminated glass pearls kept into a reactor and reactivated with 2-PAM after each inhibition step. The total toxic substances of real sample is expressed as equivalent paraoxon and calculated based on relative inhibition of the enzyme measuring the FIA peaks high before and after inhibition. The calibration graph was linear between 2 and 70 ppb paraoxon at an incubation time of 20 min. The LOD was 1.3 µg/L. A complete analysis lasted 35 min. The method was used for analysis of real water samples.

"Chemiluminescence Flow-Through Sensor For Determination Of Reserpine In Pharmaceutical Preparation And Biological Fluids Using Immobilized Reagents Technology"
Anal. Lett. 2003 Volume 36, Issue 1 Pages 41-57
Zheng-Hua Song and Ni Zhang

Abstract: A sensitive continuous-flow sensor based on chemiluminescence (CL) detection was developed for the determination of reserpine at nanogram level by the immobilization of the reagents. It was found that the CL intensity from the oxidation between luminol and periodate could be decreased in the presence of reserpine. The decrease of CL emission was correlated with the reserpine concentration in the range from 1.0 to 300 ng mL-1, and the detection limit was 0.3 ng mL-1 (3s). The system could produce an evident CL signal by water as eluent and it was also shown that the flow sensor could greatly improve the selectivity and sensitivity for determination of reserpine with a high signal-to-noise ratio. A complete analysis, including sampling and washing, could be performed in 0.5 min with a relative standard deviation of less than 3.0%. The proposed procedure was applied successfully in the assay of reserpine in pharmaceutical preparations and biological fluids samples. The flow sensor offered reagentless procedures and remarkable stability in determination of reserpine, and could be easily reused over 80 h.

"Monitoring Of Free Chlorine In Dialysis Fluids Using The Spectrophotometric N,N -diethyl-p-phenylenediamine (DPD) Method And Multivariate Calibration"
Anal. Lett. 2002 Volume 35, Issue 15 Pages 2617-2630
Paulo C. do Nascimento, Denise Bohrer, Marieli S. Marques, Luciana D. Del-Fabro

Abstract: The spectrophotometric N,N-diethyl-p-phenylenediamine (DPD) method for the determination of, free. chlorine in saline matrices used as dialysis fluids (DF) in hemodialysis treatment was investigated by multiple wavelength detection (multivariate DPD-method). This method was compared with the current standard DPD-method (univariate. DPD-method) that uses single wavelength detection (515 nm). The multivariate DPD-method showed the best performance because the influence of the high ionic strengths of the saline matrices on the equilibrium among the DPD species was well modeled only by the multivariate approach. The univariate DPD-method showed biased results towards low chlorine concentrations (ca. 25%) in DF samples. Through the developed methodology it was possible to quantify free chlorine directly in dialysis fluids. The multivariate method showed to be adequate as a last quality control before a hemodialysis session. The regression by partial least squares (PLS) using two principal components and full cross-validation was applied to the absorbance values in the interval 200-600 nm. The root mean square errors of prediction (RMSEP) was 0.08 mg L-1. Free chlorine concentrations ranging from 0.2 to 0.7 mg L-1 were assayed in DF samples.

"Flow Injection Determination Of Dopamine Based On Inhibited Electrochemiluminescence Of Luminol"
Anal. Lett. 2002 Volume 35, Issue 15 Pages 2527-2537
Liande Zhu, Yingxiu Li, Guoyi Zhu

Abstract: A flow injection method has been developed for the determination of dopamine based on its inhibition of the electrochemiluminescence of luminol. This method is simple and sensitive for dopamine detection. Under the selected experimental conditions, the decreased electrochemiluminescent intensity is linear with dopamine concentration in the range of 5.0 x 10^-8-1.0 x 10^-5 mol/L with a detection limit of 30 nmol/L. The relative standard deviation of eleven determinations is 1.9% for 1.0 x 10^-6 mol/L dopamine. The proposed method has been applied to the detection of dopamine in pharmaceutical injections with satisfactory results.

"A New Rapid And Sensitive Method For The Fluorimetric Determination Of Cationic Surfactants By Flow Injection"
Anal. Lett. 2002 Volume 35, Issue 15 Pages 2511-2526
Bin Zhang, H. P. Beck

Abstract: A new rapid and sensitive flow injection fluorimetric method for the determination of cationic surfactants (CS) is proposed. The determination mechanism is based on the enhancement of fluorescence intensity of the Europium (Eu3+)-Thenoyltrifluoroacetone (TTA) binary complex which reacts with cationic surfactants to form an ion-association complex. This complex emits a strong characteristic fluorescence at 612 nm after excitation at 345 nm. The effects of analytical and FIA variables on the determination of CS are studied and in detail especially for cetyltrimethylammonium bromide (CTAB). Under. optimum conditions the working range for this example is linear from 0.05 to 15 mg L-1 with a high correlation coefficient and a sample throughput of 120 samples h-1 at room temperature. The relative standard deviations for 10 replicates of analysis of 10.0, 1.0, and 0.2 mg L-1 CTAB are 0.2, 1.2, and 2.5%, respectively. In addition the result of FIA and batch experiments is compared, the composition of the ion-association complex is determined and the mechanism of fluorescence enhancement in the presence of CTAB is discussed. An automatic standard addition method has been designed and applied to the measurement of synthetic samples with good results.

"Electroanalytical Determination Of Codeine In Pharmaceutical Preparations"
Anal. Lett. 2002 Volume 35, Issue 15 Pages 2487-2498
Jorge M. P. J. Garrido, Cristina Delerue-Matos, Fernanda Borges, Tice R. A. Macedo, A. M. Oliveira-Brett

Abstract: A square wave voltammetric (SWV) method and a flow injection analysis system with electrochemical detection (FIA-EC) using a glassy carbon electrode were evaluated for the determination of codeine in pharmaceutical preparations. The interference of several compounds, such as acetaminophen, guaiacol, parabens, ephedrine, acetylsalicylic acid and caffeine, that usually appear associated with codeine pharmaceutical preparations was studied. It was verified that these electroanalytical methods could not be used with acetaminophen present in the formulations and that with guaiacol, parabens or ephedrine present the use of the FIA-EC ystem was impracticable. A detection limit of 5 µmol L-1 and a linear calibration range from 40 to 140 µmol L-1 was obtained with the SWV method. For the flow injection analysis procedure a linear calibration range was obtained from 7 to 50 µmol L-1 with a detection limit of 3 µmol L-1 and the FIA-EC system allowed a sampling rate of 115 samples per hour. The results obtained by the two methods, SWV and FIA-EC, were compared with those obtained using reference methods and demonstrated good agreement, with relative deviations lower than 4%.

"UV SPECTROPHOTOMETRIC FLOW-THROUGH MULTIPARAMETER SENSOR FOR THE SIMULTANEOUS DETERMINATION OF ACETAMINOPHEN, ACETYLSALICYLIC ACID, AND CAFFEINE"
Anal. Lett. 2002 Volume 35, Issue 15 Pages 2433-2447
A. Dom&iacute;nguez Vidal; J. F. Garc&iacute;a Reyes; P. Ortega Barrales; A. Molina D&iacute;az

Abstract: A single triparameter flow-through sensor with U.V. detection is described in this study for the simultaneous determination of acetaminophen, acetylsalicylic acid and caffeine. The use of an solid phase (C18 silica gel) placed in an on-line microcolumn provides the sequential arrival of the analytes to the detection solid zone (also C18 silica gel beads placed in a flow cell), making possible the determination with only one injection. A flow rate of 1.42 mL min-1 was pumped and detection wavelength was 272 nm. The linear dynamic ranges were 10^-100, 40-500 and 4-50 µg mL-1, for acetaminophen, acetylsalicylic acid and caffeine, respectively. Limit of detection were from 0.3 to 0.8 µg mL-1 and limit of quantitation were from 1.0 and 2.7 µg mL-1 with RSDs from 1.2 to 3.4 (n = 10), respectively. The proposed method was applied to the determination of acetaminophen, acetylsalicylic acid and caffeine in pharmaceutical preparations. The results were compared with those obtained from an HPLC method and they showed a good agreement.

"Cobalt Determination In Natural Water And Table Salt Samples By Flame Atomic Absorption Spectroscopy/on-line Solid Phase Extraction Combination"
Anal. Lett. 2002 Volume 35, Issue 14 Pages 2363-2374
Aslihan Uzun Karatepe, Mustafa Soylak, Latif Elci

Abstract: In the present work, a methyl acrylate resin (Chromosorb 105) was used for on-line solid phase extraction and determination of traces cobalt by flame atomic absorption spectrometry (FAAS). Cobalt is pre-concentrated at pH 9 onto mini column at NH3 media. The elution step for retained cobalt is performed with a stream of I M HCl at 4.0 mL/min and cobalt displaced is introduced directly into the nebulizer of flame atomic absorption spectrometer. The effects of analytical parameters including pH, flow rates etc., were investigated. The proposed method was successfully applied to the determination of cobalt in tap water and table salt samples. A detection limit of 2.5 µg/L for pre-concentration at 4.0 mL/min is obtained and an enrichment factor of 50 could be achieved. The recoveries of spike additions to tap water and table salt samples were greater than 95%. The relative standard deviations were also below 4%.

"Chemiluminescence Flow Injection Analysis Of Amoxycillin By A Permanganate-based Reaction"
Anal. Lett. 2002 Volume 35, Issue 14 Pages 2295-2304
Jianxiu Du, Yinhuan Li, Jiuru Lu

Abstract: A new application of chemiluminescence for the determination of amoxycillin in flow injection mode is presented. The method is based upon the direct chemiluminescence reaction of amoxycillin with KMnO4 in acidic medium in presence of quinine sulfate. The chemiluminescence intensity was linearly related to the concentration of amoxycillin within 0.05-10 µg mL-1 range with a detection limit (3s) of 0.02 µg mL-1 and a sample measurement frequency of 90 samples h-1. The relative standard deviation is 2.3% for 1.0 µg mL-1 amoxycillin solution in 11 repeated measurements. The method was successfully applied to the analysis of amoxycillin in capsules.

"FLOW INJECTION CHEMILUMINESCENCE-BASED CHEMICAL SENSORS"
Anal. Lett. 2002 Volume 35, Issue 14 Pages 2207-2220
Wei Qin

Abstract: In recent years, the design of chemiluminescence flow injection sensors with immobilized and solid-state reagents has been one of the most active areas in chemiluminescence analysis. In these systems, analytes are detected by the chemiluminescence reactions either with the immobilized reagents directly or with the dissolved reagents which are released from the immobilized substrates or the solid-state forms by some appropriate eluents or are electrogenerated on line by the electrodes. This review discusses recent advances in these fields. The main advantages of the chemiluminescence flow injection sensors are described in comparison with the conventional chemiluminescence flow systems.

"Simple Flow Injection Titration Method Based On Variation Of The Sample Volume"
Anal. Lett. 2002 Volume 35, Issue 13 Pages 2145-2155
Pawelstrok Koscielniak; Joanna Kozak

Abstract: A simple single-line flow injection system incorporating the fully rotary valve (FRV) has been developed for titration purposes. The FRV enables to inject the titrand solution to the titrant stream in four different volumes producing a set of four adequate analytical signals. Due to this fact the titration procedure can be performed with the use of only two standard solutions which allow four parallel calibration lines to be constructed. The method was tested on the example of spectrophotometric acid-base titration. Under optimized flow conditions (flow rate of 8.3 mL/min, the volumes injected of 30, 100, 300, and 800 µL, titrant containing 0.1 mmol/L NaOH and 4 x 10^-4% bromothymol blue) the analytical results of precision less than 0.6% (RSD) and of accuracy less than 0.5% (relative error) were obtained for the HCl samples of pH ranged from 1 to 2.

"Flow Injection Chemiluminescence Determination Of Sulfide By Oxidation With Chlorinated Isocyanurates"
Anal. Lett. 2002 Volume 35, Issue 12 Pages 2023-2037
Afsaneh Safavi, Mohammad Ali Karimi, Mohammad Reza Hormozinezhad

Abstract: A rapid and sensitive flow injection chemiluminescence (CL) method is described for the determination of sulfide based on the CL generated during its reaction with either sodium dichloroisocyanurate (SDCC) and trichloroisocyanuric acid (TCCA) in alkaline medium. The results of investigation of the sensitized and non-sensitized CL reactions are presented. The emission intensity is greatly enhanced for both SDCC-sulfide and TCCA-sulfide CL systems if fluorescein (for SDCC-sulfide) and dichlorofluorescein (DCF) (for TCCA-sulfide) are present in the reaction solutions, respectively. The effect of analytical and flow injection variables on these CL systems and on the determination of sulfide are discussed. The method was applied satisfactorily to the determination of sulfide in spring water samples.

"Reticulated Vitreous Carbon-based Composite Bienzyme Electrodes For The Determination Of Alcohols In Beer Samples"
Anal. Lett. 2002 Volume 35, Issue 12 Pages 1931-1944
N. Pe&ntilde;a; R. T&aacute;rrega; A. J. Reviejo; J. M. Pingarr&oacute;n

Abstract: The performance of a bienzyme amperometric composite biosensor for the determination of short-chain alcohols is reported. Alcohol oxidase and horseradish peroxidase together with the mediator ferrocene were incorporated into reticulated vitreous carbon (RVC)-epoxy resin electrode matrices. Under the optimized experimental conditions, the composite bienzyme electrode exhibited rapid amperometric responses at 0.00 V to the changes in the substrate concentration. The lifetime of each single biosensor was estimated to be ~20 days, and reproducible responses were obtained with different electrodes constructed in the same manner. Calibration plots were obtained for methanol, ethanol, propanol, butanol, and 1-pentanol. The detection limits were, in general, considerably better than those found in the literature with other AOD amperometric biosensors. The bienzyme composite electrode showed a good performance also in flow-injection systems with amperometric detection. The suitability of the bioelectrode for a simple, rapid, and selective determination of ethanol in a local beer, with a minimal sample preparation, is demonstrated.

"FLUORIMETRIC MONITORING OF MOLECULAR IMPRINTED POLYMER RECOGNITION EVENTS FOR ALUMINIUM"
Anal. Lett. 2002 Volume 35, Issue 11 Pages 1763-1774
S. Al-Kindy, R. Bad&iacute;a, M. E. D&iacute;az-Garc&iacute;a

Abstract: Novel molecular imprints were prepared against aluminium. Sensing materials were prepared via non-covalent imprinting technique, using the aluminium(III)-morin chelate as the template. Based on the fluorescent properties of the chelate, it was possible to design a selective optical flow-through sensor for Al 3+. The affinity of the polymer binding sites was higher for aluminium than for other di- and trivalent ions (e.g., Be 2+, Ca 2+, Mg 2+, Eu 3+, Zn 2+, Fe 3+), suggesting that the nature of the metal ion, its ionic radius, and the metal-morin stoichiometry play important roles in the ionic recognition.

"A STUDY ON TERBIUM SENSITIZED CHEMILUMINESCENCE OF PIPEMIDIC ACID AND ITS APPLICATION"
Anal. Lett. 2002 Volume 35, Issue 10 Pages 1705-1714
Shi-Lu Chen, Hui-Chun Zhao, Chun-Yan Sun, Ning Lian, Lin-Pei Jin

Abstract: A flow-injection chemiluminescence (CL) analysis for determination of pipemidic acid (PPA) is developed. It is based on luminescence produced by Ce(IV)-Na 2SO 3 CL system sensitized by Tb(PPA) 2 3+. The relative chemiluminescence intensity of the Tb 3+-PPA-Ce(IV)-Na 2SO 3 system is proportional to the amount of PPA. The optimized experimental conditions were determined. Accordingly, chemiluminescent method for the determination of PPA is proposed. The linear range and detection limit for PPA are 3.0 x 10 -;9-8.0 x 10 -;7 mol/L and 6.7 x 10 -;10 mol/L, respectively. The familiar excipients such as starch and dextrine do not cause interference. So this method can be applied to the determination of PPA in tablet. The content and recovery of PPA in urine can be directly detected without the pretreatment such as separation. And the mechanism of chemiluminescence is proposed.

"Determination Of Lead In Drinking Water By ICP-AES With Ultrasonic Nebulization And Flow Injection On-line Preconcentration Using An Amberlite XAD-16 Resin"
Anal. Lett. 2002 Volume 35, Issue 10 Pages 1649-1665
R. G. Wuilloud, H. A. Acevedo, F. A. Vazquez, L. D. Martinez

Abstract: An on-line lead pre-concentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated to flow injection (FI) with ultrasonic nebulization (USN) was studied. For the retention of lead, 2-(5-bromo-2-pyridylazo)-5-diethyl-aminophenol (5-Br-PADAP) and Amberlite XAD-16 were used, at pH 9.2. The lead was removed from the microcolumn in counter flow with nitric acid. A total enhancement factor of 150 was obtained with respect to ICP-AES using pneumatic nebulization (15.0 for USN and 10.0 for column). The detection limit value for the pre-concentration of 10 mL of aqueous solution of Pb was 0.2 ng mL-1. The precision for 10 replicate determinations at the 5 ng mL-1 Pb levels was 2.8% relative standard deviation (RSD), calculated with the peak heights obtained. The calibration graph using the pre-concentration system for lead was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 ng mL-1. The method was successfully applied to the determination of lead in drinking water samples.
Extraction

"ON-LINE SOLID PHASE EXTRACTION SYSTEM FOR CHROMIUM DETERMINATION IN WATER SAMPLES BY FLOW INJECTION-FLAME ATOMIC ABSORPTION SPECTROMETRY"
Anal. Lett. 2002 Volume 35, Issue 9 Pages 1519-1530
Sibel Saracoglu, Mustafa Soylak, Latif Elci

Abstract: An on-line solid phase extraction system has been established for flow injection flame atomic absorption spectrometric determination of chromium on Chromotrope 2R coated Amberlite XAD-1180 (2R-1180) resin. Some parameters such as pH, flow rates of sample and elution solution, matrix effects on the quantitative recoveries of chromium from the resin were examined. The detection limit (3s) was 2.59 µg/L for pre-concentration at 6.5 mL/min. The method was applied for the determination of traces chromium in natural water samples with satisfactory results (relative standard deviations below 5%, recoveries >95%).

"Development And Validation Of A Method For The Determination Of Mercury In Small Rat Brain Tissue Samples By Cold Vapor Atomic Fluorescence Spectrometry"
Anal. Lett. 2002 Volume 35, Issue 9 Pages 1505-1517
Keith E. Levine, Reshan A. Fernando, Glenn T. Ross, Michelle Lang, Daniel L. Morgan, Bradley J. Collins

Abstract: A rugged, sensitive, semi-automated method for the determination of trace-level mercury in small rat brain tissue samples by cold vapor atomic fluorescence spectrometry (CVAFS) is described. Small tissue aliquots (100 mg) are digested for 6-8 h at an elevated temperature in a mixture of nitric and sulfuric acids. Following digestion, samples are oxidized with potassium bromate/bromide at room temperature and treated with a continuous flow of stannous chloride to generate mercury vapor. The experimentally determined method quantitation limit (MQL) in the rat brain matrix is 10 pg Hg/mL, which corresponds to 1.5 ng Hg/g brain tissue. Replicate matrix spike preparations (n=4) at this level were determined with a high level of accuracy (89.8%) and precision (6.9% RSD). Replicates (n=36) of a certified reference material (DOLT-2, trace metals in dogfish liver) were prepared and analyzed over a four year period in order to assess the ruggedness and accuracy of the method. The average recovery for mercury in this material was 99.9% of the certified level.

"CHEMILUMINESCENCE DETERMINATION OF METOCLOPRAMIDE"
Anal. Lett. 2002 Volume 35, Issue 9 Pages 1479-1489
Shunli Fan, Zhihao Wu, Lei Zhang, Chao Lv

Abstract: A chemiluminescence (CL) system for metoclopramide combined with a flow-injection system is presented in this paper. It is based on CL produced by the oxidation of metoclopramide by permanganate. It was found that formaldehyde could highly enhance the CL intensity. The method permits the determination of metoclopramide over a concentration range of 0.06-60 µg/mL with the detection limit (signal/noise) of 0.03 µg/mL. The relative standard deviation (RSD) for 2 µg/mL metoclopramide standard solution was 1.6% (n = 11). The method has been applied successfully to the determination of metoclopramide in tablets and injections.

"Spectrophotometric Determination Of The Sum Of Rare Earth Elements By Flow-injection On-line Preconcentration With A Novel Aminophosphonic-carboxylic Acid Resin"
Anal. Lett. 2002 Volume 35, Issue 8 Pages 1401-1414
Qiaosheng Pu; Peng Liu; Zhide Hu; Zhixing Su

Abstract: A highly sensitive, selective and accurate spectrophotometric method for the microcolumn on-line pre-concentration and determination of the sum of rare earth elements (REEs) was developed. REEs were pre-concentrated and separated from matrices by being adsorbed at pH 5.0 on a microcolumn packed with a novel aminophosphonic-carboxylic acid resin (APCR). The adsorbed analytes were desorbed with 1.0 mol L-1 HCl and reacted with Arsenazo III in chloro-acetate buffer in a reactor coil for the spectrophotometric detection at 649 nm. The calibration graph was linear up to 1.0 ?g mL-1 La3+. The detection limit of 4.0 ng mL-1 was achieved with a sample loading flow rate of 2.0 mL min-1 and a sample loading time of 1.0 min. The RSD was less than 4% for 0.20 ?g mL-1 La3+. The proposed method was successfully applied to the determination of the sum of REEs in a geological sample and an aluminum alloy sample.

"Liquid Chromatographic Determination Of Lysine By Potentiometric Detection With A Biosensor"
Anal. Lett. 2002 Volume 35, Issue 8 Pages 1313-1325
N. Garc&iacute;a-Villar, J. Saurina, S. Hern&aacute;ndez-Cassou

Abstract: A liquid chromatographic method with potentiometric detection using a lysine biosensor is proposed for the determination of lysine in pharmaceutical samples. The method is based on the separation of lysine from other,species by micellar liquid chromatography and on-line neutralization of the eluent with a lithium hydroxide solution. This neutralization process is required to render the pH of the chromatographic effluent compatible with the enzymatic detection of lysine. The biosensor is composed of a lysine oxidase membrane attached to an ammonium electrode, in such a way that the ammonium generated in the enzymatic degradation of the substrate is monitored potentiometrically. The effect of experimental variables such as the acidity and composition of the mobile phase and the pH on the biosensor response is studied to optimize the detection conditions. Results obtained in the analysis of lysine in pharmaceutical preparations are compared with those obtained by the standard method. A good concordance between the two methods is found.

"Solid State Iridium Oxide-titanium Based Sensor For Flow Injection PH Measurements"
Anal. Lett. 2002 Volume 35, Issue 8 Pages 1301-1311
Saad S. M. Hassan, S. A. M. Marzouk, N. M. Badawy

Abstract: Iridium oxide-coated titanium wire is prepared by controlled electrodeposition (current density 5 mA/cm(2) for 10 min) and used as a solid state pH sensor. The sensor is sensitive for pH variations over the range 2-10 with calibration slopes of similar to 65.5 and 59.1 mV/pH unit under static and hydrodynamic modes of operation, respectively. The general performance characteristics of the sensor are similar to those of the glass electrode for direct pH monitoring of solutions. The sensor exhibits reasonable stability (±0.005 pH), reproducibility (±2%) and fast response time (20-30 s). The method of preparation is simple, utilizes an inexpensive titanium metal substrate and offers the possibility of fabrication of sensors with various geometry and/or of micro and ultramicro sizes usable for flow injection analysis. No interferences are caused by alkali and alkaline earth metal cations and various anions at level greater than or equal to 10(4) molar excess over H+.

"FLOW INJECTION SPECTROFLUORIMETRIC DETERMINATION OF MALATHION IN ENVIRONMENTAL SAMPLES USING ON-LINE PHOTOOXIDATION"
Anal. Lett. 2002 Volume 35, Issue 7 Pages 1239-1250
Tom&aacute;s P&eacute;rez-Ruiz; Carmen Mart&iacute;nez-Lozano; Virginia Tom&aacute;s; Jes&uacute;s Mart&iacute;n

Abstract: A simple, rapid, sensitive and precise method for the determination of malathion in a flow-injection system is described. The method is based on the decomposition of malathion in the presence of alkaline peroxydisulphate upon irradiation with UV light. The phosphate produced in the photochemical process is made to react with molybdate in dilute nitric acid to form phosphomolybdic acid, which oxidises thiamine to thiochrome. The thiochrome can then be fluorimetrically monitored at 440 nm with excitation at 375 nm. The new approach allows the determination of malathion in a wide concentration range (20-2000 ng mL-1) with a throughput of 70 samples per hour. The applicability of the method was demonstrated by determining malathion residues in agricultural waste water, grains and vegetables.

"FLOW INJECTION SPECTROPHOTOMETRIC DETERMINATION OF PROPOXUR WITH DIAZOTIZED 4-AMINOBENZOIC ACID"
Anal. Lett. 2002 Volume 35, Issue 6 Pages 1095-1105
R. Zanella, E. G. Primel, M. H. S. Kurz, F. F. Gon&ccedil;alves

Abstract: A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-aminobenzoic acid as the coupling agent was developed. The determination involves on-line hydrolysis at room temperature of the propoxur with sodium hydroxide. The resulting 2-isopropoxyphenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity to the spectrophotometric measurements. The calibration curve is linear over the range 1-10 mg L -;1 of propoxur. The proposed method has provided a detection limit of 0.15 mg L -;1 of propoxur and a sample frequency of 120 injections per hour. The relative standard deviation of six independent determinations of a sample containing 5 mg L -;1 propoxur was 0.74%. The suitability of the proposed procedure for the determination of propoxur in commercial pesticide formulations was studied. The procedure provides results comparable to those obtained by the liquid chromatography analysis.

"Flow Injection Extraction Spectrofluorimetric Determination Of Aluminium As The Tetraphenylphosphonium Aluminium(III) 8-hydroxyquinoline-5-sulphonate"
Anal. Lett. 2002 Volume 35, Issue 6 Pages 1085-1093
D. Thorburn Burns; P. Pornsinlapatip

Abstract: Aluminium was determined by flow injection spectrofluorimetry at 510 nm after excitation at 396 nm following extraction of tetraphenylphosphonium aluminium(III) 8-hydroxyquinoline-5-sulphoxinate into chloroform. The effects of diverse ions and masking studies are reported. The system has been applied to the determination of aluminium in steels by the method of standard additions.

"UV-spectrophotometric Stability Indicating Methods For The Quantitative Determination Of Cimetidine, Famotidine, And Ranitidine Hydrochloride In The Presence Of Their Oxidative Derivatives"
Anal. Lett. 2002 Volume 35, Issue 6 Pages 1055-1073
Khadiga M. Kelani, Azza M. Aziz, Maha A. Hegazy, Laila Abdel Fattah

Abstract: Simple, sensitive and rapid spectrophotometric techniques have been established for the determination of cimetidine (I), famotidine (II) and ranitidine hydrochloride (III) in presence of their S-oxide derivatives in both raw materials and in pharmaceutical formulations. Hydrogen peroxide was used to enhance the formation of S-oxide compounds (oxidative derivatives). The first derivative of the ratio spectra ((DD)-D-1) technique has been applied for the determination of (I) and (II). While, direct zero order (D-0), first derivative (D-1) and the second derivative of the ratio spectra ((DD)-D-2) have been carried out for the determination of drug (III). Linear calibration curves were obtained for determination of (I) and (11) by applying (DD)-D-1 at 220 and 230 nm in the concentration range of 2-20 and 4-40 µg mL-1 with the mean percentage recoveries of 99.88±0.943 (n = 10) and 99.88±0.824%, (n = 10) for (I) and (II). respectively. While for (III) linear calibration curves were obtained by applying D-0, D-1 and (DD)-D-2 at 313.334 and 255 nm. respectively. The concentration range was 2-20 µg mL-1 with the corresponding mean percentage recoveries of 100.13±0.464, 100.01±0.428 and 99.94±0.439 for (I), (II) and (III), respectively. The results obtained by the proposed methods were statistically analyzed and compared with those obtained by the official BP methods.

"Determination Of Selenium In Drinking Water With A Simple Field Device"
Anal. Lett. 2002 Volume 35, Issue 6 Pages 943-958
Enisa Omanovi&#cacute;, Helmut Moderreger, Kurt Kalcher

Abstract: A new method for the determination of total selenium in drinking water in the low ppb range was developed and optimized. The method use field device Supralab FD which was previously designed for the determination of arsenic in drinking water. The method relies on the formation of selenium hydride and its reaction with sodium perborate impregnated on a support to form a colored product, elemental selenium, which is optically detected. As a reductant, sodium borohydride is used. Thus, only Se(IV) reacts whereas Se(VI) cannot be reduced directly requiring pre-reduction with hydrochloric acid. The limit of detection of method (3s) is 0.7 µg/dm(3), the limit of quantification is 2 µg/dm(3). The total reaction tinge for concentration up to 101 µg/dm(3) is 5 min; higher concentrations require up to 15 min.
Interferences Speciation

"Highly Selective Flow Injection Spectrophotometric Determination Of Ascorbic Acid In Fruit Juices And Pharmaceuticals Using Pyrogallol Red-iodate System"
Anal. Lett. 2002 Volume 35, Issue 5 Pages 909-920
Ali A. Ensafi, B. Rezaei, M. Beglari

Abstract: Ascorbic acid present in pharmaceuticals and fruit juice was rapidly determined by the spectrophotometric method in association with flow injection analysis. The method is based on the inhibitory effect of ascorbic acid on the oxidation of pyrogallol red by iodate in sulfuric acid media. The calibration graph is linear in the range of 2.0 x 10^-6 M up to 1.0 x 10^-4 M. The throughput is 20 x 5 samples per hour and the detection limit is 0.5 muM ascorbic acid. The relative standard deviation for ten replicate determinations of 8.00 muM and 50.0 muM ascorbic acid is 3.4 and 0.60%, respectively. The influence of various species was studied for this determination.
Ascorbic acid

"Elimination Of Ascorbic Acid Interference With The Determination Of Thiamine In Pharmaceutical Preparation By Flow Injection On-line Photochemical Spectrofluorimetry"
Anal. Lett. 2002 Volume 35, Issue 4 Pages 707-720
Hailin Zhu, Qiaohong He, Qiongjun Fang, Hengwu Chen

Abstract: Elimination of ascorbic acid interference in the determination of thiamine by flow injection photochemical spectrofluorimetry was investigated. Copper(11) ion in combination with boric acid was found effective to eliminate the interference. The masking efficiency is time-dependent. During the two-minute interval from the 6th to 8th minute after the masking reaction initiated, the interference from ascorbic acid was completely removed. Further increase of the reaction time slightly decreased the masking efficiency, but the efficiency was kept at 93% 20 min after the masking reaction started. Based on these observations, a flow injection on-line photochemical spectrofluorimetry (FI-PCF) for the determination of thiamine in multi-vitamin-mineral preparations was developed. In sample pretreatment step, Cu2+ and borate buffer (pH 8.2) was made 1 µg/mL and 0.12 mol/L, respectively, in the sample solution. After standing for 30 min, the prepared test solution was subjected to FI-PCF. A calibration curve, constructed with a series of thiamine standard solutions containing 20 µg/mL ascorbic acid and the masking reagents. was used for quantification. The developed method has been successfully used to determine thiamine contents in multi-vitamin-mineral preparations.
Ascorbic acid

"Solid Phase Spectrophotometric Determination Of Copper In Water By Using Immobilized Zincon In A Sephadex A25 Resin"
Anal. Lett. 2002 Volume 35, Issue 4 Pages 635-646
Pablo Richter, M. In&eacute;s Toral, Hector Castro

Abstract: A new simple, sensitive and selective solid phase spectrophotometric method has been developed for determination of copper in water. A sensitive analytical zone was prepared by immobilization of zincon in a Sephadex A25 resin, in which copper reacts selectively, at pH 7, to form a colored complex on the surface of the resin. Absorbances can be read directly on the solid phase at 621.5 mn. The batch mode was adopted in this work, because the resin is not reusable due the reaction product that is retained irreversible on it. Physico-chemical variables of the method were optimized in order to find the best analytical conditions for the determination. Under the selected conditions copper can be accurately determined oil the range 0.4-300 ng/mL, with a detection limit of 0.12 ng/mL and a repeatability, expressed as the relative standard deviation, lower than 3.8%. The recovery in the analysis of a certified reference material was 100.4%. By changing the pH of the sample, other metals also react (Fe, Cd, Ni, Zn, Hg. Pb), indicating that this system also can be used for screening to determine the possible presence of other trace metals in waters.

"Kinetic Simultaneous Determination Of Fe(II) And Fe(III) Using Partial Least Squares (PLS) And Principal Component Regression (PCR) Calibration Methods"
Anal. Lett. 2002 Volume 35, Issue 3 Pages 533-544
J. Ghasemi, R. Amini, A. Niazi

Abstract: A method for simultaneous kinetic analysis of Fe(II) and Fe(III) using partial least squares (PLS) and principal component regression (PCR) calibration methods is proposed. The method is based on the inductive effects of Fe(II) and Fe(III) on the chromium(VI)-iodide-starch reaction in acidic medium. The calibration graphs are linear in the range of 20-500 and 20-520 ppm for Fe(II) and Fe(III), respectively. A series of synthetic and spiked real matrix solutions containing different concentrations of Fe(II) and Fe(III) were used to check the prediction ability of the PLS and PCR models. The number of significant factors for Fe(II) and Fe(III) are: 5 and 7 for PLS and 3 and 3 for PCR, respectively. RMSD parameter for Fe(II) and Fe(III) using PLS and PCR methods are 1.9135, 1.5869 and 24.3022, 48.9117, respectively. The effect of several parameters and diverse ion effect were also studied.
Kinetic

"On-line Preconcentration System For Determination Of Lead In Water And Sediment Samples By Flow Injection-flame Atomic Absorption Spectrometry"
Anal. Lett. 2002 Volume 35, Issue 3 Pages 487-499
Mustafa Soylak; Latif Elci; Yalcin Akkaya; Mehmet Dogan

Abstract: Diaion HP-20 was used for on-line separation/pre-concentration and determination of lead by flow injection flame atomic absorption spectrometry. Lead is pre-concentrated at pH 9 as its 1-nitroso-2-naphthol (NN) complex onto mini column. The elution step is performed with a stream of 1 M HNO3 at 3.0 ml/min and lead displaced is introduced directly into the nebuliser of flame atomic absorption spectro-meter. The proposed method was successfully applied to the determination of lead in a stream sediment reference material (23.9 ± 0.12 ?g/g certified value: 23.0 ?g/g) and natural water samples. The detection limit (3?) was 2.0 ?g/l for pre-concentration at 3.0 ml/min. The recoveries of spike additions to drinking water sample were greater than 95%.

"Flow Injection Chemiluminescence Determination Of Ethamsylate Based On Permanganate Oxidation"
Anal. Lett. 2002 Volume 35, Issue 3 Pages 463-472
Jianxiu Du; Yinhuan Li; Ying Tang; Jiuru Lu

Abstract: A new flow injection chemiluminescence method is described for the determination of ethamsylate. The method is based on the measurement of the chemiluminescence signal produced from oxidation of ethamsylate by potassium permanganate in acidic solution, enhanced by formic acid. The method allows the determination of ethamsylate over the range 1.0 x 10^-8-2.0 x 10^-6 g mL-1 with a sample measurement frequency of 180 samples h-1. The detection limit for ethamsylate is 5 x 10^-9 g mL-1 and the relative standard deviation is 1.4% for 5.0 x 10^-7 g mL-1 ethamsylate solution in eleven replicate measurements. The method was successfully applied to the determination of ethamsylate in pharmaceutical preparations. A brief discussion on the chemiluminescence reaction mechanism has also given.

"A Flow Analysis System For The Rapid Determination Of Sulfonamides Using A Solid Phase Photometric Sensing Zone"
Anal. Lett. 2002 Volume 35, Issue 2 Pages 269-282
A. Ruiz Medina, M. C. Cano Garc&iacute;a, A. Molina D&iacute;az

Abstract: A flow injection analysis system with solid phase spectrophotometric transduction has been developed for the assay of different sulfonamides: sulfanilamide (SN), sulfacetamide (SC), sulfamethoxazole (SM) and sulfadiazine (SD). The sensor consists in a monochannel system using Sephadex QAE A-25 resin as a microsensing zone (inside a flow-through cell) where sulfonamides are temporarily retained. The measurements of the intrinsic absorbance of sulfonamides were made at 263 nm for SC, SD and SM, and 258 nm for SN. Using a NaOH (10^-3 mol l-1)/NaCl (0.02 mol l-1) solution as carrier, the determination of sulfonamides was carried out for 40 and 600 µL of sample volume, being the carrier itself the desorbing solution, The detection limits were round to he less than 0.1 and 0.02 µg mL-1 for both sample volumes. respectively, and the linear dynamic range extended between 1-45 µg mL-1 (40 µL) and 0.2-10 µg mL-1 (600 µL). The relative standard deviations (n = 10) lower than 2.3%. A study or the potentially interfering species was carried out, included trimethoprim. The method shows good results on determination of sulfonamides in pharmaceutical preparations and urine.

"FLOW-THROUGH SENSOR FOR DETERMINATION OF BUTYLATED HYDROXYTOLUENE IN COSMETICS"
Anal. Lett. 2002 Volume 35, Issue 1 Pages 65-81
L. F. Capit&aacute;n-Vallvey; M. C. Valencia; E. Arana Nicol&aacute;s

Abstract: A flow-through optosensor with solid phase UV spectroscopic detection is proposed for the direct determination of the antioxidant Butilated Hydroxytoluene (BHT) without previous derivatization. The method is based on the transient retention of this compound in a flow-through cell packed with C18 silica using ethanol : water mixture as a carrier, and its intrinsic absorbance monitored at 274 nm. Afterwards, the recording of the analytical signal BHT was easily and quickly desorbed from the solid support by the same carrier. The calibration graphs were linear over the range 2.0-300.0 mg L-1 using area as the analytical parameter. The relative standard deviation (RSD) was between 0.5 and 1.6%. The method was applied to the determination of this antioxidant in several cosmetics samples and was validated using the standard addition methodology and an HPLC reference method.

"Potentiometric Flow Injection Determination Of Salbutamol"
Anal. Lett. 2002 Volume 35, Issue 1 Pages 39-52
N. T. Abdel-Ghani, M. S. Rizk, R. M. El-Nashar

Abstract: Potentiometric detection of salbutamol sulfate Sl(2)SO(4) using electrodes containing its ion-exchangers with phosphotungstic; phosphomolybdic acid or a mixture of both was applied in flow injection systems in the Nernastian range of the electrodes response. The selectivity of these electrodes towards different cations was studied in comparison to that obtained in batch conditions. The method was then used to determine the drug in its pharmaceutical preparations.
Capillary

"Generation Of Diborane From Boric Acid And Its Chromatographic Determination"
Anal. Lett. 2001 Volume 34, Issue 15 Pages 2771-2784
Tarek Samir Awad, Kitao Fujiwara

Abstract: A most simple, rapid and sensitive method for the determination of boron compounds using gas chromatograph (model GC-14B) is described. The method is based on the hydride generation technique. A standard sample of boric acid was well dried and mixed with about 50 mg of powdered LiAlH4 and diborane was generated by heating at 160°C. Diborane was trapped at liquid nitrogen temperature (-196°C). Factors effecting the diborane producability such as generation temperature, trapping time, and carrier flow rate have been critically studied and optimized. Boron was determined in the concentration range of 0.01-3 mg; the new system has a detection limit of 10 mug. Natural species that form gaseous hydrides and is expected to interfere with the measured diborane have been studied, It was round that phosphate interfered in this method unless its peak was clearly separated after replacing the GC column with a I m column packed with porapack Q. Finally the method was applied to two types of eve treatment solutions and one type of contact lenses washing solution. the results showed agreement with those of ICP-AES and spectrophotometer.

"The Generalized Standard Addition Method In A Closed-loop Flow System"
Anal. Lett. 2001 Volume 34, Issue 15 Pages 2735-2745
Indira Lugo, Hermes Carrero, Luis E. Leon

Abstract: A new approach using flow injection configuration is proposed as an alternative to apply the generalized standard addition method. The flow system contains a calibrated closed loop in which a spectrophotometric flow-cell is placed. The sample is entrapped into the closed loop by a suitable valve and it is allowed repetitive passages through the flow-cell: the addition of the standard solutions is made through an additional sample valve with a relatively small sample volume. After the addition, transient signals are obtained due to the repetitive passage of the added standard through the detector until it is completely dispersed into the sample by a mixing chamber. The proposed method resembles the manual, conventional procedure: a very small volume of standard solution is added to a relatively large volume of sample in such a way that the matrix of the latter is not significantly modified. Mathematical derivations that relate the concentration of the sample with that of the standard and the number of additions are performed with the analysis of the pH indicator methylorange. The analysis of iron in milk shows that good reproducibility is obtained using only one standard and one addition.
Mixing chamber

"A Rapid And Sensitive Method For The Fluorimetric Determination Of Phosphate By Flow Injection"
Anal. Lett. 2001 Volume 34, Issue 15 Pages 2721-2733
Bin Zhang, H. P. Beck

Abstract: A rapid and sensitive fluorimetric method for the determination of phosphate by flow injection analysis (FIA) has been developed. The determination is based on the following reaction: phosphate is firstly converted to 12-molybdophosphate in acid solution, which is then reacted with non-fluorescent thiamine at pH 9.0 to produce highly fluorescent thiochrome (The maximal excitation and emission wavelengths are 370 nm and 440 nm respectively.). Under the optimum operating conditions, a rather wide linear response range was obtained over the range of 0.02 mg L-1 20 mg L-1, with a detection limit of 0.01 mg L-1 (Signal/Noise = 3.0). The relative standard deviations (RSD) were 0.48%, 2.63% and 5.73% for 10 repeated analyzes of 5.0 mg L-1 0.5 mg L-1 and 0.05 mg L-1 of phosphate. respectively. The sampling throughput was 80 h-1. In addition, an automatic system was set up so that all the measurements could be accomplished by computer control. Phosphate in natural water samples was determined by the proposed method with good recovery rates.

"Flow Injection Spectrophotometric Determination Of Anionic Polyelectrolytes Using The Cationic Dyes"
Anal. Lett. 2001 Volume 34, Issue 15 Pages 2711-2719
Takashi Masadome

Abstract: The reaction of the cationic dye, crystal violet (CV) with the anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) results in a decrease of the absorbance of CV at the maximum absorption wavelength (590 nm). This change of the absorption spectra of the CV was applied to the determination of anionic polyelectrolytes using flow injection analysis (FIA) method. Anionic polyelectrolytes such as PVSK and carageenan could be determined in the concentration range from 5 x 10^-7 to 2 x 10^-5 mol/l by the proposed method. The detection limit was ~I x 10^-7 M for PVSK. The sampling rate was ~25 samples h-1. The coexistence of foreign ions (Na+, Cl-, Br-, K+, SO42-, NO3-) at 200 times excess to an anionic polyelectrolyte did not interfere with the determination of the anionic polyelectrolyte.

"Amperometric Determination Of Glucose With An MnO2 And Glucose Oxidase Bulk-modified Screen-printed Carbon Ink Biosensor"
Anal. Lett. 2001 Volume 34, Issue 15 Pages 2633-2647
Emir Turkus&#301;&#cacute;, Kurt Kalcher, Klemens Schachl, Alena Komersova, Martin Bartos, Helmut Moderegger, Ivan Svancara, Karel Vytras

Abstract: A simple biosensor, constructed by bulk-modification of carbon ink with manganese dioxide as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as amperometric detector for glucose in hydrodynamic as well as in flow injection analysis (FIA) mode. The sensor could be operated at a potential of 0.48 V under physiological conditions (0.1 M phosphate buffer. pH 7.5) and exhibited excellent reproducibility and stability. Factors influencing the amperometric response such as injection volume, flow rate and applied working potential were studied in detail. The screen-printed electrode exhibited a linear amperometric increase with the concentration of D-glucose from 2 to 2500 mg L-1 and gave a 3s detection limit of 0.085 mg L-1. Due to its remarkable stability such a sensor could be operated continuously for more than four weeks or more than 1000 sample injections. No change of signal height could be observed within an operation period of 12 h. The sensor was exploited for FIA-amperometric determination of glucose in beer and wine samples.
Glucose

"New Method For The Flow Injection Spectrophotometric Determination Of Low Concentration Chlorine Dioxide In Water Using Methylene Blue"
Anal. Lett. 2001 Volume 34, Issue 14 Pages 2485-2492
Gaizhen Wang; Hui Chen; Li Yuan

Abstract: A reverse flow injection spectrophotometric method for determination chlorine dioxide was developed with leucomethylene blue as the coloration reagent. By this method low concentrations of chlorine dioxide in water were determined in the presence of Cl2 and anion species such as OCl-, ClO2- and ClO3-. The linear range of ClO2 measurement is 0-1.91 mg/L with a detection limit of 0.02 mg/L. The presence of chlorine and hypochlorite ion can be masked by using oxalic acid. Chlorate does not interfere with the measurement. The permissible maximum concentration of ClO2- is 3.0 mg/L.

"Extraction Spectrophotometric Determination Of Lidocaine Using Flow Injection Analysis"
Anal. Lett. 2001 Volume 34, Issue 14 Pages 2457-2464
I. Nemcova, P. Rychlovsk&yacute;, V. Tomankova, Lj. Zivanovic

Abstract: A new flow-through method (flow injection analysis, FIA) for the lidocaine assay, using extraction of ion - associate with bromocresol green, was proposed. The optimum reaction and flow-through conditions (reagent concentrations, pH, flow rates of reagents, injected volume of sample, length of reaction and extraction coil, total flow rate through the separator, withdrawal rate of organic phase) were found. The Lambert-Beers law is obeyed in the concentration range of 1.4-16.2 µg mL-1.

"Semiautomated Spectrophotometric Method For The Determination Of Pectinesterase Activity In Natural And Processed Juices"
Anal. Lett. 2001 Volume 34, Issue 13 Pages 2277-2284
F. Delgado-Reyes, J. M. Fern&aacute;ndez-Romero, M. D. Luque de Castro

Abstract: An automated method for the determination of pectinesterase (PE) activity in food based on the absorbance decrease of a Bromothymol Blue (BTB) solution due to the α -D-polygalacturonate residues formed in the pectin demethoxylation catalyzed by pectinesterase is presented. The approach used is a semiautomatic flow injection (FI) approach. The method exhibits a linear range between 0.1-1.5 U/mL, with a precision, expressed as RSD, of 4.3% and a sampling frequency of 8h-1. The usefulness of the method was tested by determining PE activity in natural and manufactured juices and also applying the standard addition method. with recoveries between 84.8 and 102.6 %.

"ON-LINE PRECONCENTRATION SYSTEM WITH FAAS DETECTION FOR DETERMINATION OF CADMIUM"
Anal. Lett. 2001 Volume 34, Issue 12 Pages 2153-2158
Krystyna Pyrzynska; Hanna Szelag

Abstract: A procedure for the pre-concentration and determination of cadmium in aqueous samples was developed in the flow system coupled to flame atomic absorption spectrometer. Cadmium is quantitatively pre-concentrated in borate buffer as the complex with Tiron (4,5-dihydroxy-1,3-benzendisulfonic acid) onto a microcolumn packed with macroporous anion-exchange resin AG MP-1, eluted by a stream of 2 mol l-1 nitric acid and introduced directly into the nebuliser. A detection limit of 0.9 µg L-1 is obtained using a time-based technique for 5 min pre-concentration and an enrichment factor of 98 could be achieved. The method was applied to the analysis of natural waters.

"FLOW-INJECTION CHEMILUMINESCENCE DETERMINATION OF UREA BY OXIDATION WITH N-BROMOSUCCINIMIDE"
Anal. Lett. 2001 Volume 34, Issue 12 Pages 2141-2151
Baoxin Li, Zhujun Zhang, Yan Jin

Abstract: In this paper, a novel flow-injection chemiluminescence (CL) system for the determination of urea is described. It is based on the CL reaction of urea and N-bromosuccinimide (NBS) in alkaline medium. The CL intensity was greatly enhanced in the presence of dichlorofluorescein. The CL intensity was linear with an urea concentration of 6 x 10^-6 mol/L ~ 1 x 10-3 mol/L, the detection limit being 2.7 x 10^-6 mol/L (3 s/r). The whole process, including injection, detection and washing, could be completed in 1 min with a relative standard deviation of less than 5%. The proposed method is rapid, simple and suitable automatic and continuous analysis. This method has been applied satisfactorily to the analysis of urea in serum.

"FLOW-INJECTION BIAMPEROMETRIC DIRECT DETERMINATION OF HYDRAZINE AT TWO OXIDE-MODIFIED PLATINUM ELECTRODES"
Anal. Lett. 2001 Volume 34, Issue 12 Pages 2111-2124
Chuan Zhao, Junfeng Song, Juncai Zhang

Abstract: A new electrochemical method for the direct determination of hydrazine has been designed for flow injection analysis. The method is based on coupling two independent and irreversible electrode processes, the electrocatalytic oxidization of hydrazine and the reduction of platinum oxide, to form a biamperometric detection system. The measuring conditions are optimized. In operation, a potential difference of 0.00 V is imposed between two identical platinum wire electrodes pretreated by an anodization step, and the resulting current is measured. The linear relationship between the current and the concentration of hydrazine is obtained in the range of 1 x 10^-7 to 1 x 10^-5 mol L-1 with a detection limit of 8 x 10^-8 mol l-1. Most cations, anions and organic compounds tested are found not to cause significant interference in the determination of hydrazine. The stability of the method is shown by relative standard deviation (1.7%) for 24 replicate determinations of 2 x 10^-6 mol L-1 hydrazine. The method has been validated by the determination of hydrazine in water samples.

"SPECTROPHOTOMETRIC FLOW INJECTION DETERMINATION OF TOTAL REDUCING SUGARS IN TOBACCO BASED ON OXIDATION BY FERRICYANIDE AND FORMATION OF PRUSSIAN BLUE"
Anal. Lett. 2001 Volume 34, Issue 11 Pages 1923-1934
Jing-fu Liu and Gui-bin Jiang

Abstract: Using the Prussian blue (ferric ferrocyanide) color reaction, a simple and sensitive flow injection spectrophotometric method for the determination of total reducing sugars in tobacco is proposed. At a temperature of 110°C, sucrose was on-line hydrolyzed to reducing sugars quantitatively in 0.5 mol L-1 HCl. The reducing sugars were oxidized by alkaline potassium ferricyanide solution with equal reaction rates for glucose and fructose. The produced ferrocyanide reacted with ferric nitrate to form Prussian blue, which was detected spectrophotometrically at 690 nm for evaluation of the total reducing sugars. Using a merging zone manifold and alkaline citrate solution as carrier, the precipitation of Prussian blue on the system tube was effectively prevented. The detection limits and linear ranges were 0.1 mg L-1 and 0.5-15 mg L-1 for glucose, and 0.4 mg L-1 and 0.5-20 mg L-1 for fructose, respectively. The sampling rate was 40 per hour. The proposed method was applied to determine total reducing sugars in tobacco.

"APPLICATION OF MANGANESE-TETRASULFONATOPHTHALOCYANINE AS A NEW MIMETIC PEROXIDASE IN THE DETERMINATION OF HYDROGEN PEROXIDE BY CHEMILUMINESCENCE REACTION WITH LUMINOL"
Anal. Lett. 2001 Volume 34, Issue 11 Pages 1841-1850
Yongxin Li, Changqin Zhu, Lun Wang, Feng Gao, Maoguo Li, Leyu Wang, Yanwu Zhu

Abstract: A new promising mimetic peroxidase, manganese-tetra-sulfonatophthalocyanine (MnTSPc) has been synthesized and applied to the determination of hydrogen peroxide based on its catalytic effect on the chemiluminescence reaction between luminol and hydrogen peroxide. Under optimum conditions, the calibration graph has a linear range of 4.0 x 10^-8-2.0 x 10^-5 mol/l hydrogen peroxide, the detection limit of the method is 6.8 x 10^-9 mol/l. At a hydrogen peroxide concentration of 1.0 x 10^-6 mol/l, the relative standard deviation is 2.4% (n = 10).

"Flame Atomic Absorption Spectrometry With Flow-injection On-line Adsorption Preconcentration Using A Knotted Reactor For Cadmium Determination In Aqueous Samples"
Anal. Lett. 2001 Volume 34, Issue 10 Pages 1763-1779
I. Garrido, R. M. Soto, A. Carlosena, P. L&oacute;pez-Mah&iacute;a, S. Muniategui, D. Prada

Abstract: A knotted reactor flow injection on-line pre-concentration system coupled to a flame atomic absorption spectrometer (FAAS) was developed for the direct determination of cadmium in aqueous samples. Diethyldithiocarbamate was used to complex the analyte and then, it was adsorbed on the walls of a knotted reactor (KR) made from PTFE tubing. All the FI and chemical variables were optimized. The complex elution was performed on-line using ethanol. The sample loading time and flow rate were set at 60 s and 6 mL/min, respectively. An enhancement factor of 33 was achieved, resulting in a sampling frequency (h-1) of 30. The limit of detection was 3.44 µg/L. The accuracy of the method was tested by the analysis of three certified reference materials (Certified Aqueous Standard 7878, Reference Water TM-24 and Trace Elements in Water 1643d). The results obtained are within the certified ranges at a 95% confidence level and a good precision was also achieved (<2.7%, n=6). The proposed procedure was applied to the Cd determination in rain and sea water samples.
Knotted reactor

"FLOW INJECTION CHEMILUMINESCENCE DETERMINATION OF RUTIN BASED ON ITS ENHANCING EFFECT ON THE LUMINOL-FERRICYANIDE/FERROCYANIDE SYSTEM"
Anal. Lett. 2001 Volume 34, Issue 10 Pages 1741-1748
Jianxiu Du, Yinhuan Li, Jiuru Lu

Abstract: A new flow injection chemiluminescence (CL) method has been developed for determination of rutin. It is based on the direct CL from the reaction of rutin with luminol in the presence of potassium ferricyanide and potassium ferrocyanide in alkaline solution. The linear range for the determination of rutin is 0.1-2 µg/ml and the detection limit is 0.03 µg/ml rutin. The relative standard deviation is 0.8% for 0.4 µg/ml rutin solution in eleven repeated measurements. The method has been successfully applied to the determination of rutin in commercial rutin tablets. The reaction mechanism has also been discussed briefly.

"Evaluation Of The Turmeric (Curcuma Longa L.) Based On The Flow Injection Analysis With Ultraviolet And Fluorometric Detections"
Anal. Lett. 2001 Volume 34, Issue 10 Pages 1711-1718
Koichi Inoue, Yoshihiro Yoshimura, Hiroyuki Nakazawa

Abstract: A new method for the evaluation of the turmeric food colorants (Curcuma longa L.) of the powdered yellow pigments, based on the flow injection analysis system with on-line ultraviolet detection (UV) and fluorometric detection (FL), is described. The limits of detection were calculated according to IUPAC that UV was 30.0 ng/ml and FL was 2.0 ng/ml. The linearities of the calibration graphs for curcumin had correlation coefficients exceeding 0.999. Proposed method thus could be useful for a routine determination of curcuminoids at a roughly estimation using curcumin standard. The aim of this study is to establish the simple and accurate method for the determination of the turmeric food colorants.

"FLOW INJECTION CHEMILUMINESCENT ANALYSIS OF ISONIAZID BY DIRECT HEXACYANOFERRATE(III) OXIDATION"
Anal. Lett. 2001 Volume 34, Issue 10 Pages 1703-1710
Yuming Huang and Zhujun Zhang

Abstract: A very simple chemiluminescence (CL) flow system is described for the determination of isoniazid based on its direct oxidation by hexacyanoferrate(III) solution in an alkaline media. The system responds linearly to isoniazid concentration in the range 0.05-2 µg/mL with a detection limit (3s) of 0.01 µg/mL. Relative standard deviation (RSD) is 1.6% for 0.5 µg/mL of isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations. The measurement could be performed in 30 s with sampling rate of 120 times per hour.

"Principles And Capabilities Of Electroinjection Analysis"
Anal. Lett. 2001 Volume 34, Issue 10 Pages 1569-1583
Victor P. Andreev, Gary D. Christian

Abstract: Electroinjection analysis, its principles, and its applications are reviewed. The signal-enhancing effect of kinematic focusing is explained, and new results to demonstrate the effect are presented. The potential of electroinjection analysis for investigation of the complex-forming ability of natural samples is illustrated by the reaction of copper and lead with peat samples; the fraction of uncomplexed metal is reacted in the column with EDTA for detection. Reaction kinetic studies with EIA are presented, along with the novel ability to detect reaction intermediates. Electroinjection analysis is compared with flow injection analysis, capillary electrophoresis with precolumn reaction. electrophoretically mediated microanalysis, and affinity capillary electrophoresis.
Sequential injection

"SIGNAL PROCESSING ALGORITHM FOR SCHLIEREN EFFECT CORRECTION IN FLOW ANALYSIS"
Anal. Lett. 2001 Volume 34, Issue 9 Pages 1553-1567
V. David; J. Mart&iacute;nez Calatayud; J. V. Garc&iacute;a Mateo

Abstract: Due to the radial refractive index gradients that sometimes develop in flow cells during the travelling of the samples through them, the absorbance records obtained in such conditions have a strange shape, particularly at low analyte levels. To correct this phenomenon, called Schlieren effect, a simple and reliable signal processing algorithm is described in correlation to the detector characteristics of noise. The algorithm is illustrated in nitrite and nitrate determinations with proflavin from more real samples. It has a solid theoretical support and involves the subtraction from the sample records of a smoothed signal, acquired by working with a blank solution.

"Kinetic Study And Analytical Applications Of The Exchange Reactions Of Lanthanides(III) Using Flow Injection Techniques"
Anal. Lett. 2001 Volume 34, Issue 9 Pages 1487-1501
L. K. Shpigun, M. N. Tsuntsaeva, V. K. Lunina, Yu. A. Zolotov, G. V. Prochorova

Abstract: The exchange reactions involving complexes of the light lanthanides (cerium subgroup) and Y(III) with a number of water-soluble complexones and bisazo-dyes have been studied kinetically by using flow-injection (FI) methodology and spectrophotometric measurements under the stopped-flow conditions. Kinetic data on displacement of the lanthanides (Ln) from their complexes with ethylenediamino-N,N,N,N-tetraacetic acid (EDTA) by copper(II) ions have been exploited to develop a simple and fast FI method for indirect potentiometric determination of the sum Ln(III) concentration using a copper ion-selective electrode (Cu-ISE). A reliable FI method based on monitoring the ligand substitution reactions between the complexes of Ln(III) with 2,7-bisazo-derivatives of chromotropic acid and complexones was proposed for spectrophotometric determination of Ln(III) concentration in multicomponent solutions. The differential kinetic analysis of binary mixtures such as La-Pr (Nm) and Pr (Nm)-Eu was achieved by utilizing the quantitative differences between the rates of ligand substitution reactions of Ln(III)-Chlorophosphonazo III and Ln(III)-Carboxynitrazo complexes with EDTA or triethylentetramine-N,N,N,N, N,N-hexaacetate (TTGA) in the pH range 3.0-6.5. The new FI methods have been applied to the analysis of artificial samples.

"USE OF YEAST CRUDE EXTRACT FOR SEQUENTIAL INJECTION DETERMINATION OF CARBOHYDRATES"
Anal. Lett. 2001 Volume 34, Issue 8 Pages 1377-1388
Fernando V. Silva, Gilberto B. Souza, Ana Rita A. Nogueira

Abstract: A sequential injection procedure for enzymatic-potentiometric determination of non-structural carbohydrates content (sucrose, fructose and glucose) in forrage plants was developed. In the proposed methodology, a yeast crude extract (Saccharomyces cerevisae) solution was employed as source of invertase to promote the sucrose hydrolysis. Periodate reduction monitoring was used as quantitative parameter. The periodate remained from reduction reaction between IO4- ions and sugar reducing units was monitored using a periodate tubular selective electrode. Agreement results were obtained when the developed procedure was compared with the spectrophotometric method used for carbohydrate determination (anthrone). Detection limit of 0.13% (m/v) sucrose, relative standard deviation <2.0% (n = 10) and analytical frequency of 24 samples h-1 could be observed when 280 µL of sample and yeast crude extract with activity around 5,000 I.U. were employed. The use of crude extract solution associated with sequential injection approach was easy to perform and presented reproductive results.

"Determination Of Hydrazine By Flow Injection With Chemiluminescence"
Anal. Lett. 2001 Volume 34, Issue 8 Pages 1323-1330
Jiagen Lv, Yuming Huang, Zhujun Zhang

Abstract: The oxidation of hydrazine by potassium hexacyanoferrate(III) in alkaline luminol solution leads to chemiluminescence, This can be used to determine individual hydrazines using flow injection system. Calibration data are reported for 2,4-dinitrophenylhydrazine, isoniazid, N-acetylphenylhydrazine, and hydrazine sulfate. The system has been successfully applied to the determination of isoniazid in pharmaceuticals and hydrazine in air, respectively.

"Amperometric Detection Of Biogenic Amines In Cheese Using Immobilised Diamine Oxidase"
Anal. Lett. 2001 Volume 34, Issue 6 Pages 841-854
D. Compagnone, G. Isoldi, D. Moscone, G. Palleschi

Abstract: Diamine oxidase from Lens culinaris has been used for the amperometric detection of biogenic amines in cheese. The enzyme has been immobilized onto polymeric membranes or glass beads and coupled with a Pt based hydrogen peroxide electrode. The resulting enzyme electrode and reactor have been optimized For the response to the six biogenic amines more frequently found in cheese: histamine, tyramine, putrescine, cadaverine, phenylethylamine and tryptamine. Detection limits were Found to be in the micromolar range with a linearity up to 3 orders of magnitude. Rejection of the electrochemically active compounds present in cheese was effective by the electropolymerization of 1,4-diaminebenzene onto the Pt surface. The best performances in terms of sensitivity and selectivity were obtained using the enzyme reactor.
Enzyme

"An Amperometric Biosensor For Hydrogen Peroxidase Based On The Co-immobilization Of Catalase And Methylene Blue In An Al2O3 Sol-gel Modified Electrode"
Anal. Lett. 2001 Volume 34, Issue 5 Pages 687-699
Dandan Chen, Baohong Liu, Zhengjiu Liu, Jilie Kong

Abstract: A novel biosensor for the amperometric detection of hydrogen peroxide was developed based on the co-immobilization of catalase and methylene blue on an Al2O3 sol-gel fabricated glassy carbon electrode. The membrane structure;of the sol-gel-immobilized catalase and methylene blue was studied with scanning electron microscopy. Cyclic voltammetric and amperometric measurements demonstrated that methylene blue co-immobilized with catalase in this way displayed good stability and efficiently shuttled electron between the immobilized enzyme and the electrode. Electrocatalytic reduction of H2O2 at the electrode was evaluated with respect to solution pH, operating potential and selectivity.:The biosensor was stable at least for 3 weeks.
Membrane

"Analytical Chemistry In Brazil"
Anal. Lett. 2001 Volume 34, Issue 4 Pages 471-490
Graciliano de Oliveira Neto, Solange Cadore, Lauro Tatsuo Kubota

Abstract: An overview of analytical chemistry research in Brazil over the last five years is presented. Analytical chemistry is one of the great areas of research in Brazil. There are 37 graduate programs in chemistry spread over the country, but only some universities have a specific graduate program in analytical chemistry. It is important to note that almost all the research involves graduate and undergraduate students supervised by teachers and professors. This review intends only to provide a general overview of the state of the art of analytical chemistry in Brazil, confined mainly to research being conducted in the universities.

"Chemiluminescence Flow Sensor For Hydrazine With Immobilized Reagents"
Anal. Lett. 2001 Volume 34, Issue 3 Pages 399-413
Zhenghua Song; Lin Wang; Tiezhu Zhao

Abstract: A novel chemiluminescence (CL) sensing system for hydrazine combined with flow-injection technique is presented in this paper. The analytical reagents, luminol and hexacyanoferrate(III), were both immobilized on an anion-exchange column. The CL signal produced by the reaction between luminol and hexacyanoferrate(III), which were eluted from the column through sodium phosphate injection, was decreased in the presence of hydrazine. The decrease in CL intensity is linear with hydrazine concentration in the range from 0.1 to 100.0 ng ml-1; and the detection limit was 0.04 ng m1-1 (3s). A complete analysis could be performed in 2 min with a relative standard deviation of less than 5.0%. The flow sensor was stable for over 400 analyzes and was applied successfully to the determination of hydrazine in artificial samples.

"Sequential Injection Determination Of Iron (II) In Antianemic Pharmaceutical Formulations With Spectrophotometric Detection"
Anal. Lett. 2001 Volume 34, Issue 3 Pages 389-397
Paulo C. C. Oliveira, Jorge C. Masini

Abstract: A direct, rapid and selective Sequential Injection Analysis (SIA) method for determination of iron in pharmaceutical products is proposed. The method is based on monitoring the absorbance at 523 nm due to the complex formed between Fe (II) and 2,2-bipyridyl (α,α-bipyridyl) in acetate buffer at pH 4.5. Commercial formulations without turbidity were analyzed directly after appropriated dilution. The results presented good agreement with the values cited in the manufacturers label and determined by flame atomic absorption spectrometry (FAAS). The method presented a linear dynamic range from 5.0 to 40.0 mg L-1 (r = 0.999) and a detection limit of 0.97 mg L-1, with a sampling frequency of 100 h-1.

"Fast Amperometric FIA Procedure For Heavy Metal Detection Using Enzyme Inhibition"
Anal. Lett. 2001 Volume 34, Issue 1 Pages 17-27
D. Compagnone, A. S. Lupu, A. Ciucu, V. Magearu, C. Cremisini, G. Palleschi

Abstract: The inhibition effect of heavy metals ions such as Hg(II), Cu(II), V(V), and Ni(II) on the activity of oxidase enzymes such as alcohol oxidase, glycerol 3-P oxidase, and sarcosine oxidase has been studied and used for the construction of calibration curves in flow injection analysis. A platinum-based H2O2 probe was used to measure the enzymatic activity of the selected oxidase enzymes. The most sensitive detection system was obtained using the glycerol 3-P oxidase/Hg(II) couple. A calibration curve was obtained in the 0.05-0.4 ppm range, with a detection limit of 0.05 ppm, and a 50% of inhibition (I-50) Of 0.2 ppm. The enzyme alcohol oxidase was used to construct calibration curves for Cu(II) and V(V). The detection limits were 2 and 0.5 ppm, respectively, with I50 ppm for cu(II) and 2.7 ppm for V(V). Ni(II) was detected in the 1-6 ppm range, using the enzyme sarcosine oxidase; I-50 was 3.8 ppm. Relative standard deviations were less than or equal to5% for each enzyme/ion metal couple. The analytical behavior was comparable to measurements in batch analysis. The analysis time was in the range of 10^-15 minutes, which makes the system suitable for fast analysis of heavy metals in the 0.1-10 ppm range. The method could be usefully adopted as on-line control or screening field-test for contaminated water samples (typically industrial effluents) according to the detection limits. This will reduce the number of samples to he analyzed by standard methods based on AAS or ICP/MS detection.

"A Sensitive Photoinduced Chemiluminescence Method For The Determination Of Riboflavin With Flow Injection Analysis"
Anal. Lett. 2000 Volume 33, Issue 15 Pages 3285-3302
Zhang, G.F.;Chen, H.Y.

Abstract: A sensitive chemiluminescence (CL) induced by light for the determination of riboflavin with now injection analysis is developed. Riboflavin shows a strong enhancement effect on the CL reaction of luminol oxidized by periodate after the photochemical reaction of riboflavin in alkaline solution, and the enhancing effect of riboflavin disappears under dark conditions. Oxygen can further improve the enhancing effect of the riboflavin in this CL system, and the effects were also investigated. And based on this phenomenon, a very sensitive method of various surfactants, beta -cyclodextrin and organic solvents on this CL system for the determination of riboflavin was described. The range of the linear response for riboflavin using this method is ~2.4 x 10^-8 similar to 1.0 x 10^-6 mol/L, and the detection Limit (S/N = 3) is 1.0 x 10^-8 mol/L. The applicability of the method was demonstrated by the determination of riboflavin in pharmaceutical preparation.

"Determination Of Gallic Acid By Flow Injection With Electrochemiluminescent Detection"
Anal. Lett. 2000 Volume 33, Issue 15 Pages 3239-3252
Sun, Y.G.;Cui, H.;Li, Y.H.;Li, S.F.;Lin, X.Q.

Abstract: Potential dependent inhibition and enhancement effects of gallic acid on the electrochemiluminescence (ECL) of luminol in alkaline solutions were found. On the basis of the enhancement effect, a flow injection method was developed for the determination of gallic acid. The method was simple, convenient and sensitive. A detection limit of 1.8 x 10^-8 mol/L, linear range of 3.0 x 10^-8 1.0 x 10^-4 mol/L, relative standard deviation of 1.0% for eleven measurements of 5.0 x 10^-6 mol/L of gallic acid was found. This method was successfully applied to determine the content of gallic acid in Chinese gall (moshizi).

"Flow Injection Analysis Of Some Phenolic Sympathomimetic Drugs"
Anal. Lett. 2000 Volume 33, Issue 14 Pages 2927-2938
Ahmad E. El-Gendy

Abstract: A new, rapid and economical flow injection (FI) method For determining some phenolic sympathomimetic drugs is proposed. These drugs are etilefrine hydrochloride (ET), fenoterol hydrobomide (FT), hexoprenaline sulfate (HP), orciprenaline sulfate (OP) and reproterol hydrochloride (RT). The determination is based on the reaction of the studied phenolic sympathomimetic drugs with 4-aminoantipyrine (4-AAP) and potassium hexacyanoferrate (III). The chemical reaction variables and also the Fl variables, were optimized on the basis of sensitivity, sampling rate and reagent consumption. The proposed technique was applied to the analysis of pure raw materials in concentrations ranging from 2-20 mug mL-1 in case of ET, 4-30 µg mL-1 in case of FT and OP and from 8-50 µg mL-1 in case of HP and RT. Samples can be introduced at rates of about 130 per hour. The suggested procedure retained its accuracy and precision when applied to the analysis of pharmaceutical dosage forms containing the corresponding drugs, as judged by the RSD (%) and students test. The results of the analysis were found to agree statistically with those obtained by applying either the official or the referee methods. Furthermore, the validity of the results was assessed by applying the standard addition technique.

"Determination Of Riboflavin Using Flow Injection Inhibitory Chemiluminescence"
Anal. Lett. 2000 Volume 33, Issue 13 Pages 2767-2778
Zhenghua Song; Lin Wang

Abstract: A new flow injection method for the determination of riboflavin based on the inhibition of the intensity of chemiluminescence (CL) from the luminol-K3Fe(CN)(6) system is described. While riboflavin mixed with K3Fe(CN)(6), by the fast oxidation reaction between riboflavin and K3Fe(CN)(6). K4Fe(CN)(6) was generated, which then inhibited the CL reaction of K3Fe(CN)(6) and luminol in alkaline aqueous solution. The CL emission was correlated with the riboflavin concentration in the range from 0.032 to 100 µg mL-1, and the detection limit was 0.01 µg mL-1 (3s). A complete analysis could be performed in 2 min with a relative standard deviation of less than 2.2%. The influence of foreign species was studied and the method has been applied successfully to the determination of riboflavin in pharmaceutical samples, the recovery was from 98.0% to 102%.

"Flow Injection On-line Two-stage Solvent Extraction Preconcentration Coupled With ET-AAS For Determination Of Bismuth Tn Biological And Environmental Samples"
Anal. Lett. 2000 Volume 33, Issue 13 Pages 2747-2766
Jianhua Wang; Elo Harald Hansen

Abstract: A robust flow injection/sequential injection(FIA/SIA) on-line two-stage solvent extraction separation/pre-concentration procedure coupled to electrothermal atomic absorption spectiometry (ETAAS) is described and demonstrated for the determination of trace-levels of bismuth. In 1-4% (v/v) nitric acid medium, diethyldithiophosphate (DDPA) chelates bismuth and the chelating complex formed is extracted into isobutyl methyl ketone (IBMK), which is separated from the aqueous phase by means of cavity gravitational phase separation. Both single and two-stage separations are used. In each case, 40 µl of the concentrate is entrapped and metered in a loop, and subsequently delivered via air-segmentation into a pyrolytically coated graphite tube. The ETAAS determination is performed in parallel with the pre-concentration process of the ensuing sample. Enrichment factors of 17.8 and 31.5, detection limits of 12 ng L-1 and 10.5 ng L-1 for single and two-stage extractions, respectively, along with a sampling frequency of 13 h-1 were obtained with 100 s of sample loading time at a sample flow rate of 5.4 mi min-1. The relative standard deviations were 2.8% and 1.9% for single and two-stage extractions, respectively. The procedure was validated by determining the bismuth content in a certified reference material and in human urine samples.

"Chemiluminescence Flow Injection Analysis Of Menadione Sodium Bisulfite Based On Luminol Reaction"
Anal. Lett. 2000 Volume 33, Issue 13 Pages 2677-2688
Yuming Huang; Zhujun Zhang; Daojian Zhang

Abstract: A chemiluminescence(CL) flow system is described for the determination of menadione sodium bisulfite based on its repression on the chemiluminescence(CL) emission produced upon mixing hexacyanoferrate(III) solution with an alkaline luminol solution in the absence of co-oxidizer. The system responds linearly to menadione sodium bisulfite concentration in the range 0-1 µg/mL with a detection limit (3s) of 0.01 µg/mL. Relative standard deviation (RSD) of 0.16% for 0.4 µg/mL menadione sodium bisulfite (n=11). The system has been successfully applied to the determination of menadione sodium bisulfite in tablets and injections.

"Flow Injection Determination Of Trace Amounts Of Iodide With Spectrophotometric Detection By Its Catalytic Effect On The 4,4 -bis(dimethylamino)diphenylmethane-chloramine T Reaction"
Anal. Lett. 2000 Volume 33, Issue 12 Pages 2553-2562
B. Rezaei

Abstract: A simple and accurate flow injection spectrophotometric procedure was developed for the determination of iodide based on its catalytic effect on the oxidation of 4,4-bis (dimethylamino) diphenylmethane (tetrabase) by Chloramine T in a weakly acidic solution. The optimum analytical conditions have been established. The linear range of the detection is 4-110 ng/mL, with a limit of detection 3 ng/mL. The method has been used to determine iodide traces in water.

"Quantitation Of Monosodium Glutamate Using Immobilized Glutamate Oxidase/peroxidase And Flow Injection Analysis"
Anal. Lett. 2000 Volume 33, Issue 12 Pages 2407-2423
U. Mankasingh; D. Narinesingh; T. T. Ngo

Abstract: A rapid and sensitive now injection method is developed for tbe quantitation of glutamate in food samples. The method incorporates a covalently immobilized glutamate oxidase and peroxidase bioreactor linked in tandem. The H2O2 liberated from the glutamate samples as a result of enzymatic action is monitored spectrophotometrically at 552 nm using 4-aminoantipyrine and 3-dimethylaminobenzoic acid as a new chromogenic reagent. Glutamate calibration curves are linear up to 140 µM with a detection limit of 1 µM. Recovery yields from soup matrices are in the range 97 - 101%. Inter- and intra-day precision studies gave CVs of less than 3.5%. The immobilized enzymes show good storage and operational stabilities. Up to 40 samples h-1 can be manually analyzed. Excellent correlation is obtained from a comparison of the glutamate content of various soup brands and matrix type (solid, condensed and broths) obtained by the proposed FI method with those obtained for the same samples analyzed by the standard reference method (y = 0.99x + 0.034).

"Novel Pre-oxidizing Cell For Elimination Of Electroactive Interferents During Biosensor Analysis. Application To Glucose Determination In Real Samples"
Anal. Lett. 2000 Volume 33, Issue 12 Pages 2391-2405
Vasilis G. Gavalas; Maria G. Fouskaki; Nikolas A. Chaniotakis

Abstract: The application of a pre-oxidizing cell for the on-line elimination of electrooxidizable interferents in a flow-system equipped with an amperometric biosensor is presented. The reactor cell is based on vitreous carbon foam with large surface areas for the fast oxidation of electroactive compounds. The efficiency of the cell is evaluated using the most significant interferences found in real samples, those of ascorbic acid uric acid and acetaminophen. The application of the cell, in the online analysis of glucose in real samples is finally demonstrated. The results are in agreement with those obtained by chromatography measurements (correlation coefficient: 1.04±0.02).
Glucose

"Flow Injection Analysis Of Tannic Acid With Inhibited Electrochemiluminescent Detection"
Anal. Lett. 2000 Volume 33, Issue 11 Pages 2281-2291
Yu-Gang Sun; Hua Cui; Ying-Hui Li; Hua-Zhang Zhao; Xiang-Qin Lin

Abstract: A flow injection method has been developed for the determination of tannic acid based on its inhibition of the electrochemiluminescence of luminol. The method is simple, rapid and sensitive with a detection limit of 2 x 10^-8 mol/l. It is effective to determine tannic acid in the range 5 x 10^-8 - 1 x 10^-5 mol/l. The variation coefficient of eleven determinations is 1.4% for 5 x 10^-6 mol/l. The method has been successfully applied to the determination of tannic acid in real Chinese gall and hop pellet samples.

"Automation Of The Photodegradation Spectrophotometric Method For The Determination Of Diethylstilbestrol By Flow Injection"
Anal. Lett. 2000 Volume 33, Issue 11 Pages 2231-2242
C. S. Ballesteros Lpez; A. V. Lopez Gmez; J. Martinez Calatayud

Abstract: An spectrophotometric determination of diethylstilbestrol is proposed on the basis of on-line photo-degradation and measurement at 330 nm. The procedure is accomplished by means of flow injection assembly including a photo-reactor formed by a PTFE 168 cm long coil around a low-pressure mercury lamp 6 w; this photo-reactor was nested between the injection valve and the spectrophotometric flow-cell. The sample solution was injected into a carrier stream of aqueous di-potassium hydrogen ortophosphate flowing at 5.0 mL min-1. Influence of the physic-chemical and hydrodynamic parameters was studied and optimized. The calibration graph was linear up to 65 mg L-1, and the procedure presented a reproducibility (rsd of the calibration slope) 1.4%, and a sample throughput of 52 h-1. The influence of foreign compounds was tested.

"Kinetic Determination Of Ruthenium By On-line Microwave Flow Injection Analysis"
Anal. Lett. 2000 Volume 33, Issue 10 Pages 2075-2089
Huaiwen Wang; Yongyao Zhou; Yunkun Zhao; Yue Ning; Xingguo Chen; Zhide Hu

Abstract: A new rapid high sensitive and selective on-line: microwave flow injection method has been developed for the determination of micro-amounts of ruthenium, based on its catalytic effect on the oxidation of dibromocarboxyarsenazo (DBM-AsA) by potassium periodide in acidic medium. The assay is performed in a microwave-induced flow injection analyzer by measuring the absorption of DBM-AsA at 538 nm spectrophotometrically. Microwave irradiation has been found efficient to supply enough energy for the reaction in a very short time and give a lower detection limit. Under the optimized experimental conditions, ruthenium can be determined in the range 5 similar to 200 ng mL-1 with the detection limit of 2.1 ng mL-1 and the sampling frequency of 72 h-1. The proposed method has been successfully applied to the determination of ruthenium in refined ore samples with the recovery of 93.0 similar to 99.9%.

"Determination Of Copper, Nickel And Cadmium By FAAS After Preconcentration With Zinc-piperazinedithiocarbamate Loaded On Activated Carbon By Solid-phase Extraction"
Anal. Lett. 2000 Volume 33, Issue 10 Pages 1991-2004
Hasan Cesur; Mustafa Macit; Bekir Bati

Abstract: A method was developed for the pre-concentration of copper, nickel and cadmium in water samples, prior to their determination by FAAS, using the Zn-piperazinedithiocarbamate complex (ZnPDC) loaded on activated carbon. in this method, Cu, Ni and Cd in liquid phase quantitatively replaced zinc on a ZnPDC-activated carbon solid phase. Afterwards, the metals on the solid phase were easily eluted by Hg(II) solution into aqueous phase, and were measured by FAAS. The optimum experimental parameters such as pH, sample volume, and effect of matrix ions for the pre-concentration of the metals were investigated. The range of linearity 0-6, 0-5, 0-3 µg mL-1, correlation coefficient 0.9981 0.996, 0.999, detection limits 15.7, 23.5, 11.8 ng mL-1, and determination limits 136, 179, 98 ng mL-1 in final Hg(II) solution were obtained for Cy Ni and Cd, respectively. The proposed method has been employed for the determination of Cu Ni and Cd in various standard metal alloys and natural water samples.

"Design Of The Fluoride Ion-selective Electrode As Tubular Detector For Flow Injection Analysis"
Anal. Lett. 2000 Volume 33, Issue 9 Pages 1811-1825
Marija Bralic; Silvestar Krka

Abstract: Design of the fluoride ion-selective electrode (FISE) as the tubular detector used in the now injection analysis (FIA) has been described. Among other things, this design makes it possible to use various internal contacts. The effect of pH on peak height and detection limit in the pH range from 2.8 to 8.0 has been examined. The effect of now rate and sample injection volume on peak height and range of linear response has also been examined. The flow rates range from 0.56 mL/min to 4.05 mL/min, while the injection volumes are 100 and 200 µL. The optimum conditions are carrier solution (0.1 M KNO3 buffer pH 4 and 10^-6 M NaF), flow rate 1.54 mL/min and sample injection volume 100 µL. Applicability of the FISE as the tubular detector in determination of Fe(III)-ions and Al(III)-ions by now injection analysis has been examined at pH values of 2.8 and 3.4.

"Luminol Electrochemiluminescence-based Biosensor For Total Cholesterol Determination In Natural Samples"
Anal. Lett. 2000 Volume 33, Issue 9 Pages 1779-1796
Christophe A. Marquette; Stephanie Ravaud; Loic J. Blum

Abstract: A new cholesterol flow injection analysis biosensor is described. It is based on a luminol/hydrogen peroxide electrochemiluminescence (ECL) reaction induced by a glassy carbon electrode polarised at + 425 mV vs a Pt pseudo reference. The cholesterol biosensor sensing layer is based on cholesterol oxidase (COD) immobilized on either UltraBind™ membrane or Immunodyne membrane. The physicochemical properties of the UltraBind™ type membranes enable a high-performance biosensor to be obtained. A high salt concentration. 3 M NaCl, is shown to induce a 400% increase of the immobilized COD activity, and intermediate salt concentrations, from 1 to 1.5 M NaCl, induce a 230% increase of the H2O2 sensor performances. Both phenomena enable the achievement of a sensitive ECL cholesterol biosensor which exhibited a 800% increase of its performance in the presence of 2 M NaCl. in those optimized conditions, the determination of free cholesterol could be performed with a detection limit of 0.6 nmol and a detection ranging over at least two decades. When used in conjunction with a cholesterol esterase in solution, the biosensor enables the detection of free and total cholesterol in human sera, in 15 minutes with a good accuracy. The biosensor operational stability was satisfactory either with buffered standard solutions or with complex matrices since a total of 55 and 43 assays, respectively, could be performed with good reproducibility (CV = 4.8% and 8.3%) and without detectable loss of sensitivity.

"Acousto-optic Tunable Filter: A New Generation Monochromator And More"
Anal. Lett. 2000 Volume 33, Issue 9 Pages 1711-1732
Chieu D. Tran

Abstract: The acousto-optic tunable filter is a compact, all solid state electronic monochromator. It is based on the acousto-optic interaction in an anisotropic crystal. Compared to conventional grating monochromtors, the AOTF has no moving parts, wider spectral tuning range (from UV though visible and near- IR to IR), higher throughput, higher resolution (few angstroms), faster scanning speed (ys) and imaging capability. These features make it possible to use the filter to develop novel instruments which are not possible otherwise. The instrumentation development and unique advantages of such AOTF based instruments including a multidimensional fluorimeter, detectors for HPLC and flow injection analysis, and a multispectral imaging instrument are described.
Laser Detector

"Comparison Of The Adsorbed Mercury Screening Method With Cold-vapor Atomic Absorption Spectrophotometry For Determination Of Mercury In Soil"
Anal. Lett. 2000 Volume 33, Issue 8 Pages 1665-1689
Donald F. Easterling; Edward S. Hovanitz; Kenneth W. Street

Abstract: A field screening method for the determination of elemental mercury in environmental soil samples involves the thermal desorption of the mercury from the sample onto gold and then the thermal desorption from the gold to a gold-film mercury vapor analyzer. This field screening method contains a large number of conditions that could be optimized for the various types of soils encountered. In this study, the conditions were optimized for the determination of mercury in silty clay materials, and the results were comparable to the cold-vapor atomic absorption spectrophotometric method of determination. This paper discusses the benefits and disadvantages of employing the field screening method and provides the sequence of conditions that must be optimized to employ this method of determination on other soil types.

"Development Of Flow Analytical Systems For Monitoring Thiocyanate Biodegradation In Waste Waters"
Anal. Lett. 2000 Volume 33, Issue 8 Pages 1603-1614
D. L. Recalde-Ruiz; E. Andres-Garcia; M. E. Diaz-Garcia

Abstract: Metallurgical waste waters have a very complex composition. Different reactions take place in such waters. Among them, the reaction of pyretic materials with free cyanide results in the production of thiocyanate, another hazard to the aqueous media. Biological cleanup (bioremediation) is one of the methods to eliminate SCN- of waste waters and, consequently, it is necessary to develop sensitive and convenient methods for thiocyanate analysis in this bioprocess in order to assure environmental quality control. In the work presented here different spectrophotometric flow systems based on the reaction between Fe(III) and SCN- are studied to control thiocyanate in crude and biologically treated coke plant waste waters, using a conventional now cell and a fiber optical continuous flow system. Chemical and physical parameters of the now systems were studied. A simple, fast and sensitive continuous now system with optical fibers is proposed for monitoring thiocyanate degradation in a waste water biological reactor.

"Flow Injection Chemiluminescence Determination Of Gentamycin Using On-line Electrogenerated Co(III) As The Oxidant"
Anal. Lett. 2000 Volume 33, Issue 8 Pages 1577-1590
Baoxin Li; Zhujun Zhang; Manli Wu

Abstract: A novel flow-injection chemiluminescence (CL) system for the determination of gentamycin is described, based on the direct chemiluminescence reaction of gentamycin and Co(III) in sulfuric acid media. The unstable strongly oxidative Co(III) was electrogenerated on-line with constant current electrolysis. The chemiluminescence intensity was linear with gentamycin concentrations of 0.01 to 80 µg/ml, the detection limit being 0.005 µg/ml. The whole process could be completed in 1 min with a relative standard deviation of less than 3.2%. The proposed method is rapid and simple and is suitable for automatic and continuous analysis. This method has been applied satisfactorily to the analysis of gentamycin in pharmaceutical preparations.

"Applications Of Amperometric Silica Sol-gel Modified Enzyme Biosensors"
Anal. Lett. 2000 Volume 33, Issue 8 Pages 1467-1477
Juan Li; Swee Ngin Tan

Abstract: The applications. of amperometric sol-gel modified enzyme biosensors in numerous analyzes of clinical, industrial and environmental importance have been demonstrated. Certain biosensors have been employed as the sensor in a FIA amperometric detector. The results obtained by the biosensors generally corroborate well with the classical or official method. In many cases, the recovery results obtained by the biosensor have been satisfactory.
Sol-gel

"Multielement Preconcentration And Removal Of Trace Metals By Solid-phase Extraction"
Anal. Lett. 2000 Volume 33, Issue 7 Pages 1441-1450
Krystyna Pyrzynska; Zbigniew Jonca

Abstract: The solid phase extraction of trace amounts of some metal ions from their mixtures using cation exchanger Dowex 50Wx4, cellulose sorbent with phosphonic acid groups Cellex P, chelating resin Chelex 100 and SIO2-TPP sorbent which contains porphyrin ligand covalently attached to aminopropyl silica gel was investigated. With respect to multielement pre-concentration Cellex P and Chelex 100 seem to be the best sorbents; the recovery test for Al, Be, Cd, Ni, Pb and Zn were > 90%. Additionally, Cellex P appeared to be suitable for enrichment of Co and Mn. Silica-TPP sorbent could be applied as a selective collector for Mo(VI) and V(IV).
Resin

"Flow Injection Extraction Spectrophotometric Determination Of Niobium As The Ethylene Bis(triphenyl Phosphonium) Thiocyanatoniobate(V)"
Anal. Lett. 2000 Volume 33, Issue 7 Pages 1433-1440
D. Thorburn Bums; P. Pornsinlapatip

Abstract: Niobium was determined by now injection spectrophotometry at 393 nm after extraction of ethylene-bis(triphenylphosphonium)thiocyanatoniobate(V) into chloroform. The effects of diverse ions are reported. The system has been applied to the determination of niobium in steels by the method of standard additions.
Extraction

"Determination Of Phenols In Natural Waters With A Flow-analysis Method And Chemiluminescence Detection"
Anal. Lett. 2000 Volume 33, Issue 7 Pages 1373-1386
Jacek Michalowski; Piotr Halaburda; Anatol Kojlo

Abstract: A simple now-manifold with time based sample introduction system was elaborated and used to determine phenols in natural waters. Use of computer controlled solenoid valves and direct chemiluminescence detection enables very low reagent consumption. A quantity of less than 1.5 µmol of potassium permanganate and 600 µmol of sulphuric acid per determination is used. The use of on-line pre-concentration column filled with XAD-4 resin enables determination with the detection limit of 5 ng mL-1. The sample throughput is 12 h-1 when the column is used and 60 h-1 without a column.
Multicommutation Multicommutation Preconcentration

"Analytical Chemistry In Poland"
Anal. Lett. 2000 Volume 33, Issue 7 Pages 1203-1229
Adam Hulanicki; Zygfryd Witkicewicz

Abstract: The paper presents the main achievements of analytical chemistry in Poland on the basis of papers published mainly in the last decade. The selection is somewhat arbitrary but should show the most important directions of research. The citations generally refer to papers published in regular journals. The following topics were discussed: general aspects, chemical methods and reagents, spectrophotometry, speciation studies, atomic spectrometry, electrochemical methods, chemo- and biosensors, chromatography and related techniques. Short reviews on the history and present status of analytical chemistry have been published elsewhere(1,2) and this review is intended to present the more detailed overview of the recent fields of interest, based on some selected publications from the nineties. Such selection is obviously to some extent arbitrary and this is mainly based on information sent by colleagues from various centres. it seemed however, necessary to indicate where appropriate, the roots and earlier achievements.

"Flow Injection Chemiluminescence Determination Of Fluoroquinolones"
Anal. Lett. 2000 Volume 33, Issue 6 Pages 1117-1129
Yi Rao; Yan Tong; Xinrong Zhang; Guoan Luo; Willy R. G. Baeyens

Abstract: A new flow injection CL method was developed for the determination of fluoroquinolones including ofloxacin, norfloxacin, ciprofloxacin and lomefloxacin in pharmaceutical preparations, based on the chemiluminescence reaction of sulfite with cerium(IV) sensitized by these compounds. The linear ranges are 0.04 to 4.0 µg mL-1 for ofloxacin and 0.4 to 40.0 µg mL-1 for norfloxacin, ciprofloxacin and lomefloxacin, respectively. The detection limits are 0.016 µg mL-1 for ofloxacin and 0.16 µg mL-1 for norfloxacin, ciprofloxacin and lomefloxacin, respectively. The relative standard deviations (RSD) are 2.1 to 2.6% (n = 10) for these fluoroquinolones. The analytical procedure has been applied to the determination of the fluoroquinolones in pharmaceutical commercial formulations. The results are in agreement with those obtained by the official methods.

"Potentiometric Dipyridamole Sensors Based On Lipophilic Ion Pair Complexes And Native Ionic Polymer Membranes"
Anal. Lett. 2000 Volume 33, Issue 6 Pages 1037-1055
Saad S. M. Hassan; Nashwa M. H. Rizk

Abstract: ion exchange sites in a plasticized PVC matrix. A plasticized native polymer (e.g., carboxylated polyvinyl chloride) is also used. These sensors exhibit linear and near- Nernstian responses for 1 x 10^-2 - 1 x 10^-6 M dipyridamole with cationic slopes of 53.4 - 55.1 mV/decade and the working pH range is 2-5. No interferences are caused by many inorganic and organic cations due to complete dissociation and high exchange equilibrium of the ion-association electroactive complexes in the membrane phase. Fairly good thermodynamic ionic exchange process at the membrane/drug solution interface and good mechanical and thermal stability are obtained up to 60°C. The sensors proved useful for determining dipyridamole in various dosage forms with an average recovery of 98.7% and a mean standard deviation of 0.6%.

"Determination Of Nitrite With A PTFE-membrane Covered Electrode After Reduction To Nitrogen Oxide In A Reagent Saving Flow Injection System"
Anal. Lett. 2000 Volume 33, Issue 6 Pages 1013-1023
Hiroyuki Kobayashi; Motohiko Hikuma

Abstract: Nitrite was reduced in acidic potassium iodide solution to produce nitrogen oxide which was measured amperometrically by a modified gold electrode covered with a PTFE-membrane as the permeability barrier for interfering substances in the sample. The calibration curve was linear up to 30 µM of nitrite and 10 samples could be determined per hour. The average current and the standard deviation for 10 µM standard solution (N = 10) were 1.51 x 10^-2 µA and 6.4 x 10^-5 µA (RSD = 0.42%), respectively. The detection limit was 0.25 µM.No response was observed for electrochemical interferant substances such as ascorbic acid and FeSO4. The reducing reagent could be reused. Recovery tests were satisfactory (101-103%). The results obtained with this sensor and with the diazotization method for a fish culture water agreed within 8.6%.

"Biosensors In Wine Production Monitoring"
Anal. Lett. 2000 Volume 33, Issue 6 Pages 963-996
M.D. Luque de Castro; J. L. Luque-Garcia

Abstract: An overview of probe-type and flow-through biosensors, together with biosensing systems, both batch and continuous biosensing systems, for monitoring typical species in wine processes is presented with the aim of showing the advantages and disadvantages involved in the use of each type of devices. Thus, biosensors and biosensing systems for the determination of ethanol (individual or together with that of other compounds), organic acids, glycerol, reducing sugars, acetaldehyde and sulfur dioxide/sulfite anions are reviewed and critically compared. The versatility and capability of continuous biosensing systems as compared with biosensors, particularly with probe-type biosensors working in a discontinuous, batch manner, is demonstrated.

"Spectrofluorimetric Flow Injection Determination Of Glycerol & Ethylene Glycol With Alizarin Navy Blue"
Anal. Lett. 2000 Volume 33, Issue 5 Pages 941-951
B. Rezaei

Abstract: A simple and accurate procedure for indirect spectrofluorimetric determination of glycerol and ethylene glycol in aqueous media was developed. Alizarin Navy Blue can be oxidized by potassium periodate to produce a fluorescent compound, that can be detected fluorimetrically (lambda(ex) = 370 nn, lambda(em) = 516 mm) by a flow through method. Glycerol and ethylene glycol react with periodate decreasing its concentration and thus the forming the basis for an indirect determination of these compounds. The influence of acid concentration, reagent concentration and manifold variables were studied. For glycerol and ethylene glycol linear calibration curves were obtained in the ranges of 4.8 x 10^-7 - 8.7 x 10^-5 M and 6.4 x 10^-7 - 8.7 x 10^-5 M, respectively. The limit of detection (defined as the concentration that gives a signal three times the standard. deviation of the background signal) for glycerol and ethylene glycol was 3.2 x 10^-7 M and 4.3 x 10^-7 M, respectively. The proposed method was applied for determination of glycerol and ethylene glycol in synthetic and real samples. The results obtained were satisfactory.

"A Bead Injection System For Copper Determination"
Anal. Lett. 2000 Volume 33, Issue 5 Pages 929-940
Claudio C. Oliveira; Elias A. G. Zagatto; Jaromir Ruzicka; Gary D. Christian

Abstract: A bead injection system for copper determination is proposed. Chelex-100 resin beads are introduced in the system as a suspension that is trapped in the Jet Ring Cell. The passage of the sample zone by the beads promotes the sorption of Cu(II). When the colorimetric reagent (APDC) perfuses the beads it reacts with copper ions, forming a colored complex that is monitored at 436 nn. After the measurement, the spent beads are sent to waste and a new portion of fresh beads is trapped in the system. The bead injection system is versatile and can be used to concentrate analyte in different sample volumes, permitting determinations of a wide range of copper concentrations. The detection limit is 0.5 µg L-1 with a 500 µL sample, and 1.2 µg L-1 a 100 µl sample.
Copper(II) Water Spectrophotometry Chelex Preconcentration Bead suspension Jet ring cell APDC

"The Recent Status Of Analytical Chemistry In Greece"
Anal. Lett. 2000 Volume 33, Issue 5 Pages 753-792
Demetrius S. Papastathopoulos

Abstract: The aim of this review is to present a very concise report of the research activities in the area of Analytical Chemistry performed in Greece during the last decade. Since, research in chemical analysis conducted by Greek scientific institutions covers a very large variety of analytical methodologies and techniques, it is found preferable to organize this review based on a separate presentation of the scientific activities of each Greek University or Scientific Institution, operating analytical laboratories or other divisions involved in analytical chemistry research. Table I shows all the Greek Scientific Institutions (with full addresses) involved in analytical chemistry research. The references of this article are limited to papers published in scientific journals, conference proceedings, book chapters, reports, MS or PhD thesis etc., are excluded. Also, the review is directed exclusively to works performed in the headquarters of the Greek Universities or Institutions. All the published papers (from 1990) of each university or institution are presented, under chronological order and summarised in groups according to the basic analytical technique used for the detection of the analyte. Also, in order to keep the text short, there is no reference to researchers names.

"Chemiluminescence Flow Injection Determination Of Copper (II)"
Anal. Lett. 2000 Volume 33, Issue 4 Pages 667-675
A. Safavi; M. R. Baezzat

Abstract: A sensitive and selective flow injection chemiluminescence method for the determination of copper over the range of 0.5-7.5 ng is described. The method is based on quenching effect of copper (II) on the chemiluminescent reaction of dichlorofluorescein and hydrogen peroxide in alkaline media. Method development includes optimization of reagent concentrations and flow conditions. The optimized method yielded a detection limit (3s) of 0.2 ng. The method is simple, fast, selective and precise and was used for the determination of copper in blood sera.

"Simplex Optimisation Of A Flow Injection Analysis (FIA) System To Determine Rare Earth Elements (REE) With Arsenazo III"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 553-569
J. M. Sanchez; M. Hidalgo; M. Valiente; V. Salvado

Abstract: A Flow Injection Method (FIA) for the determination of Rare Earth Elements (REE) in mixed solutions is described and the parameters involved are optimized mathematically by a modified simplex method (MSM). The performance of the system permits the determination of REE from solutions with pHs ranging from 0 to 6. A linear calibration range of up to ~30 mg L-1 for-an injection volume of 70 µL and a concentration of Arsenazo III equal to 1.22 mM is achieved representing a tenfold increase over previously reported values. The detection limit of the method is 0.70 mg L-1 for all the elements studied except Yb which is less sensitive (1.27 mg L-1). In the case of Yb, an increase in the linear range of up to ca 40 mg L-1 is achieved. The FIA method can be applied in the analysis of mixtures containing different pairs of REE elements with a relative error of less than 5%.
Simplex Extraction

"Flow Injection Analysis Of Pyridoxine Hydrochloride By Coupling With The Diazonium Ion Of P-sulfanilic Acid"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 539-552
Llorenc Monferrer-Pons; Lluis Alvarez-Rodriguez; Josep Esteve-Romero; M. Celia Garcia-Alvarez-Coque

Abstract: A flow injection (FI) procedure is proposed for the determination of pyridoxine. In the FI manifold, a solution of p-sulfanilic acid in a micellar medium of N-cetylpyridinium chloride (NCPC) was diazotized with nitrite in acidic medium, and the pH was then adjusted to 7 with monohydrogenphosphate; the sample was injected into this stream and the absorbance measured at 450 Mn. The surfactant catalyzed the derivatization reaction and enhanced the sensitivity of the FI procedure. Consequently, the addition of toxic mercury(II) acetate, used in the conventional procedure performed in non-micellar medium, was no longer required. The signals obtained with other surfactants, such as sodium dodecyl sulfate or Triton X-100, were smaller. Under optimized FI conditions, the calibration curve was linear from the limit of detection, 5 x 10^-5 M up to 1 x 10^-3 M, and the sampling frequency was 60 h-1. The procedure was applied to the determination of pyridoxine hydrochloride in commercial pharmaceutical preparations, with recoveries close to 100%.

"Determination Of Copper By FAAS After Preconcentration With Lead-4-methylpiperidinedithiocarbamate On Microcrystalline Naphthalene By Solid-phase Extraction"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 489-501
Hasan Cesur; Bekir Batl

Abstract: By using the Pb-4-methylpiperidinedithiocarbamate complex (Pb(4-MPDC)(2)) on microcrystalline naphthalene in a column a method was developed for the pre-concentration of copper in water samples prior to its determination by FAAS. In this method, copper in liquid phase quantitatively replaces lead on the Pb(4-MPDC)(2)-naphthalene solid phase in the column, forming solid Cu(4-MPDC)(2) complex. Afterwards, copper on Cu(4-MPDC)(2)- naphthalene can be easily eluted by potassium cyanide into the aqueous phase, and the Cu is measured by FAAS. The optimum experimental parameters such as pH, flow rate,sample volume, Pb(4-MPDC)2-naphthalene ratio, concentration of the potassium cyanide solution and effect of matrix ions for the pre-concentration of copper were investigated. The obtained recovery was nearly 100 %, when the enrichment factor was 100 for standard solutions and spiked water samples. The proposed method has been employed for the determination of copper in various standard metal alloys and natural water samples.

"Capillary Electrophoresis Immunoassay For 2,4-dichlorophenoxyacetic Acid"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 443-453
Kim R. Rogers; Alma B. Apostol; William C. Brumley

Abstract: A capillary electrophoresis (CE) immunoassay format for 2,4-dichlorophenoxyacetic acid (2,4-D) is demonstrated. A fluorescent labeled 2,4-D analog competes with the analyte of interest for a finite number of binding sites provided by anti-2,4-D monoclonal antibodies. CE then provides a means of separating and measuring both the free and antibody-bound fluorescent tracer using laser-induced fluorescence detection. For this assay format, the amount of free tracer is a sensitive indicator for the concentration of analyte present in the sample. A sequential injection format allows the rapid analysis of a small number of samples. The dynamic concentration range for 2,4-D in either buffer or river water is 5 ppb to 1000 ppb.

"Microbiosensor For Salicylate Based On Modified Carbon Fibre"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 425-442
Rosangela M. de Carvalho; Graciliano de Oliveira Neto; Lauro T. Kubota

Abstract: A microbiosensor is proposed for a quick and easy amperometric determination of salicylate. The methodology involves the use of the enzyme salicylate hydroxylase (SH) to convert salicylate to catechol, which is then oxidized at the carbon fiber electrode. The covalent immobilization of the enzyme onto a carbon fiber electrode via carbodiimide results in an amperometric biosensor with high sensitivity, low detection limit and good stability. The response of the biosensor is linearly proportional to the salicylate concentration between 1.0 10^-7 and 2.0 10^-6 mol L-1, at an applied potential of 300 mV vs SCE, with a response time of 3.5 s and a detection limit of 3.3 10^-8 mol L-1. The relative standard deviation for the determination was 4.1% for n=10. The biosensor was applied to determine salicylate in urine and pharmaceutical samples and compared to the reference method with a good correlation.

"Minireview: A Critical Review Of The Transition Metal Ions Influence On Peroxyoxalate Chemiluminescence"
Anal. Lett. 2000 Volume 33, Issue 3 Pages 391-404
Margareth Mie Nakamura; Sergio Adriano Saraiva; Nina Coichev

Abstract: A detailed study and evaluation of the presence of Cr(III), Zn(II) and Pb(II) and various parameters affecting the intensity of the chemiluminescent reaction of TCPO and 2-NPO with hydrogen peroxide in the presence of 3-aminofluoranthene, as the fluorophore, and imidazole (IMI) as catalyst, is presented. Depending on the unprotonated imidazole and fluorophore concentrations, these metal ions enhance the intensity of the fluorophore at pHs higher than 8.0. At pH = 7.0, in the presence of IMI/HIMI+ (IMI = 1 x 10^-2 mol.L-1), tris(hydroxymethyl)aminomethane or HPO42-/H2PO4- buffers, no effect of these metal ions was observed. A critical comparison with the data reported in the literature is presented.
Optimization

"Tuning The Performance Of Room Temperature Phosphorescence Sensing Materials For Oxygen Using Factorial Designs"
Anal. Lett. 2000 Volume 33, Issue 2 Pages 307-322
R. Badia; ME. Diaz Garcia

Abstract: The effects of three experimental factors (pH, precursors, alcohol) on the sensing characteristics of these materials were screened by means of two-level factorial designs. The resulting materials turned out to be useful as luminescent probes for the measurement of dissolved and gaseous oxygen. The photochemical properties and the analytical performance of the RTP sensing phases have been studied by using both gas flow injection analysis and continuous liquid now-through systems. The proposed sensing materials were particularly suitable for measuring dissolved oxygen in natural waters. The detection limit attained was 0.004 mg mL-1 and a typical precision of ±1.0% at a 0.6 mg mL-1 oxygen level was achieved. Response time for 90% of the final RTP value was less than 90s in a continuous flow mode. No hysteresis effects were noticed.

"Flow Injection Biamperometry Of Phenol"
Anal. Lett. 2000 Volume 33, Issue 2 Pages 237-248
A. Kojlo; E. Wolyniec; J. Michalowski

Abstract: A simple and rapid method determination of phenol is described, using a bromination reaction and biamperometric detection. The method is based on measurements of the intensity of current passing through two identical inert electrodes giving the concentration of phenol in samples. The sample is injected into a stream of carrier and merged with a stream of acidic bromine solution which brominates phenol in the reaction coil. A linear relationship between peak height and phenol concentration is observed in the range of 0.05 to 8 µg mL-1 of phenol. The relative standard deviation was 2.8% for analysis of 5 µg mL-1 phenol and the sampling rate was 70 h-1.

"Flow Injection Chemiluminescence Determination Of Hydrogen Peroxide With In-situ Electrogenerated Br-2 As The Oxidant"
Anal. Lett. 1999 Volume 32, Issue 15 Pages 3013-3028
heng xingwang; Yang mei; Zhujun Zhang

Abstract: By designing a novel flow-through electrolytic cell, Br-2, an unstable and toxic reagent, can be produced in-situ on the near region of a platinum electrode surface by constant current oxidizing KBr in H2SO4 medium. At the same time, it was found that a strong CL signal was produced when the basic H2O2 solution was injected into the electrolytic cell. Based on this observation, a simple, rapid and selective ECL method for the determination of H2O2 was proposed. Factors affecting the determination of H2O2, including the chemical and flow injection parameters as well as the design of flow- through electrolytic cell, were investigated, and the possible ECL reaction mechanism was also discussed. Under the optimum conditions, the ECL emission intensity was linear with H2O2 concentration in the range of 1.0 x 10^-6 -4.0 x 10^-3 mol/L and with 3.5 x 10^-7 mol/L detection limit.

"Spectrophotometric Determination Of Cefadroxil In Drug Formulations Using Flow Injection Analysis"
Anal. Lett. 1999 Volume 32, Issue 15 Pages 2977-2988
I. F. Al-Momani; I. Awni; H. S. Khalil; F. Esmadi

Abstract: A flow injection analysis method for the determination of cefadroxil is proposed. The method is based on the hydrolysis of cefadroxil in sodium hydroxide solution followed by treatment with 1,4-phenylenediamine and Fe(III) in sulfuric acid solution to produce a violet color which has a maximum absorption at 600 nn. Variables such as acidity, reagent concentrations, flowrate of reagents and other Fl parameters were optimized to produce the most sensitive and reproducible results. The calibration graph is linear between 80 -320 mg/l. The detection limit is 40 mg/l with a relative standard deviation, RSD (n=6) of 1.8%. The proposed method, combining the advantages of speed and accuracy was applied to the determination of cefadroxil in pharmaceutical preparations. The results have been compared with those obtained using HPLC method (USP-procedure). Excellent agreement between the results of the proposed method and the HPLC method was observed.
Cefadroxil Pharmaceutical Spectrophotometry Optimization Method comparison

"Flow Injection Catalytic Spectrophotometric Determination Of Trace Amounts Of Nitrite"
Anal. Lett. 1999 Volume 32, Issue 14 Pages 2887-2897
Hui Chen; Yan-jun Fang; Tai-cheng An; Xing-long Jin

Abstract: A flow injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on potassium bromate oxidation of acridine orange in phosphoric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of acridine orange at 491.5 nm coupling with the stopped-flow technique. The calibration curve was linear between 3.4 and 65 ng/mL, and the detection limit was 2.2 ng/mL. Up to 30 samples can be analyzed per hour with a relative precision of ~1.9%. The proposed method was successfully applied to the determination of nitrite in waters and food samples with satisfactory results.

"Chemiluminescent Determination Of Menadione Sodium Bisulfite"
Anal. Lett. 1999 Volume 32, Issue 14 Pages 2789-2798
Yuming Huang; Zhiqiong Chen; Zhujun Zhang

Abstract: A chemiluminescence (CL) system for menadione sodium bisulfite (MSB) combined with a now-injection system is presented in this paper. It is based on CL produced by the oxidation of bisulfite liberated from MSB by Ce(IV). The system responds linearly to MSB concentration in the range of 0.01 similar to 10 µg/mL with the detection limit (3s) of 2 x 10^-3 µg/mL. The relative standard deviation for 2 µg/mL MSB was 3.45% (n=10). The system has been applied successfully to the determination of MSB in injections.

"Determination Of Rutin By Flow Injection With Inhibited Chemiluminescence Detection"
Anal. Lett. 1999 Volume 32, Issue 14 Pages 2751-2759
Caixia He; Hua Cui; Xiaoyu Zhao; Huazhang Zhao; Guiwen Zhao

Abstract: A simple, rapid, convenient and highly sensitive flow injection procedure with chemiluminescence detection has been developed for the determination of rutin based on its inhibition of the chemiluminescence from the luminol-potassium hexacyanoferrate(111) system. The linear range is 2 x 10^-8 -8 x 10^-6 g/mL and the detection limit is 6.7 x 10^-9 g/mL. The method has been successfully applied to determine rutin in sophora japonica L. (traditional Chinese medicine).

"Optimisation Of A Flow Injection System With A Piezoelectric Quartz Crystal Detector For The Determination Of Inorganic Mercury"
Anal. Lett. 1999 Volume 32, Issue 14 Pages 2715-2723
M. Teresa; S. R. Gomes; Elisa V. Morgado; Joao A. B. P. Oliveira

Abstract: A new method combining flow injection methodology with quartz crystal microbalance (QCM) detection is proposed for inorganic mercury analysis. A modified simplex method is used in order to maximise the observed analytical signals (crystal frequency decrease). Six parameters were optimized: the concentration of the acidic carrier solution, the lengths of the sample loop and mixing coil, and the flow rates of the sample carrier, the reductant stream (SnCl2), and the carrier of the mercury vapor (N-2). An increase of 18% in the signal of the centroid of the calibration line was achieved, as well as an increase in the sensitivity from 290 Hz µg^-1 to 313 Hz µg^-1. Following the proposed procedure, detection limits of 47 µg L-1 of inorganic mercury were found for sample volumes of 0.5 mL.

"Parameters Affecting The Peroxyoxalate Chemiluminescence"
Anal. Lett. 1999 Volume 32, Issue 12 Pages 2471-2487
Margareth Mie Nakamura; Sergio Adriano Saraiva; Nina Coichev

Abstract: A careful study of the parameters affecting the chemiluminescent reaction of TCPO (bis(2,4,6-trichlorophenyl)oxalate) and 2-NPO (bis(2- nitrophenyl)oxalate) with hydrogen peroxide, in the presence of imidazole (used as buffer and catalyst) and the fluorophore 3-AFA (3- aminofluoranthene), was carried out in acetonitrile/water medium. The data are reported in terms of the time (t(Imax)) required for the relative maximum chemiluminescence intensity (I-max) and the area (A) under the curve of intensity Ils. time. At controlled acidity and high unprotonated imidazole concentration([IMI] = 1 x 10^-2 mol.L-1), the I-max and t(Imax) values do not depend on the acetonitrile/water ratio. The CL intensity is maximum at around pH 6.0 (higher buffer capacity). For 1 x 10^-2 < [IMI] < 1 x 10^-4 mol.L-1, the area is largest when [IMI] = 1 x 10^-3 mol.L-1 and linearly dependent on the hydrogen peroxide concentration (10^-5 -10^-3 mol.L-1). The area is also enhanced by increasing the fluorophore concentration. The acidity controls the unprotonated imidazole and Hf concentration. Several errors can arise from quantitative analyzes carried out without control of the HIMI+ and IMI concentrations.

"A Microbial Biosensor Using Pseudomonas Putida Cells Immobilised In An Expanded Bed Reactor For The Online Monitoring Of Phenolic Compounds"
Anal. Lett. 1999 Volume 32, Issue 12 Pages 2379-2393
Renu Nandakumar; Bo Mattiasson

Abstract: A cell based biosensor for phenolic substances has been developed. The set up is based on a flow injection system with an expanded bed column with immobilized Pseudomonas cells. The cells were immobilized on glass particles pretreated with poly (ethylene diamine). The system responds to a range of phenolic substances. Storage and operational stabilities are good. The expanded bed concept makes the system reliable also when treating samples with particulate matter.

"Flow Injection Catalytic Determination Of Vanadium Using The Indicator Reaction Between Victoria Blue B And Bromate And A Citric Acid Activator"
Anal. Lett. 1999 Volume 32, Issue 10 Pages 2115-2126
Zhi-Qi Zhang; Xiu-Ping Liu; Han-Ying Zhan

Abstract: A flow injection catalytic method is proposed for determination of trace vanadium based on its catalytic action on a new indicator reaction between Victoria blue B (VBB) and potassium bromate in the presence of citric acid as an activator and in dilute sulfuric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of VBB injected at the maximum absorption wavelength of 618 nm. The detection limit is 0.5 ng mL-1 and is independent of the initial valence state of vanadium. The relative standard deviation is 1.5% obtained from 11 standard solutions each containing 40 ng mL-1 of vanadium. The sampling rate is about 15 samples per hour. This method is very simple and has been applied to the determination of trace vanadium in some natural waters with recoveries of 93-103%.

"Study Of The Simultaneous Determination Of Trace Arsenic And Mercury By Flow Injection/hydride Generation/ICP-AES"
Anal. Lett. 1999 Volume 32, Issue 10 Pages 2105-2114
Yu Xin; Liao Zhenhuan; Jiang Zucheng; Chen Jianguo; Wang Songqin

Abstract: A combined system of flow injection/hydride generation coupled with multichannel plasma spectrometer was put forward and applied to the simultaneous determination of trace arsenic and mercury. The interface between flow injection hydride generation (FI-HG) and ICP-AES, gas/liquid separator and main experimental parameters were described. The detection limits of the proposed method could be achieved to 0.x µg/L level, The RSD 1.4% and 1.3% at 10 ng/mL levels of As and Hg respectively. The frequency of sampling was 150/h with 80 µL sampling volume. The proposed method has been applied to the simultaneous determination of As and Hg in some real samples.
Membrane

"The Determination Of Cadmium, Copper And Lead In Potable Water And Plant Material By Flame-AAS After Online Preconcentration Of DDTP-NH4 Metal Complexes On A C18 Column"
Anal. Lett. 1999 Volume 32, Issue 10 Pages 2091-2104
Silvia M. Sella; Akie K. Avila; Reinaldo C. Campos

Abstract: An online pre-concentration method, based on complex formation with ammonium diethyldithiphosphate (DDTP-NH4) and sorption on a C-18-bonded silica reversed phase sorbent, for the determination of Pb, Cd and Cu in potable water and biological samples was investigated. Preconcentration factors of 25; 38 and 86 and detection limits of 7, 3 and 7 µg/L for Pb, Cd and Cu, respectively, were obtained, with sample throughputs of 26, 38 and 29 samples/h. The system was efficient at low pH ranges and good agreement between found and certified values was observed in the analysis of certified reference materials.
Preconcentration

"Comparison Between Three Amperometric Sensors For Phenol Determination In Olive Oil Samples"
Anal. Lett. 1999 Volume 32, Issue 10 Pages 1981-1990
iviana Campo Dall'Orto; Claudia Danilowicz; Irene Rezzano; Michele Del Carlo; Marco Mascini

Abstract: The analytical performance of two modified electrodes (a tyrosinase biosensor and a glassy carbon electrode (GCE) covered with poly[Ni(protoporphyrin IX)dimethyl ester]) in comparison with the bare electrode has been evaluated in a flow injection system using standard solutions of oleuropein and olive oil samples. The tyrosinase biosensor appeared to be an appropriate device for the selective determination of phenols, moreover it can be easily incorporated in an online system. This method was used to evaluate the stability of the samples.

"The State Of The Art Of Analytical Chemistry In Argentina"
Anal. Lett. 1999 Volume 32, Issue 10 Pages 1939-1959
Gustavo A. Rivas

Abstract: This article focuses on the research activities performed in Argentina in the field of Analytical Chemistry in the last five years. It is organized in four major areas: I) Spectroscopy, II) Mass Spectrometry, III) Chromatography and IV) Electrochemistry. Citations, in general, are limited to journal articles and usually do not include patents, proceedings, reports and dissertations.
Stopped-flow

"An Integrated Microdistillation Flow Injection System For Ammonia Measurement"
Anal. Lett. 1999 Volume 32, Issue 9 Pages 1847-1865
. Lane; C. W. K. Chow; D. E. Davey; D. E. Mulcahy; S. McLeod

Abstract: The development of an online ammonia pre-concentration system based on microdistillation is reported. The combination of microdistillation and flow injection gives rise to an improved analytical technique. This method has good throughput (15-20 samples per hour), requires a small sample volume (6.0 ml) and has a low detection limit (2 µg/l). Microdistillation brings the further advantage of using a pH electrode, non-specific for ammonia, as the sensing device. Evaluation of the method showed excellent correlation with the standard phenate method, and good precision for ammonia determination.
Preconcentration Permeation

"Spectrophotometric And Spectrofluorimetric Determination Of Famotidine And Ranitidine Using 1,4-benzoquinone Reagent"
Anal. Lett. 1999 Volume 32, Issue 7 Pages 1403-1419
Abdel Kader S. Ahmad; M. Abdel Kawy; M. Nebsen

Abstract: Spectrophotometric and spectrofluorimetric methods were adopted for the analysis of Famotidine and Ranitidine depending on their reaction with 1,4 Benzoquinone reagent at pH 5.2 and 5.6, respectively. The absorbances of the resulting condensation products were measured at 502 and 508 nm for Famotidine and Ranitidine, respectively. Concentrations adhering to Beers law were from 40-160 µg mL-1 for Famotidine and from 20-100 µg mL-1 for Ranitidine. Furthermore the resulting condensation products exhibited fluorescence at 665 nm when excited at 290 nm and the calibration graphs were rectilinear from 0.4-1.4 µg mL-1 for Famotidine and from 0.21 µg mL-1 for Ranitidine. Different parameters affecting these reactions were thoroughly studied. Also these methods were applied to the pharmaceutical preparations and the results were satisfactory. The validities of the methods were ascertained by the standard addition technique revealing fine results in consideration to the mean recovery percent and standard deviation. The spectrofluorimetric method was a hundred times more sensitive then the spectrophotometric method. The proposed methods were sensitive, accurate, and precise as statistically compared with the official methods of analysis of Famotidine and Ranitidine.
Pharmaceutical Plasma Human Spectrophotometry Fluorescence Standard additions calibration Standard method Optimization

"A Rapid Method For Mercury Determination In Urine Of Workers Exposed To Mercury Vapor"
Anal. Lett. 1999 Volume 32, Issue 7 Pages 1339-1349
Odair Zenebon; Alice M. Sakuma; Franca D. de Maio; Isaura A. Okada; Jaim Lichtig

Abstract: It is shown that the urine from workers exposed to mercury vapor contains practically only inorganic mercury (II), which can be easily determined by now injection cold vapor atomic absorption spectrometry after adding only HNO3 to the urine at room temperature. If organic mercury is suspected to be present, the sample is treated with KMnO4/ H2SO4 at 80°C -100°C and total mercury is determined. On using HNO3 only, 30 -40 urine samples/h can be easily processed. The method presents good accuracy, precision and high sensitivity, achieving a limit of detection and a limit of quantification (L.O.Q), respectively, of 0.12 mg/L and 0.4 mg/L Hg (II) in the final dilution, using 1.0 mL urine. Urine reference SRM -NIST as well as samples from workers exposed to mercury vapor were analyzed by the proposed methodology.

"A Sensitive Chemiluminescence Flow System For The Determination Of Sulfite"
Anal. Lett. 1999 Volume 32, Issue 6 Pages 1211-1224
Yuming Huang; Chao Zhang; Xinrong Zhang; Zhujun Zhan

Abstract: A novel chemiluminescence (CL) now system for sulfite with flow injection analysis is presented in this paper. It is based on the wet chemiluminescence produced by auto-oxidation of sulfite in the presence of Rh6G, immobilized electrostatically on a cation exchange column. Tween 80 surfactant micelles showed a strong enhancement effect on this weak chemiluminescence. The system responds linearly to sulfite concentration in the range of 0.01-5 mg L-1 (r2=0.996) with a detection limit (3s) of 0.01 mg L-1. Interfering metal ions coexisting in sample solutions could be effectively eliminated online by an upstream cation exchanger. A complete analysis could be performed in 1 min with a relative standard deviation of less than 5% (n=11). The system is stable for over 500 determinations and has been successfully applied to the determination of sulfite in VK3 injections and sulfur dioxide in air.
Immobilized reagent

"Determination Of Nitrite In Aqueous Solutions Using The Linear Sweep Voltammetry Technique"
Anal. Lett. 1999 Volume 32, Issue 6 Pages 1203-1210
R. B. Almeida; S. S. S. Borges; M. G. Gomes

Abstract: An electrochemical method using linear sweep voltammetry techniques was developed to determine nitrite ion in aqueous solution in the presence of nitrate. Nitrite solutions exhibited a well-defined oxidation wave at +1.0 V vs SCE at vitreous carbon, while no oxidation process was observed for nitrate solutions. The pH of the nitrite solutions varied from 2.37 to 5.60 and no change was observed in the Ep values, except for the pH 5.60 solution, where little change was verified. The potential also did not vary with change in the nitrite concentration in the 5.0 x 10^-5 to 7.0 x 10^-4 mol L-1 range. Very good straight lines for plots of current versus nitrite concentration in the 7.0 x 10^-5 to 7.0 x 10^-4 mol L-1 range were obtained; the correlation coefficient was never worse than 0.990. The nitrite determination was also performed in the presence of 1.0 x 10^-3 mol L-1 of NO3-ions. The addition of NO3-did not change significantly the current values even when it was added in one hundred times molar excess.

"Cerium (IV)-based Chemiluminescence Analysis Of Analgin"
Anal. Lett. 1999 Volume 32, Issue 5 Pages 933-943
Yuming Huang; Chao Zhang; Xinrong Zhang; Zhujun Zhang

Abstract: A flow injection chemiluminescence (CL) analysis for the determination of analgin is presented. It is based on the CL reaction of analgin with Ce (IV) in sulfuric acid sensitized by the fluorescent dye Rhodamine 6G. The proposed procedure has a linear range of 0.05-10 µg/mL, with a relative standard deviation (RSD) of 2.1% at 10 ug/mL. The detection limit (3s) is 0.02 ug/mL. The method has been successfully applied to the determination of analgin in tablets.

"Study Of The Catalytic Effect Of Copper(II)-protein Complexes On Luminol-H2O2 Chemiluminescence Reaction And Its Analytical Application"
Anal. Lett. 1999 Volume 32, Issue 5 Pages 901-913
Zhengping Li; Ke'an Li; Shenyang Tong

Abstract: Through flow injection analysis experiments, it was discovered that unsaturated complexes of Cu(ll) with proteins had a much stronger catalytic effect on the luminol-H2O2 chemiluminescence reaction than did Cu(II). Based on this, a new rapid and sensitive method for determination of some proteins in the range 0.1-20.0 µg mL-1 was established. The detection limits were at the 0.03-0.05 µg mL-1 level for bovine serum albumin (BSA), human serum albumin (HSA), human γ-globulin (γ-G), and egg albumin (EA). The method was used for the determination of proteins in human serum with satisfactory results.

"The Determination Of Manganese(II) In Water By Reversed Flow Injection Spectrophotometry"
Anal. Lett. 1999 Volume 32, Issue 4 Pages 787-797
Hui Chen; Dongbin Wei; Taicheng An; Yanjun Fang

Abstract: This paper describes a reversed now injection spectrophotometric method for determination of manganese(II) at low levels. A new chromogenic system TCMOPPH2-Cd(II)-imidazole has been set up using a novel synthetic chromogenic reagent meso-tetra[4-(carboxymethylenoxy)phenyl]porphyrin [TCMOPPH2] by a substitution reaction of Mn(II) and Cd(II)-TCMOPP complex. The linear range extends from 0.01 to 1.75 mg.L-1 with a sampling frequency of 90 h-1. Co(II), Cu(II), Cr(III) and Fe(II) exert no interference until their concentrations are up to 30, 32, 15 and 23 times of that of Mn(II), respectively. The proposed method is proved to be simple, sensitive and suitable for online determination of Mn(II), and it has been used in analysis of Mn(II) in water samples of Liaohe Oil Field water treat plant during the on spot purification. The detection limit was 2.8 µg.L-1.

"Flow-through Solid Phase UV Spectrophotometric Determination Of Amoxycillin"
Anal. Lett. 1999 Volume 32, Issue 4 Pages 729-742
A. Ruiz Medina; M.L. Fernandez de Cordova; A. Molina Diaz

Abstract: The determination of amoxycillin using a flow injection method with spectrophotometric detection is described. The method is based on the measurement of the intrinsic absorbance of amoxycillin fixed on Sephadex QAE A-25 resin. The determination of amoxycillin, using optimized variables, was carried out for three different sample volumes (300, 600 and 1200 µl), giving linear calibration graphs over the ranges 2-50, 1-25 and 0.5-15 µg mL-1, respectively. The relative standard deviations were less than or equal to 1%. The proposed method allows a very sensitive, rapid, and simple determination of amoxycillin in the presence of other penicillins, antibiotics, additives and excipients, without performing a prior separation or derivatization. A noticeable increase in sensitivity and lower detection limits can be easily achieved by increasing the sample volume injected. The method was successfully applied for the determination of amoxycillin in pharmaceutical formulations.

"Enzymatic Flow Injection Analysis Of Metabolites Using New Type Of Oxygen Sensor Membranes And Phosphorescence Phase Measurements"
Anal. Lett. 1999 Volume 32, Issue 4 Pages 701-716
Alexandr N. Ovchinnikov; Vladimir I. Ogurtsov; Wolfgang Trettnak; Dmitri B. Papkovsky

Abstract: A simple system for enzymatic flow injection analysis of metabolites is described which is based on the phosphorescence lifetime based detection of molecular oxygen using phase-modulation techniques and a simple instrument -phosphorescence phase detector equipped with a fiber-optic probe. The phase detector is connected to the oxygen sensor membrane and allows real-time continuous monitoring of the phosphorescence phase shift. This parameter is related to the phosphorescence lifetime of the oxygen probe, therefore giving a measure of the dissolved oxygen concentration, and its changes as a result of the enzymatic oxidative reaction with the substrate. The sensor membrane is positioned in a compact integrated flow-through cell and exposed to the flow stream. Using glucose as a test analyte and glucose oxidase enzyme, two different sensor setups were tested: 1) the membrane type biosensor in which the enzyme is immobilized directly on the oxygen sensor membrane; 2) the microcolumn type biosensor in which the enzyme is immobilized separately, on a microparticle sorbent (controlled pore glass) and put into a microcolumn with the oxygen sensor membrane placed at the column outlet. In either case a new type of oxygen sensitive material was used, which provides a number of advantages over the existing materials. In this material the oxygen-sensitive coating was applied on a microporous scattering support, the latter comprised of a layer of cellulose particles on polyester support. Performance and main working characteristics for the two setups and the new oxygen sensor membranes were investigated and compared.

"Flow Injection Continuous Liquid-liquid Extraction Using A Hollow Fiber Membrane Separator For Determination Of Copper In Water"
Anal. Lett. 1999 Volume 32, Issue 3 Pages 601-612
Pablo Richter; M. Ines Toral; Roberto Manriquez

Abstract: A simple flow injection photometric method for the determination of copper was developed based on the formation and liquid-liquid extraction of the analyte-bathocuproine-perchlorate ternary complex. The analytical reaction of complex formation is integrated with the continuous liquid-liquid extraction procedure. A hollow fiber-type membrane separator was specially constructed for the determination. The analytical properties like sensitivity, precision, accuracy and rapidity were evaluated. The sensitivity of the method depends on the injection volume. By using an injection volume of 0.6 ml, the detection limit (3s) found was 15 ng mL-1 copper, with a determination range of 48 -3000 ng/ml. The repeatability of the method, expressed as the relative standard deviation, was in all instances less than 3.0%. The sampling rate was of 20 h-1. The accuracy of the method was tested with certified reference materials, and the mean error was calculated to be less than 5 %. The method was successfully applied to the determination of copper in river water.

"Flow Injection Spectrophotometric Determination Of Carbofuran In Commercial Pesticides Formulations"
Anal. Lett. 1999 Volume 32, Issue 3 Pages 593-600
R. Zanella; R. M. Dallago; E. M. M. Flores; A. F. Martins

Abstract: A simple and rapid procedure was developed for the flow injection (FI) spectrophotometric determination of carbofuran in pesticides formulations. The determination was based on the alkaline hydrolysis, at room temperature, of the carbofuran to yield carbofuran-phenol which can be coupled with diazotized sulfanilic acid in order to achieve an appropriate selectivity and sensitivity. The calibration graph is linear over the range 0.5-60 mg / L of carbofuran. The method has provided a detection Limit of 0.5 mg / L, and the precision was better than 0.6% (RS.D.) at a throughput of 80 samples per hour.

"Chemiluminescence Determination Of Sulfur Dioxide In Air Using Tris(1,10-phenanthroline)ruthenium-KIO4 System"
Anal. Lett. 1999 Volume 32, Issue 2 Pages 401-410
Zhike He; Fengwu Wu; Hui Meng; Liangjie Yuan; Qingyao Luo; Yun'e Zeng

Abstract: The emission produced by sulfite in its oxidation by periodate in acidic solution in the presence of Ru(phen)(3)(2+) is used to determine 1.0 x 10^-7 to 1.5 x 10^-4 mom sulfite. The limit of detection is 7 x 10^-10 mol/L and the relative standard deviation is 2.3% for a 4 x 10^-5 mol/L sulfite solution (n=9). The method was applied satisfactorily to the determination of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.

"Application Of An Ion Pair Reagent To Biosensors"
Anal. Lett. 1999 Volume 32, Issue 2 Pages 251-269
Yu-Qing Zhang; Ren-Ao Gu; Wei-De Shen; Xiao-Jian Zheng

Abstract: The biosensors based on the enzyme electrode in a flow injection analysis suffer an interference from hemacyte, macromolecules and some lower molecular weight species in whole blood, plasma, serum or urine, besides endogenous electroactive species such as ascorbate. This often results in an increasingly serious tailing phenomenon in the response current peak of substrates. A unique method used daily is to cover the outer enzyme membrane with a porous ultrafilter film to isolate it from hemacyte and macromolecules but not from some smaller molecules. In the present paper, we first introduce a tailing inhibitor-ion pair reagent into the flowing buffer system for eliminating the tailing phenomenon from the complex matrices on biosensors. When 0.25 or 0.5% tetrabutylammonium chloride (V/V) was added to 0.02 M phosphate buffer, serious lags of whole blood, plasma, serum and urine on the two biosensors for uric acid and glucose disappeared entirely so that their response time was shortened to about 50 seconds; their base lines also became more smooth and stable. Thus, the resulting two biosensors were capable of detecting over 60 biosamples per hour. The reported experiment shows that the tailing inhibitor has effects on the response current and response time of various biosamples and on the concentration of the dissolved oxygen in buffer, with no evident effect on the recoveries of glucose and mate in biosamples with both sensors. The finding confirmed that some lower molecular weight species with negative charge result in the serious tailing phenomenon in the response current peaks of various biosamples on the glucose and mate biosensors in a now injection system.
Membrane

"Sequential Simplex Optimization - An Update"
Anal. Lett. 1999 Volume 32, Issue 2 Pages 193-212
Frederick Walters

Abstract: Sequential Simplex Optimization was popularized by Deming and coworkers at Emory University and the University of Houston in the 1980s. A text, Sequential Simplex Optimization was published by CRC Press in 1991. This article provides an updated bibliography from 1992 to present.
Chemometrics

"Analysis Of Metals In Marine Sediments By Microwave Extraction And Flame, Hydride Generation And Cold Vapor Atomic-absorption Spectrometry"
Anal. Lett. 1999 Volume 32, Issue 1 Pages 139-157
M. L. Martinez-Garcia; A. Carlosena Zubieta; S. Muniategui Lorenzo; P. Lopez-Mahia; D. Prada Rodriguez

Abstract: A simple and fast metal extraction method that combines closed vessels and microwave heating for the simultaneous extraction of ten selected heavy metals (As, Cd, Co, Cr, Hg, Mn, Ni, Ph, Zn) from marine sediments is proposed. Digestion conditions, i.e. power and times microwave irradiation, reagent extractant, sample amount, were optimized to recover the potentially available metallic fraction not bound in silicates. A nitric acid and two step microwave program was established. The resulting solutions were analyzed by flame (FAAS) hydride generation (HG-AAS) and cold vapor (CV-AAS) atomic absorption spectrometry. Quantifications were made using direct calibration with aqueous standards. The recoveries of the spiked samples investigated ranged from 89 to 113%. The results obtained from analyzing the BCR certified reference sediment CRM 277 Estuarine Sediment were in good agreement with the certified values (93-105%), except for low values for chromium (79%). The relative standard deviations for the determination of metals were less than 4%. Finally, the technique designed herein was applied to sediment samples from La Coruna estuary, NW Spain.

"Flow Injection Spectrophotometric Determination Of Nickel By Complexation And Factorial Design Optimization Method"
Anal. Lett. 1999 Volume 32, Issue 1 Pages 111-122
Ali A. Ensafi; T. Khayamian; B. Hemmateenejad

Abstract: A simple flow injection method is proposed for the determination of nickel by its complexation with ammonium 2-amino-cyclohexene dithiocarbamate (AACD). The dark red complex can be detected by spectrophotometric determination at 535 nn. The FIA factors that influence on sensitivity were optimized by factorial design analysis. The model of absorbance vs. these factors was constructed and the correlation of these factors with each other was studied. Nickel can be determined as low as 0.007 µg/ml and Beers law was obeyed in the range of 0-2.5 µg/ml of Ni(II). The effect of more than thirty potential interfering cations and anions were studied. The evaluation of the method was examined by the determination of Ni(II) in hydrogenated vegetable oil and synthetic samples.

"Amperometric Detection With Microelectrodes In FIA: Studies On The Conversion Of Nitrate To Nitrite In Human Saliva"
Anal. Lett. 1999 Volume 32, Issue 1 Pages 25-37
Vania Mori; Mauro Bertotti

Abstract: A flow injection method for the determination of nitrate and nitrite in human saliva is described, It is based on the reaction of nitrite with iodide in acidic medium, the triiodide formed being amperometrically monitored at +0.2 V with a platinum microelectrode (r = 5 µm) in a wall-jet cell. The method is very sensitive owing to the association of hydrodynamic transport in a flowing solution and the high mass transport rate at a microelectrode, the limit of detection for nitrite and nitrate being 0.07 and 0.25 µM respectively. The sample throughput was 60 h-1 and the standard deviation for 5 injections of 1 µM nitrite was 1.9% (1.3% for nitrate). The method was used in the study of the conversion of nitrate to nitrite in the oral cavity by bacteria, experimental data concerning die salivary concentration of both ions being obtained before and after treatment with an antiseptic solution. The results showed the decline of nitrite concentration after the oral treatment followed by a proportional increase in the nitrate concentration, proving that the majority on salivary nitrite comes from bacterial reduction of nitrate.

"Chemiluminescence Flow Injection System For Rapid Detection Of Red Tide Phytoplankton, Chattonella Antiqua"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2279-2288
Ryoichi Asai; Ritsuko Matsukawa; Kazunori Ikebukuro; Isao Karube

Abstract: A chemiluminescent flow injection analysis (FIA) system to detect the red tide phytoplankton, Chattonella antiqua, was developed based on a Cypridina luciferin analog, 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-α]-pyrazin-3-one (MCLA), which strongly emits light at 465 nm in the presence of superoxide. The system consists of a 2-reagent feeding stream, a sample injector, a joint for mixing MCLA and sample, a chemiluminescence (CL) reaction cell, a CL detector, and a recorder unit. Response time is ~1 min/measurement cycle. The FIA system has an optimum pH of 10.7. Calibration curves for C. antiqua displayed linearity from 2 x 103 to 2 x 104 cells/mL. When used to measure C. antiqua, sensitivity of the FIA system was ~10 times higher than that of the cytochrome c method. The FIA system is a rapid, practical method to detect C. antiqua.
Phytoplankton, chattonella antiqua, red tide Sea Chemiluminescence Optimization pH Method comparison

"Flow Injection Spectrophotometric Determination Of Free And Total Sulfite In Wines Based On The Induced Oxidation Of Manganese(II)"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2195-2208
Rosa Lina G. N. P. Silva; Cintia S. Silva; Joaquim A. N&oacute;brega; Eduardo A. Neves

Abstract: The sulfur(IV) content in wines was determined with a flow injection spectrophotometric system by treating each sample in the donor channel with sulfuric acid to release free SO2, which diffuses through a PTFE membrane to the acceptor solution containing Mn(II) in acetate buffer at pH 5.5. The induced oxidation of Mn(II) takes place proportionally to the free S(IV) content and the oxidized species formed reacts with iodide to form iodine which can be spectrophotometrically measured at 352 nm. A linear plot of absorbance vs. S(IV) concentration. is observed up to 26 mg SO2/L with a detection limit of 1.0 mg/L. Matrix effects required the standard additions of sulfite to the samples for obtaining accurate results. A previous treatment of the sample with tris(hydroxymethylaminomethane) and EDTA decomposed the hydrogen-sulfite/aldehyde adducts and allowed the determination of the total S(IV) content. As expected, total S(IV) concentration. in wines has been found to be much higher than free sulfite. A recovery-addition experiment with red and white wines led to recoveries varying from 91.5 to 109.7% by applying the free and total sulfite developed procedures. This is a good indication of the accuracy of both proposed procedures.
Sulfite Wine Red Wine White Spectrophotometry Teflon membrane Gas diffusion Indirect Standard additions calibration

"Dilution Methods In Flow Injection Analysis. Evaluation Of Different Approaches As Exemplified By The Determination Of Nitrosyl In Concentrated Sulfuric Acid"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2181-2194
Ulla V. J&oslash;rgensen; Steffen Nielsen; Elo H. Hansen

Abstract: Instigated by developing a flow injection procedure for assay of nitrosyl in concentrated H2SO4, different approaches for reliable and robust online dilution in FIA were evaluated. These comprised the application of mixing tees in conjunction with mixing coils (including knotted reactors) of different internal diameter, zone sampling, the use of a mixing chamber, micro-sampling, and sample injection by pseudo-hydrodynamic injection. The individual approaches are described in detail, their advantages and disadvantages being emphasized in regard to their practical applicability. For each approach the criteria stipulated were that the procedure should allow a dilution factor of ~100, yet without excessive zone spreading, so that it, on one hand, could effectively eliminate the pronounced Schlieren effect encountered when mixing concentrated H2SO4 with an aqueous diluent, and, however, would permit the sample material to be appropriately conditioned for the ensuing chemical derivatization procedure. This most reliably could be effected by a combination of pseudo-hydrodynamic injection comprising a mixing point and the use of mixing tees in conjunction with knotted reactors of relatively large internal diameter (1.5 mm). The optimized FI-manifold was used with the Griess method for the spectrophotometric assay of nitrosyl (nitrite) in standards prepared in the matrix of concentrated H2SO4 (detection limit 0.16 mg/L NO+-N (3s)) and in practical WSA-samples.
Nitrosyl Concentrated Spectrophotometry Optimization Dilution Manifold comparison Dispersion Knotted reactor Zone sampling Mixing chamber Hydrodynamic injection

"Direct Electrochemistry Of Hemoglobin At Silver Electrode Modified By Lipoic Acid Monolayer"
Anal. Lett. 1998 Volume 31, Issue 13 Pages 2159-2171
Song Zhang; Wen-liang Sun; Wen Zhang; Katsunobu Yamamoto; Shuguang Tao; Jiye Jin

Abstract: The direct electrochemistry of Hb was studied by cyclic voltammetry (CV) and flow injection analysis (FIA) on a silver electrode modified by a self-assembled monolayer of lipoic acid (LA). Lipoic acid molecules can strongly absorb onto the Ag electrode surface through the cleavage of the S-H bond and the formation of the Ag-S bond. The observed adsorption coverage of LA demonstrates that the LA molecules spontaneously form a self-assembled monolayer. Experimental data show that LA can promote the redox process of Hb at the modified electrode surface. This chemical modified electrode (CME) exhibits good stability in the CV and FIA. Linear sweep voltammetric measurement of Hb at the CME reveals a linear relationship between the oxidative peak current and the concentration of Hb in the range of 5.0 x 10^-7 - 1.5 x 10^-5 mol/L. The relative standard derivation (RSD) for six replicate measurements of 5.0 x 10^-6 mol/L Hb in FIA is 2.8%. The detection limit is 2.0 x 10^-7 mol/L. The reaction mechanism involves the hydrogen bond/salt bridge formation between the carboxylate of LA and the protonated lysine residues of Hb that can enhance the electron transfer reaction. It can be used to detect Hb in real examples.
Hemoglobin Voltammetry Electrode Electrode Apparatus Detector

"Flow Injection Chemiluminescence Determination Of Etamsylate With Electrogenerated Hypochlorite"
Anal. Lett. 1998 Volume 31, Issue 11 Pages 1917-1928
Chengxiao Zhang; Jiachu Huang; Manliang Feng; Zhujun Zhang

Abstract: A fast and simple method for the determination of etamsylate is described. The method uses chemiluminescence intensity quenching in the luminol-hypochlorite system with electrogenerated unstable reagent in a flow injection setup. The system anal. response was linear in the etamsylate concentrations range of 1 x 10^-9 to 8 x 10^-9 g/mL. The detection limit was 6 x 10^-10 g/mL. The relative standard deviation was 3.1% at 2 x 10^-9 g/mL. The method is suitable for automated and continuous anal. and was tested for determination of etamsylate in pharmaceutical formulations.
Etamsylate Pharmaceutical Chemiluminescence Electrochemical reagent generation Indirect Quenching

"Flow Injection Determination Of Glucose By A Photoinduced Chemiluminescent Reaction"
Anal. Lett. 1998 Volume 31, Issue 11 Pages 1837-1855
Tomas Parez-R&uacute;z; Carmen Martinez-Lozano; Virginia Tomas; Antonio Sanz

Abstract: A flow injection procedure for the photochem. determination of glucose was developed. The method is based on the photooxidn. of glucose sensitized by 9,10-anthraquinone-2,6-disulfonate (disodium salt). The hydrogen peroxide formed in the photochem. reaction was measured by the chemiluminescent reaction with luminol and hematin. A linear calibration graph was obtained over the range 2.0 x 10^-6-8.5 x 10^-5 mol L-1. The method was applied to determining glucose in blood serum, urine and fruit juices.
Glucose Blood Serum Urine Fruit Chemiluminescence Photochemistry

"Flow Injection Spectrophotometric Determination Of Oxalate, Citrate And Tartrate Based On Photochemical Reactions"
Anal. Lett. 1998 Volume 31, Issue 8 Pages 1413-1427
Tom&aacute;s P&eacute;rez-Ruiz; Carmen Mart&iacute;nez Lozano; Virginia Tom&aacute;s; Antonio Sanz

Abstract: A flow injection configuration for the spectrophotometric determination of oxalate, citrate and tartrate is proposed. The procedure is based on the photochem. decomposition of the complexes formed between iron(III) and these anions. The iron(II) produced in the photochem. reactions was detected by measuring the absorbance after complexation with ferrozine (λmax=562 nm). Linear calibration graphs were obtained over the concentration. ranges 5.0 x 10^-6 - 1.0 x 10^-4 M, 8 x 10^-6 - 1.8 x 10^-4 M and 1.0 x 10^-6 - 2 x 10^-5 M for oxalate, citrate and tartrate, respectively. The relative standard deviations at the 1 x 10^-5 M concentration. level were within the range 1.29 - 1.47%. The sampling frequency was about 40 samples/h. The usefulness of the method was tested in the determination of oxalate in urine and spinach, of citrate in pharmaceuticals and soft drinks and of tartrate in pharmaceuticals. For the determination of oxalate in urine samples a prior separation of the analyte by precipitation with calcium chloride is recommended.
Oxalate Citrate Tartrate ion Pharmaceutical Soft drink Urine Vegetable Spectrophotometry Photochemistry Complexation

"Spectrofluorimetric Determination Of Iproniazid And Isoniazid In A FIA System Provided With A Solid Phase Reactor"
Anal. Lett. 1998 Volume 31, Issue 7 Pages 1209-1218
J. A. Garc&iacute;a Bautista; J. V. Garc&iacute;a Mateo; J. Mart&iacute;nez Calatayud

Abstract: A single-channel flow injection analysis (FIA) assembly is proposed for the fluorimetric determination of iproniazid and isoniazid. The oxidation of both drugs was carried out by H2O2. The excess of reagent was destroyed and removed from the flow injection manifold by a metallic copper reactor which acted as a catalyst in the decomposition of H2O2 and a degaser. The calibration graphs were linear up to 14 µg iproniazid/mL and 10 µg isoniazid/mL and the respectively. limits of detection were 0.008 and 0.005 µg/mL. The sample throughput was 24 h-1 for both drugs. The influence of interfering compounds was evaluated and the procedure was applied to the determination of iproniazid and isoniazid in pharmaceutical formulations.
Isoniazid Iproniazid Pharmaceutical Fluorescence Interferences Reduction column

"Flow Injection Fluorometric Determination Of Cationic Surfactants Using 3,6-bis(dimethylamino)-10-dodecylacridinium Bromide"
Anal. Lett. 1998 Volume 31, Issue 6 Pages 1071-1079
Takashi Masadome

Abstract: The anionic surfactant Na dodecylbenzenesulfonate (DBS) reacts with 3,6-bis(dimethylamino)-10-dodecylacridinium bromide (AO-10-D) to quench the fluorescence of AO-10-D. When a cationic surfactant is added to the mixed solution of AO-10-D and DBS, the fluorescence intensity increases with increasing concentration. of cationic surfactant because added cationic surfactant preferentially forms an ion associate with the DBS. The detection of increase in the fluorescence intensity was applied to the flow injection determination of a cationic surfactant. Cationic surfactants such as Zephiramine could be determined in the concentration. range from 1 x 10^-6 to 4 x 10^-5 mol/L by the proposed method. The sampling rate was ~10 samples h-1. The presence of Triton X 100, tetramethylammonium chloride, or tetraethylammonium chloride at concentrations. of 5, 25, or 25 times, respectively, in excess of that of the cationic surfactant did not interfere with the determination of the cationic surfactant.
Surfactants, cationic Zephiramine Fluorescence Indirect Interferences

"Rapid Determination Of Warfarin By Sequential Injection Analysis With Cyclodextrin-enhanced Fluorescence Detection"
Anal. Lett. 1998 Volume 31, Issue 5 Pages 891-901
Lian X. Tang; Frederick J. Rowell

Abstract: A procedure for rapid and reproducible measurement of warfarin was described. The method is based on a computer-controlled sequential injection analysis (SIA) system. The formation of drug inclusion complexes with β-cyclodextrin in aqueous solution was used to obtain fluorescence enhancement. Cyclodextrin and warfarin solutions were sequentially injected and mixed within seconds using the automated system and the fluorescence was monitored immediately. The calibration curve was linear over the measured concentration. range of 0.1 to 1 µg/mL (r2 = 0.998, n = 5) with a limit of detection of 0.02 µg/mL. The measurement was fast with response time of 20 s, and was also reproducible with coefficient of variation at 1.5%(n=10) at a concentration. of 0.5 µg/mL. Water samples spiked with warfarin were successfully measured using the method.
Warfarin Water Fluorescence Sequential injection Complexation

"Flow Injection Potentiometric Determination Of Atrazine In Herbicide Formulations"
Anal. Lett. 1998 Volume 31, Issue 5 Pages 777-791
Saad S. M. Hassan; M. N. Abbas; G. A. E. Moustafa

Abstract: A novel atrazinium-selective membrane sensor consisting of an atrazine phosphomolybdate ion-pair complex dispersed in a PVC matrix plasticized with dioctyl phthalate is described and electrochemistry evaluated under static and hydrodynamic modes of operation. The sensor is incorporated in a flow-through sandwich cell and used as a detector for flow injection determination of atrazine herbicide. The intrinsic characteristics of the detector in a low-dispersion manifold are determined and compared with those of a conventional-shaped sensor. In a phosphate buffer of pH 5, the detector exhibits a rapid near-Nernstian response (52.3 mV/decade) for atrazinium cation over the concentration. range 10^-2-10-5M. Concentrations as low as 0.3 µg atrazine/mL can be detected with an average recovery of 98.3% (mean standard deviation 0.6%), and the sample input rate is 60 sample per h. The sensor is used for determining atrazine in herbicide formulations, and in extracts of water and soil. No interferences are caused by herbicide diluents and excipients nor by most common anions and cations normally present in water and soil. The results compare favorably with data obtained by gas chromatography
Atrazine Commercial product Environmental Environmental Potentiometry Electrode Electrode Electrode Sample preparation Interferences Method comparison

"Flow Injection Biamperometric Determination Of Nitrite And Nitrate"
Anal. Lett. 1998 Volume 31, Issue 5 Pages 751-764
Andrei F. Danet; Vasile David

Abstract: A simple and efficient FIA method was used with good results to determine nitrite in residual waters and nitrate in natural waters. Nitrite determination is based on the reaction with iodide occurring in acidic media and biamperometric detection of the formed iodine at 2 Pt electrodes polarized at 100 mV. Nitrate is similarly determined after its previous reduction to nitrite in a Cd column. The method does not need the solution deaeration. However, the calibration graphs present 2 regions of linearity owing to the catalytic effect of the dissolved O on the iodide oxidation by nitrite.
Nitrate Nitrite Environmental Biamperometry Electrode Reduction column Interferences

"A Fluorescence-based Sensor For Ammonium And Nitrate"
Anal. Lett. 1998 Volume 31, Issue 4 Pages 555-567
Satoshi Sasaki; Yoshihiro Ando; Makiko Dejima; Yoshiko Arikawa; Isao Karube

Abstract: Measurement of nitrite and nitrate in rain samples was performed using a fluorescence-based sensor. Nitrite and nitrate were reduced to ammonia using Devarda's alloy, and the gas was then passed through a membrane and reacted with o-phthaladehyde. A linear relationship between the nitrate concentration and the luminescence intensity was observed over the concentration range of 1-5 mg/l, with a relative standard deviation (RSD) of 2.3% at a nitrate concentration of 1 mg/l (n = 5). The system did not show any response toward sulfate or chloride. Results obtained from the measurement of river water samples using the sensor showed good agreement with those obtained using a conventional method.
Ammonium Nitrate Nitrite River Rain Fluorescence Method comparison Membrane Interferences

"Aza-arenophilic Gels As Supports For The Reversible Immobilization Of Enzymes-bioanalytical Applications"
Anal. Lett. 1998 Volume 31, Issue 4 Pages 543-553
S. Jogie; D. Narinesingh; T. T. Ngo

Abstract: A method is described for the simple, reversible immobilization of enzymes to an aza-arenophilic support. The support is prepared by reacting Sepharose CL-4B first with 3,5-dichloro-2,4,6-trifluoropyridine and 4-dimethylaminopyridine followed with 2-mercaptoethanol. The enzymes were non-covalently adsorbed using a phosphate buffer (0.5M, pH 7.4) and readily desorbed using sodium acetate (0.1 M, pH 2.9). The same solid support could be used many times to reversibly bind enzymes. Urease bioreactors prepared by this method were incorporated into a flow injection manifold and used for the quantitation of urea. Calibration curves were found to be linear up to 120 mgdL-1 urea with a detection limit of 0.08 mgdL-1. Recovery yields varied between 98 - 103%. The within day RSD was <1.9% and the day to day RSD was <2.8 for a 20 mgdL-1 solution. There was no detectable decrease in bioreactor activity over a period of 34 days. Up to 18 urea samples can be analyzed manually per hour.
Urea Immobilized enzyme

"A Simple Optical Flow Injection Ammonia Sensor"
Anal. Lett. 1998 Volume 31, Issue 3 Pages 395-410
B. Kuswandi; R. Narayanaswamy

Abstract: The optical system consisted of a 100-W quartz halogen lamp light source, modulated by an optical chopper and focussed by means of a lens onto one branch of a bifurcated optical fiber, the end of which was positioned near the surface of a non-bleeding cellulose-immobilized pH indicator strip; the other arm of the bifurcated optical fiber served to lead the reflected light to a photomultiplier tube, coupled to a current amplifier and a lock-in amplifier. The indicator strip was mounted in a flow cell equipped with a hydrophobic gas membrane to permit diffusion of the analyte. The system was used as a detector for a FIA system for the assay of ammonia, using a water carrier stream (0.75 ml/min) and a 10 mM NaOH reagent stream (0.75 ml/min). The sample solution containing ammonia was merged with the reagent stream and a 150-l portion of the mixture was injected into the carrier stream and pumped through the flow cell. The ammonia present in the mixture diffused through the gas membrane, resulting in a color change of the indicator strip; this change was monitored at 620 nm by the photomultiplier tube. Response was linear for the range 1-7 mM ammonia. The method was also applied for the assay of urea using 0.06% urease in 20 M Tris-HCl buffer of pH 7 as the carrier solution. Response was linear for 2-10 mM.
Ammonia Sensor Apparatus Detector

"Flow Injection Analysis Determination Of Ascorbic Acid With Spectrofluorometric Detection"
Anal. Lett. 1998 Volume 31, Issue 2 Pages 333-342
Ali A. Ensafi; B. Rezaei

Abstract: A flow injection system for the fluorescence determination of low level of ascorbic acid is proposed. The method is based on the rapid oxidation of ascorbic acid by Tl(I). The fluorescence signal at 419 nm is proportional to the amt. of ascorbic acid in the range of (1.4-28.0) x 10^-7 mole. The relative standard deviations for ten replicate measurements of 1.4 x 10^-6 mole of ascorbic acid was 1.3%. The sample rate of 45 ± 5 sample per h was achieved. The usefulness of the method was tested in the determination of ascorbic acid in fruit juices and vitamin C tablets.
Ascorbic acid Fruit Pharmaceutical Fluorescence Indirect

"Flow Injection Spectrophotometric Determination Of Amino Acids By Using 1,2-naphthoquinone-4-sulfonate Immobilized On An Ion Exchange Resin"
Anal. Lett. 1998 Volume 31, Issue 2 Pages 313-331
M. Vela; J. Saurina; S. Hern&aacute;ndez-Cassou

Abstract: A spectrophotometric flow injection method based on the immobilization of 1,2-naphthoquinone-4-sulfonate reagent in an anion-exchange Amberlite IRA 904 packed reactor is proposed for the determination of amino acids. The reagent was attached on this solid bed by electrostatic binding between the sulfonate and the ammonium quaternary groups. This solid phase reactor was used as a source of reagent since it could be desorbed by a HCl solution The reagent liberated to the flow system reacts with the amino acids in a thermostated reaction coil to give the corresponding derivatives The spectrophotometric detection was performed at 480 nm. For glycine, the response was linear up to 1.5 x 10^-3 M, the detection limit was 5.3 x 10^-4 M, the repeatability 0.4% and the reproducibility 5.4%. The method was applied to the anal. of some amino acids in several pharmaceutical samples. Results obtained were in good agreement with those from the standard method for amino acid anal.
Amino Acids Glycine Pharmaceutical Spectrophotometry Amberlite Immobilized reagent Method comparison

"Automatic Liquid-liquid Extraction Flow Injection Analysis Determination Of Trace Amounts Of Perchlorate With Spectrophotometric Detection"
Anal. Lett. 1998 Volume 31, Issue 1 Pages 167-177
Ali A. Ensafi; B. Rezaei

Abstract: An extractive flow injection analysis for rapid, sensitive and selective determination of perchlorate by spectrophotometric detection is proposed. The method is based on the extraction of perchlorate with Brilliant Cresyl Blue into Me iso-Bu ketone at pH 6.0. Perchlorate can be determined at 0.008-1.00 µg/mL with a limit of detection of 0.003 µg/mL and rate of 30 ± 5 samples/h. The effects of reagent concentration, pH, manifold variables and diverse ions are completely studied. The usefulness of the method was tested for the determination of perchlorate in salt samples.
Perchlorate Inorganic compound Spectrophotometry Solvent extraction MIBK Optimization

"Potentiometric Flow Injection Detection Of Copper(II) With A Graphite Carbon Electrode"
Anal. Lett. 1998 Volume 31, Issue 1 Pages 13-25
ZuLiang Chen; Peter W. Alexander

Abstract: A graphite C electrode was evaluated in a potentiometric flow injection system for the detection of Cu2+. The electrode response characteristics were studied by both cyclic voltammetry and potentiometry, and probably the electrode potential change results in the adsorption of Cu2+ at the electrode surface. The C electrode was used for the flow injection potentiometric detection of Cu2+ in 0.05 mol/L NaOAc-0.2 mol/L NaCl at pH of 6.0 carrier solution A linear response in concentration. range of 1 x 10^-5-1 x 10^-2 mol/L was obtained with a detection limit of 5 x 10^-5 mol/L. The electrode described in this paper is simple and low cost.
Copper(II) Sea Electrode Potentiometry Apparatus Detector

"Flow Injection Determination Of Chloride Ions With Spectrophotometric Detection"
Anal. Lett. 1997 Volume 30, Issue 15 Pages 2847-2858
Mihaela Cheregi; Andrei F. Danet

Abstract: A single-line FIA system with a stream-sample splitting device for chloride determination is presented. The analytical method is based on the Fe3+/Hg(SCN)2/Cl- system and the absorbance of the red Fe(SCN)2+ species monitored spectrophotometrically at 480 nm. Using a stream-sample splitting device, the recorded signal is composed of two merged peaks. Three calibration curves were obtained, once injecting the standard solution series, two using the maximum heights of P1 and P2 peaks and one using the height of T trough. The FIA system showed three linear responses to the concentration of chloride in the ranges 10^-100 ppm (P1)-, 10^-500 ppm (P2) and 20-1000 ppm (T), respectively. Also, it was capable of detecting chloride ions in different types of water with a throughout of 15 samples h-1 and the RSD for 240 ppm of Cl- (n = 10) were 1.67% (P1); 2.38% (P2) and 1.23 % (T), respectively. The interference of several ions (commonly found in water) on the FIA outputs was investigated.
Chloride Water Spectrophotometry Interferences Sample splitting

"Application Of Flow Injection Method For The Determination Of Thioridazine"
Anal. Lett. 1997 Volume 30, Issue 15 Pages 2733-2742
A. Kojlo; E. Wolyniec; H. Puzanowska - Tarasiewicz

Abstract: A simple flow injection spectrophotometric method for the determination of thioridazine is described. The method is based on the oxidation of thioridazine with phosphotungstic acid in hydrochloric acidic media. Concentrations of thioridazine in the range 10 - 60 ppm are determined with a relative standard deviation of 1.1%. The method was applied to the determination of thioridazine in pharmaceutical formulations.
Thioridazine Pharmaceutical Spectrophotometry Redox

"Electrocatalytic Oxidation And Flow Detection Of NAD(P)H At A Histidine Modified Silver Electrode"
Anal. Lett. 1997 Volume 30, Issue 15 Pages 2691-2703
Long Yi-Tao; Zou Jie; Chen Hong-Yuan

Abstract: L-Histidine, a biologically important amino acid, has been modified onto the silver electrode through covalent bonding. The coenzyme dihydronicotinamide adenine dinucleotide (NAD(P)H) was electrocatalytically oxidized to NAD(P)+ at the L-histidine modified silver electrode (His/Ag). The electrochemical processes at the His/Ag electrode were investigated by using UV-visible spectroelectrochemistry in detail. Amperometric determination of NAP(P)H, at a potential of 0.25 V (SCE) gave a linear response in the range of 1 x 10^-7 - 2 x 10^-5 mol/L with a detection limit of 0.05 µmol/L. The His/Ag electrode has been used in a FIA system with satisfactory results. Meanwhile, other proteins and chemicals present in samples do not interfere in the assay.
Nicotinamide adenine dinucleotide oxidized Nicotinamide adenine dinucleotide phosphate oxidized Biological Electrode Electrode Amperometry Interferences

"Flow Injection Determination Of Hydrogen Peroxide Using A Carbon Paste Electrode Modigied Witha Manganese Dioxide Film"
Anal. Lett. 1997 Volume 30, Issue 15 Pages 2655-2673
Klemens Schachl; Hailemichael Alemu; Kurt Kalcher; Jitka Jezkova; Ivan Svancara; Karel Vytras

Abstract: The parallel C paste electrodes of a thin-layer flow cell were coated with a MnO2 film by passing deaerated NH3/NH4Cl buffer (buffer A) containing 20 mg/l Mn2+ (as chloride) through the cell at 0.5 ml/min whilst applying 0.6 V for 60 min. Rain water (100 ml) was mixed with 100 l buffer A and a portion (50 l) of the solution was injected into a flow (1 ml/min) of 0.2 M buffer A which then passed through the thin-layer flow cell for detection of H2O2 at 0.46 V vs. Ag/AgCl. The calibration graph was linear from 1-450 mg/l H2O2, the detection limit was 4.7 g/l H2O2, the RSD (n = 10) at 10 g/ml H2O2 was 2.3% and the electrodes were stable for 14 days. The effects of interferents are tabulated. Recoveries of H2O2 from spiked rain water were 97.9-102%.
Hydrogen peroxide Rain Amperometry Electrode Electrode Interferences

"Flow Injection Determination Of L-ascorbic Acid In Natural Juice With Biamperometric Detection"
Anal. Lett. 1997 Volume 30, Issue 14 Pages 2625-2640
Mihaela CHEREGI; Andrei F. DANET

Abstract: A flow injection system with biamperometric detection for L-ascorbic acid (vitamin C) determination was designed. The method is based on L-ascorbic acid oxidation to dehydroascorbic acid, in acidic medium, using iodine-iodide solution as oxidizing reagent. The iodine amount consumed in the redox reaction was biaperometrically detected and it was proportional to the amount of L-ascorbic acid from the sample. The calibration graph was linear over the range of concentration 5 X 10^-5 -5 X 10^-4 M of vitamin C. The RSD for a 2.5 X 10^-4 M standard solution of vitamin C was 1.08% (n=10) and the throughput was 60 samples h-1. The selectivity of the proposed FIA method was verified using an ascorbate oxidase solution as carrier stream. It was found that L-ascorbic acid could be determined in natural products with a good selectivity and rapidity.
l-Ascorbic acid Fruit Biamperometry Indirect Selectivity

"Batch And Flow Injection Fluorimetric Determination Of Fluoxetine"
Anal. Lett. 1997 Volume 30, Issue 14 Pages 2493-2502
Gonzalez Martin, M.I.;Gonzalez Perez, C.

Abstract: A method for the fluorimetric determination of fluoxetine in continuous and discontinuous systems is reported. The method is based on the hydrolysis of fluoxetine in acid medium. The fluorescent product has a spectrum with excitation and emission maxima at 253 and 306 nm respectively. The method was applied to the determination of fluoxetine in pharmaceutical products.
Fluoxetine Pharmaceutical Fluorescence Batch injection analysis

"A Bioelectrochemical Method For The Determination Of Acetate With Immobilized Acetate Kinase"
Anal. Lett. 1997 Volume 30, Issue 14 Pages 2469-2483
Xiao-Jing Tang; Gillis Johansson

Abstract: sample solution containing acetate was injected into a flow (0.1 ml/min) of water, which merged with a flow (0.1 ml/min) of 0.1 M imidazole buffer of pH 7.6 containing 0.1 M KNO3, 0.015 M magnesium nitrate, 6 mM ATP, 2 mM phosphoenolpyruvate and 0.25 mM NADH and then passed through an enzyme reactor containing acetate kinase, pyruvate kinase and lactate dehydrogenase. The stream then merged with a flow (0.1 ml/min) of 0.1 M sodium acetate buffer of pH 4.5 and passed through a flow cell equipped with a Meldola Blue-modified graphite working electrode, a Pt auxiliary electrode and a SCE reference electrode for amperometric detection at an applied voltage of 0 V. The calibration graph was linear from 0.3-2 mM acetate, the detection limit was 0.2 mM acetate and the RSD was 3.4%. The method was suited to the determination of acetate in fermentation liquors where acetate is the carbon source.
Acetate ion Fermentation broth Electrochemical analysis Immobilized enzyme

"Indirect Potentiometric Determination Of Chlorpromazine With An Oxidative Column In A Flow Injection System"
Anal. Lett. 1997 Volume 30, Issue 13 Pages 2353-2363
Anatol Kojlo

Abstract: A flow injection method is proposed for the determination of chlorpromazine and other N-substituted phenothiazines. The procedure is based on the oxidation of analyte with lead dioxide entrapped into polymeric material in a packed-bed reactor. The oxidation of the drug yields soluble Pb-2+, which is monitored by means of the lead ion selective electrode in the wall-jet configuration. The calibration graph is linear over the range of 0.01-2 µg mL-1 of chlorpromazine with relative standard deviation of 1.4% and sample throughput 20 h-1. The developed method was applied to the determination of chlorpromazine in pharmaceutical preparations.
Chlorpromazine Pharmaceutical Potentiometry Electrode Solid phase reagent Oxidation column Indirect

"Detection Of Sulfur-dioxide Using A Piezoelectric Quartz-crystal Microbalance"
Anal. Lett. 1997 Volume 30, Issue 12 Pages 2159-2174
Orliney M. Guimar&atilde;es; Jos&eacute; F. Andrade; Denise P. Ruys

Abstract: Sulfur dioxide was detected and determined in air by a piezoelectric quartz crystal sensor coated with 4-aminoantipyrine/1-hydroxyetil-2-heptadecenyl imidazol (amine 220) solution (1:1 v/v in chloroform). The analytical response curve is linear over the concentration range from 0.70 to 5.0 ppm of SO2. Good linearities (r = 0.9990, 0.9995 and 0.9968) and sensitivities (18.0, 33.4 and 50.7 Hz/ppm) were found, respectively for exposure times of 30, 60 and 90 seconds. The sensor can be used for more than six months without loss in sensitivity and presented good reversibility and reproducibility. Among some possible interferents tested, only nitrogen dioxide and moisture caused major frequency changes. 18 References
Sulfur dioxide Environmental Microbalance Interferences Gas phase detection

"Determination Of Total Mercury In Soils, Waste-water And Sewage Effluents"
Anal. Lett. 1997 Volume 30, Issue 8 Pages 1579-1590
M. T. M. Zaki; M. A. Esmaile

Abstract: The cationic mercury(II)-1,10-phenanthroline binary chelate reacts with the acidic dye Thymol Blue (TB), in the pH range 5.2-7.0, to form an ion-pair extractable into chloroform. The effect of primary ligand and counter ion concentrations, pH, extraction solvent, extractability, standing time and co-existing ions has been thoroughly investigated. The molar absorptivity of the ion-pair, in chloroform, is 1.27 x 10(5) L mol-1 cm-1 at 420 nm. The calibration graph is rectilinear for 0.09-1.72 µg mL-1 of mercury. The sensitivity index of the method is 0.0002 µg Hg cm-2 and the detection limit is 0.018 µg mL-1 of mercury. The stoichiometry of the extracted ion-pair is 1:2:1 (Hg-Phen-TB). The developed method has been successfully used to determine total mercury in soils, waste water and sewage effluents. 23 References
Mercury Environmental Waste Water Spectrophotometry Sample preparation Chelation Ion pair extraction Organic phase detection

"Enzymic Determination Of Ethanol Using 'reagentless' Electrocatalyzed Luminol Chemiluminescence"
Anal. Lett. 1997 Volume 30, Issue 8 Pages 1445-1453
NAJames E. Atwater; James R. Akse; Jeffrey DeHart; Richard R. Wheeler Jr.

Abstract: The carrier stream comprised water (4.5 ml/min) flowing sequentially through a 2.5 mL solid-phase basification (SPB) bed, a 0.5 mL crystallized luminol bed and a 5 mL SPB bed. The resulting carrier stream comprised 50 mg/l luminol of pH 10.3. The sample stream consisted of water, equilibrated with atmospheric O2 containing aqueous ethanol was passed through a 1.2 mL immobilized alcohol oxidase bed at a rate of 3 ml/min corresponding to a carrier stream-to-analyte stream flow ratio of 3:2. The carrier and analyte streams were mixed at the inlet of the electrocatalyzed chemiluminescence cell. The intensity of the resulting chemiluminescence was measured by a photomultiplier tube. The method was suitable for the determination of aqueous ethanol concentrations ranging from 3-340 µM.
Ethanol Water Chemiluminescence Column Solid phase reagent Electrochemical product conversion Immobilized enzyme

"Differential-pulse Voltammetric Determination Of Serum Aspartate-aminotransferase Activity Using DCIP As Redox Mediator At A Gold Micro Electrode"
Anal. Lett. 1997 Volume 30, Issue 7 Pages 1279-1291
Ya-Nan He; Hong-Yuan Chen; Xun-Yang Luo

Abstract: Human serum aspartate amino- transferase(AST) activity, was measured voltammetrically at a gold µelectrode. 2,6-dichloroindophenol(DCIP) was used as the redox mediator and electroactive species. Sensitive measurements free from spectrophotometric interferences can be made by a differential pulse voltammetric detection technique. The instrumentation is simple and inexpensive. The method yields reproducible results that were in excellent agreement with those obtained using tile standard spectrophotometric method for determining serum AST activity in the clinical laboratory. 14 References
Enzyme, aspartate aminotransferase Serum Human Voltammetry Electrode Electrode Interferences Redox Method comparison

"Stopped-flow Spectrophotometric Determination Of Dopamine And Methyldopa With Sodium Hydroxide"
Anal. Lett. 1997 Volume 30, Issue 6 Pages 1109-1120
Juan J. Berzas; Jos&eacute; M. Lemus; Prado Buitrago

Abstract: Sample (350 µL) was injected into a water carrier stream and merged with 0.6 M NaOH (0.6 ml/min) at 60°C. A schematic diagram of the stopped-flow manifold is given. The resulting solution passed into a reactor (1 m x 0.5 mm i.d.) and the solution passed into a flow cell (1.25 ml/min). Thirty seconds after the sample injection, the pump was stopped manually and the variation of the absorbance at 360 nm was monitored throughout the reaction. Calibration graphs were linear up to 0.2 mM dopamine and 0.3 mM methyldopa, respectively. The corresponding detection limits were 3.5 µM and 0.43 µM. The method was applied to the determination of the catecholamines in pharmaceutical formulations.
Methyl dopa Dopamine Catecholamines Pharmaceutical Spectrophotometry Stopped-flow Heated reaction

"Flow Injection Online Preconcentration And Flame AAS Determination Of Copper, Cadmium And Lead In Marine Sediment Samples"
Anal. Lett. 1997 Volume 30, Issue 5 Pages 1037-1050
S. Kartikeyan; B. Vijayalekshmy; S. Chandramouleeswaran; T. P. Rao; C. S. P. Iyer

Abstract: Marine sediment (0.25 g) was mixed with 5 mL of 48% HF, 30 mL of 70% HNO3 and 2-5 drops of 98% H2SO4 and the mixture was digested (details given). Sample and ammoniacal dithizonate solutions were pumped simultaneously and mixed online. Preconcentration was performed on a C18 column over 1 min and Cu, Cd and Pb were eluted with acidified methanol and injected directly into the nebulizer for atomization in an air-acetylene flame. The calibration graph was linear from 1-40, 0.6-8 and 3-40 ppb, with detection limits of 1.2, 0.6 and 3 ppb Cu, Cd, and Pb, respectively. RSD were
Copper Cadmium Lead Marine Sample preparation Spectrophotometry C18 Preconcentration

"Flow Injection Chemiluminescence Determination Of Tetracyclines"
Anal. Lett. 1997 Volume 30, Issue 4 Pages 797-807
Zheng LI; Manliang Feng; Jiuru Lu; Zhilong Gong; Hailong Jiang

Abstract: A mixture of antibiotics (10 mg/ml) and octylphenyl polyglycol ether were injected into a stream of KMnO4 and HCl solutions (flow rate 2 ml/min), and the chemiluminescence measured. The calibration graph was linear from 1-1000 µg/ml, with a RSD of n=11) at 50 µg/ml for each antibiotic. The detection limit for tetracycline hydrochloride, oxytetracycline hydrochloride, chlortetracycline hydrochloride was 0.4, 0.52 and 0.6 µg/ml respectively, with recoveries of between 92-105%. Further development of the technique is discussed.
Tetracycline hydrochloride Oxytetracycline hydrochloride Chlortetracycline hydrochloride Chemiluminescence Redox

"Flow Injection Analysis Of Norepinephrine Bitartrate By Ion Association With Anionic Surfactant Using A Piezoelectric Detector"
Anal. Lett. 1997 Volume 30, Issue 4 Pages 663-671
Mo Zhihong; Zhang Minjuan; Li Menglong; Xia Zhiling

Abstract: A portion (50 µL) of commercially available formulations, or spiked samples of norepinephrine bitartrate (10 mg/ml), were injected on to a 300 mm mixing coil with sodium dodecyl phenyl sulfonate or sodium dodecyl sulfonate solution (details given) at a flow rate of 2 ml/min. The resultant mixture was passed into a PTFE cell and levels of norepinephrine bitartrate were detected by piezoelectric quartz crystal and silver electrodes. The calibration graph was linear from 0.01-1.2 mg/l; the detection limit was 5 µg/ml. RSD was 0.18% (n=10). Levels of norepinephrine bitartrate in pharmaceutical preparations and recoveries are reported. The merits of the method are discussed.
Norepinephrine bitartrate Pharmaceutical Sensor Microbalance Surfactant Ion pair formation

"An Enzymatic Method For The Determination Of ATP And Glycerol With An Automated FIA System"
Anal. Lett. 1997 Volume 30, Issue 3 Pages 537-552
E. R. Kiranas; M. I. Karayannis; S. M. Tzouwara-Karayanni

Abstract: The flow manifold was equipped with two enzyme reactors coupled in series containing glycerol kinase (GK) and glycerol-3-phosphate oxidase (GPO) immobilized on to non-porous glass beads. The glycerol assays were performed by injecting 85 µL sample solution into a carrier stream of Tris/HCl buffer of pH 8.2 at a flow rate of 0.45 ml/min. The carrier stream was merged with a reagent stream, at a flow rate of 0.06 ml/min, containing ATP/MgCl2 (1:17). The mixture was passed through the GK reactor where glycerol was phosphorylated to produce α-glycerophosphate (α-GP). The flow was then passed through the GPO reactor where α-GP was oxidized to dihydroxyacetone phosphate producing H2O2. Detection was at 510 nm by merging the flow with a colorimetric reagent at a flow rate of 0.06 ml/min containing horseradish peroxidase/4-aminoantipyrine/3.5-dichloro-2-hydroxymethyl sulfonic acid. To determine ATP the first reagent was changed to glycerol/MgCl2. Calibration graphs were linear from 4-70 and 2-160 µM ATP and glycerol, respectively. The method was applied to the determination of glycerol in wines following a 1:5100 dilution and in human serum following deproteinization by gel filtration.
Adenosine-5'-triphosphate Glycerol Wine Blood Serum Spectrophotometry Immobilized enzyme Glass beads

"Amperometric Immunosensor For The Detection Of 2,4-dichlorophenoxyacetic Acid (2,4-D) In Water"
Anal. Lett. 1997 Volume 30, Issue 3 Pages 515-525
M. Wilmer; D. Trau; R. Renneberg; F. Spener

Abstract: An amperometric immunosensor for the determination of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) in water has been developed using sequential injection analysis techniques. The system is based on a rapid competitive enzyme immunoassay employing an alkaline phosphatase-labeled monoclonal antibody directed against the herbicide and an immunoreactor with 2,4-D immobilized via bovine serum albumin either to Eupergit in a column or directly to the surface of a glass capillary. The detection limit of the immunosensor at 0.1 µg 2,4-D/L without enrichment of the analyte makes automatic measurements of 2,4-D in drinking and groundwater feasible.
2,4-dichlorophenoxyacetic acid Endothall sodium Water Ground Amperometry Sequential injection

"Iridium-dispersed Carbon-paste Amino-acid Oxidase Electrodes"
Anal. Lett. 1997 Volume 30, Issue 3 Pages 489-501
Rivas, G.A.;Maestroni, B.

Abstract: An amino-acid biosensor was fabricated by immobilizing L- or D-amino-acid oxidase in a carbon paste electrode containing dispersed iridium. The performance of the biosensor was evaluated using 0.03 M NaCl in 0.05 M phosphate buffer of pH 7.4 as the supporting electrolyte. The working potential was 0 V vs. Ag/AgCl with a Pt auxiliary electrode. The optimum response was obtained with a biosensor composition of 2.3% Ir and 8.5% enzyme. Calibration graphs were linear from 0.1-1.5 mM L-phenylalanine using FIA with a carrier flow rate of 1 ml/min and an injection volume of 20 µL. The detection limit was 0.05 mM; RSD was 3.7% (n = 32) for 0.75 mM L-phenylalanine. Similar responses were obtained for other L- and D-amino-acids.
Amino Acids Phenylalanine Sensor Electrode Electrode

"'Reagentless' Flow Analysis Determination Of Hydrogen Peroxide By Electrocatalysed Luminol Chemiluminescence"
Anal. Lett. 1997 Volume 30, Issue 1 Pages 21-31
James E. Atwater; James R. Akse; Jeffery DeHart; Richard R. Wheeler Jr.

Abstract: A schematic diagram is shown of the flow system. water carrier stream was passed sequentially through a 2.5 mL solid-phase basification (SPB) bed, a 0.5 mL crystallized luminol bed and a 5 mL SPB bed. The resulting carrier stream contained 50 mg/l of luminol of pH 10.3 and was mixed with the sample stream (3:2) just before the electrochemiluminescence cell. The chemiluminescence reaction was electrocatalyzed by a potential of ~0.6 V with a Au foil working electrode, a Au mesh counter electrode and a Ag/AgCl reference electrode. The calibration range extended from 0.033-16.65 mg/l of H2O2 (graph shown). The method should be applicable to both continuous-flow and flow injection systems.
Hydrogen peroxide Chemiluminescence Electrode Column Solid phase reagent Electrochemical product conversion

"Flow Injection Chemiluminescence Sensor For The Determination Of Free Chlorine In Tap Water"
Anal. Lett. 1997 Volume 30, Issue 1 Pages 11-19
Wei Qin; Zhujun Zhang; Shuna Liu

Abstract: A schematic diagram is given of the flow system. Luminol was immobilized on an anion-exchange column. A 0.15 M NaOH (200 µL) stream was mixed with a water carrier stream and injected via a six-way valve into the anion-exchange column. The alkaline aqueous solution eluted luminol from the column which was then mixed with a sample stream which had already passed through a cation-exchange column to remove interfering metal ions. The streams were mixed just before the flow cell and the resulting chemiluminescence was measured. The response of the sensor was linear from 10 ng/l to 40 µg/l with a detection limit of 8 ng/ml. The sample throughput was 60/h. The RSD (n = 7) was The effects of foreign ions on the determination were investigated. Recoveries ranged from 95-106%.
Chlorine, free Water Chemiluminescence Ion exchange Sensor Immobilized reagent Resin Interferences

"Indirect Catalytic Spectrophotometric Determination Of Metamizol Following Oxidation By Lead Dioxide Immobilized In A Polyester Resin Bed"
Anal. Lett. 1996 Volume 29, Issue 15 Pages 2667-2678
J. A. Garc&iacute;a Bautista; L. Lahuerta Zamora; J. Garc&iacute;a Mateo; J. Mart&iacute;nez Calatayud

Abstract: A spectrophotometric-indirect procedure for the determination of metamizol is described. The method is based on the reaction of the drug in a solid-phase (lead dioxide immobilized in a polyester resin bed) in acidic media (perchloric acid 0.01 M as carrier). The lead dioxide reactor provides simultaneously an effective oxidation of the drug and a controlled liberation of Pb(II) which acts as catalyst on the reaction pyrogallol red-potassium persulfate; the oxidation of the red pyrogallol results in a less colored solution. The decreased red color (negative FIA peaks) is monitored at 520 nm. The calibration graph is linear in the interval 2-16 ppm in metamizol. The relative standard deviation for the determination of 10.4 ppm of metamizol is 2.9% (n = 23) and the sample throughput is 72 h-1. A schematic of the FIA manifold is given. Metamizol (dipyrone; I) solution containing 50 ppm of the drug in 0.01 M HClO4 as carrier (905 µL) was injected (4 ml/min). The method is based on the reaction of the drug on lead dioxide immobilized on a polyester resin (A1-100; 20 g). The effect of the lead dioxide reactor (35 cm x 1.5 mm i.d.) was to oxidize the drug and produce a controlled release of Pb(II) which in turn catalyses the reaction with 0.1 M potassium persulfate and 0.2 mM pyrogallol red of pH 8.6 (1.4 ml/min). The result of the oxidation of red pyrogallol is to produce a less colored solution (red) which was monitored at 520 nm. The calibration graph was linear from 2-16 ppm I. The RSD (n = 25) at the 10.4 ppm I level was 2.9%. The sampling rate was 72/h. The effects of interferents were determined. The method was applied to the determination of I in two pharmaceutical formulations.
Drugs Metamizol Pharmaceutical Spectrophotometry Catalysis Solid phase reagent Immobilized enzyme Resin Interferences Indirect

"Development Of A Dual Channel Chemiluminescence FIA System For Rapid Measurement Of Fish Freshness"
Anal. Lett. 1996 Volume 29, Issue 14 Pages 2499-2513
Kenji Hayashi; Takuji Okugawa; Yoshiaki Kozuka; Satoshi Sasaki; Kazunori Ikebukuro b; Isao Karube

Abstract: A dual channel chemiluminescence FIA system (schematic given) comprising a pair of chemiluminescence FIA for measuring inosine 5'-monophosphate (I), inosine (II) and hypoxanthine (III) and the other for II and III was developed. A co-immobilized enzyme reactor was also used immobilized with alkaline phosphatase, purine nucleoside phosphorylase and xanthine oxidase for measuring I, II or III. The H2O2 produced in the reactors was measured by the chemiluminescence reaction in the flow cells via the photodiodes. The whole measurement process took place in 1 month. For an injection volume of 20 µl, calibration graphs were linear from 0.06-100 µM. The method was suitable for determining fish freshness.
Inosine 5'-phosphate Inosine Hypoxanthine Marine Chemiluminescence Dual detection Immobilized enzyme Reactor Photodiode

"A Fluorosensor With Immobilized Cyclodextrin As A Substrate"
Anal. Lett. 1996 Volume 29, Issue 14 Pages 2441-2452
Gong Zhilong; Zhang Zhujun

Abstract: A flow-through optosensor for phenylalanine and tyrosine is described in this paper. The sensor is developed in conjunction with a flow-injection analysis system and uses immobilized b.β-cyclodextrin as the sensing agent. The analytical performance characteristics of the proposed sensor for analysis of very low levels of phenylalanine and tyrosine were as follows: the detection limits for phenylalanine and tyrosine were 0.20 b.mug mL-1 and 8.9 ng mL-1, respectively. The observed relative standard deviations were 1.03% for 50 b.mug mL-1 of phenylalanine (n = 7) and 3.6% for 0.1 b.mug mL-1 of tyrosine (n = 7), respectively.
Phenylalanine Tyrosine Fluorescence Sensor Immobilized reagent Silica gel Optosensing

"Flow Injection Piezoelectric Determination Of Brix In Sugar Cane Juice And In The Alcoholic Fermentation Process"
Anal. Lett. 1996 Volume 29, Issue 13 Pages 2411-2419
Adriana Magna; A. Fernando de Oliveira; Orlando Fatibello-Filho

Abstract: A schematic of the piezoelectric FIA system is given. Sample (500 µL) was aspirated from the fermentation reactor at 1 ml/min and transported by the water carrier to the piezoelectric cell. The flow of solution was directed to the centre of one side of the 10 MHz AT-cut piezoelectric crystal coated with Au on both sides. The calibration graph was linear from 0.5-20% brix (total dissolved solids) with a detection limit of 0.3%. The RSD (n = 15) was ?. The results were comparable with those obtained from refractometric and densitometric measurements.
Brix Fermentation broth Sensor Piezoelectric crystal Method comparison

"Chemiluminescent Determination Of Cholesterol By Flow Injection Analysis With Immobilized Cholesterol Oxidase"
Anal. Lett. 1996 Volume 29, Issue 13 Pages 2281-2288
A. Nabi; A. Rashid; M. Yaqoob

Abstract: The method was based on the chemiluminescence produced from the oxidation of luminol in the presence of Co(II) as catalyst. A schematic diagram of the FIA manifold is given. Sample (30 µL) was injected into 0.1 M phosphate buffer of pH 7 (0.6 ml/min) and passed through an immobilized cholesterol oxidase column (2 cm x 2.5 mm i.d.). The resulting H2O2 was merged 1.8 cm downstream in a glass coil (8 cm x 1 mm i.d.) with 0.1 M carbonate buffer of pH 10.5 containing 0.01 mM luminol and Co(II). The chemiluminescence produced was detected by a photom The detection limit was 0.1 mg/dl of cholesterol and the RSD over the range 10^-60 mg/dl was The method was applied to the determination of I in serum. The results compared well with those obtained by spectrophotometry.
Cholesterol, total Blood Serum Chemiluminescence Immobilized enzyme Method comparison

"A Jet Ring Cell With A Renewable Solid Support For Amperometric Detection Of Glucose In A Sequential Injection Analysis System"
Anal. Lett. 1996 Volume 29, Issue 13 Pages 2257-2267
Tom Lindfors; Ilkka L&auml;hdesm&auml;ki; Ari Ivaska

Abstract: A new amperometric method for the detection of glucose has been developed. A jet ring cell with a renewable solid support (JRR) is connected to a sequential injection analysis (SIA) system. The solid support, consisting of small spherical particles of agarose gel, with a mean bead size of 90 b.mum, is coupled with the enzyme glucose oxidase (GOD). The suspension is injected through a multiport valve in the SIA-system and is trapped in the JRR cell by a gap of 10 b.mum between the glassy carbon (GC) working electrode and a stainless steel counter electrode. The subsequent injection of glucose results in formation of hydrogen peroxide, which is detected by oxidation at 1.0 V (vs. Ag/AgCl/KCl (3 M)). Thereafter the suspension is removed by reversing the pump flow and subsequently replaced with fresh suspension for the next determination of glucose. The linear working range for the JRR-sensor, at this stage of the work, is 100 b.muM - 5 mM.
Glucose Amperometry Sequential injection Interferences Jet ring cell

"Testosterone Determination Using Rapid Heterogeneous Competitive-binding For Enzyme-linked Immunosorbent Assay In Flow Injection"
Anal. Lett. 1996 Volume 29, Issue 12 Pages 2125-2139
Di Benedetto, L.T.;Dimitrakopoulos, T.;Davy, R.M.;Iles, P.J.

Abstract: Heparinized blood or serum (50 µL) and 200 µL horseradish peroxidase-testosterone conjugate were incubated in polystyrene wells coated with testosterone antibody. After washing the plates with Tween 20, 200 µL H2O2/tetramethylbenzidine in acetate/citrate buffer was added and the plates re-incubated. The reaction was terminated by the addition of 50 µL 1 M H2SO4. The tetramethylbenzidine species were measured spectroscopically at 450 nm via flow injection. The ELISA kit used was a FERTIGENIX TESTO-EASIA (Medgenix Diagnostics, Australia) testosterone ELISA kit. The analysis time was reduced to 1 h compared with the conventional 150 min by reducing the antibody incubation time. The results agreed well with those obtained by an IRMA. The calibration range extended up to 12.2 ng/ml of testosterone and the assay was applied to male and female patients. The RSD was 0.5% for peak height precision.
Testosterone Human Blood Serum Human Immunoassay Spectrophotometry Method comparison

"Simultaneous Determination Of Adrenaline And Noradrenaline By First-derivative Spectrophotometry In A FIA Assembly"
Anal. Lett. 1996 Volume 29, Issue 12 Pages 2115-2124
G. A. Rivas; S. Laredo Ortiz; J. Mart&iacute;nez Calatayud

Abstract: A schematic diagram of the FIA manifold is given. Sample (914.3 µL) was merged with 0.3 M NaOH reaction medium in a mixing coil (132.6 cm). The resulting solution was injected into 0.15 M NaOH carrier stream and carried downstream through a 168.6 cm coil to the spectrophotometer. All flow rates were 1.75 ml/min. The selected wavelengths (first derivative) were 394 and 342 nm for noradrenaline (I) and adrenaline (II), respectively, with an integration time of 0.4 s. Calibration graphs were linear from 2-30 ppm for both I and II. The method was applied to different synthetic mixtures of I and II.
Adrenaline Noradrenaline Spectrophotometry Spectroscopy

"Kinetic Flow Injection Spectrophotometric Determination Of Nitrite By Its Catalytic Effect On The Oxidation Of Chlorophosphonazo-pN By Bromate"
Anal. Lett. 1996 Volume 29, Issue 11 Pages 2015-2023
Chen Xingguo; Wang Ketai; Hu Zhide; Zhao Zhengfeng

Abstract: Sample (120 µL) was injected into the carrier stream (H2O; 0.8 ml/min) and mixed in a mixing coil (12 cm length) with 2-(4-chloro-2-phosphonophenylazo)-7-(4-nitrophenylazo)-1,8- dihydroxynaphthalene-3,6-disulfonic acid/H2SO4 (0.8 ml/min). The resulting stream was merged with 6 mM KBrO3 (1-2 ml/min) in a reaction coil (100 cm length) at 80°C. The resulting decrease in absorbance was monitored with a 1 cm path flow cell at 551 nm. The sampling frequency was 83 samples/h. The calibration graph was linear from 0.05-1 µg/ml of nitrite with a detection limit of 0.018 µg/ml. Chloride interference could be removed by precipitation with AgNO3. The RSD (n = 7) was 1% at the 1 µg/ml level (based on peak height). The method was applied to the determination of nitrite in water and soil.
Nitrite Environmental Environmental Spectrophotometry Catalysis Interferences Heated reaction Kinetic

"Flow Injection Spectrophotometric Determination Of Trace Amounts Of Tellurium By Catalytic Reduction Of Toluidine Blue"
Anal. Lett. 1996 Volume 29, Issue 10 Pages 1851-1860
Mousavi, M.F.;Almasian, M.R.

Abstract: Sample (110 µL) was injected via a flow injection manifold (diagram given) onto a water carrier stream and merged with Toluidine Blue (25 µg/ml) solution, sulfide solution (30 µg/ml) and 2% citrate buffer of pH 5.3 at 30°C in a reaction coil (650 cm). The flow rate of all the reagent streams was 1 ml/min. The absorbance of the solution was measured at 635 nm. The calibration graph was linear from 80-3800 ng/ml with a detection limit of 60 ng/ml. The RSD (n = 10) was 1.5% at the 1.5 µg/ml level. The sampling rate was 25 samples/h.
Tellurium Spectrophotometry

"Direct Determination Of Potassium In Human Blood Serum By Flow Injection Flame Photometry With Automatic Dilution"
Anal. Lett. 1996 Volume 29, Issue 10 Pages 1719-1727
Ana Cl&aacute;udia de Paiva; Graciliano de Oliveira Neto; Matthieu Tubino; Nelci F. Hoehr

Abstract: Serum (100 ml) was injected into the flow system via a flow injection manifold (schematic given) and diluted fourfold with water. The flow was diluted into two parts by a splitter and mixed with water in a ratio of 1:8 with a final dilution to ~1.32 after passing through a second splitter. Readings were taken with use of a flame photometer. The sampling rate was ~60 samples/h. The sampling flow rate was 3 ml/min (other flow rates are fixed by the tube diameter and are given). Calibration was linear up to 12.5 mM K+. The experimental error was ±5%. The results compared well with those obtained by a manual photometric method.
Potassium Serum Human Spectrophotometry Automation Dilution Method comparison Sample splitting

"Micellar Effect Upon The Lucigenin Chemiluminescent Reaction System With Isoprenaline"
Anal. Lett. 1996 Volume 29, Issue 9 Pages 1589-1602
Alwarthan, A.A.;Al Lohedan, H.A.;Issa, Z.A.

Abstract: The effect of various surfactants, viz., hexadecyltrimethylammonium hydroxide, hexadecyltrimethylammonium bromide, sodium laurylsulfate and Brij-35 on the chemiluminescence reaction of isoprenaline (I) was studied. I was injected (50 ml) into a carrier solution containing the surfactant and NaOH (2.4 ml/min) and merged with a lucigenin stream (2.4 ml/min) at a PTFE T-piece. The resulting chemiluminescence was detected by a photomultiplier tube (schematic of the FIA manifold is given). With the cationic and anionic micellar surfactants, the chemiluminescence was lowered but the non-ionic micelles of Brij-35 enhanced the chemiluminescence. A method was developed using Brij-35 for the determination of I in pharmaceutical preparations with a detection limit of 0.05 µM.
Isoprenaline Pharmaceutical Chemiluminescence Micelle

"Electrocatalytic Reduction And Flow Injection Analysis Of Organic Peroxides At Polymeric Tetra-amino Iron Phthalocyanine Modified Electrode"
Anal. Lett. 1996 Volume 29, Issue 9 Pages 1575-1587
Jim Wang

Abstract: Tetra-amino iron phthalocyanine was polymerized on a vitreous C electrode by electropolymerization of the monomer. The electrode was used to develop an FIA method for the determination of organic peroxides using a mobile phase of phosphate buffer of pH 3.2, ionic strength of 0.2 M (1 ml/min) and detection at +0.35 V (vs. SCE). Detection limits were 2 µM-t-butyl-hydroperoxide and 0.7 µM-peracetic acid. The calibration graph was linear from 2.5 µM to 1 mM peracetic acid. The RSD was 2.3%.
Peroxide ion Voltammetry Electrode

"Flow Injection Analysis Of Chlorophenoxy Herbicides Using Photochemically Induced Fluorescence Detection"
Anal. Lett. 1996 Volume 29, Issue 8 Pages 1447-1461
Luisa F. Garcia; Sergei Eremin; Jean-Jacques Aaron

Abstract: Sample (300 µL) was injected into a water carrier stream and passed through a PTFE photoreactor (200 cm length) where it was irradiated for 90 s to 12 min via a low-pressure Hg lamp. Two modes of irradiation were utilized: (i) stopped-flow for all herbicides; and (ii) continuous-flow for 2-methyl-4-chlorophenoxyacetic acid, mecoprop and 4-(2-methyl-4-chlorophenoxy) butyric acid. The fluorescence of the resulting photoproducts was measured at 292 nm (excitation at 276 nm). Fluorescence intensity was increased by photolysis in a 50% methanol/pH 5 buffer solution. The sensitivity of the method was greater by the stopped-flow mode compared with the continuous-flow mode. Detection limits ranged from 23-98 ng/ml of chlorophenoxy herbicides. RSD were 0.7-2.7%. The method was applied to the determination of the herbicides in water; recoveries ranged from 96-108%.
Herbicides, chlorophenoxy Environmental Environmental Fluorescence Photochemistry Stopped-flow Buffer UV reactor

"NMR-studies Of The Interaction Of Catechol And Ascorbic-acid With The Crown-ether"
Anal. Lett. 1996 Volume 29, Issue 8 Pages 1309-1318
Lunsford, S.K.;Striley, C.A.;Ma, Y.L.;Zimmer, H.;Kreishman, G.;Mark, H.B.

Abstract: Various crown ethers have been electropolymerized onto a platinum electrode for the determination of catechol and catecholamines by static potentiometry and potentiometric-flow injection analysis(FIA). The response mechanism of this modified electrode was investigated by scanning electron microscopy (SEM), electron dispersive X-ray analysis (EDAX), and electron spectroscopy for chemical analysis(ESCA). However, these studies were not conclusive with respect to possible mechanisms, and, therefore, nuclear magnetic resonance (NMR) studies were carried out on similar soluble crown ethers to determine the mode of interaction. As the crown ether resonances were shifted to higher fields by the added catechol in D2O but not d(6)-DMSO, it is postulated that the crown ether and catechol associate via interactions between hydrophobic surfaces. Hydrophilic ascorbic acid showed no NMR shifts which is consistent with its lack of potentiometric response. The EDAX and ESCA results indicated that then was also an interaction of catechol with the crown itself but the NMR shows that this interaction is a secondary effect in the overall electrode response. Several crown ethers were electropolymerized on to Pt electrodes for the determination of catechol and catecholamines by static potentiometry and flow injection potentiometry. The response mechanism of the resulting electrodes was investigated by scanning electron microscopy, electron dispersive X-ray analysis and electron spectroscopy for chemical analysis. These results were inconclusive and so 400 MHz 1H NMR Spectra were recorded with use of a Bruker AMX-400 MHz multinuclear spectrometer. NMR data indicated that crown ether aromatic rings and catechol rings were stacking on top of each other. Hydrophobic interaction seemed to be the major form of interaction which was confirmed by NMR studies in DMSO.
Ascorbic acid Catecholamines Catecholamine, derivatives Electrode Nuclear magnetic resonance Potentiometry Crown ether

"Spectrophotometric Flow Injection Determination Of Osmium"
Anal. Lett. 1996 Volume 29, Issue 7 Pages 1177-1191
Ensafi, A.A.

Abstract: Sample (200 µL) was injected (schematic of FIA manifold given) into water and merged at 30°C with 0.2 mM gallocyanine/3% EDTA/0.03 M borate buffer of pH 8 solution and H2O2. The solutions (30 ml/h) were mixed in a reaction coil (300 cm length) before detection at 625 nm. The method is based on the catalytic effect of Os on the oxidation of gallocyanine by H2O2 at 30°C. The calibration graph was linear from 0.01-100 ng/ml of Os as osmium tetraoxide with a detection limit of 3 pg/ml. RSD ranged from 0.6-1.4% (n not given). EDTA acted as a masking agent for possible metal interferents. The method was applied to real samples.
Osmium Spectrophotometry Interferences

"Fast Analysis Of Lysine In Food Using Protein Microwave Hydrolysis And Electrochemical Biosensor"
Anal. Lett. 1996 Volume 29, Issue 7 Pages 1125-1137
Marconi, E.;Panfili, G.;Messia, M.C.;Cubadda, R.;Compagnone, D.;Palleschi, G.

Abstract: Sample (equivalent to 100-140 mg protein) was hydrolyzed with 6 or 8N-HCl under N2 in a 630 W microwave digestion system (Mod. MSD 2000; CEM Corp.). The hydrolysis conditions were: 80% power, 100°C, 100 psi for 1 min for the first cycle; and 80% power, 155°C, 100 psi for 5 min for the second cycle. The hydrolysate (20 µL) was injected into a flow injection system equipped with a lysine probe comprising an amperometric H2O2 transducer and lysine oxidase covalently immobilized on a preactivated polymeric support. At pH 4.2, interference from arginine was insignificant and the calibration range was linear from 0.01-0.5 mM lysine. The optimum flow rate was 200 µL/min at which phenylalanine interference is at a minimum. The result compared well with those obtained by traditional hydrolysis - ion-exchange chromatographic procedures with relative errors of 10%.
Lysine Food Sensor Sample preparation Interferences

"Sequential Injection Analysis Of Ethanol Using Immobilized Alcohol Dehydrogenase"
Anal. Lett. 1996 Volume 29, Issue 7 Pages 1109-1124
Hedenfalk, M.;Mattiasson, B.

Abstract: A sequential injection analysis (SIA) system (schematic of manifold is given) was developed for the determination of ethanol in fermentation broth. The system was optimized in terms of pH, cofactor concentration in the reagent segments and stopping time using the aspiration sequence: 1-6 mL wash/carrier buffer, NAD+ in buffer (0.15 ml), sample or standard (15 ml) NAD+ in buffer (0.15 ml) and wash/carrier buffer (0.14 ml). The optimum pH was 8.8 but the type of buffer, i.e. Tris hydrochloride or glycine/NaOH was unimportant. The stopping time had little effect reaching a plateau after 30 s. The optimum concentration of cofactor was 0.5 µmol cofactor/assay. The assay cycle was complete within 140 s. The SIA system was based on the use of immobilized NAD+ dependent alcohol dehydrogenase and the calibration range (non-linear) extended from 0.25-100 mM ethanol. The RSD (n = 50) was 1.4% at the 2 mM ethanol level.
Ethanol Fermentation broth Sequential injection Immobilized enzyme

"Flow Injection Analysis Of Phenolic Compounds With Carbon Paste Electrodes Modified With Tyrosinase Purchased From Different Companies"
Anal. Lett. 1996 Volume 29, Issue 7 Pages 1055-1068
Lindgren, A.;Ruzgas, T.;Emmeus, J.;Csoregi, E.;Gorton, L.;Marko Varga, G.

Abstract: Tyrosinase-modified C paste electrodes were prepared by several methods: (i) direct mixing of tyrosinase powder with graphite and oil vs. adsorption of tyrosinase from solution on to graphite powder, drying and mixing with oil; (ii) preparation of tyrosinase-modified paste doped with mediator vs. mediatorless; and (iii) preparation of C paste using porous graphite vs. non-porous vitreous C powder. Each design was evaluated for nine phenolic compounds including six substituted catechols. Samples (220 µL) were aspirated into a flow injection system (schematic given) and injected into a 0.1 M phosphate buffer of pH 6 carrier stream (0.8 ml/min). After mixing, detection was at tyrosinase-modified paste electrodes inserted into a flow-through wall-jet electrochemical cell, with Pt and Ag/AgCl as counter and reference electrodes, respectively, operated at -0.05 V vs. AgCl. The tyrosinase-modified C paste electrode response was limited by the rate of the enzymatic reaction; higher responses were obtained for direct mixing of the enzyme powder on to the paste and mediator-doped pastes exhibited a higher response for some phenols.
Phenols Catecholamine, derivatives

"Continuous-flow Injection Reaction/stopped-flow Detection Using Derivative Spectrophotometry. Determination Of Cobalt And Iron In Mixtures"
Anal. Lett. 1996 Volume 29, Issue 6 Pages 1013-1025
Richter, P.;Toral, M.I.;Hernandez, P.

Abstract: A schematic diagram of the two-channel flow injection manifold is given. Sample was injected into a sodium acetate/acetic acid buffer of pH 5 (1.2 ml/min). The Fe in the sample was reduced in the first mixing coil (50 cm x 0.5 mm i.d.) before both analytes reacted with ferrozine in the second mixing coil (100 cm x 0.5 mm i.d.) at 2.4 ml/min. The Fe(II) and Co(II)-ferrozine complexes were then detected at 550 nm. When the signal reached the maximum height the flow was stopped and the absorption spectra were scanned from 400-700 nm with transformation to the first-derivative using a Δλ of 1.6 nm. Calibration ranges were 1.2-25 and 0.15-6 µg/ml of Co and Fe, respectively. The corresponding detection limits were 0.33 and 0.045 µg/ml. The method was applied to the determination of Co and Fe in water.
Cobalt Iron Environmental Environmental Spectrophotometry Spectroscopy Stopped-flow

"Kinetic FIA Determination Of Mercury(II) Based On Its Catalytic Effect On The Reaction Between Safranin And Iodide"
Anal. Lett. 1996 Volume 29, Issue 5 Pages 807-819
Afsaneh Safavi; Mohammad Reza Baezzat

Abstract: A schematic diagram of the FIA manifold is given. Safranin-buffer solution of pH 5 (0.75 ml/min) was merged with iodide solution in a 1 m coil. The sample (300 µL) was injected into a carrier stream of water (0.75 ml/min) and merged with the safranin-buffer - iodide mixture in a 5 m coil at 10°C. The stream from the reaction coil was measured at 520 nm. The detection limit was 90 ng Hg(II). There was little chemical interference. The method was applied to the determination of Hg in contact lens cleaning solution and hair.
Mercury(II) Contact lens Hair Spectrophotometry Interferences Kinetic

"Ultraviolet Determination Of Chloride In Water By Flow Injection Analysis"
Anal. Lett. 1996 Volume 29, Issue 5 Pages 793-806
Amin T. Haj-Hussein

Abstract: Water (50 µL) was aspirated into the sample loop via a syringe and injected into 0.01 M EDTA in acetate buffer of pH 4.6 as carrier stream (0.74 ml/min). The sample was merged with 1 mM Hg-EDTA reagent (0.74 ml/min) also buffered at pH 4.6 and passed through a 25 cm reaction coil. Detection was at 250 nm. The calibration graph was linear from 1.8-35.5 ppm chloride with a detection limit of 0.2 ppm. The sampling rate was 60 samples/h. The method was applied to tap, well, spring and river water. Recoveries ranged from 97.5-101.2%.
Chloride Water River Spring Well Spectrophotometry

"Flow Injection Potentiometric Determination Of Coke Acidity And Acetic Acid Content In Vinegar Using An Antimony Electrode"
Anal. Lett. 1996 Volume 29, Issue 5 Pages 711-724
Capelato, M.D.;Marli Dos Santos, A.;Fatibello, O.;Gama, R.

Abstract: An Sb/Sb2O3 electrode was used to measure the acidity of coke and vinegar samples by FIA. Sample (50 µL) was injected into a carrier solution of 0.1 M NaNO3 of pH 6.5 (2 ml/min) via a flow manifold (schematic given). Phosphate buffer solutions were used as pH standards. Solutions passed through a 50 cm helicoidal tubular reactor and on to a potentiometric detector cell comprising a circular plane Sb indicator electrode and a Ag/AgCl/0.1 M NaCl, 3 M NaNO3 as reference electrode. A linear response to acidity was achieved for 3.16-100 mM acetic acid with a slope of 30.1 mV/decade and a sample throughput of 23 samples/h. The average standard deviation was ±0.5%. The method should be suitable for routine analyzes.
Acetic acid pH Soft drink Coca cola Food Potentiometry Electrode Reactor

"Activation Of Supports Containing Hydroxyl-groups Using Bis(4-nitrophenyl)carbonate"
Anal. Lett. 1996 Volume 29, Issue 4 Pages 547-564
Narinesingh, D.;Ngo, T.T.

Abstract: The hydroxyl groups carrying supports, Sepharose Cl-4B and Fractogel HW75F, were facilely activated under anhydrous conditions using bis(4-nitrophenyl) carbonate (BPNPC), a stable and readily available compound. The activation time at room temperature can be as short as 0.5 hour. The activated supports can be stored at 4°C for at least one month without any loss of coupling capacity. Amines can be coupled to the activated support at pH 7 to 10. Coupling of Protein A to BPNPC activated supports yielded immobilized Protein A affinity supports having a high IgG binding capacity. For example, the Protein A-Sepharose and Protein A-Fractogel prepared by using the BPNPC activation method were able to bind, respectively 13 - 14 mg and 8 - 9 mg human IgG with phosphate buffer saline as the loading buffer. In contrast the use of a high yield binding buffer increases the binding capacity of the two affinity supports to 25 - 28 mg and 22 mg respectively.
Immunoglobulin G Sepharose beads

"Relationship Between Peak Width And Sample Concentration In Continuous-flow Injection Titration"
Anal. Lett. 1996 Volume 29, Issue 2 Pages 313-319
Wu, N.S.;Shi, W.J.;Su, H.W.

Abstract: A mathematical expression relating the measured time interval and the sample concentration in continuous-flow titrimetry was developed. All calculations were performed on an IBM-PC using BASIC programming.
Peak width Titrations

"Simultaneous Determination Of L- And D-lactate By Enzyme Modified Carbon Paste Electrodes"
Anal. Lett. 1996 Volume 29, Issue 2 Pages 181-201
Narasaiah, D.;Spohn, U.;Gorton, L.

Abstract: Enzyme modified C paste electrodes were prepared based on D-lactate dehydrogenase and L-lactate oxidase for L- and D-lactate. The electrodes were mounted in wall-jet flow cells inserted into a split flow for FIA. Ag/AgCl (in 0.1 M KCl) and Pt wires were used as reference and auxiliary electrodes, respectively. A diagram of the FIA set-up is given; 0.1 M sodium phosphate buffer was used as the carrier. Sample was injected into the carrier (1.2 ml/min) and mixed in a mixing coil before being split (0.6 ml/min) between the two detectors. D- and L-lactate could be detected as NADH by an amperometric cell from -50 to 50 mV (vs. Ag/AgCl) and up to 40 samples/h could be analyzed. Calibration graphs were linear from 10 µM to 10 mM L-lactate and from 100 µM to 20 mM D-lactate.
Lactate d-Lactate Electrode Amperometry

"An Enzymic Chemiluminescence Optrode For Choline Detection Under Flow Injection Conditions"
Anal. Lett. 1996 Volume 29, Issue 1 Pages 1-17
Lapp, H.;Spohn, U.;Janasek, D.

Abstract: A chemiluminometric bienzyme membrane-based optrode was developed for the detection of choline (I). Choline oxidase and fungal peroxidase were immobilized on a nylon (biodyne) membrane preactivated with 25% glutardialdehyde for 12 h. The addition of polyethylenimine to the mixed enzyme solution before glutardialdehyde crosslinking improved the sensitivity and the long-term stability of the membrane. Up to 200 determinations were possible with an RSD of 0.8%. The calibration graph was linear from 0.1-2 mM I with a detection limit of 1 µM.
Choline Chemiluminescence Optrode

"Isomeric Transformation Of 4-aminobiphenyl By UV Radiation And Its Influence On The Determination By Flow Injection Analysis With Amperometric And Spectrophotometric Detection"
Anal. Lett. 1995 Volume 28, Issue 15 Pages 2683-2697
Hernandez Blanco, M.;Quintana, M.C.;Hernandez, P.;Vicente, J.;Hernandez, L.

Abstract: Sample (200 µL) containing 4-aminobiphenyl (I; 0.1-1 µg/ml in methanol) was injected into a carrier stream (5.5 ml/min) containing 0.04 M Britton-Robinson buffer of pH 8 via a single-flow injection manifold. The streams were mixed in a reactor (20 cm x 0.5 mm i.d.) before amperometric detection in a wall-jet flow-cell with a working electrode potential of +0.9 V. Vitreous C, Ag/AgCl and Au were used as working, reference and auxiliary electrodes, respectively. Spectrophotometric measurements were performed similarly except that a 400 µL sample (containing 0.8-24 µg/ml of I in methanol) and a 0.02 M buffer of pH 10 were used. Detection was at 274 nm. For amperometric detection the calibration graph was linear from 0.1-1 µg/ml of I; quantitation and detection limits were 0.11 and 0.05 µg/ml, respectively. RSD were 2.5%. For the spectrophotometric method, the linear calibration range was 0.8-24 µg/ml of I; quantitation and detection limits were 0.4 and 0.05 µg/ml, respectively. RSD were 2.4%. Sample throughputs were 200 and 240 samples/h for amperometric and spectrophotometric detection, respectively. The methods were applied to the determination of I in food colorings. Two flow injection methods for the determination of 4-aminobiphenyl by amperometry (glassy carbon electrode) and spectrophotometry are proposed. A sample volume of 200 or 400 µl containing an analyte concentration of 0.1-1.0 µg mL-1 or 0.8-24.0 µg mL-1 for amperometric or spectrophotometric detection, respectively, is injected into a carrier stream containing 0.04 or 0.02 M Britton-Robinson buffer at pH 10.0 or 8.0, respectively. (11 References)
4-Aminobiphenyl Food Amperometry Electrode Spectrophotometry Photochemistry

"Enzyme Electrode For Amplification Of NAD+/NADH Using Glycerol Dehydrogenase And Diaphorase With Amperometric Detection"
Anal. Lett. 1995 Volume 28, Issue 15 Pages 2595-2606
Tang, X.J.;Johansson, G.

Abstract: An NAD+/NADH amplifying electrode was prepared from a vitreous C electrode covered with a gelatin membrane comprising glycerol dehydrogenase and diaphrose protected by an outer dialysis membrane. Measurements were performed with use of a two-channel flow injection system (diagram given). The channels contained 0.1 M KH2PO4/30 mM ammonium sulfate buffer of pH 8 with glycerol or hexacyanoferrate(III). Samples (100 µL) were injected, mixed with the solution stream (0.08 mL/min) in knitted tubing and detected via a potentiostat at 450 mV (vs. SCE). The method is based upon the product of the first enzyme reaction being the substrate to the second and the product of the second reaction being the product of the first so producing recycling and amplification which is electrochemically detectable. In this instance each cycle produces two [Fe(CN)6]4- molecules which are electrochemically oxidized at the electrode surface at 450 mV (vs. SCE). The system is limited by the low activity of diaphorase requiring 20 min measurement times. The calibration range was linear from 0.03-0.06 µM NADH; the response decreasing to 70% after 7 days. The biosensors should be useful detectors in immunoassays with alkaline phosphatase as a marker.
Nicotinamide adenine dinucleotide reduced Sensor Electrode Electrode Amperometry Catalysis Reagent recycling Dialysis Knotted reactor

"Cyclic Enzymatic Determination Of L-lactate By Differential PH Measurement"
Anal. Lett. 1995 Volume 28, Issue 14 Pages 2475-2490
Compagnone, D.;Mosca, A.;Palleschi, G.

Abstract: An electrochemical procedure for the analysis of L-lactate based on the lactate dehydrogenase/lactate oxidase reaction cycle has been developed and applied in whole blood and wine. The reaction of lactate with lactate oxidase produces pyruvate, which is the substrate, at physiological pH, of the enzyme lactate dehydrogenase. This enzyme, in the presence of NADH, converts pyruvate to lactate consuming H+. An automated software controlled differential pH meter was used for H+ detection and the Delta pH measured was correlated to the lactate concentration present in the sample. (24 References)
l-Lactate Wine Whole Electrode Potentiometry Immobilized enzyme Indirect

"A Microdialysis Probe Coupled With A Miniaturized Thermal Glucose Sensor For In Vivo Monitoring"
Anal. Lett. 1995 Volume 28, Issue 13 Pages 2275-2286
Amine, A.;Digua, K.;Xie, B.;Danielsson, B.

Abstract: A miniaturized thermal biosensor was coupled with a microdialysis probe (MP) for subcutaneous glucose (I) monitoring. The thermal biosensor measured the heat evolved during enzyme catalyzed reactions and consisted of a stainless steel column (15 mm x 1.5 mm i.d.) filled with controlled pore glass beads (125-140 µm) onto which glucose oxidase and catalase had been co-immobilized. The temperature signal was measured with a Wheatstone bridge. The biosensor was incorporated into a FIA system equipped with a 1 µL sample loop and operated with 0.1 M sodium phosphate buffer carrier stream (60 µL/min). The MP was fitted with a polycarbonate-polyether co-polymeric membrane (1.6 cm x 0.5 mm i.d., 20 000 Da molecular weight cut-off) and 0.1 M PBS at pH 7.2 was used as the perfusion fluid at 3 µL/min. The thermal sensor exhibited a linear response from 1-50 mM I and a response time of ~e;85 s. In vivo experiments were performed by inserting a 1 cm portion of the MP hollow fiber into the skin of a healthy volunteer who had been orally dosed with I and the levels of I in subcutaneous fluid was measured at 5 min intervals over a period of 180 min after dosage and the results were compared with levels of I in blood measured at 20 min intervals. Subcutaneous concentrations were found to follow the blood concentrations with a time lag of 18 min.
Glucose Subcutaneous Fluid Blood Sensor Thermistor Dialysis Controlled pore glass Membrane In vivo monitoring Perfusion

"Direct Spectrophotometric Determination Of Platinum By Microwave-oven Induced Flow Injection Analysis"
Anal. Lett. 1995 Volume 28, Issue 12 Pages 2227-2238
Li, G.B.;Xu, Y.J.;Chen, X.G.;Hu, Z.D.

Abstract: A microwave-oven induced flow injection analyzer. was developed (schematic given). Sample (200 µL) containing Pt(II) or (IV) was injected into a water carrier stream (2.05 ml/min) between two parts of reagent by a 16-way valve. The reagent used was 0.6 mM 5-(5-bromo-2-pyridylazo)-2,4-diaminotoluene in acetic acid/sodium acetate buffer (400 µL). After the sample had flowed entirely (15 s) into the microwave oven in a reaction coil (9 m x 0.5 mm), the microwave oven was switched on. The microwave power (70-700 W) and the irradiation time (0-99 s to 0-99 min) was microprocessor controlled. After the reaction, the mixture was passed through a cooling coil to a spectrophotometer. The maximum absorption wavelength was 600 nm for the Pt(II) complex and 560 nm for the Pt(IV) complex. Beer's law was obeyed from 2-25 µg/ml of Pt(II) (ε = 7800) with a detection limit of 3 µg/ml. Equal concentration of Co2+, Pd2+, Ru3+, Rh3+ and Ir2+ interfered seriously. The method was used to determine Pt in industrial Pt catalysts on Al supports.
Platinum Platinum Spectrophotometry Heated reaction Microwave Computer Interferences

"Approaches For Improving The Precision And Sensitivity Of Continuous Pervaporation Processes"
Anal. Lett. 1995 Volume 28, Issue 11 Pages 2063-2076
I. Papaefstathiou a; M. D. Luque de Castro

Abstract: A flow injection method using pervaporation was used to determine sulfide. Samples were injected in to a stream (1.3 ml/min) of TCA buffer of pH 1.16 and carried through a reaction coil (30 cm x 0.7 mm i.d.). The H2S produced was carried to a pervaporation unit maintained at 60°C; the lower donor chamber was packed with 3 mm diameter glass beads. The H2S diffused through the PTFE membrane and into an acceptor stream (1.3 ml/min) of 1.92 mM p-diethylaminoaniline in the TCA buffer. This merged with a stream (0.7 ml/min) of 3.73 mM ammonium iron(III) sulfate, passed through a reaction coil (100 cm x 0.7 mm i.d.) and the ethylene blue produced was detected at 670 nm. The effects of using a 280 cm donor chamber waste tube and halting the flow of both acceptor and donor streams (in sample injection mode) or acceptor stream (continuous-flow mode) for 5 min were investigated. Sensitivity was improved with the longer waste tube; calibration graphs were linear for 0.1 to 5-7 µg/ml sulfide, the detection limit was 0.07 µg/ml and the RSD were 1.61-2.86%. In sample injection mode, halting the flow also enhanced the sensitivity and precision.
Sulfide Spectrophotometry Pervaporation Glass beads Teflon membrane

"Amperometric Determination Of Bilirubin With Flow Injection Analysis System"
Anal. Lett. 1995 Volume 28, Issue 10 Pages 1775-1783
Bae, Z.U.;Lee, H.L.;Park, T.M.;Seo, M.L.

Abstract: Samples (20 µL) were injected into a carrier stream (1 ml/min) of physiological solution of pH 7.4 (cf. Palleschi et al., Anal Biochem., 1986, 159, 114) and transported to a flow cell incorporating a vitreous C working electrode, a Ag/AgCl reference electrode and a stainless-steel auxiliary electrode. The oxidation current at +0.5 V was measured. The system was regenerated with 0.1 M NaOH. The calibration graph was linear for 1 µM- to 1 mM bilirubin and the detection limit was 0.4 µM; the RSD (n = 4) was 3.2%. Haemoglobin did not interfere but indican did. Sample throughput was 20/h.
Bilirubin Blood Amperometry Electrode Interferences

"Potentiometric Biosensing Of Penicillins Using A Flow-through Reactor With Penicillinase Or Penicillin Amidase Immobilized By γ-irradiation"
Anal. Lett. 1995 Volume 28, Issue 10 Pages 1735-1749
Macca, C.;Solda, L.;Palma, G.

Abstract: A mixture of 2-hydroxyethyl methacrylate, NN'-methylene-bis-acrylamide and penicillinase or penicillin amidase in phosphate buffer was added dropwise to n-hexane cooled to -78°C. The suspension of frozen droplets was irradiated at 0.4 Gy/s for 5 h with 60Co γ-rays. The resulting polymer spheres (~0.5 mm diameter) were packed into a column (50 or 100 mm x 4.6 mm i.d.) to form a reactor for FIA of penicillins. Samples (20 µL) were injected into a phosphate buffer carrier stream, and after passing through the reactor they were carried to a wall-jet flow cell (Ramos et al., Anal. Chem., 1994, 66, 1931) with a pH sensor (Galiatsatos et al., Biosens. Bioelectron., 1990, 5, 47). Linear or logarithmic responses to penicillins were obtained for both enzymes depending on the carrier buffer capacity and flow rate (details given). The optimal pH range was 5.8-6.8. Sensitivity increased as buffer concentration decreased but the dynamic range was narrower.
Penicillins Electrode Potentiometry Linear dynamic range Immobilized enzyme pH Optimization

"Catalytic Oxidation Of NADH At A Methylene-green Chemically Modified Electrode And FIA Applications"
Anal. Lett. 1995 Volume 28, Issue 9 Pages 1579-1591
Chen, H.Y.;Yu, A.M.;Han, J.L.;Mi, Y.Z.

Abstract: Graphite powder (0.98 g) was mixed with 0.02 g Methylene Green in 5 mL ethanol, the solvent was evaporated off and a portion (0.5 g) of the resulting powder was mixed with 0.3 mL Nujol oil. The resulting modified C paste was packed into an electrode body to form the NADH sensor. For FIA, the sensor was incorporated into an electrochemical thin-layer cell comprising two plexiglass blocks tightly compressing a 50 µm PTFE film with a 13 x 5 mm channel. Samples (20 µL) were injected into a stream (2 ml/min) of 0.1 M phosphate buffer of pH 7 and Pt wire counter and SCE references electrodes were used for the measurements. At a potential of 0.2 V, the calibration graph was linear for 5-1000 µM-NADH and the detection limit was 1 pmol. The RSD were 1% (n = 10).
Nicotinamide adenine dinucleotide reduced Amperometry Electrode Electrode Sensor

"Liposome Membrane Permeability Assay Using A Glucose Biosensor Flow Injection System"
Anal. Lett. 1995 Volume 28, Issue 9 Pages 1571-1578
Katsu, T.;Wei, H.;Hu, W.;Zhang, X.;Zhang, X.

Abstract: A suspension of liposomes containing glucose enclosed in the inner aqueous liposome phase (preparation described) was incubated with melittin or gramicidin S for 10 min at 30°C. The reaction mixture was injected into a carrier stream (3 mL/min) of 10 mM sodium phosphate buffer of pH 7 containing 0.15 M NaCl and released glucose was determined with use of a glucose analyzer incorporating a glucose electrode. The electrode was based on an O2 electrode with a BSA/glucose oxidase/glutaraldehyde-modified PTFE membrane (cf. Zhang et al., 'Collected papers in Biotechnology,' Chinese Chemical Industrial Press, Beijing, 1994, p. 22). The calibration graph for the biosensor system was linear for 0.1-7 mM glucose and the detection limit was 50 µM. The RSD was 2.8% at 4.75 mM glucose (obtained by disrupting liposomes with Triton X-100). The system was suitable for determining liposome membrane permeability.
Glucose Amperometry Electrode Sensor Liposomes Permeability

"Dextrose Sensor In Food Analysis"
Anal. Lett. 1995 Volume 28, Issue 7 Pages 1173-1180
Wei, D.;Lubrano, G.J.;Guilbault, G.G.

Abstract: Non-viscous liquids were measured without any sample preparation of after dilution with 0.1 M phosphate buffer of pH 7 for FIA and spectrophotometry. Carbonated drinks were diluted at 5°C; viscous samples and powders were diluted with phosphate buffer; and dry solids were ground to a powder before dilution. For steady-state measurements, a 100-200 l sample was added to 5 mL 0.1 M phosphate buffer of pH 7. The steady state of the amperometric glucose biosensor was measured. For FIA, the sample was diluted with 0.1 M phosphate buffer of pH 7 and injected (100 l) into a carrier stream of phosphate buffer (loc. cit). Peak heights were recorded. Flow-rates of 1 ml/min and the wall-jet mode were used for different food types. The calibration graph had a greater linear range (20-200 ng/dl) for the FIA method compared with the steady-state method. Good precision (RSD <10%), a fast response time (30 s) and a 1-2 min recovery time were observed. The biosensor was stable for similar4 months. The results compared well with those obtained by spectrophotometry.
Dextrose Food Sensor

"A Novel Strategy For Preparation Of Solid-phase Reactors. Fluorimetric Determination Of Emetine Hydrochloride"
Anal. Lett. 1995 Volume 28, Issue 6 Pages 971-978
Laredo Ortiz, S.;Martinez Calatayud, J.

Abstract: Emetine (I) was determined by measuring its fluorescence at 458 nm (excitation at 350 nm) after oxidation by I2. A solid-phase reactor was constructed by passing aqueous I2 solution through PTFE tubing for 120 min. The reagent became impregnated in the inner wall of the tubing. The reactor was incorporated in to a flow injection manifold (illustrated). water was used as carrier (4.2 ml/min). The modified simplex method was used for optimization of the flow injection parameters. A 40 cm column (1.3 mm i.d.), a sample volume of 670 µL and flow rate of 3 ml/min were optimal. The calibration graph was linear for 0.1-100 µg/ml I and the RSD was 1.3%. No detection limit is given. Sample throughput was 75/h. Details of interferences are given. The method was applied to I injection solutions. Samples (2.5 ml) were mixed with 5 mL phosphate buffer of pH 6.31 and diluted to 100 mL with H2O.
Emetine Pharmaceutical Fluorescence Solid phase reagent Simplex Optimization Interferences

"FIA Fluorimetric Determination Of Calcium Pantothenate. Validation And Quantitation In Multivitamin Preparations"
Anal. Lett. 1995 Volume 28, Issue 5 Pages 821-833
Blanco, M.;Coello, J.;Iturriaga, H.;Maspoch, S.;Pages, J.

Abstract: Powdered tablets were suspended in 0.02 M HCl, sonicated for 10 min and centrifuged. The resulting solution was appropriately diluted and injected (35 µL) into the flow injection manifold (diagram given). Calcium pantothenate (I) was hydrolyzed in a 10 m loop by mixing with 0.6 M NaOH (0.9 ml/min) and heating at 85°C. Following hydrolysis, the solution was mixed with the derivatization solution (1 ml/min) comprising 0.373 mM o-phthaldialdehyde 38 µM-2-mercaptoethanol and 0.4 M H3BO3 in a 3 m coil. The emitted fluorescence was measured at 455 nm (excitation at 350 nm). The calibration graph was linear from 0.2-40 mg/l of I. The sampling rate was 25 samples/h. Detection and quantitation limits were 0.02 and 0.09 mg/l, respectively. The method was applied to multivitamin preparations.
Pantothenate Pharmaceutical Fluorescence Heated reaction

"Application Of A Multichannel Potentiostat To Metal Ion Determinations In Flow Injection Analysis"
Anal. Lett. 1995 Volume 28, Issue 4 Pages 685-696
McGrath, M.J.;Fang, T.;Diamond, D.;Smyth, M.R.

Abstract: A multi-channel potentiostat (Fang et al. Anal. Chim. Acta, in press) was used to control the four working electrodes (vitreous C rods 1 mm diameter in a radial flow cell configuration) of an amperometric array incorporated into a FIA system for the determination of metal ions. The stainless steel outlet plate of the flow cell served as the counter electrode and a Ag/AgCl reference electrode was used. The potentiostat was controlled via a PC with Analog Devices RTI815 and RTI817 data acquisition/control cards; software was written in Micosoft QuickBasic. Display of 2-D and 3-D voltammograms was possible. Samples were injected into a carrier stream (0.2-0.5 ml/min) of 50 mM phosphate buffer of pH 7.4 or 0.1 M KCl containing 0.5% HNO3. Details of the voltages applied are given. The calibration graph for Cu(II) was linear from 100 ppb to 500 ppm and the RSD were 0.87-3.05%. The calibration graph for PB(II) was linear for 50 ppb to 250 ppm and the RSD was 2.6%. The array was able to determine individual components in a mixture or Cu(II) and Fe(III) without prior separation.
Copper Iron Lead Potentiometry Electrode Computer

"Determination Of Glutamine In Mammalian Cell Cultures With A Flow Injection Analysis - Wall-jet Electrode System"
Anal. Lett. 1995 Volume 28, Issue 4 Pages 593-603
Huang, Y.L.;Khoo, S.B.;Yap, M.G.S.

Abstract: The cited system (diagram given) incorporated a reactor (2 cm x 5 mm i.d.) containing glutamate dehydrogenase (GDH) immobilized on aminopropyl-derivatized controlled-pore glass beads (AMP-CPG; 120-200 mesh) which was situated upstream of a second reactor (3 cm x 1 mm i.d.) packed with glutamate oxidase and glutaminase co-immobilized on AMP-CPG (immobilization methods given). Cell culture supernatants were pumped at 0.42 ml/min into a carrier stream (1 ml/min) of 0.1 M potassium phosphate buffer of pH 5.5. The glutamine was converted to H2O2 in the second reactor; the GDH reactor eliminated interference from up to 0.08 g/l glutamate. H2O2 was determined at the wall-jet electrode (Gunasingham and Tan, Anal. Chim. Acta, 1990, 234, 321) at +0.65 V vs. Ag/AgCl (using 3 mm Pt disc working and 5 mm vitreous C disc counter electrodes). The calibration graph was linear from 0.01-0.2 g/l glutamine and the RSD was 5.1%. No detection limit is given. Recoveries were 98%. After 70 determinations 70% of the initial reactor activity remained. The results generally agreed well with those obtained by HPLC.
Glutamine Cell Amperometry Electrode Electrode Immobilized enzyme Controlled pore glass Glass beads Interferences Method comparison

"Separation And Preconcentration Of Cobalt And Nickel With 3-(trimethoxysilyl)-1-propanethiol Loaded On Silica Gel"
Anal. Lett. 1995 Volume 28, Issue 2 Pages 357-368
Koklu, U.;Akman, S.;Gocer, O.;Doner, G.

Abstract: Preconcentration of Co and Ni on 3-(trimethoxysilyl)-1-propanethiol - modified silica gel (cf. Akman et al., Anal. Sci., 1991, 7, 799) prior to determination by graphite-furnace AAS, was investigated by batch and column methods. For batch experiments, 5 mL phosphate or borate buffer was shaken with 5 mL metal solution (5 ppm Co and Ni, prepared from Merck Titrisol concentrates) and 0.1, 0.15 or 0.2 g modified silica for 30 min, the mixture was filtered and the filtrate was diluted to 25 mL and analyzed by AAS. Adsorption of Co and Ni was initiated at similarpH 2 and was maximal at similarpH 8. Adsorbed Co was recovered quantitatively using 25 mL 2 M HCl. For column experiments, metal solutions (1 mg/ml; 500 ml) of pH 7.5 or 8.5 were applied to a burette containing 5 g modified silica. Optimal conditions for pre-concentration were a sample pH of 7.5, a sample flow rate of 0.5 ml/min, an eluent pH of 2 and an eluent flow rate of 0.5 or 1 ml/min for Co and Ni, respectively. Under these conditions, recoveries were quantitative with RSD of 5%.
Cobalt Nickel Spectrophotometry Silica gel Preconcentration

"Determination Of Sodium Nitroprusside By Flow Injection With Spectrophotometric Detection"
Anal. Lett. 1995 Volume 28, Issue 2 Pages 295-306
Alwarthan, A.A.

Abstract: Samples (150 µL) were injected into a carrier stream (0.72 ml/min) of 0.15 M NaOH which merged with a stream (0.72 ml/min) of 5 mM sulfadiazine in 0.5 M HCl before passing to a reaction coil (150 cm x 0.8 mm i.d.) maintained at 70°C, where nitrite ions liberated from sodium nitroprusside (I) were diazotized. After merging with a stream (0.72 ml/min) of 0.1 mM N-(1-naphthyl)ethylene-diamine dihydrochloride in 0.5 M HCl, the solution passed through a second reaction coil (100 cm x 0.8 mm i.d.) where coupling occurred and the absorbance of the resulting purple azo dye was measured at 545 nm. Beer's law was obeyed from 0.1-100 µg/ml of I and the detection limit was 0.05 µg/ml. The RSD at 10 µg/ml I was 1.78%. Sample throughput was 17.5/h. Glucose and riboflavin interfered. The method was applied to a pharmaceutical preparation. Ampoule contents (50 mg I were dissolved in and diluted to 250 mL with 0.15 M NaOH; the recoveries were 99.5-100.25%.
Nitroprusside Pharmaceutical Spectrophotometry Heated reaction Interferences

"Enzymic Flow Injection Determination Of γ-aminobutyric Acid"
Anal. Lett. 1995 Volume 28, Issue 2 Pages 259-266
Horie, H.;Rechnitz, G.A.

Abstract: Samples (20 µL) were mixed with 20 µL 2.5 µM-NADP/10 µM-2-oxoglutarate and injected into a carrier stream (0.1 or 0.8 ml/min) of 50 mM Tris hydrochloride buffer of pH 8 containing 1 mM 2-mercaptoethanol and 200 mM Na2SO4 which passed to an enzyme reactor. The reactor comprised a column (3.5 cm x 3 mm i.d.) packed with 200 mg glutaraldehyde-treated glass beads that had been mixed with 80 mg/ml GABAse (4-aminobutyrate:2-oxoglutarate aminotransferase and succinic semialdehyde:NADP+ oxidoreductase) in 0.2 mL 50 mM sodium phosphate buffer of pH 7 overnight, then washed with phosphate buffer. The NADPH produced was determined fluorimetrically at 460 nm (excitation at 360 nm). The calibration graphs were linear from 1-500 and 0.5-500 µM-γ-aminobutyric acid (GABA) at 0.8 and 0.1 ml/min, respectively. No RSD are given. At 0.8 ml/min samples could be injected every minute. The enzyme reactor retained >60% activity over 10 days. Recoveries of GABA from spiked green tea infusions were 97-104% at a flow rate of 0.1 ml/min.
4-aminobutyric acid Plant Fluorescence Glass beads Immobilized enzyme Column

"FIA-fluorimetric Determination Of Adrenaline By Oxidation With A Solid-phase Reactor Of Manganese Dioxide Incorporated In Polyester Resin Beads"
Anal. Lett. 1995 Volume 28, Issue 2 Pages 239-247
Kojlo, A.;Martinez Calatayud, J.

Abstract: Samples were injected into a carrier stream (1.75 ml/min) of water which passed through a solid-phase reactor (45 cm x 1.2 mm i.d.) containing MnO2 (cf. Lahuerta Zamora et al., Anal. Chim. Acta., 1992, 263, 81) before merging with a stream (0.79 ml/min) of aqueous 1.5 M NaOH/0.5 mM ascorbic acid and passing through a mixing coil (55 cm x 0.8 mm i.d.). The oxidized adrenaline was determined fluorimetrically at 540 nm (excitation at 330 nm). The calibration graph was linear from 0.5-20 µg/ml of adrenaline and the detection limit was 0.4 µg/ml. The RSD was 2% and sample throughput was 65/h. Interferences by foreign compounds are tabulated. The method was applied to a pharmaceutical formulation.
Adrenaline Pharmaceutical Fluorescence Interferences Solid phase reagent Resin

"Determination Of Tellurium By Gas Phase Molecular-absorption Spectrometry After Hydrogen Telluride Generation"
Anal. Lett. 1995 Volume 28, Issue 1 Pages 121-146
Sanz Asensio, J.;Galban Bernal, J.;Gonzalez, F.G.;Benito Grande, J.

Abstract: Sample (1 ml) and 0.35 mL NaBH4 (30 g/l) were placed inside a generation flask, N2 was introduced to remove the air and the reference measurement was made whilst N2 was passing through the flow cell. After 2 min, 2 mL 2 M HCl was injected. Both hydrogen telluride and hydrogen were generated and carried by N2. The hydrogen telluride was transported to a flow cell placed in a UV-visible molecular absorption spectrophotometer. The absorption spectra was measured from 190-300 nm. The conditions were optimized based on height and area of absorbance vs. time profile of hydrogen telluride generated. The calibration graph was linear from 5-100 g/ml Ti. Detection limits were 1.1 and 3.1 g/ml of Te(IV) and Te(VI), respectively. RSD were 3-7%. The method was applied to additives used in synthetic rubber.
Tellurium Additive Spectrophotometry Gas phase detection Volatile generation Volatile generation

"Flow Injection Analysis Of Nitrite Generated By Neutrophils And Endothelial Cells"
Anal. Lett. 1994 Volume 27, Issue 15 Pages 3081-3093
Hybertson, B.M.;Dunham, A.J.;Thompson, D.C.;Terada, L.S.;Repine, J.E.

Abstract: Solutions from cultures of bovine pulmonary artery endothelial cells or human neutrophils were injected via a 100 µL sample loop into a stream of 0.1 M NaI/0.1 M H3PO4. The mixture flowed into microporous tubing (20 cm x 1 mm i.d.) in a glass bulb with gas inlet and outlet parts. He gas was swept through the bulb at ~100 ml/min and into a Nitric Oxide Chemiluminescence Analyzer (Sievers Instruments model 270B, Boulder, CO, USA). The calibration graph was linear for 10^-5000 nM-nitrite.
Nitrite Cell Brain Chemiluminescence

"Alcohol Electrodes In Beverage Measurements"
Anal. Lett. 1994 Volume 27, Issue 15 Pages 3027-3037
Rebelo, M.J.F.;Compagnone, D.;Guilbault, G.G.;Lubrano, G.J.

Abstract: Alcoholic beverage (50-200 µL) was added to 5 mL 0.1 M phosphate buffer of pH 8 (or to 200 µL of diluted buffer for beverages of >20% alcohol content) and a peroxide system alcohol sensor was dipped in the solution with stirring. The steady state current was measured and the background current was subtracted. The calibration graph was linear for 50-700 mg/dl of ethanol; the RSD (n = 3-5) was 0.2-0.84%. The electrode was used in a wall jet mode FIA system. Beverages diluted in 0.1 M phosphate buffer of pH 8 (100 µL) was injected into a phosphate buffer carrier stream at 1 ml/min. The calibration graph was linear for 60-300 mg/dl of ethanol with RSD (n = 10) of 0.4%. The results from the analysis of wines, beers, liqueur, port and vodka were compared with those obtained by the Sigma ethanol test kit. The batch method results agreed well with those reported by the beverage manufacturers.
Ethanol Beer Port Spirit Vodka Wine Electrode Steady state Method comparison

"Flow Injection Amperometric Biosensor Based On Immobilized L-lysine-α-oxidase For L-lysine Determination"
Anal. Lett. 1994 Volume 27, Issue 15 Pages 2849-2860
Simonian, A.L.;Badalian, I.E.;Berezov, T.T.;Smirnova, I.P.;Khaduev, S.H.

Abstract: Silica gel was modified by Robinsons method and lysine oxidase was covalently linked to the silica gel by continuous stirring for 4 h at 10°C. The resulting silica gel was washed with 50 mM potassium phosphate buffer of pH 8.2 and put into a mini reactor (11 cm x 4 mm i.d.). The minireactor was installed in a FIA system (block diagram given). A 50 mM phosphate buffer solution of pH 8 was pumped using a peristaltic pump at 400 ml/h through the system. A sample (70 µL) was injected into the buffer stream, through the minireactor for detection by a Clark O2 electrode. The calibration graph was linear up to 5.5 mM L-lysine with a detection limit of 0.2 mM. The specificity of the assay is tabulated.
l-Lysine Biological Amperometry Sensor Immobilized enzyme Silica gel

"Determination Of Glucose In Diluted Blood With A Thermal Flow Injection Analysis Biosensor"
Anal. Lett. 1994 Volume 27, Issue 14 Pages 2639-2645
Harborn, U.;Xie, B.;Danielsson, B.

Abstract: Sample (20 µL) was injected into a buffer stream (0.1 M phosphate buffer containing 2 g/l NaF, 1 g/l EDTA and 9 g/l NaCl; 50 µL/min) and was passed through the miniaturized thermal biosensor. This consisted of a stainless-steel column (15 mm x 1.5 mm i.d.) packed with glucose oxidase and catalase co-immobilized on a solid support of superporous agarose (details given). The heat produced when the sample passed through the column was measured with a thermistor connected to a Wheatstone bridge. The biosensor was calibrated with standard solutions of glucose; linear response was observed up to 1.6 mM glucose (which corresponded to 16 mM in whole blood). The RSD was 3-5%. It was possible to inject 100 tenfold diluted samples of whole blood without clogging the column. Results are discussed.
Glucose Blood Sensor Thermistor Agarose beads Immobilized enzyme

"Simultaneous Stopped-flow Determination Of Tetracycline And Doxycycline In Serum Based On Lanthanide-sensitized Luminescence"
Anal. Lett. 1994 Volume 27, Issue 12 Pages 2303-2316
Izquierdo, P.;Gomez Hens, A.;Perez Bendito, D.

Abstract: The intramolecular energy transfer from tetracycline (I) and doxycycline (II) to Eu ions was used for the rapid, simultaneous resolution of mixtures of these antibiotics in serum. The method is based on the formation of the corresponding ternary chelates in the presence of thenoyltrifluoroacetone (III). A syringe drive of the stopped-flow module was filled with a solution containing 54 µM-III, 0.2 mM Eu(III) and 10 mM Tris buffer. The other syringe was filled with a solution containing I and II of 0.1-10 and 0.15-5 µg/ml, respectively (or serum), 0.01% Triton X-100 and 10 mM Tris buffer. In each run, each solution was mixed in the mixing chamber and the variation of luminescence intensity with time monitored at 612 nm (excitation at 342 nm) over 30 s. Optimization of variables is discussed. Calibration graphs were linear for 0.1-10 and 0.15-5 µg/ml for I and II, respectively. Mean recoveries for I and II from serum were 98.7 and 96.4%, respectively, the corresponding within-assay RSD (n = 10) were 1.8 and 2.4% and the between-assay RSD (n = 5) 2.2 and 2.5%.
Tetracycline Doxycycline Blood Serum Fluorescence Stopped-flow Triton X Optimization Surfactant

"Determination Of Catechols In The Presence Of Ascorbic Acid And Uric Acid By Flow Injection Analysis Employing A Potentiometric Dibenzo-18-crown-6 Electrode Detector"
Anal. Lett. 1994 Volume 27, Issue 11 Pages 2141-2151
Lunsford, S.K.;Galal, A.;Akmal, N.;Ma, Y.L.;Zimmer, H.;Mark, H.B.

Abstract: A polished Pt disc electrode was modified by the electropolymerization of dibenzo-18-crown-6 (DB-18-C-6) on to its surface using an applied potential of +3.2 V (vs. Ag/AgCl) for 5 min in an electrolyte containing 0.025 M DB-18-C-6 and 200 mM tetrabutylammonium tetrafluoroborate. The modified electrode and a Ag/AgCl reference electrode were mounted in a thin-layer flow cell of a FIA system. The potentiometric response of the electrode to catechol and catecholamine was measured using a 20 µL injection loop and 0.1 M potassium phosphate buffer of pH 9.4 as the mobile phase (1 ml/min). The calibration graph was linear for 1 µM to 10 mM catechol and the detection limit was 0.5 µM. Similar results were obtained for the neurotransmitters. Interferences from ascorbic acid and uric acid were not significant until the concentration of the interferent exceeded a 10-fold excess.
Catechols Brain Electrode Electrode Potentiometry Interferences

"Reagentless Bioluminescent Sensor For NADH"
Anal. Lett. 1994 Volume 27, Issue 11 Pages 2055-2069
Gautier, S.M.;Michel, P.E.;Blum, L.J.

Abstract: The reagentless fiber optic biosensor was based on the bioluminescence reaction of NADH with flavin mononucleotide (FMN) and n-decyl aldehyde (decanal) in the presence of the catalysts, oxidoreductase and luciferase. The reactants, FMN and decanal, were immobilized in poly(vinyl alcohol) (PVA) matrices using two different procedures, viz., by polymerization with glutaraldehyde or by a cyclic freezing-thawing process. The catalysts were immobilized on to a polyamide membrane. The sensor was constructed by clamping the PVA and polyamide membranes on to the sensing tip of the optic fiber bundle. The assembled sensor was mounted in a flow cell (125 µL) of a FIA system. The carrier stream (0.74 ml/min) consisted of 2 mM DTT in 50 mM phosphate buffer of pH 6.9 and the luminescence intensities were measured using a Lumac Bicounter M 2500 luminometer. The sensor exhibited a linear response to 10^-500 pmol NADH and a detection limit of 10 pmol (50 µL injection volume). After the stabilization period of 30-50 min, the sensor gave a reproducible response for 1-1.5 h with a RSD (n = 16 or 22) of 3% for 500 pmol NADH.
Nicotinamide adenine dinucleotide reduced Sensor Bioluminescence Optical fiber Immobilized enzyme

"Spectrophotometric Determination Of Uranium(VI) With Chlorophosphonazo-mN By Flow Injection Analysis"
Anal. Lett. 1994 Volume 27, Issue 10 Pages 1989-1998
Sun, J.Y.;Chen, X.G.;Hu, Z.D.

Abstract: Sample (100 µL) was injected into 0.3 M HNO3 (0.8 ml/min) and 0.298 mM chlorophosphonazo-mN (0.8 ml/min) passed through a mixer coil (12 cm x 0.5 cm i.d.) and together with 1% DTPA (0.8 ml/min) through a reactor coil (90 cm x 0.5 mm i.d.). The U(VI) - chlorophosphonazo-mN complex (1:2) was measured at 680 nm. Beer's law was obeyed for 1-15 µg/ml of U(VI). The detection limit was 0.5 µg/ml of U(VI). The sampling frequency was 60/h. In the presence of DTPA a large excess of the most common cations, with the exception of Ca(II), did not interfere with the determination of 3 µg/ml of U(VI); criterion for interference was ±5% deviation of the expected signal. The method was used to determine U(VI) in standard ores and the results (tabulated) agreed well with those obtained by the standard Arsenazo III method.
Uranium(VI) Geological Spectrophotometry Interferences Method comparison Standard method

"New Poly(vinyl Chloride) Matrix Membrane Electrode For Manual And Flow Injection Determination Of Pilocarpine In Some Pharmaceutical Preparations"
Anal. Lett. 1994 Volume 27, Issue 10 Pages 1863-1874
Elnemma, E.M.

Abstract: Solutions of 10 mM pilocarpine hydrochloride (I) and 10 mM ammonium reineckate were mixed, the 1:1 complex was dried and ground. The ion-pair was added to PVC in THF and tributylphosphate, poured into a petri dish and the solvent evaporated at room temperature. The modified PVC membrane electrode was pre-conditioned in 10 mM I for 2 days. Potentiometric measurements were made with a double junction Ag/AgCl as reference electrode. The modified PVC electrode exhibited a fast response for 0.1 M 40 µM-pilocarpine (II) at pH 4-6.5 and the detection limit was 12 µM-II. Interference from basic nitrogenous compounds and some inorganic cations was negligible. The electrode was not selective for I over some other alkaloids such as quinine, narcotine and cinchonine. The average recovery of samples containing 14.7-2.447 mg/ml of II by direct potentiometric determination was 98.2% with an RSD (n = 3) of ±0.6%. With sodium tetraphenylborate the average recovery 98.9% with an RSD (n = 3) of ±0.3%. The membrane was incorporated in a sandwich flow injection cell (details given) for measurements of 24 µg/l to 2.4 mg/ml of II. The average recovery was 99% and RSD were ±0.3%.
Pilocarpine hydrochloride Pharmaceutical Electrode Potentiometry Interferences

"Application Of Differential Pulse Anodic-stripping Voltammetry With A Stopped-flow System For The Simultaneous Determination Of Lead, Copper, Antimony And Bismuth In Environmental Samples"
Anal. Lett. 1994 Volume 27, Issue 9 Pages 1779-1787
Wang, F.Q.;Li, S.Y.;Lui, S.D.;Zhang, Y.;Liu, Z.

Abstract: River water (250 ml) was mixed with 10 mL of HNO3 and evaporated to ~10 mL. Additional 10 mL portions of HNO3 and HCl were added, the solution was evaporated to near dryness and the residues dissolved in 25 mL of 1 M HCl. The solution was pumped at 1.5 ml/min for 40 s through a 100 µL flow cell containing a Ag/AgCl reference electrode and a dropping-Hg electrode maintained at -0.5 V. A stripping solution of 0.25 M malonic acid in 1 M HCl was pumped through at 1.5 ml/min for 20 s at the same potential. The flow was stopped and anodic voltammetry performed. Calibration graphs were linear for 1-1000 nM-Cu, Sb, Bi and Pb. At 1 µM-Cu, 0.5 µM-Sb and Bi and 0.48 µM-Pb RSD of better than 0.5% were obtained with recoveries of 100±7% at 10 nM for each metal. Using a deposition time of 5 min, a detection limit of ~8 nM was obtained. Mn(II), Se(IV), Te(IV) and As(III) at a 10-fold excess and Cd, Zn, Ni, Al, In(III), Ti(I), Co(II), and Fe(III) at a 50-fold excess did not interfere.
Lead Copper Antimony Bismuth Environmental River Voltammetry Electrode Interferences Stopped-flow

"Fluorimetric Determination Of Cisapride"
Anal. Lett. 1994 Volume 27, Issue 9 Pages 1713-1718
Gonzalez Martin, M.I.;Gonzalez Perez, C.;Blanco Lopez, M.A.

Abstract: Cisapride (I) was dissolved in methanol, diluted with water and analyzed spectrofluorimetrically at 355.2 nm (excitation at 310 nm). Calibration graphs were linear for 1-30 µM-I using a slit width of 5 nm with a detection limit of 32 nM using a slit width of 5 nm and for 1-400 µM-I with a detection limit of 65 nM using a slit width of 3 nm. At 20 mM I, a RSD of 1.3% was obtained. Using 8 mM Britton-Robinson buffer over the pH range 2-6 the fluorimetric response was constant and samples were stable for at least 50 min. A FIA system was also used with an optimum injection volume of 110 mL and a carrier (not specified) flow rate of 0.92 ml/min. With a slit width of 5 nm, peak height calibration graphs were linear over the range 8-400 µM-I with a detection limit of 6.5 µM. At 20 mM I a RSD of 2.2% was obtained. Both discontinuous and FIA analyzes were applied to the determination of I in tablets.
Cisapride Pharmaceutical Fluorescence

"Comparison Of Immobilization Procedures For Development Of An Electrochemical PPO-based Biosensor For Online Monitoring Of A Depuration Process"
Anal. Lett. 1994 Volume 27, Issue 9 Pages 1659-1669
Canofeni, S.;Di Sario, S.;Mela, J.;Pilloton, R.

Abstract: Polyphenol oxidase (PPO) derived from potato, mushroom and purified tyrosinase was membrane-immobilized by either cross-linking with BSA-glutaraldehyde, covalent immobilization upon a nylon net or PALL Biodyne membranes or physical entrapment (details given). The various biocatalysts were mounted onto the surface of a Clark electrode and covered with an outer dialysis membrane. Using FIA with a carrier of 0.1 M phosphate buffer of pH 6.5 at 2.4 ml/min, amperometric analyzes of catechol (I) and phenol (II) were performed. Calibration graphs and analytical performance data for the various sensor types are presented. Optimum performance was obtained with sensors prepared from tyrosinase immobilized upon a nylon net, with a linearity range of 1-10 mM I and II and a sensor lifetime of ~30 days. Applications of the sensors to the analysis of polyphenols in waste water from the production of olive oil are discussed.
Catechol Phenol Waste Sensor Dialysis

"Turbidimetric Determination Of Potassium By Flow Injection Analysis"
Anal. Lett. 1994 Volume 27, Issue 8 Pages 1625-1636
De Oliveira Torres, J.R.;Tubino, M.

Abstract: The FIA system comprised two aqueous 2% glycerol carrier solution (1.2 ml/min) into which 400 µL of a 3% sodium tetraphenylboron solution (prep. described) and 400 µL of sample solution containing 2% glycerol were separately introduced. The carrier streams were mixed in a reaction bobbin (1.5 m x 1 mm i.d.) of polyethylene tubing and the absorbance was read at 420 nm. To enhance sensitivity to 1 µg/ml, a stream of aqueous KCl solution (1.5-3 µg/ml; 0.36 ml/min) was introduced into the aqueous glycerol carrier solution The calibration graphs were linear for up to 20 µg/ml of K, the detection limit was ~1 µg/ml and the RSD were ~1%. The sampling rate was 60/h. The method was applied to plant leaves (chicory, cabbage, kale), mineral water and serum rehydration solution; the results agreed well with those obtained by flame photometry (plants) or with the expected values.
Potassium Leaves Blood Serum Mineral Turbidimetry

"New Chemiluminometric Method For The Determination Of Glycerol In Wine By Flow Injection Analysis With Immobilized Glycerol Dehydrogenase In Combination With NADH Oxidase"
Anal. Lett. 1994 Volume 27, Issue 8 Pages 1489-1505
Kondruweit, S.;Dremel, B.A.A.;Schmid, R.D.

Abstract: Wine (100 µL) and 40 µL of aqueous 5 mM NAD+ were introduced into a stream (0.8 ml/min) of 0.1 M potassium phosphate buffer of pH 9 containing 0.02% sodium azide (buffer A) and, for fluorimetric determination, carried to an enzyme reactor (30°C) containing glycerol dehydrogenase (GDH) immobilized onto controlled-pore glass with glutaraldehyde, where glycerol was converted to dihydroxyacetone; the NADH produced was detected at 460 nm (excitation at 340 nm). The calibration graph for glycerol is shown; no detection limit or RSD are given. For chemiluminometric (CL) determination, the sample first passed to an enzyme reactor (30°C) containing immobilized GDH, and then to a reactor (30°C) containing immobilized NADH oxidase, before merging with pre-mixed streams of 0.8 mM luminol and 40 mM potassium hexacyanoferrate(III), both in buffer A, for detection of H2O2. The calibration graphs for H2O2 and glycerol are shown and the detection limits were 1 nM and 25 µM, respectively; the working range was from 0.1-10 mM glycerol (RSD 2%). For both systems, sample throughput was 40/h.
Glycerol Wine Fluorescence Chemiluminescence Controlled pore glass Immobilized enzyme

"Piezoelectric Quartz Crystal Biosensor As A Direct Affinity Sensor"
Anal. Lett. 1994 Volume 27, Issue 8 Pages 1475-1487
Minunni, M.;Skladal, P.;Mascini, M.

Abstract: AT-cut piezoelectric quartz crystals with a basic resonant frequency of 10 MHz were fixed inside a flow-through thin-layer cell (30 µL) with one electrode in contact with the flowing liquid (70 µL/min); the crystal electrodes were connected to the detector (PZ 106; Universal Sensors, New Orleans, LA, USA). Adsorption of human IgG onto the Au electrode of the crystal was investigated. Measurements were performed in the continuous-flow mode using electrodes that had been treated sequentially with 1.2N-NaOH (20 min), water, 1.2N-HCl (5 min), concentrated HCl (2 min), then washed and dried in air. A graph of resonant frequency shifts for protein concentrations of 1 µg/ml to 10 mg/ml is shown; the analysis time was 5 h. The binding of mAb to 2,4-dichlorophenoxyacetic acid (2,4-D) immobilized onto the electrodes was also studied. The 2,4-D was activated with tributylamine and isobutylchloroformiate in dioxane, and immobilized with BSA onto γ-aminopropyltriethoxysilane-treated electrodes using glutaraldehyde (details given). The affinity reacton occurred in 10 min. A similar method was applied to determine 2,4-D in tap water.
Immunoglobulin G 2,4-dichlorophenoxyacetic acid Biological Water Electrode Sensor

"Fluorigenic Derivatization Of Oxazepam. Application To Its Determination In Pharmaceuticals"
Anal. Lett. 1994 Volume 27, Issue 7 Pages 1295-1306
Berrueta, L.A.;Lajusticia, L.F.;Gallo, B.;Vicente, F.

Abstract: The fluorescence reaction of oxazepam in mixtures of acetic acid and methanol and its use as a fluorescence detection system were studied. The best excitation and emission wavelengths were 364 and 469 nm, respectively. A reaction time of 5 min, a heating temperature of 100°C and a methanol/acetic acid ratio of 7:25 were the optimum conditions. The calibration graph was linear from 0.025-50 µg/ml of oxazepam and the detection limit was 0.014 µg/ml. Intra-day RSD (n = 6) was 4.25-4.13%. An FIA analytical method was developed (details given). The calibration graph for the FIA method was linear from 0.1-100 µg/ml and the detection limit was 0.035 µg/ml. The within-day reproducibility RSD (n = 3) was 5 and 0.2% for 0.5 and 50 µg/ml, respectively. The static and FIA methods were applied to the determination of oxazepam in five commercial pharmaceutical formulations (details given). HPLC was used as a reference method.
Oxazepam Pharmaceutical Fluorescence HPLC

"Enzymic Assay Of Oxalate In Urine By Flow Injection Analysis Using Immobilized Oxalate Oxidase And Chemiluminescence Detection"
Anal. Lett. 1994 Volume 27, Issue 7 Pages 1239-1253
Hansen, E.H.;Winther, S.K.;Gundstrup, M.

Abstract: The FIA manifold (schematic diagram given) consisted of a peristaltic pump, propagating a carrier stream of 66 mM citric acid buffer of pH 3.5, into which a 50 µL sample was injected, and the reagent streams [luminol and hexacyanoferrate(III)] needed for the chemiluminescent determination of the H2O2 generated by the enzymatic conversion process in the immobilized oxalate oxidase reactor. L-Ascorbic acid at concentrations >2.5 mM was the only significant chemical interference. The elimination of this interference by addition of NaNO2 did not improve the selectivity of the approach. The method was used for urine analysis. The detection limit was 34 µM in undiluted urine. The method provides a convenient and rapid means of screening.
Oxalate Urine Chemiluminescence Interferences Immobilized enzyme

"Composition Of 'copper(II)-poly(3-methylthiophene) Conducting Polymer' Electrodes"
Anal. Lett. 1994 Volume 27, Issue 7 Pages 1225-1237
Xue, Z.L.;Karagzler, A.E.;Zimmer, H.;Amer, A.;Ataman, O.;Mark, H.B.

Abstract: The electrode material formed by the chemical polymerization of 3-methylthiophene using Cu(II) salts as catalysts had previously been reported to be a poly(3-methylthiophene) incorporating co-ordinately bound Cu(II). The Cu-based substance was used as a working electrode in an amperometric detector for the detection of inorganic anions in flow injection mode. Its commercial viability made it important to elucidate the composition. The Cu-based material was analyzed by FTIR, XPS, elemental analysis and cyclic voltammetry. The material was a composite of Cu(I) and Cu(II) cations with cyano- and hydroxo-groups and some lattice or co-ordinated water molecules.
Copper(I) Copper(II) Environmental Spectrophotometry Voltammetry Electrode Amperometry

"Flow Injection Fluoroimmunoassay For Human Transferrin Using A Protein A Immunoreactor"
Anal. Lett. 1994 Volume 27, Issue 6 Pages 1067-1074
Ren, X.Z.;Miller, J.N.

Abstract: Transferrin (I) was determined in serum by flow injection fluoroimmunoassay using Lucifer Yellow VS as the label, with detection at 525 nm (excitation at 433 nm). A controlled-pore glass micro-column (5 cm x 3 mm i.d.) of PROSEP-A with two injection valves was used. Goat anti-human transferrin (50 µL) was injected into binding buffer (PBS, pH 7.4) through one valve and sample (50 µL) through the other. When washing of tracer was complete, the flow was switched to elution buffer (0.1 M citrate, pH 3) for 6 min, then switched back to binding buffer for 4 min. Flow rates were 0.25 ml/min throughout. The calibration graph was linear for up to 500 µg/ml of I. The RSD (n = 8) for 102 and 208 µg/ml of I were 10.6 and 9.4%, respectively.
Transferrin Blood Serum Immunoassay Fluorescence Controlled pore glass

"Fluorimetric Determination Of Mercury(II) Based On The Inhibition Of The Enzymic Activity Of Urease"
Anal. Lett. 1994 Volume 27, Issue 5 Pages 867-878
D. W. Bryce; J. M. Fern&aacute;ndez-Romero; M. D. Luque de Castro

Abstract: Urease was immobilized and stored at 4°C in 100 mM KH2PO4 buffer of pH 7. Glass tubes were packed with the support-enzyme conjugate. A urea solution was injected into a 5 mM phosphate buffer stream of pH 6.5, (0.7 ml/min) and passed through the enzymatic reactor (1 cm x 0.5 mm i.d.). The reaction plug then merged with the o-phthalaldehyde/N-acetyl-L-cysteine stream. Derivatization took place in an open reactor (400 cm) and was monitored at 458 nm (excitation at 340 nm). A schematic diagram of the flow manifold is given. For optimization of the inhibition process, the flow injection analysis variables were important, such as total flow rate, the flow rate of the sample and the time of sample loading. The calibration range was linear from 0.5-100 ng/ml of Hg2+. The RSD was 6.5% and the sampling frequency was 6 samples/h. The method cannot be applied to water analysis due to its low selectivity but it could be applied to special samples that do not contain Cu, Ni or Cd, or are present at such low concentrations as to cause no interference.
Mercury(II) Urine Fluorescence Interferences Optimization

"Entirely Automated Glucose Monitoring System Based On A Flow Injection Analysis Apparatus"
Anal. Lett. 1994 Volume 27, Issue 5 Pages 833-848
Pilloton, R.;Mignogna, G.;Fortunato, A.

Abstract: A polysulfone hollow fiber membrane (HFM) was used to immobilize a β-galactosidase enzyme by pumping 500 mL of β-galactosidase solution (1 g/l) with 0.1% glutaraldehyde, BSA (0.5 g/l) in 25 mM citrate buffer of pH 4.5, into the HFM module (1 ml/min) using a back-flushing configuration for 6 h. This was followed by a washing solution comprising 30 mM glycine/25 mM citrate buffer of pH 4.5. A glucose biosensor was constructed by coupling an amperometric H2O2 sensor with glucose oxidase enzyme. A 10 µL sample loop was used to inject the sample into the carrier stream of 0.1 M phosphate buffer of pH 7, with 0.01% NaN3 and amperometric detection at 0.65 V vs. Ag/AgCl. To control data acquisition, sampling and calibration, a GWBASIC program was developed. The method improved the upper limit of detection 30-fold up to 150 mM compared to that possible with the conventional amperometric biosensor and the RSD was ±2%. The system could be expanded and used to control fermentation processes; it may also be possible to extend the work to lactose and lactic acid.
Glucose Lactose Lactic acid Fermentation broth Amperometry Sensor Electrode

"Spectrophotometric Determination Of Palladium By Microwave FIA"
Anal. Lett. 1994 Volume 27, Issue 4 Pages 793-805
Xu, Y.J.;Hu, Z.D.

Abstract: In the cited FIA system (diagram given) samples (392.4 µL) and reagent [127.5 µL of 141 µM-2-(4-chloro-2-phosphonophenylazo)-7-(3-nitrophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (chlorophosphonazo-mN)] were injected into a stream (1.78 ml/min) of 10 mM H2SO4 and carried to a reaction coil (10 m x 0.5 mm i.d.), 7 m of which was situated in a microwave oven operated for 30 s at 553 W. Formation of the blue complex was monitored at 615 nm (ε = 18 200); the sampling frequency was 20/h. Beer's law was obeyed from 2-10 µg/ml of Pd and the detection limit was 1 µg/ml; the RSD was 5.6% and the recovery was 95%.
Palladium Environmental Spectrophotometry Sample preparation Microwave Heated reaction

"Flow Injection Determinations Of Creatine And Creatinine Using Packed Bed Enzyme Reactors Under Equilibrium Conditions"
Anal. Lett. 1994 Volume 27, Issue 3 Pages 495-510
Moges, G.;Johansson, G.

Abstract: Plexiglas tube reactors were included in series in a flow injection system for determination of creatinine (I) and creatine (II). The tubes contained immobilized enzymes on CPG-10 controlled-pore glass pre-silanized with aminopropylsilane and activated with glutaraldehyde. The immobilized enzymes were creatinine amidohydrolase (E.C. 3.5.2.10.) in reactor A for determination of I and creatine kinase (E.C. 2.7.3.2), pyruvate kinase (E.C. 2.7.1.40.) and lactate dehydrogenase (E.C. 1.1.1.27.) in reactor B for determination of II, pyruvate and ADP. The flow stream buffer contained 13 mM magnesium acetate, 13 mM potassium acetate, 1.1 mM ATP, 1 mM phosphenol pyruvate and 0.25 mM NADH in 70 mM imidazole acetate of pH 7.8 and detection was at 340 nm. Reactor A was bypassed if only II was determined. Linear calibration graphs were obtained for 5-400 µM-I and -II with detection limits of 6.4 µM-I and 3 µM-II. The RSD was 0.7% for 100 µM of both I and II. Reactor working lives were >5 months for A and 3 months for B.
Creatine Creatinine Biological material Spectrophotometry Controlled pore glass

"Determination Of Inorganic Phosphate By The Use Of Immobilized Enzymes In A FIA System"
Anal. Lett. 1994 Volume 27, Issue 2 Pages 309-321
Mori, H.;Kogure, M.;Kawamata, S.;Nagamoto, A.;Yamamoto, H.

Abstract: Inorganic phosphate was determined after conversion into NADPH by passage in a carrier solution (0.4 ml/min) of Tris buffer of pH 8 containing 0.1 M sucrose, 3 mM MgCl2, 1 mM NADP+ and 50 µM-glucose 1,6-diphosphate through a 8 cm reaction column at 30°C containing 40 iu each of sucrose phosphorylase, phosphoglucomutase and glucose-6-phosphate dehydrogenase bonded via glutaraldehyde to aminopropyl-bonded glass beads. A 12 µL flow cell was used for fluorimetric detection at 460 nm (excitation at 340 nm). The calibration graph was linear from 0.2 µM to 0.1 mM phosphate with a detection limit of 0.1 µM-phosphate and RSD of 4.1% at 10 µM (n = 5). For test determination of P in calf thymus this method gave the same value (5%) as the established molybdenum blue method.
Phosphate Biological material Fluorescence Glass beads Immobilized enzyme

"Determination Of Peroxide Value In Vegetable Oils By An Organic-phase Enzyme Electrode"
Anal. Lett. 1994 Volume 27, Issue 2 Pages 299-308
Mannino, S.;Cosio, M.S.;Wang, J.

Abstract: Vegetable oil (50 µL) was injected without pre-treatment into a carrier solution of CHCl3 (0.7 ml/min) saturated with aqueous 0.1 M phosphate buffer and containing 2 mM ferrocene as mediator and 0.1 M tetrabutylammonium bromide for FIA. Detection was at an enzymatic electrode operated at -0.1 V vs. an undefined reference electrode. The enzymatic electrode was prepared by coating a rough vitreous-carbon electrode with a horse-radish peroxidase/Eastman AQ-55D ester-sulfonic acid polymer mixture applied as solution and dried in situ. The calibration graph was linear from 5-200 ppm of lauroyl peroxide with test recoveries of 98-101%. The RSD (n = 7) were 2.8 and 3.1% for 10 and 52 ppm, respectively.
Peroxide ion Oil Electrode

"Flow-through Fluorimetric Sensor For The Determination Of Aluminum At The Nanogram Per Millilitre Level"
Anal. Lett. 1994 Volume 27, Issue 2 Pages 247-262
P. Ca&ntilde;izares; M. D. Luque de Castro; M. Valc&aacute;rcel

Abstract: An aqueous aluminum nitrate solution (0.5 ml) was injected into a flow stream of acetate buffer of pH 5-5.5 and after passage through a 30 cm coil was blended with a 0.025% solution of salicylaldehyde picolinylhydrazone in aqueous 40% ethanol. The resulting stream was fed at 1 ml/min through a 4 m reaction coil to a detector cell packed to a height of 9 mm with C18-bonded silica beads (60-100 mesh) on to which the reagent complex was adsorbed for fluorimetric detection at 472 nm (excitation at 372 nm). The silica beads were cleaned up by passage of 0.2 mL of 2 M HCl containing 1 M K2SO4 before arrival of the next flow injection sample and a sample throughput of 45/h was possible. The calibration graph was linear up to 200 ng/ml of Al and the determination limit was 8 ng/ml. The RSD was 6.7%. The method compared favourably with batch and conventional flow injection methods.
Aluminum Fluorescence Sensor

"Flow-through Analysis Of Glutathione In Human Erythrocytes With An Amperometric Biosensor"
Anal. Lett. 1994 Volume 27, Issue 1 Pages 15-27
Compagnone, D.;Federici, G.;Scarciglia, L.;Palleschi, G.

Abstract: Glutathione oxidase in 0.1 M phosphate buffer of pH 6.5 (buffer A) was bonded to a pre-activated Immobilon-AV membrane as described by Villarate et al. (Talanta, 1991, 38, 49). The sensor was assembled by placing the membrane in contact with the gas-permeable membrane of a Clark oxygen electrode then mounted in a flow-through cell. Buffer A was pumped through the cell until a constant current from the reduction of O2 at -0.68 V vs. Ag/AgCl was reached. Sample solution was then injected and the current change was recorded. Calibration graphs were linear for 10^-1000 µM-glutathione with a detection limit of 5 µM. At 0.1 mM, the RSD was 4.5% (n = 20) with response time of 1 min. The method was used to determine glutathione in erythrocytes. Twenty samples were analyzed by this method and by a spectrophotometric method; the correlation coefficient was 0.975. The recovery of 1-3 mM glutathione added to haemolysed erythrocytes was 95-103%.
Glutathione Human Electrode Electrode Spectrophotometry Sensor Amperometry

"Study On The Peak Type Of Flow Injection Analysis"
Anal. Lett. 1993 Volume 26, Issue 12 Pages 2679-2686
Wu, N.S.;Chen, Y.;Zhao, H.Z.

Abstract: Two equations for justifying whether a FIA peak is a gamma peak, an exponentially modified Gaussian peak, or neither, are presented. Measurements were made using: (i) a single-line manifold for reaction between CuSO4 solution (25 µg/ml) and 4-(2-pyridylazo)resorcinol in 1N-H2SO4 (0.2 µg/ml) with detection at 540 nm; (ii) a two-line manifold for reaction between phospho-molybdic acid, ascorbic acid and KH2PO4 (20 µg/ml; 30 µL injected) with detection at 660 nm; and (iii) a flow injection extraction manifold for reaction between CuSO4 (0.8 µg/ml) and sodium diethyldithiocarbamate (0.2 µg/ml) with CCl4 extraction and detection at 435 nm. Calculations were run on a PC using a BASIC program. Peak widths and asymmetry were measured manually. All peaks obtained were determined as being gamma peaks.
Spectrophotometry Peak analysis Peak width

"A New Sensor For Perchlorate Ion"
Anal. Lett. 1993 Volume 26, Issue 12 Pages 2555-2563
Fernandes, J.R.;Kubota, L.T.;Gushikem, Y.;De Oliveira Neto, G.

Abstract: A potentiometric sensor for perchlorate anion was developed by mixing a silica gel, chemically modified with 1,4-diazabicyclo (2.2.2)octane, with an epoxy polymer and carbon. The electode showed Nernstian response to the perchlorate ion in the concentration range of 10^-1 and 10^-4 mol L-1. [References: 13]
Perchlorate Electrode Electrode Electrode Potentiometry Sensor

"Model Online Flow Injection Fluorescence Immunoassay Using A Protein A Immunoreactor And Lucifer Yellow"
Anal. Lett. 1993 Volume 26, Issue 12 Pages 2543-2553
Palmer, D.A.;Ren, X.Z.;Fernandez Hernando, P.;Miller, J.N.

Abstract: A diagram of the system used is given. Transferrin antiserum (1:49 dilution in 0.15 M PBS of pH 7.4), followed by a mixture of Lucifer yellow VS-labelled transferrin (model analyte; prep. described) and transferrin standard were injected on to the immunoreactor (glass microcolumn of 5 cm x 3 mm packed with controlled pore glass protein A) using Tris buffer of pH 8.8 (0.5 ml/min). After 350 s the flow was changed to citrate buffer (0.5 ml/min) of pH 2.5 to elute the bound complex which was detected fluorimetrically at 530 nm (excitation at 430 nm); the flow was switched back to the Tris buffer after 500 s. The calibration graph was linear from 25 (detection limit) to 600 µg/ml of transferrin. The method was applied to human serum diluted 1:9 or 1:19 with 0.15 M PBS of pH 7.4 with RSD of 4.5 and 3.8%, respectively. The immunoreactor needed replacing after ~60 runs. The method could be applied to different analytes.
Immunoassay Fluorescence Reactor Controlled pore glass

"Flow Injection Analysis Of Famotidine With Spectrophotometric Detection"
Anal. Lett. 1993 Volume 26, Issue 10 Pages 2183-2191
Kamath, B.V.;Shivram, K.;Vangani, S.

Abstract: Powdered tablets equivalent to 40 mg of famotidine (I) were shaken with 60 mL of 0.2 M acetate buffer of pH 5 (buffer A) for 5 min. After dilution to 100 mL with buffer A, the mixture was filtered and a 100 µL portion of the filtrate was injected into a carrier stream of buffer A at 1.6 ml/min. This stream merged with a stream of 0.025 M cupric acetate at 0.8 ml/min then passed through a 2 m reaction coil before the absorbance was measured at 630 nm. A 5 mL portion of the initial filtrate was further diluted to 50 mL then subjected to analysis as above with the absorbance being monitored at 314 nm. Calibration graphs were linear for 10^-50 µg/ml of I with detection at 314 nm and 50-500 µg/ml with detection at 630 nm. Up to 60 samples an hour could be analyzed with a RSD of 1.4%. Recoveries were 98-100.6% and the results are comparable with those obtained by official methods.
Famotidine Pharmaceutical Sample preparation Spectrophotometry Method comparison

"Flow Microcalorimetric Determination Of Cellobiase Activity And Its Inhibition By Glucose"
Anal. Lett. 1993 Volume 26, Issue 10 Pages 2107-2112
Beran, M.;Paulicek, V.

Abstract: An assay is described for cellobiase (β-glucosidase) activity of the Trichoderma reesei CCF 1853 cellulase complex. Analysis was performed using a flow-mix system coupled with a free standing multichannel microcalorimeter. Sample solution was merged with a stream of 5 mM citrate buffer solution of pH 5 in the flow-mix cell, before passing through the measuring cell. Once a stable baseline was obtained , the clean buffer solution was changed step by step for solution with different concentrations of cellobiose or cellobiose and glucose. The heat generated by the enzymatic reaction and other side reactions was recorded in the measuring cell and the signal was corrected by the subtraction of the individual dilution heat flows of cellobiose and glucose, the interaction heat flows of cellobiose and glucose and the interaction heat flows of glucose and sample solution The flow rate was 55 mL/h and the residence time was 40 s. The method allowed the determination of cellobiase activity or cellobiose concentration with a detection limit of 10 µM-cellobiose. Results are discussed.
Enzyme, β-glucosidase Calorimetry

"Determination Of Enzymic Activities Based On An Optical Flow-through P-nitrophenol Sensor"
Anal. Lett. 1993 Volume 26, Issue 9 Pages 1847-1866
J. M. Fern&aacute;ndez-Romero; M. D. Luque de Castro; M. Valc&aacute;rcel

Abstract: The activity of β-glucuronidase (I) in serum was assayed by monitoring its catalysis of the conversion of a p-nitrophenyl derivative to p-nitrophenol (II) using an optical flow-cell. Sample solution in 100 mM dipotassium hydrogen phosphate buffer of pH 6.8 (buffer A) was injected into a carrier stream of buffer A which was merged with the stream of 0.32 mM p-nitrophenyl-β-D-glucuronide in buffer A. After passing through a 250 cm reaction coil and merging with a stream of 10 mM NaOH, the stream was passed through a 50 cm reaction coil, followed by a Dowex-1 anion-exchange resin support (chloride form; 2% cross-linked and 100-200 mesh) packed in the flow cell, where I was retained; elution was effected with 0.1 M ethylenedinitrilo tetra-acetic acid disodium salt using a switching valve. All flow rates were 1.7 ml/min. The retention-elution process was monitored continuously at 405 nm. The calibration graphs for I and II were linear from 0.1-20 iu/l and 0.1-5 µg/ml, respectively with corresponding RSD of 1.7-3.0% and 2.0-2.4%. The sampling rate was 20 samples/h with recoveries of 95-104%.
Enzyme, β-glucuronidase Sensor Dowex Resin Buffer

"Highly Selective And Sensitive Amperometric Biosensing Of Glucose At Ruthenium-dispersed Carbon-paste Enzyme Electrodes"
Anal. Lett. 1993 Volume 26, Issue 9 Pages 1819-1830
Wang, J.;Fang, L.;Lopez, D.;Tobias, H.

Abstract: A carbon paste containing 5% Ru was mixed with octadecylamine (5%), dissolved in CHCl3 and the solvent was allowed to evaporate overnight. Glucose oxidase (5%) was added to the paste, which was mixed thoroughly before packing into a PTFE tube (3 mm i.d.). A Cu wire was inserted into the paste and the resulting electrode was used for the amperometric determination of glucose. Measurements were performed at room temperature in the optimal potential range of -0.15 - 0.2 V. This low-potential operation was possible due to the powerful electrocatalytic efficiency of the Ru sites, which accelerated the reductive detection of the liberated peroxide species and minimized the contributions from easily oxidized species (e.g., acetaminophen, uric acid, ascorbic acids or catecholamines) which are common interferents in the amperometric determination of glucose. The fast response time of the electrode permitted its application in the flow injection determination of glucose. The peak width was ~15 s, allowing an injection rate of 80 samples/h. The calibration graph was linear up to 50 mM glucose and the RSD (n = 30) was 4% (30 mM glucose).
Glucose Amperometry Electrode Sensor Interferences Peak width

"Indirect Flow Injection Analysis Of Ascorbic Acid By Photochemical Reduction Of Methylene Blue"
Anal. Lett. 1993 Volume 26, Issue 8 Pages 1741-1750
Leon, L.E.;Catapano, J.

Abstract: Sample (185 µL) was injected into a carrier stream (1.5 ml/min) of buffered methylene blue solution of pH 3.2 (12.7 µg/ml). The stream was passed through a reactor coil (1.5 m x 0.7 mm) immersed in a thermostatically-controlled water bath at 32°C and irradiated by means of a 500-W halogen lamp. The resulting change in absorbance of the carrier solution was monitored at 666 nm. The detection limit was 0.34 µg/ml of ascorbic acid (I). The calibration graph was rectilinear for 0.18-6.12 µg/ml of I and RSD ranged from 0.3-2.1%. Glucose, fructose, saccharose, sodium tartrate, citric acid, sodium benzoate, maleic acid, caffeine and nicotine did not interfere. The cited method was applied in the analysis of vitamin C tablets. Results agreed well with those obtained by the official AOAC method.
Ascorbic acid Pharmaceutical Spectrophotometry Photochemistry Method comparison Standard method Interferences Indirect

"Flow Injection Analysis Of Glucose By Fibre-optic Chemiluminescence Measurement"
Anal. Lett. 1993 Volume 26, Issue 7 Pages 1493-1503
Suleiman, A.A.;Villarta, R.L.;Guilbault, G.G.

Abstract: The cited system consisted of a reagent stream (0.3 ml/min) of 1 mM luminol in 25 mM Na2CO3, which was merged with a second stream of 10 mM K3Fe(CN)6. The sample stream (0.3 ml/min) consisted of 50 mM acetate buffer of pH 5.6 and was passed over a column of immobilized glucose oxidase reactor, which oxidized the glucose present in the sample to gluconic acid and H2O2. The latter was transported by the sample stream to a flow cell, where it reacted with the mixed reagent stream. The resulting chemiluminescence was passed through an optical bundle to a detector and recorded. The calibration graph was rectilinear for 0.25-2.5 mM with an RSD of 5%. The cited method was applied to the determination of glucose in baby fruit juices. Results agreed well with those obtained by official AOAC methods. No interferences were observed by the presence of fructose, ascorbic acid, citric acid and other polysaccharides.
Glucose Fruit Chemiluminescence Optical fiber Immobilized enzyme Interferences

"Novel Protein Binding Capacity And Selectivity Of Immobilized Pyridinium Pseudo-affinity Gels: Applications In Immunoglobulin G Purification And Quantitative Determination"
Anal. Lett. 1993 Volume 26, Issue 7 Pages 1477-1491
Ngo, T.T.

Abstract: Gels were prepared by suspending Sepharose Cl-4B (100 ml) in water (100 ml) on a rotary shaker. Dry acetone (1 l) was added gradually and resuspended in dry DMF. The operation was repeated several times except that the gel was resuspended sequentially in DMF containing 27.5 mM 4-dimethylaminopyridine, 10% 2-mercaptoethanol in 0.1 M NaHCO3 (pH 9), 0.1 M NaOH and finally PBS, in which it was stored. The affinity of the gel towards protein was illustrated with some specific applications, e.g., purification of IgG antibodies and quantitative determination of the antibodies by FIA. A mechanism for the protein adsorption to the gel was proposed and discussed. The calibration graph was rectilinear from 0.25-2.5 mg/ml of IgG. Recoveries were 99-101%.
Proteins Sample preparation Extraction

"Flow Injection Immunosensor For Theophylline"
Anal. Lett. 1993 Volume 26, Issue 7 Pages 1425-1439
Palmer, D.A.;Edmonds, T.E.;Seare, N.J.

Abstract: Glass micro-columns (5 cm x 3 mm) were packed with controlled pore glass-protein A and mounted on an FIA system. Theophylline (I) antisera in PBS (pH 7.4) was injected into a Tris buffer (pH 8.8) carrier stream (0.5 ml/min) and immobilized on the column. A mixture of alkaline labelled I and I standard was similarly loaded onto the reactor column. The label and standard competed for the immobilized antibody. A solution of p-aminophenol was measured amperometrically. The calibration range (not linear) was from 60-300 ng/ml of I. The detection limit was 25 ng/ml of I. Recoveries were 85%. Intra- and inter-day RSD ranged from 8.9-7.7% and 10.4-11.7%, respectively.
Theophylline Immunoassay Amperometry Sensor Controlled pore glass

"FIA Potentiometric And Solvent Extraction Studies Of Alkali Metal And Alkaline-earth Cation Complexation By Bis(t-butylbenzo)-21-crown-7"
Anal. Lett. 1993 Volume 26, Issue 7 Pages 1413-1424
Attiyat, A.S.;Christian, G.D.;McDonough, J.A.;Strzelbicka, B.;Goo, M.J.;Yu, Z.Y.;Bartsch, R.A.

Abstract: Portions (200 µL) of standard solution containing Cs+, Rb+, K+, Na+, Li+, Sr2+, Ca2+ and Mg2+ were injected on to the FIA system described by Xie et al. (Anal. Chim. Acta, 1986, 184, 259). Amperometric detection was used by employing an electrode membrane prepared by coating the tip of a Ag wire with a mixture containing o-nitrophenyl oct