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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
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Fresenius Journal of Analytical Chemistry

  • Publisher: Springer
  • FAD Code: FJAC
  • CODEN: FJACES
  • ISSN: 0937-0633
  • Abbreviation: Fresenius J. Anal. Chem.
  • DOI Prefix: 10.1007/s00216-,10.1007/BF
  • Other Name(s): Fresenius Zeischrift fur Analytische Chemie
  • Language: English,German
  • Comments: Fulltext from 1862 V1

Citations 549

"Derivative Hydride Generation Atomic Absorption Spectrometry And Determination Of Lead Traces In Waters"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 8 Pages 1154-1157
Han-wen Sun, Jing Ha, Jian-min Sun, Li-li Yang, De-qiang Zhang

Abstract: Fundamentals of derivative hydride-generation atomic absorption spectrometry (DHGAAS) are described. A linear relationship was obtained between the derivative absorbance and the concentration of analysis in a sample. The new DHGAAS method was applied to the determination of traces of lead in water. The conditions affecting the derivative absorbance of lead were evaluated and optimized. The detection limit and sensitivity of the proposed method were 26 times and 8.8 times better, respectively, than those of conventional hydride-generation atomic absorption spectrometry. The characteristic concentration (for a derivative absorbance of 0.0044) and detection limit (3s) for lead were 0.017 and 0.096 ng mL-1, respectively, for a 2 mV min-1 sensitivity range setting. The recovery range was 92.5-103%.

"Coupling Pervaporation To AAS For Inorganic And Organic Mercury Determination. A New Approach To Speciation Of Hg In Environmental Samples"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 8 Pages 1124-1129
Consuelo Fernandez-Rivas, Riansares Muñoz-Olivas, Carmen Camara

Abstract: The design and development of a new approach for Hg speciation in environmental samples is described in detail. This method, consisting of the coupling of pervaporation and atomic absorption spectrometry, is based on a membrane phenomenon that combines the evaporation of volatile analytes and their diffusion through a polymeric membrane. It is proposed here as an alternative to gas chromatography for speciation of inorganic and organic Hg compounds, as the latter compounds are volatile and can be separated by applying the principles mentioned above. The interest of this method lies in its easy handling, low cost, and rapidity for the analysis of liquid and solid samples. This method has been applied to Hg speciation in a compost sample provided by a waste water treatment plant.
Extraction Derivatization

"Flow Injection Analysis Of Nitrate By Reduction To Nitrite And Gas-phase Molecular Absorption Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 8 Pages 1113-1118
Behzad Haghighi, Abdollah Tavassoli

Abstract: Two flow injection manifolds have been investigated for the determination of nitrate. These manifolds are based on the reduction of nitrate to nitrite and determination of nitrite by gas-phase molecular absorption spectrophotometry. Nitrate sample solution (300 µL) which is injected to the flow line, is reduced to nitrite by reaction with hydrazine or passage through the on-line copperized cadmium (Cd-Cu) reduction column. The nitrite produced reacts with a stream of hydrochloric acid and the evolved gases are purged into the stream of O-2 carrier gas. The gaseous phase is separated from the liquid phase using a gas-liquid separator and then swept into a flow-through cell which has been positioned in the cell compartment of an UV-visible spectrophotometer. The absorbance of the gaseous phase is measured at 204.7 nm. A linear relationship was obtained between the intensity of absorption signals and concentration of nitrate when Cd-Cu reduction method was used, but a logarithmic relationship was obtained when the hydrazine reduction method was used. By use of the Cd-Cu reduction method, up to 330 µg of nitrate was determined. The limit of detection was 2.97 µg nitrate and the relative standard deviations for the determination of 12.0, 30.0 and 150 µg nitrate were 3.32, 3.87 and 3.6%, respectively. Maximum sampling rate was approximately 30 samples per hour. The Cd-Cu reduction method was applied to the determination of nitrate and the simultaneous determination of nitrate and nitrite in meat products, vegetables, urine, and a water sample.

"Preconcentration Of Chromium(III) And Speciation Of Chromium By Electrothermal Atomic Absorption Spectrometry Using Cellulose Adsorbent"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 7 Pages 1037-1040
Farzaneh Shemirani, Maryam Rajabi

Abstract: A simple and sensitive method has been developed for species selective determination of chromium(III) and chromium(VI) in water by electrothermal atomic absorption spectrometry. The procedure is based on selective absorption of Cr(III) on a cellulose µcolumn (pH 11, 0.5 mol L-1 NaCl). Total chromium was subsequently determined after appropriate reduction of Cr(VI) to Cr(III). Recoveries of more than 97% were found. A concentration factor of 100 was achieved. The relative standard deviations (n=10) at the 40 ng L-1 level for chromium(III) and chromium(VI) were 2.3% and 1.8% and corresponding limits of detection (based on 3C) were 1.8 ng L-1 and 5.1 ng L-1, respectively. No interference effects have been observed from other investigated species and the method has been successfully applied to natural water samples.

"Potentiometric Sensor Array For The Determination Of Lysine In Feed Samples Using Multivariate Calibration Methods"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 7 Pages 1001-1008
N. García-Villar, J. Saurina, S. Hernández-Cassou

Abstract: A potentiometric sensor array has been developed for the determination of lysine in feed samples. The sensor array consists of a lysine biosensor and seven ion-selective electrodes for NH4+, K+, Na+, Ca2+, Mg2+, Li+, and H+, all based on all-solid-state technology. The potentiometric lysine biosensor comprises a lysine oxidase membrane assembled on an NH4+ electrode. Because the selectivity of the lysine biosensor towards other cation species is not sufficient. there is severe interference with the potentiometric response. This poor selectivity can be circumvented mathematically by analysis of the richer information contained in the multi-sensor data. The sensor array takes advantage of the cross-selectivity of lysine for each electrode, which differs from the other species and quantification of lysine in complex feed sample extracts is accomplished with multivariate calibration methods, such as partial least-squares regression. The results obtained are in a reasonable agreement with those given by the standard method for amino acid analysis.

"Determination Of Low Cadmium Concentrations In Wine By On-line Preconcentration In A Knotted Reactor Coupled To An Inductively Coupled Plasma Optical Emission Spectrometer With Ultrasonic Nebulization"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 7 Pages 989-993
R. F. Lara, R. G. Wuilloud, J. A. Salonia, R. A. Olsina, L. D. Martinez

Abstract: An on-line cadmium pre-concentration and determination system implemented with inductively coupled plasma optical emission spectrometry (ICP-OES) associated to flow injection (FI) with ultrasonic nebulization system (USN) was studied. The cadmium was retained as the cadmium-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, Cd-(5-Br-PADAP), complex, at pH 9.5. The cadmium complex was removed from the knotted reactor (KR) with 3.0 mol/L nitric acid. A total enhancement factor of 216 was obtained with respect to ICP-OES using pneumatic nebulization (12 for USN and 18 for KR) with a pre-concentration time of 60 s. The value of the detection limit for the pre-concentration of 5 mL of sample solution was 5 ng/L. The precision for 10 replicate determinations at the 5 µg/L Cd level was 2.9% relative standard deviation (RSD), calculated from the peak heights obtained. The calibration graph using the pre-concentration system for cadmium was linear with a correlation coefficient of 0.9998 at levels near the detection limits up to at least 1000 µg/L. The method was successfully applied to the determination of cadmium in wine samples.

"Speciation And Oxidation Kinetics Of Arsenic In The Thermal Springs Of Wiesbaden Spa, Germany"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 7 Pages 927-933
Susanne P. Schwenzer, Caterina E. Tommaseo, Michael Kersten, Thomas Kirnbauer

Abstract: Since 1886 arsenic has been known to be present as a trace component in the Wiesbaden thermal waters at concentrations of over 100 µg L-1. In this study for the first time molecular level speciation of arsenic was measured both in the water (by HG-AAS) and in well-stone scale deposits (by XANES). Most of the arsenic in the anoxic NaCl-type waters is in the reduced arsenite form. Hydrous ferric oxide (HFO) precipitates in the scale deposits scavenge only the minor dissolved arsenate portion which is, however, accumulated up to 3% w/w. Isothermal precipitation experiments at in-situ temperatures showed a difference between the progress of both arsenic and iron oxidation and precipitation. This can be explained in terms of adsorption of the aqueous arsenite and heterogeneous oxidation on the HFO surface, but subsequently rapid release of the arsenate thereby formed back into the aqueous phase at enhanced temperature and increased pH. Such relatively rapid pseudo-homogeneous arsenite oxidation is too slow to efficiently retard the As(III) load already on the wellhead, but fast enough to prevent arsenic seepage into ground water aquifers.
Adsorption

"Automated Flow Injection Spectrophotometric Determination Of Nitrosamines In Solid Food Samples"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 6 Pages 891-895
Encarnación Luque-Pérez, Angel Ríos, Miguel Valcárce

Abstract: A spectrophotometric method using a flow injection system is proposed for the determination of nitrosamines in foods (cured-meats). The method is based on the photochemical cleavage of the N-NO bond of the nitrosamine to yield the corresponding amine and nitrite. The nitrite is then detected spectrophotometrically, at 542 nm, by use of its reaction with a modified Griess reagent. Different linear ranges between 0.8 and 2000 ng mL-1 are obtained for the method, depending on the time of exposure of the sample to the UV radiation. The relative standard deviation varies between 2.0 and 3.9% and the sample throughput is between three and seven samples per hour, depending on the experimental conditions. The proposed method was successfully applied to the analysis of N-nitrosodimethylamine in cured ham and loin, bacon, and sausages. [Journal Article; In English; Germany]

"Development And Evaluation Of A Calibration Gas Generator For The Analysis Of Volatile Organic Compounds In Air Based On The Injection Method"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 6 Pages 798-805
Erwin Rosenberg, Rainer A. Hallama, Manfred Grasserbauer

Abstract: The development and operational evaluation of a calibration gas generator for the analysis of volatile or ganic compounds (VOC) in air is described. Details of the construction, as well as of the evaluation of the apparatus are presented here. The performance of the test gas generator is validated both by on-line GC analysis of the calibration gas produced and by off-line analysis of adsorptive samples taken from the generated calibration gas. Both, active and passive sampling have been used, and the results demonstrate the excellent accuracy and precision of the generated test gas atmosphere: For the 11 investigated organic compounds (aromatic and halogenated compounds), the found values were in most cases within 5% of the target value with a reproducibility of better than 3% RSD (as determined by the analysis of the sampled adsorbent tubes). Custom made adsorbent tubes were used for active and passive sampling and in both cases were analyzed by thermal-desorption GC. Particularly the combination of passive sampling and thermodesorption-GC analysis offers significant advantages over the commonly used active sampling on activated charcoal, followed by CS2 desorption in terms of avoidance of hazardous solvents, potential for automation and improved detection limits. Both sampling techniques are capable for monitoring VOCs at concentrations and under conditions relevant for workplace monitoring. [Journal Article; In English; Germany]

"Mercury Speciation By HPLC-cold-vapor Radiofrequency Glow-discharge Optical-emission Spectrometry With On-line Microwave Oxidation"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 6 Pages 746-752
Roberto Martínez, Rosario Pereiro, Alfredo Sanz-Medel, Nerea Bordel

Abstract: Hollow-cathode (HC) radiofrequency glow-discharge (rf-GD) optical-emission spectrometry (OES) has been used as detector for the determination of inorganic mercury by cold-vapor (CV) generation in a flow injection (FI) system. Both NaBH4 and SnCl2 were evaluated as reducing reagents for production of mercury CV. The conditions governing the discharge (pressure, He flow rate, and delivered power) and Hg CV generation (NaBH4 or SnCl2 concentration and reagent flow rate) were optimized using both reducing agents. The analytical performance characteristics of FI-CV-rf-GD-OES for mercury detection were evaluated at the 253.6 run emission mercury line. Detection limits (DL) of 0.2 ng mL-1 using SnCl2 and 1.8 ng mL-1 using NaBH4 were obtained (100 µL sample injections were used). When the optimized experimental conditions using SnCl2 had been determined, the analytical potential of this CV-rf-GD-OES method was investigated as on-line detector for high-performance liquid chromatographic (HPLC) speciation of mercury (Hg(II) and methylmercury). The HPLC-CV-rf-GD-OES detection limits for 100 µL sample injections were found to be 1.2 and 1.8 ng mL-1 (as mercury) of inorganic mercury and methylmercury, respectively. The reproducibility observed was below 8% for both species. Finally, the HPLC-CV-rf-GD-OES system developed was successfully applied to the determination of methylmercury (speciation) in two certified reference materials, Dorm-2 and Dolt-2.
Preconcentration

"Optimization Of Electrochemical Hydride Generation In A Miniaturized Electrolytic Flow Cell Coupled To Microwave-induced Plasma Atomic Emission Spectrometry For The Determination Of Selenium"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 6 Pages 740-745
S. Schermer, L. Jurica, J. Paumard, E. Beinrohr, F.-M. Matysik, J. A. C. Broekaert

Abstract: The optimization of a continuous flow system for electrochemical hydride generation coupled to microwave-induced plasma atomic emission spectrometry (MIP-AF-S) for the determination of Se is presented. A small electrolytic cell with a porous glassy carbon working electrode was used for hydride generation. When using an Ar MIP operated in a TE101 cavity a detection limit of 0.6 ng mL-1 (3s) could be achieved. The calibration curve was linear up to 1 µg mL-1. A standard deviation of less than 2% (10 replicate analyzes) could be achieved. It was shown that interferences of transition metals are of the same order of magnitude as with a larger electrolysis cell described earlier, and light elements hardly caused any signal depression as tested. It was possible to distinguish between Se(IV) and Se(VI) species and seleno-DL-methionine, because under optimized conditions of an electrolysis current of 10 mA, a microwave power of 210 W, an Ar flow rate of 15 L h-1 and a sample flow rate of 2.5 mL min-1 only Se(IV) was transformed to H2Se and transferred into the plasma. Finally, the possibility of an electrochemical pre-enrichment was shown to enable it to further decrease the detection limit.

"New Application Of A Traditional Analytical Method - Arsenic Removal From Water Works Sludge During Iron(III) Chloride Coagulant Production"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 5 Pages 629-636
Dietrich Maier, Matthias Maier, Frank Oberacker

Abstract: The Marsh Test, the original means of determination of arsenic by hydride generation, has been modified to remove arsenic from water works sludge, with iron used instead of zinc as the main agent. Water works sludge (main compound iron(III) oxyhydrate) generated during groundwater treatment can be enriched in arsenic up to several g kg-1. Acidic dissolution of this sludge to produce FeCl3 coagulant liberates the arsenic. Addition of elemental iron reduces this dissolved As(V) mainly to dispersed elemental As(O) particles, which can be removed by filtration. If the reaction temperature is kept below 50°C, more than 99% of the arsenic can be removed from the coagulant solution and less than 10% will escape as gaseous arsine (AsH3). Severe foaming and silicic acid gel formation occurs during the acidic dissolution, however. For technical and economic reasons the use of the water works sludge for FeCl3 coagulant production is not competitive when compared with other recycling methods.

"HG/LT-GC/ICP-MS Coupling For Identification Of Metal(loid) Species In Human Urine After Fish Consumption"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 5 Pages 586-590
J. Kresimon, U. M. Grüter, A. V. Hirner

Abstract: Human urine samples after fish consumption have been investigated by low-temperature gas chromatography with inductively coupled plasma mass spectrometric detection after sample derivatization by hydride generation (HG/LT-GC/ICP-MS). This analytical technique enabled the identification of organometal(loid) compounds in human urine; species of the six elements germanium, arsenic, selenium, tin, antimony, and mercury were determined. Three different organic selenium species, two germanium species, seven arsenic species, four tin species, five antimony species, and one species of mercury were found; 18 of the 22 species detected could be identified. The relative detection limits ranged between 2 and 12 pg L-1 (x=element). These organometal(loid) compounds probably build up in the human body under the influence of micro-organisms, in the presence of hydrogen sulfide and methane, in the human intestine.

"Ruthenium And Ruthenium Dioxide-modified Graphite-ethylene/ Propylene/diene And Graphite-teflon Composite Electrodes As Amperometric Flow Detectors. Application To The Determination Of Methionine"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 4 Pages 507-513
María Pedrero, Pilar Salas, Rocío Gálvez, F. Javier Manuel de Villena, José M. Pingarrón

Abstract: The flow injection amperometric performance of solid composite graphite electrodes with ethylene/propylene/diene (EPD) or Teflon as binding agents, and with Ru or RuO2 particles as electrocatalytic modifiers has been compared. Both, Ru and RuO2 modified electrodes exhibited electrocatalytic properties on the methionine oxidation process in alkaline media. The electrodes composition and the hydrodynamic and chemical variables were optimized. Graphite-EPD (GEPD) electrodes showed a better analytical performance than graphite-Teflon (GPTFE) electrodes. Furthermore, a better sensitivity, repeatability and reproducibility was observed for RuO2-GEPD electrodes when compared with Ru-GEPD electrodes. At an applied potential of +0.50 V, a detection limit for methionine of 4.8 x 10^-5 mol L-1, similar to those reported in the literature for other RuO2-modified electrodes, was obtained. The analytical applicability of RuO2-GEPD electrodes was demonstrated by determining methionine in a complex pharmaceutical formulation. [Journal Article; In English; Germany]

"Antibody-based Methods For Surfactant Screening"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 4 Pages 456-466
M. Fránek, J. Zeravík, S. A. Eremin, J. Yakovleva, M. Badea, A. Danet, C. Nistor, N. Ocio, J. Emnéus

Abstract: This brief overview summarises the immunoassay-based results obtained in the course of two years of the European INCO-Copernicus project BIOTOOLS. The project is aimed at simplifying the procedures for detection of surface active compounds (SAC) using, among others, antibody-based methods, i.e., microtiter plate-based enzyme-linked immunosorbent assays (ELISA), polarisation fluoro immunoassays (PFIA), and enzyme flow injection immunoassays (FIIA). Thirty-three rabbits were immunised with five different sulphophenyl moieties and three p-hydroxyphenyl moieties conjugated to protein immunogens to produce analytical antibodies against linear alkylbenzene sulphonates (LAS) and nonylphenol (NP). Although most of the antibodies exhibited binding reaction in indirect ELISA, only a few showed the required assay sensitivity. The best antibodies for LAS exhibited a 50% binding inhibition at IC50 19.8 µg L-1 in indirect ELISA. Similar inhibition was observed for direct ELISA using peroxidase tracers. Antibodies against NP allowed the establishment of an indirect assay operating in the mg L-1 range. A rapid and simple protocol for the screening of NP and LAS using homogeneous PFIA is described. The assay time for 10 samples was 7 minutes, thus allowing fast detection of the selected SAC at the mg L-1) level. A generic competitive FIIA system, using a protein G column for separation of free and antibody-bound β-galactosidase (β-Gal) tracer, was developed for the screening of LAS, NP, and nonylphenol decaethoxylate (NPEO10). The FIIA had a sample throughput (STP) of 5-10 samples per hour, with limits of detection (LOD) for LAS, NP, and NPEO10 of 19.5, 52, and 2.4 µg L-1, respectively. The developed FIIAs were applied to spiked rain and surface water.

"Hyphenation Of Gas-diffusion Separation And Ion Chromatography Part 1: Determination Of Free Sulfite In Wines"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 4 Pages 425-430
Sara Fäldt, Bo Karlberg, Wolfgang Frenzel

Abstract: The hyphenation of gas-diffusion separation and ion chromatography (IC) is described as a convenient, reliable, robust, and economic method for in-line sample pre-treatment. The high selectivity associated with this method permits direct analysis of samples containing microparticulates, colloidal matter, and/or high molecular weight compounds. The determination of sulfite serves as a first example of its application. The method is based on the diffusional separation of SO2. following in-line oxidation with hydrogen peroxide to sulfate and final determination of the sulfate formed using IC. The influence of operational parameters has been thoroughly investigated and gas-diffusion cells of different geometries compared with respect to the gas-transfer rates obtained. Application to the analysis of wines demonstrates the utility of the method.

"Spectrophotometric Determination Of Chloride In Mineral And Drinking Waters Using Sequential Injection Analysis"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 3 Pages 396-399
J. F. van Staden, S. I. Tlowana

Abstract: An on-line sequential injection system has been developed for spectrophotometric determination of chloride in drinking mineral. natural, and ground waters. Samples containing different concentrations of chloride were analyzed. The analysis is based on detection of the red iron(Ill) thiocyanate complex. The complex was monitored spectrophotometrically at 480 run using de-ionized water as the carrier stream at a flow rate of 3.21 mL min-1. The method was found to be linear within the range 0-50 mg L-1 chloride. the detection limit was 3.01 mg L-1. The fully automated method can be used to analyze 37 samples per hour with a relative standard deviation (RSD) better than 2.50%.

"Determination Of Zinc In Pharmaceutical Products By Use Of A Sequential Injection Analysis System"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 3 Pages 376-379
J. Koos F. van Staden, M. Tsanwani

Abstract: A sequential injection analysis (SIA) system is proposed for the determination of zinc in pharmaceutical samples. The method is based on the spectrophotometric detection of zinc using xylenol orange as a color reagent at 568 nm. The system can be used to monitor zinc at a frequency of 30 samples h-1 with an average recovery of±98.5% and a relative standard deviation of less than 1%. A linear relationship between peak height and zinc concentration is obtained between 10 and 60 mg L-1. The results obtained are in good agreement with those obtained by use of a standard method.

"Flow Injection Manifold For The Simultaneous Spectrophotometric Determination Of Fe(III) And Fe(III) Using 2,2 -dipyridyl-2-pyridylhydrazone And A Single-line Double Injection Approach"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 3 Pages 364-368
Demetrius G. Themelis, Paraskevas D. Tzanavaras, Fotini S. Kika, Michael C. Sofoniou

Abstract: A simple and rapid flow injection (FI) method is reported for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) in pharmaceutical products. The method is based on the reaction of Fe(II) with 2,2-dipyridyl-2-pyridylhydrazone (DPPH) in acidic medium to form a water-soluble reddish complex (lambda (max)=535 nm). Fe(III) reacts with DPPH under flow conditions only after its on-line reduction by ascorbic acid (AsA). Both analytes were determined in the same run via a double-injection valve, which enabled the simultaneous injection of two sample volumes in the same carrier stream (,,singleline double-injection approach). The two well-defined peaks produced corresponded to total iron [Fe(II)+Fe(III)] and Fe(II). Speciation of the analytes in their mixtures was achieved by multiple regression analysis. The calibration curves obtained were linear over the ranges 0-30 and 0-50 mg L-1 for Fe(II) and Fe(III), respectively, and the precision [s(r)=1.0% for Fe(II) and 1.5% for Fe(III)] was satisfactory. The method proved to be selective and adequately sensitive (c(L)=0.25 and 0.17 mg L-1 for Fe(III) and Fe(II), respectively, in mixtures). Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 99.0-102.0% for both Fe(II) and Fe(III) and the mean relative error was e(r)=1.0%.
Preconcentration Tiron

"On-line Mercury And Methylmercury Pre-concentration By Adsorption Of Their Dithiophosphoric Acid Diacyl Ester Chelates On A C-18 Column And Cold-vapor Atomic-absorption Detection"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 3 Pages 353-357
Alcicléa da C. P. Monteiro, Ly S. N. de Andrade, Reinaldo C. de Campos

Abstract: The pre-concentration of mercury(II) and methylmercury by adsorption of their dithiophosphoric acid diacyl ester (DDTP) chelates on a C-18 column, then detection with cold-vapor atomic-absorption spectrometry was investigated. Conditions such as sample pH, reductant and chelating agent flow and concentration, and eluent and carrier gas flow were optimized. Optimization was performed by use of evolutionary operation with a proper factorial design. At a sample flow of 5.3 mL min-1 and a loading time of 4.5 min, column adsorption efficiency ranged from 88 to 93% for both species. Detection limits down to 10 ng L-1 were obtained at a sample throughput of 12 h-1. There was good agreement between found and certified values in the analysis of certified reference materials after their microwave-assisted mineralization with HNO3 and H2O2.
Preconcentration

"Multi-layer Microfluidic Glass Chips For Microanalytical Applications"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 2 Pages 261-269
Antoine Daridon, Valia Fascio, Jan Lichtenberg, Rolf Wütrich, Hans Langen, Elisabeth Verpoorte, Nico F. de Rooij

Abstract: A new, versatile architecture is presented for microfluidic devices made entirely from glass, for use with reagents which would prove highly corrosive for silicon. Chips consist of three layers of glass wafers bonded together by fusion bonding. On the inside wafer faces a network of microfluidic channels is created by photolithography and wet chemical etching. Low dead-volume fluidic connections between the layers are fabricated by spark-assisted etching (SAE), a computer numerical controlled (CNC)-like machining technique new to microfluidic system fabrication. This method is also used to form a vertical, long path-length, optical cuvette through the middle wafer for optical absorbance detection of low-concentration compounds. Advantages of this technique compared with other, more standard, methods are discussed. When the new glass-based device for flow injection analysis of ammonia was compared with our first-generation chips based on silicon micromachining, concentration sensitivity was higher, because of the longer path-length of the optical cuvette. The dependence of dispersion on velocity profile and on channel cross-sectional geometry is discussed. The rapid implementation of the devices for an organic synthesis reaction, the Wittig reaction, is also briefly described. [Journal Article; In English; Germany]

"Multiport Flow-control System For Lab-on-a-chip Microfluidic Devices"
Fresenius J. Anal. Chem. 2001 Volume 371, Issue 2 Pages 106-111
Ring-Ling Chien, Wallace J. Parce

Abstract: A multiport system suitable for pressure control on a lab-on-a-chip microfluidic device is described. An algorithm and a strategy for calculating pressures were developed to control the flow from multiple reservoirs for the microfluidic devices. Dye mixing and enzyme assay titration experiments were performed using pressure-driven flow only. Results show a good linear response over two orders of dynamic range.

"Flow Injection Chemical Vapor-generating Procedure For The Determination Of Au By Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 8 Pages 1065-1070
Xiaoguang Du, Shukun Xu

Abstract: Volatile Au species in an acidified medium were generated at room temperature by reduction with NaBH4 in acidified aqueous medium using a flow injection chemical vapor-generation atomic absorption spectrometric (FI-CVG-AAS) system in the presence of µamounts of sodium diethyldithiocarbamate (DDTC). Precision of 2.0% RSD (n = 11, 2.0 mg L-1 level) was obtained at a sample throughput of 180 h-1. A detection limit of 24 ng mL-1 (3s) was obtained with 300 µL sample solution. The method was used for the determination of gold in ore sample digests, and the results obtained agreed well with those obtained by flame AAS.

"A Simple Flow-injection On-line Clean-up System For Microwave Plasma-torch Atomic Emission Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 8 Pages 1061-1064
Liwei Zhao, Minjing Li, Xiaohang Xie, Daqian Song, Yuan Tian, Lijuan Zhang, Danhong Jin, Hanqi Zhang, Q. Jin

Abstract: A simple flow injection (FI) on-line clean-up system has been developed for microwave plasma-torch atomic emission spectrometry (MPT-AES). A non-selective strongly acidic cation-exchange resin was used to achieve the goal of on-line clean-up. Ag and Zr, which form halogen-complex anions in halide acid media. and Cr. Mo, and P, which exist as acid group anions or acids (neutral) in acidic solution, were determined and the interfering matrix cations were removed on-line. Satisfactory analytical results were obtained from some practical samples by use of this procedure.
Preconcentration Interferences Column

"Analytical Methodologies For Aluminum Speciation In Environmental And Biological Samples - A Review"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 8 Pages 984-996
S.-p. Bi, Xiao-di Yang, Fu-ping Zhang, Xian-long Wang, Gong-wei Zou

Abstract: It is recognized that aluminum (Al) is a potential environmental hazard. Acidic deposition has been linked to increased Al concentrations in natural waters. Elevated levels of Al might have serious consequences for biological communities. Of particular interest is the speciation of Al in aquatic environments, because Al toxicity depends on its forms and concentrations. In this paper, advances in analytical methodologies for Al speciation in environmental and biological samples during the past five years are reviewed. Concerns about the specific problems of Al speciation and highlights of some important methods are elucidated in sections devoted to hybrid techniques (HPLC or FPLC coupled with ET-AAS, ICP-AES. or ICP-MS), flow injection analysis (FIA), nuclear magnetic resonance (Al-27 NMR), electrochemical analysis, and computer simulation. More than 130 references are cited.

"Development Of A Low-cost Microfluidic Capillary-electrophoresis System Coupled With Flow Injection And Sequential-injection Sample Introduction (review)"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 8 Pages 978-983
Z.-L. Fang, Qun Fang

Abstract: Microfabrication techniques used for the production of MEMS (micro electro-mechanical systems) have been successfully used to produce highly efficient microfluidic capillary electrophoresis chip systems. A limitation of this approach are the difficulties associated with the creation of the micrometer-sized structures in glass or other substrates, which currently involve specialized and expensive lithographic and etching processes. A further limitation is that hitherto most microfluidic chips are not designed for continuous introduction of a series of different samples, which limits the overall throughput of such systems. This article reviews the development of a microfluidic system for rapid CE separations, produced at a low cost of less than a dollar each, using equipment and materials readily available in the ordinary laboratory. Applications of the system, after coupling to flow injection and/or sequential-injection sample introduction, for the determination of FITC-labeled amino acids by laser-induced fluorescence, trace metals by chemiluminescence, carbohydrates by amperometry, and inorganic and organic anions by indirect UV absorbance are exemplified to illustrate the performance and versatility of the microfluidic system.

"Membrane-controlled Reagent-delivery Systems - A New Approach For The Continuous Production Of Reagent And Standard Solutions"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 7 Pages 893-898
H. Albus, B. Neidhart

Abstract: A new simple and robust system for the production of standard solutions, based on the mass-transfer of analytes through membranes, is described. The device consists of a cone-shaped reservoir vessel, filled with a concentrated solution of the analyte and separated from a liquid acceptor stream by a membrane. Mass-flow from donor to acceptor solution is controlled by the mass-transfer-affecting properties of the active membrane area, which is determined by the hole in a template (diameter 0.8 mm) placed between the membrane and the acceptor-channel. Using nitrate as model analyte and a track-etched membrane filter (pore size 0.1 mum) dilution factors up to 2,400,000 with long-term reproducible accuracy of < 2% have been achieved. Adjustment of a requested concentration is possible by varying either the flow rate of the acceptor stream or the concentration of the reservoir solution.
Dialysis Calibration

"Solid-phase Reactors In Sequential Injection Analysis. Determination Of Manganese(II) In Tap Water And Effluent Streams Using A Solid-phase Lead(IV) Dioxide Reactor In A Sequential Injection System"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 6 Pages 776-780
E. B. Naidoo, J. F. van Staden

Abstract: The determination of manganese(II) in tap water and effluent streams, using a solid-phase reactor incorporated into a sequential injection system was investigated. Mn2+-ions in samples injected into a carrier stream, were oxidized by solid lead(IV) dioxide suspended on silica gel beads to form MnO4--ions which were detected spectrophotometrically at 526 nm. The linear range of the system is from I to 7 mg L-1 with a detection limit of 0.62 mg L-1. The proposed system is suitable for the determination of manganese(II) in tap and effluent streams at a rate of approximately 50 samples per hour with a relative standard deviation of better than 3%. Statistical comparison between the proposed sequential injection system and a standard ICP method revealed that there is no significant difference between the two methods at the 95% confidence level for effluent streams and at 99.9% for tap water.

"Electrolytic Hydride Generation Atomic Absorption Spectrometry For The Determination Of Antimony, Arsenic, Selenium, And Tin - Mechanistic Aspects And Figures Of Merit"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 6 Pages 735-743
E. Denkhaus, F. Beck, P. Bueschler, R. Gerhard, A. Golloch

Abstract: This article deals with the electrocatalytic and electrochemical mechanisms of hydride formation and their dependence on hydrogen overvoltage. A three-electrode-arrangement was used to determine the hydrogen overvoltage of different cathode materials (Pt, Au, Ag, glassy carbon, Cd, Pb, amalgamated Ag). The applicability of these cathode materials was tested for hydride formation using As(III), As(V), Sb(III), Sb(V), Se(IV), and Sn(IV). Glassy carbon is the most suitable cathode material for hydride generation with As(III), Sb(III), Se(IV), and Sn(IV). Hg-Ag is well suited for the production of stibine and arsine. As(III), As(V), Sb(III), and Sb(V) were all converted into their hydrides with efficiencies > 90%. A detection limit in the range of 0.11-0.13 µg L-1 for As and Sb (sample volume 200 µL) was obtained for cathode materials with a high hydrogen overvoltage. The precision of replicate measurements was better than 5% calculated as variation coefficient. The accuracy of the presented method was verified by analysis of certified reference materials and tissues of cancer patients. The recovery rates for As and Se were calculated to be 93-108%.

"Determination Of Ultratrace Dissolved Arsenite In Water - Selective Coprecipitation In The Field Combined With HGAFS And ICP-MS Measurement In The Laboratory"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 4 Pages 408-412
J. T. van Elteren, Zdenka Slejkovec, Marta Svetina, Andrej Glinsek

Abstract: Because stabilization of arsenite in water samples during transit and storage is troublesome, this work deals with a method to prevent this by on-site selective coprecipitation of arsenite with dibenzyldithiocarbamate and recovery of the coprecipitate by filtration through a 0.45-mum membrane filter. In the laboratory arsenic on the filter is quantitatively released by oxidation of arsenite to arsenate with H2O2 (6%) in alkaline medium (8 mmol L-1 NaO) at elevated temperature (85°C) for 30 min followed by ultratrace determination by routine HGAFS and ICP-MS. It is shown that arsenate contamination of the coprecipitate is so low that arsenate concentrations three orders of magnitude higher than the arsenite concentration do not interfere; this is essential, because arsenate is usually the dominant arsenic species in water. Because significant pre-concentration can be achieved in the solution obtained from the leached filter (normally a factor 20 but easily increased to 100) very low detection limits can be obtained (only limited by the purity of the materials and the cleanliness of working); a realistic limit of determination is 0.01 µg L-1 arsenite. The procedure was used for the determination of arsenite in two ground waters from an ash depository site in the Salek valley (Slovenia). The matrix contained some elements at very high levels but this did not impair the efficiency of arsenite coprecipitation. The results obtained by use of HGAFS and ICP-MS were not significantly different at the 5% level for sub-mug L-1 arsenite concentrations.
Speciation

"An Evaluation Of Analytical Techniques For Determination Of Lead, Cadmium, Chromium, And Mercury In Food-packaging Materials"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 1 Pages 76-81
L. Perring, Marie-Isabelle Alonso, Daniel Andrey, Bernard Bourqui, PascalZbinden

Abstract: Closed microwave digestion and a high-pressure asher have been evaluated for wet-oxidation and extraction of lead, cadmium, chromium, and mercury from a range of typical packaging materials used for food products. For the high-pressure asher a combination of nitric and sulfuric acids was efficient for destruction of a range of packaging materials; for polystyrene, however, nitric acid alone was more efficient. For microwave digestion, a reagent containing nitric acid, sulfuric acid, and hydrogen peroxide was used for all materials except polystyrene. Use of the high-pressure asher resulted in the highest recoveries of spiked lead (median 92%), cadmium (median 92%), chromium (median 97%), and mercury (median 83%). All samples were spiked before digestion with 40 µg L-1 Cd, Cr, and Pb and 8 µg L-1 Hg in solution. The use of indium as internal standard improved the accuracy of results from both ICP-MS and ICP-AES. Average recovery of the four elements from spiked packaging materials was 92±14% by ICP-MS and 87±15% (except for mercury) by ICP-AES. For mercury analysis by CVAAS, use of tin(II) chloride as reducing agent resulted in considerably better accuracy than use of sodium borohydride reagent.

"Determination Of Trace Amounts Of Lead In Mussels By Flow Injection Flame Atomic-absorption Spectrometry Coupled With On-line Minicolumn Preconcentration"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 1 Pages 64-68
M. C. Yebra, M. F. Enr&iacute;quez, A. Garc&iacute;a, A. Moreno-Cid

Abstract: A minicolumn packed with poly(aminophosphonic acid) chelating resin incorporated in an on-line pre-concentration system for flame atomic-absorption spectrometry was used to determine ultratrace amounts of lead in mussel samples at µg L-1 level. The pre-concentrated lead was eluted with hydrochloric acid and injected directly into the nebulizer for atomization in an air-acetylene flame for measurement. The performance characteristics of the determination of lead were: pre-concentration factor 26.8 for 1 min pre-concentration time, detection limit (3s) in the sample digest was 0.25 µg g-1 (dry weight) for a sample volume of 3.5 mL and 0.2 g sample (pre-concentration time 1 min), precision (RSD) 2.3% for 25 µg L-1 and 2.0% for 50 µg L-1. The sampling frequency was 45 h-1. The method was highly tolerant of interferences, and the results obtained for the determination of lead in a reference material testify to the applicability of the proposed procedure to the determination of lead at ultratrace level in biological materials such as mussel samples.
Extraction

"Application Of High-surface-area ZrO2 In Preconcentration And Determination Of 18 Elements By On-line Flow Injection With Inductively Coupled Plasma Atomic Emission Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 1 Pages 52-59
E. Vassileva, N. Furuta

Abstract: A flow-injection analysis (FIA) system incorporating a micro-column of ZrO2 has been used for the development of an on-line multi-element method for the simultaneous pre-concentration and determination of Al, Bi, Cd, Co, Cr, Cu, Fe, Ga, In, Mn, Mo, Ni, Pb, Tl, V, Sb, Sn, and Zn by inductively coupled plasma atomic emission spectrometry (ICP-AES). The conditions for quantitative and reproducible pre-concentration, elution, and subsequent on-line ICP-AES determination were established. A sample (pH 8) is pumped through the column at 3 mL min-1 and sequentially eluted directly into the ICP-AES with 3 mol L-1 HNO3. With a sample volume of 100 mL and an elution volume of 1 mL signal enhancement 100 times better than for conventional continuous aspirating systems was obtained for the elements studied. The reproducibility (RSD %) Of the method at the 10 ng mL-1 level in the eluate is acceptable - less than 8% for five replicates. Recoveries between 95.4% and 99.9% were obtained for the elements analyzed. ZrO2, with a specific surface area of 57 m(2) g-1 and a capacity of approximately 5 mg g-1 for the elements studied, was synthesized by hydrolysis of ZrCl4. The pre-concentration system was evaluated for several simple synthetic matrices, standard water samples and synthetic seawater. The effect of foreign ions on the efficiency of pre-concentration of the elements studied was investigated. The application of a micro-column filled with high-surface-area ZrO2 and flow injection inductively coupled plasma atomic emission spectrometry enables pre-concentration and simultaneous determination of 18 elements at low concentrations (ng L-1) in different water samples.

"Flow Injection Spectrophotometric Multidetermination Of Metallic Ions With A Single Reagent Exploiting Multicommutation And Multidetection"
Fresenius J. Anal. Chem. 2001 Volume 370, Issue 1 Pages 22-27
F&aacute;bio R. P. Rocha, B. F. Reis, Jarbas J. R. Rohwedder

Abstract: A flow system designed by computer-controlled discrete commutation devices is proposed for the multidetermination of metallic ions with a single chromogenic reagent. Intermittent addition of masking agents and changes of the reaction pH were exploited to implement selective determination of four species. Multidetection with an optical-fiber CCD-array spectrophotometer enabled simultaneous measurements at different wavelengths for multidetermination. The proposed system was applied to the determination of iron, copper, nickel and zinc in alloys and pharmaceutical preparations, yielding results in agreement with those obtained by flame atomic absorption spectrophotometry at the 95% confidence level. The sampling rate was estimated to be 80 determinations per hour. Coefficients of variation lower than 2% (n = 20) were achieved for all species.
Speciation

"Partial Multifactorial Design In Modelling Of UV-spectrometric Assays Of Ascorbic Acid With Nitrosobenzene And P-nitro-nitrosobenzene"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 7-8 Pages 719-726
S. Ursic, S. Luterotti, D. Ljubas

Abstract: Two new reagents, nitrosobenzene (PhNO) and p-nitro-nitrosobenzene (p-NO2-PhNO), have been studied for the analysis of ascorbic acid (AA) by its hypochromic effect on the reagents. The partial multifactorial design of experiments coupled with analysis of parallelism of calibration lines was used to optimize the experimental conditions and evaluate the parameters which affect the sensitivity and accuracy. Two levels at which variable parameters are to be examined should be chosen carefully if a single-step examination is expected to be sufficient. If any parameter roughly influences the system it results not only in severe rotational and translational effects, but also in false results and low selectivity of the approach, in such a case a second step of examination is necessary. The optimization procedures indicated that both PhNO and p-NO2-PhNO are advantageous analytical reagents for the UV-spectrometric assay of AA at pH 3 when measuring, the decrease of the absorbance of the reagent peak as analytical signal after 10 and 1 min, respectively. After proper modelling both systems were sufficiently robust to be successfully applied for accurate, selective, sensitive, precise and simple analyzes of AA even in pharmaceutical preparations with acetylsalicylic acid. Respective analytical performances characterizing AA-PhNO and AA-p-NO2-PhNO systems were: linearity range 2-100 and 2-70 µmol L-1, CS 0.0094 and 0.0115 L µmol-1, accuracy 101.5 and 98.0%. LOQ 1.3-2.1 and 3.1-3.6 µmol L-1 and RSD 1.3-3.5 and 1.9-3.8%.

"Efficient Flow Injection And Sequential Injection Methods For Spectrophotometric Determination Of Oxybenzone In Sunscreens Based On Reaction With Ni(II)"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 7-8 Pages 684-689
Alberto Chisvert, A. Salvador, M.-C. Pascual-Mart&iacute;, Joan G. March

Abstract: Spectrophotometric determination of a widely used UV-filter, such as oxybenzone, is proposed. The method is based on the complexation reaction between oxybenzone and Ni(II) in ammoniacal medium. The stoichiometry of the reaction, established by the Job method, was 1:1. Reaction conditions were studied and the experimental parameters were optimized, for both flow injection (FI) and sequential injection (SI) determinations, with comparative put-poses. Sunscreen formulations containing oxybenzone were analyzed by the proposed methods and results compared with those obtained by HPLC, Data show that both Fl and SI procedures provide accurate and precise results. The ruggedness, sensitivity and LOB are adequate to the analysis requirements. The sample frequency obtained by Fl is three-fold higher than that of SI analysis. SI is less reagent-consuming than FI.

"Development Of A New Flow-through Bulk Optode For The Determination Of Manganese(II)"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 7-8 Pages 680-683
C. Sanchez-Pedre&ntilde;o, M. S. Garc&iacute;a, J. A. Ortu&ntilde;o, M. I. Albero, E. Ballester

Abstract: A flow-through bulk optrode based on the use of 1-(2-pyridylazo)-2-naphthol (PAN) immobilized in a plasticized poly(vinyl chloride) membrane entrapped in a cellulose support, in conjunction with the flow injection analysis technique, is proposed for the determination of manganese(II). The calibration graph obtained at 570 nm was linear in the range 0.27-27.5 mg L-1 (5 x 10^-6 - 5 x 10^-4 M) Mn(II) with a detection limit of 0.18 mg L-1. The coefficients of variation of the sensor response for 5.5 mg L-1 of Mn(II) were ±0.22% for consecutive measurements (n = 10) ±0.48% between days in = 5) and ±0.38% between different membranes (n = 6). The sensor was readily regenerated with the carrier acetic acid/acetate buffer of pH 4.5. The method was applied to the determination of manganese in steels, waters and lemon tree leaves.
Membrane

"Speciation Of Butyltin Compounds In Marine Sediments With Headspace Solid Phase Microextraction And Gas Chromatography-mass Spectrometry"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 6 Pages 510-515
N. Cardellicchio, S. Giandomenico, A. Decataldo, A. Di Leo

Abstract: A method for the determination of organotin compounds (monobutyl = MBT, dibutyl = DBT, and tributyltin = TBT) in marine sediments by headspace Solid Phase Microextraction (SPME) has been developed. The analytical procedure involved 1) extraction of TBT, DBT and MBT from sediments with HCl and methanol mixture, 2) in situ derivatization with sodium tetraethylborate and 3) headspace SPME extraction using a fiber coated with poly(dimethylsiloxane). The derivatized organotin compounds were desorbed into the splitless injector and simultaneously analyzed by gas chromatography - mass spectrometry. The analytical method was optimized with respect to derivatization reaction and extraction conditions. The detection limits obtained for MET, DBT and TBT ranged from 730 to 969 pg/g as Sn dry weight. Linear calibration curves were obtained for all analytes in the range of 30-1000 ng/L as Sn. Analysis of a standard reference sediment (CRM 462) demonstrates the suitability of this method for the determination of butyltin compounds in marine sediments. The application to the determination of TBT, DBT and MBT in a coastal marine sediment is shown.

"Determination Of Tartaric Acid In Wines By FIA With Tubular Tartrate-selective Electrodes"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 5 Pages 446-450
M. Goreti F. Sales, Carolina E. L. Amaral, C. M. Delerue Matos

Abstract: A flow injection analysis (FIA) system comprising a tartrate- (TAT) selective electrode has been developed for determination of tartaric acid in wines. Several electrodes constructed for this purpose had a PVC membrane with a complex of quaternary ammonium and TAT as anion exchanger, a phenol derivative as additive, and a more or less polar mediator solvent. Characterization of the electrodes showed behavior was best for membranes with o-nitrophenyl octyl ether as solvent. On injection of 500 µL into a phosphate buffer carrier (pH = 3.1; ionic strength 10^-2 mol/L) flowing at 3 mL/min, the slope was 58.06±0.6 with a lower limit of linear range of 5.0 x 10^-4 mol/L TAT and R-2 = 0.9989. The interference of several species, e.g. chloride, bromide, iodide, nitrate, gallic acid, tannin, sucrose, glucose, fructose, acetate, and citrate, was evaluated in terms of potentiometric selectivity coefficients. The Hofmeister series was followed for inorganic species and the most interfering organic ion was citrate. When red and white wines were analyzed and the results compared with those from an independent method they were found to be accurate, with relative standard deviations below 5.0%.

"Continuous Determination Of Chloroquine In Plasma By Laser-induced Photochemical Reaction And Fluorescence"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 5 Pages 438-441
J. Amador-Hern&aacute;ndez, J. M. Fern&aacute;ndez-Romero, M. D. Luque de Castro

Abstract: A flow injection fluorimetric method is proposed for the determination of chloroquine based on the photochemical derivatization in an alkaline medium of the analyte and fluorescence generation after irradiation with a pulsed Nd:YAG laser operated at 355 nm. Chemical, hydrodynamic and laser variables were studied in order to obtain the best conditions for quantification. A linear range from 25 to 600 µg/L was achieved, with a correlation coefficient of 0.997 (n = 8), an RSD of 4.3% (n = 11) and a detection limit of 8 µg/L (3s). The sample throughput was 10 h(-1.) The method was successfully applied to the determination of chloroquine in human plasma. The increase of sensitivity with respect to the method based on monitoring the intrinsic fluorescence of chloroquine itself was 1.7 times.

"Development And Analytical Applications Of Multispectral Imaging Techniques: An Overview"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 3-4 Pages 313-319
C. D. Tran

Abstract: A multispectral imaging spectrometer is an instrument that can simultaneously record spectral and spatial information of a sample. Chemical and physical properties of the sample can be elucidated from such images. By synergistic use of an acousto-optic tunable filter and a progressive scan camera capable of snap shot recording it was possible to develop a novel imaging spectrometer with a spatial resolution of a few microns and which can record, grab and store up to 33 images per second (at a function of time) or 16 images per second (as a function of wavelength). This overview article summarizes the instrumentation development of various imaging spectrometers and their applications including its use as the detector for the determination of identity and sequences of peptides synthesized by the combinatorial solid phase method.

"Quinoprotein Glucose Dehydrogenase Modified Thick-film Electrodes For The Amperometric Detection Of Phenolic Compounds In Flow Injection Analysis"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 2 Pages 145-152
Andreas Rose, Frieder W. Scheller, U. Wollenberger, Dorothea Pfeiffer

Abstract: The use of thick-film electrodes as basic transducers for highly sensitive amperometric biosensors using PQQ (pyrroloquinoline quinone) dependent glucose dehydrogenase (GDH) with short response times is described. The enzyme is embedded in a polyurethane matrix on top of a platinum based thick film electrode and its ability to reduce oxidized phenolic compounds is exploited. The electrochemical amplification is based on the oxidation of the analyte on the surface of the electrode followed by its enzymatic reduction. Different parameters of the glucose dehydrogenase electrode system using dopamine as a model analyte were optimized, e.g., membrane thickness, pH value, buffer system, flow rate and storage conditions. Using optimized parameters the sensitivity and detection limits for various phenolic compounds were evaluated. The comparison of electrodes from the identical as well as from different batches shows the ability to produce a number of well reproducible sensors showing remarkably small differences with respect to parameters as sensitivity, response times, and measuring range.

"Determination Of Phosphate In Urine By Sequential Injection Analysis"
Fresenius J. Anal. Chem. 2001 Volume 369, Issue 1 Pages 96-102
B. M. Simonet, F. Grases, J. G. March

Abstract: Two simple turbidimetric methods for the determination of phosphate in urine are presented and compared. One method is based on the calcium phosphate crystallisation, and the other one on the inhibitory action of phosphate on the calcium carbonate crystallisation. The analytical features of both methods were: linear range 0.2-1.5 g L-1, LOD = 14 mg L-1 and RSD 1.1-2.0% for the calcium phosphate method, linear range = 0.1-1.8 mg L-1, LOD = 0.01 mg L-1 and RSD 0.97-1.90% for the inhibitory method. Urines with high calcium content (greater than or equal to 400 mg L-1) can interfere the method based on the crystallisation of calcium phosphate. This interference was solved using a cation exchange resin as a part of the manifold. Considering the low toxicity of used reagents, these methods can be considered as a contribution to Green Analytical Chemistry.

"Arsenic Speciation Based On Ion Exchange High-performance Liquid Chromatography Hyphenated With Hydride Generation Atomic Fluorescence And On-line UV Photo Oxidation"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 8 Pages 803-808
He Bin, Jiang Gui-bin, Xu Xiao-bai

Abstract: An on-line method capable of the separation of arsenic species was developed for the speciation of arsenite As(III), arsenate As(V), monomethylarsenic (MMA) and dimethylarsenic acid (DMA) in biological samples. The method is based on the combination of high-performance liquid chromatograph (HPLC) for separation, UV photo oxidation for sample digestion and hydride generation atomic fluorescence spectrometry (HGAFS) for sensitive detection. The best separation results were, obtained with an anion-exchange AS11 column protected by an AG11 guard column, and gradient elution with NaH2PO4 and water as mobile phase. The on-line UV photo oxidation with 1.5% K2S2O8 in 0.2 mol L-1 NaOH in an 8 m PTFE coil for 40 s ensures the digestion of organoarsenic compounds. Detection limits for the four species were in the range of 0.11-0.15 ng (20 µL injected). Procedures were validated by analysis of the certified reference materials GBW09103 freeze-dried human urine and the results were in good agreement with the certified values of total arsenic concentration. The method has been successfully applied to speciation studies of blood arsenic species with no need of sample pretreatment. Speciation of arsenic in blood samples collected from two patients after the ingestion of realgar-containing drug reveals slight increase of arsenite and DMA, resulting from the digestion of realgar.
Optimization

"Determination Of Low-level Mercury Based On A Renewable-drops Sensing Technique"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 8 Pages 797-802
RongHua Yang, KeMin Wang, Dan Xiao, Kan Luo, XiaoHai Yang

Abstract: The design and characteristics of a novel drop-based fluorescence-detection technique for the determination of mercury(II) are described. The method, using a flow injection technique, is based on the renewable-drops of 3,3,5,5-tetramethylbenzidine(TMB), which are formed at the bottom tip of a silica capillary tube connected to the end of the flow system. An excitation beam from a high-pressure Hg lamp directly illuminates the drops, the fluorescence emission is conducted to a photodiode (PD) to convert the photocurrent into a voltage signal (mV). Optimum analytical conditions for Hg(II) assays have been established. In NaAc/HAc buffer at pH 3.09 this assay has a wide linear range for Hg(II) from 8.0 x 10^-8 to 2.0 x 10^-5 mol/L with a detection limit of 2.0 x 10^-8 mol/L. The use of renewable drops allowing a fresh reaction surface for each sample is of particular value to solving the problems of irreversible reactions. Besides its high sensitivity, the method permits a simple, fast, and inexpensive measurement with only micro-quantities of reagent consumption. The technique described provides a simple and sensitive way to fabricate sensors of feasible prospects and commercial advantages.

"Polydiphenylamine-dodecyl Sulfate Films For The Simultaneous Amperometric Determination Of Electroinactive Anions And Cations In Ion-exclusion Cation-exchange Chromatography"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 8 Pages 791-796
Qun Xu, Chun Xu, Yanping Wang, Wen Zhang, Litong Jin, Kazuhiko Tanaka, Hiroki Haraguchi, Akihide Itoh

Abstract: An amperometric detector with two working electrodes both modified with polydiphenylamine-dodecyl sulfate (PDPA-DS) was successfully used for the simultaneous determination of electroinactive anions (SO42-, Cl-, NO3-) and cations (Na+, NH4+ and K+) in single-column ion-exclusion cation-exchange chromatography (IEC-GEC). The PDPA-DS chemical modified electrode (CME) was based on the incorporation of dodecyl sulfate (DS) into PDPA by electropolymerization of diphenylamine in the presence of sodium dodecyl sulfate. The electrochemical responses against the anions and cations at the PDPA-DS CME in differential pulse voltammetry were studied. A set of well-defined peaks of electroinactive anions and cations were obtained. The anions and cations were detected conveniently and reproducibly in a linear concentration range 0.01-5.0 mmol/L and their detection limits were in the range 5-9 µmol/L at a signal-to-noise ratio of 3 (S/N = 3). The proposed method was quick, sensitive and simple and was successfully applied to the analysis of lake water samples. The working electrode was stable over one week period of operation with no evidence of chemical and mechanical deterioration.
Detector

"Application Of A Modified Simplex Method To The Multivariable Optimization Of A New FIA System For The Determination Of Osmium"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 8 Pages 780-785
Hongping Xu, Huitao Liu, Huaiwen Wang, Lijun Dong, Xingguo Chen, Zhide Hu

Abstract: A methodology based on the coupling of experimental design and a modified simplex method is proposed for the optimization of a new flow injection-kinetic system for the spectrophotometric determination of Os (IV) with m-acetylchlorophosphonazo, which has for the first time been used as chromogenic reagent in the quantitative analysis of this element. An orthogonal array design is utilized to design the experimental protocol, in which six variables are varied simultaneously, and obtain the initial simplex using 25 experiments. A modified simplex method is applied to continuously optimize the data of the orthogonal array design; the search for optimum conditions of 6 variables using the modified simplex method required only 25 experiments. The efficiency and simplicity of the coupling of the experimental design and the modified simplex method are attractive for the development of new analytical methods. The method has been applied to the determination of Os (TV) in a refined ore as well as in a secondary alloy and provided satisfactory results.

"Extraction Of Antimony And Arsenic From Fresh And Freeze-dried Plant Samples As Determined By HG-AAS"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 7 Pages 702-707
M. Krachler, H. Emons

Abstract: Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (similar to 220 mg) of the freeze-dried samples were analyzed by flow injection hydride generation atomic absorption spectrometry (m-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analyzed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L-1 NaOH liberated highest amounts of Sb with similar to 10% for poplar leaves, and similar to 19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7-9% from fresh elder and poplar leaves, respectively, and 8-13% for freeze-dried samples for Sb. The corresponding values for As were 10^-35% for the fresh material and 7-37% for the freeze-dried samples.
Speciation

"Fiber-in-tube Solid-phase Microextraction: A Fibrous Rigid-rod Heterocyclic Polymer As The Extraction Medium"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 7 Pages 641-643
Y. Saito, Y. Nakao, M. Imaizumi, T. Takeichi, Y. Kiso, K. Jinno

Abstract: A novel fiber-in-tube configuration has been applied to the extraction tube of solid phase microextraction (SPME), and the direct coupling of the extraction process to liquid chromatography (LC) has been accomplished for the analysis of n-butylphthalate in wastewater. By using this fiber-in-tube SPME/LC system the pre-concentration factor for the phthalate was about 160 with 20 min extraction and no interference peak was observed in the chromatogram The results also showed the potential applications of this fiber-in-tube SPME/LC for the analysis of sub-ppb level (i.e., lower than 1 ng/mL) of various organic analytes in aqueous sample matrix without a large solvent consumption during the pre-concentration process.
Capillary

"Individual Sample Conditioning In Flow Analysis. Determination Of N-total In Plant Materials"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 5 Pages 496-500
J. M. T. Carneiro, R. S. Honorato, E. A. G. Zagatto

Abstract: A flow-batch system allowing in-line individual sample matrix matching is proposed for analysis of sample lots with high variability in acidity. The feasibility of the approach is demonstrated in the spectrophotometric determination of total nitrogen in Kjeldahl digests, using a column with a slightly soluble reagent (AgCl). The solutions are sequentially injected by means of an 8-port selecting valve and processed in a mixing chamber that is also used as a monitoring unit. The system yields reproducible results (RSD usually < 2.5%) and the sampling rate is 14 samples/h. The analytical curve is linear within 1.00 and 6.00% N (dry basis), and the regression coefficient is > 0.999 (n = 6). Results are in agreement with certified values of standard reference materials and with results obtained by conductometry.
Sequential injection

"Speciation Of Major Arsenic Species In Seawater By Flow Injection Hydride Generation Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 5 Pages 484-489
Jean Yves Cabon, Nolwenn Cabon

Abstract: Arsenic present at 1 µg L-1 concentrations in seawater can exist as the following species: As(III), As(V), monomethylarsenic, dimethylarsenic and unknown organic compounds. The potential of the continuous flow injection hydride generation technique coupled to atomic absorption spectrometry (AAS) was investigated for the speciation of these major arsenic species in seawater. Two different techniques were used. After hydride generation and collection in a graphite tube coated with iridium, arsenic was determined by AAS. By selecting different experimental hydride generation conditions, it was possible to determine As(III), total arsenic, hydride reactive arsenic and by difference non-hydride reactive arsenic. On the other hand, by cryogenically trapping hydride reactive species on a chromatographic phase, followed by their sequential release and AAS in a heated quartz cell, inorganic As, MMA and DMA could be determined. By combining these two techniques, an experimental protocol for the speciation of As(III), As(V), MMA, DMA and nonhydride reactive arsenic species in seawater was proposed. The method was applied to seawater sampled at a Mediterranean site and at an Atlantic coastal site. Evidence for the biotransformation of arsenic in seawater was clearly shown.

"A Sequential Injection Cold-vapor Atomic Absorption Method For The Determination Of Total Mercury"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 5 Pages 475-479
W. E. Doering, R. R. James, R. T. Echols

Abstract: A sequential injection (SI) method for the determination of mercury via cold vapor atomic absorption spectrophotometry is presented. The method differs from flow injection (FI) cold vapor methods for the determination of mercury because of the simplicity of the system required for the method: one pump, one valve, a gas-liquid separator, and an atomic absorption spectrophotometer equipped with a quartz cell. Under optimal conditions, the method has the following figures of merit: a linear calibration range of 1.0 to 20 µg L-1; a detection limit of 0.46 µg L-1; and a precision of 0.90% RSD (8 µg L-1). The procedure allows for a sampling rate of one injection per 80 s (excluding sample pretreatment). Results from the determination of mercury in water and fish specimens are also presented. The figures of merit of the method are compared to two other SI methods for the determination of mercury.

"Stability Of Inorganic Mercury And Methylmercury On Yeast-silica Gel Microcolumns: Field Sampling Capabilities"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 5 Pages 471-474
Ma Perez-Corona

Abstract: The stability of methylmercury and inorganic mercury retained on yeast-silica gel microcolumns was established and compared with the stability of these species in solution. Yeast-silica gel columns with the retained analytes were stored for two months at three different temperatures: -20°C, 4°C and room temperature. At regular time intervals, both mercury species were eluted and quantified by cold vapor atomic absorption spectrometry (CVAAS). Methylmercury was found stable in the columns over the two-month period at the three different temperatures tested while the concentration of inorganic mercury decreased after one weeks storage even at -20°C. These results are of great interest since the use of these microcolumns allows the pre-concentration and storage of mercury species until analysis, thus saving laboratory space and avoiding the problems associated with maintaining species integrity in aqueous solution.
Speciation

"Simultaneous Determination Of Trace Metals By Solid Phase Absorptiometry: Application To Flow Analysis Of Some Rare Earths"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 5 Pages 443-448
Y. Tennichi, S. Matsuoka, K. Yoshimura

Abstract: Solid phase absorptiometry was applied to the simultaneous flow analysis of trace metals in combination with a µblack flow-through cell packed with ion exchanger beads and a multi-channel photodetector connected with optical fibers. A 4.0 mL sample solution containing five rare earth metal ions (Dy, Ho, Tm, Er and Nd) was introduced into a flow system and these metal ions were concentrated on a cation exchanger (Muromac 50W-X4) in a flow-through cell. The absorbance increases originating from the f-f or d-f transition bands of these metal ions were directly and continuously measured at 910 nm for Dy, at 530 nm for Ho, at 683 nm for Tm, 522 nm for Er and at 790 nm for Nd, respectively. A multi-variable analysis method was combined with the flow analysis because the absorption spectra of the five rare earth metal ions partly overlapped one another. Although no coloring reagents were used, the proposed method was about 200 times more sensitive than the corresponding solution method. The reproducibility of this method was less than ± 5%. The detection limits were 0.03, 0.40, 0.30, 0.35 and 0.23 mg L-1 for Dy, Ho, Tm, Er and Nd, respectively. Five rare earth metal ions could be precisely determined in practical samples such as yttrium concentrate.

"A Flow Injection Chemiluminescence System For The Determination Of Isoniazid"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 4 Pages 429-431
Y. Huang, Z. Zhang, D. Zhang, J. Lv

Abstract: A chemiluminescence (CL) flow system is described for the determination of isoniazid based on its enhancement on the chemiluminescence (CL) emission produced upon mixing a hexacyanoferrate(III) solution with an alkaline luminol solution. The system responds linearly to isoniazid concentration in the range 0-1 mg/L with a detection limit (3s) of 0.03 µg/L, relative standard deviation (RSD) of 1.2% for 0.1 mg/L isoniazid (n = 11). The system has been successfully applied to the determination of isoniazid in pharmaceutical preparations.

"Determination Of Arsenic By Continuous Hydride Generation With Direct Introduction Into An O-2-argon Microwave Plasma Torch Atomic Emission Spectrometer"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 4 Pages 418-420
Peihong Liang, Anmo Li

Abstract: The determination of arsenic was studied with a simple and economic method. A continuous hydride generation system is interfaced to a microwave plasma torch atomic emission spectrometer (MPT-AES). Arsenic hydride is transferred directly and continuously by the carrier gas into the plasma torch without separation of hydrogen. When oxygen is introduced into the outer tube of the plasma torch, the plasma is more stable and has a higher tolerance to hydrogen. The detection limit (3s) is 5.2 µg/L when the forward power is 100 W with argon as support gas. Application to the standard sample coal fly ash showed a comparable result to the certified quantity.
Speciation

"Determination Of Trace Impurities In Some Nickel Compounds By Flame Atomic Absorption Spectrometry After Solid Phase Extraction Using Amberlite XAD-16 Resin"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 4 Pages 358-361
L. El&ccedil;i, M. Soylak, A. Uzun, E. B&uuml;y&uuml;kpatir, M. Dogan

Abstract: A simple flame atomic absorption spectrometric (FAAS) procedure for the determination of lead, bismuth, gold, palladium and cadmium as impurities in Raney nickel and nickel oxide was developed using a pre-concentration step on an Amberlite XAD-16 resin packed column. Lead, bismuth, gold, palladium and cadmium were quantitatively recovered and separated from a solution containing 1 M HCl and 0.3 M NaI by the column system. Effects of the various parameters such as reagent concentrations, sample volume, matrix effects, etc, have been investigated. Under optimized conditions, the relative standard deviation of the combined method of sample treatment. pre-concentration and determination with FAAS (n = 7) is generally lower than 12%. The limit of detection (3s, n = 20) was between 10^-270 ng/g. The results were used for separation and pre-concentration of five trace elements from nickel matrices.
Preconcentration

"Electrothermal Atomic Absorption Spectrometric Determination Of Cobalt In Biological Samples And Natural Waters Using A Flow Injection System With On-line Preconcentration By Ion-pair Adsorption In A Knotted Reactor"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 2-3 Pages 288-292
Karima Benkhedda, Heidi Goenaga Infante, E. Ivanova, F. Adams

Abstract: An on-line flow injection pre-concentration-ETAAS method is developed for trace determination of cobalt in biological materials and natural samples by ion-pair sorption on the inner walls of a PTFE knotted reactor. The ion-pair is formed between the negatively charged cobalt-nitroso-R-salt complex and the tetrabutylammonium counter-ion. An enhancement factor of 15, a sampling frequency of 17 and a concentration efficiency of 4 are obtained for a pre-concentration time of 60 s and a sample loading flow rate of 5 mL min-1. The detection limit (3s) is 5 ng L-1. The relative standard deviation at the 0.2 µg L-1 level is 2.3%. The analytical results obtained for standard reference materials are in good agreement with the certified or indicated values and satisfactory recoveries of spiked cobalt in tap water are obtained.

"Determination Of Arsenic By Inductively Coupled Plasma Mass Spectrometry - Comparison Of Sample Introduction Techniques"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 2-3 Pages 162-165
Hilde Uggerud, W. Lund

Abstract: A comparison is made of four sample introduction techniques for the determination of As by inductively coupled plasma mass spectrometry. The techniques studied were 1) flow injection with pneumatic nebulization (FIA-PN), 2) direct electrothermal vaporization (ETV): 3) continuous hydride generation (HG) and 4) hydride generation with in situ trapping followed by electrothermal vaporization (HG-ETV). It was found that FIA-PN and ETV gave similar detection limits in concentration units (about 20 pg mL-1), although ETV had a much lower absolute detection limit (0.2 pg). Sample introduction by hydride generation gave an inferior detection Limit (100-200 pg mL-1), also in combination with in situ trapping and ETV, owing to the blank signal from traces of As in NaBH4 which is difficult to eliminate. The results indicate that the more elaborate sample introduction techniques based on ETV and HG may not offer significant advantages compared to normal solution nebulization for the determination of As in simple sample matrices such as natural fresh waters, where matrix removal is not required.
Preconcentration Interferences

"A New HG/LT-GC/ICP-MS Multi-element Speciation Technique For Real Samples In Different Matrices"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 1 Pages 67-72
U. M. Gr&uuml;ter, J. Kresimon, A. V. Hirner

Abstract: An improved speciation technique is presented for metal(loid)organic compounds, enabling identification and quantification of species from twelve elements: germanium, arsenic, selenium, molybdenum, tin, antimony, tellurium, iodine, tungsten, mercury, lead and bismuth. At this time it is possible to identify 29 species with boiling points between -88.5°C and 250°C in gaseous, liquid and solid samples in a few minutes. This study shows as an example results from measurements of soil samples from municipal waste deposits. The HG/LT-GC/ICP-MS-(hydride generation/low temperature-gas chromatography/inductively coupled plasma-mass spectrometry) apparatus contains a home-built gas chromatograph that enables satisfactory separation of various species with a boiling point difference of greater than or equal to 14°C. The absolute detection limits for the elements mentioned above were below 0.7 pg.

"Speciation Of Antimony(III) And Antimony(V) In Cell Extracts By Anion Chromatography/inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 1 Pages 62-66
N. Ulrich, Pninit Shaked, Dan Zilberstein

Abstract: An analytical method for the separation and quantification of Sb(III) and Sb(V) using anion chromatography with ICP-MS is presented. The optimum conditions for the separation of the antimony species were established with 15 mmol/L nitric acid at pH 6 as eluent system on a PRP- x 100 column. The retention times for antimony(V) and antimony(III) were 85 s and 300 s with detection limits of 0.06 µg/L and 0.29 µg/L, respectively The proposed method was applied to cell extracts of Leishmania donovani, which were incubated with antimony(III) and antimony(V). Some metabolism seemed to occur within the cells.

"A Novel High-temperature (360 Degrees C)/high-pressure (30 MPa) Flow System For Online Sample Digestion Applied To ICP Spectrometry"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 1 Pages 52-58
Stephan Haiber, H. Berndt

Abstract: A flow injection sample digestion system has been developed comprising an indirectly electrically heated Pt/Ir capillary. Such a capillary allows reaction temperatures of up to 360°C and pressures of up to 30 MPa (300 bar) and withstands concentrated acids. This temperature is 130°C to 160°C higher compared to the operating temperatures of microwave heated flow systems. A combination of an ultrasonic nebulizer and membrane desolvator serves as an interface between the flow digestion system and an ICP/AES spectrometer. The membrane desolvator removes interfering gaseous digestion products so effectively before the sample stream enters the plasma that the measured residual carbon concentration falls in the region of the detection limit of ICP/OES measurements. Sewage sludge samples were digested using nitric acid and the elemental traces online determined. The detection limits related to the original dry substances amount to the lower µg/g range.

"Mass Spectrometry With Plasma Sources At Atmospheric Pressure - State-of-the-art And Some Developmental Trends"
Fresenius J. Anal. Chem. 2000 Volume 368, Issue 1 Pages 15-22
J. A. C. Broekaert

Abstract: The state-of-the art and trends of development in ICP-MS are presented. Special reference is made to progress in plasma sources, which can be used as ion sources and, especially, the inductively coupled plasma and new microwave plasma sources. Further, progress in sample introduction for plasma mass spectrometry is discussed with special reference to new pneumatic nebulizers, enabling, e.g., work with microflows of solutions at high efficiency, new developments in ultrasonic nebulization, in electrothermal evaporation, laser ablation and hydride generation. Innovation in the types of mass spectrometers used is discussed with special reference to the use of reaction and collision cells, sector field mass spectrometry, time-of-flight mass spectrometry and multicollector mass spectrometers. Challenging applications in the field of speciation, especially in environmental samples with the example of the chromium speciation, and in materials analysis, with special reference to the analysis of ceramic powders with and without on-line matrix removal, are also discussed.

"Determination Of Underivatized Amino Acids By High-performance Liquid Chromatography And Electrochemical Detection At An Amino Acid Oxidase Immobilized CuPtCl6 Modified Electrode"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 8 Pages 707-713
Jianhong Pei, Xiao-yuan Li

Abstract: AII amperometric sensor for amino acids based on the immobilization of amino acid oxidase on the surface of a CuPtCl6/GC is described. The amperometric current is due to the oxidation of H2O2 liberated during the enzyme reaction on the surface of the enzyme electrode. The electrode response characteristics as well as kinetic parameters have been evaluated. The enzyme electrode was characterized as an electrochemical biosensor, which was used as detector in high performance liquid chromatography (HPLC) for the determination of a mixture of amino acids with satisfactory results.

"Soil-modified Carbon Paste Electrode: A Useful Tool In Environmental Assessment Of Heavy Metal Ion Binding Interactions"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 8 Pages 701-706
Irena Grabec Svegl, Bozidar Ogorevc

Abstract: Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable fur application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying pre-electrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Ng(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities fur the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate fur fast on-site testing of polluted soils.
Adsorption Complexation Preconcentration

"Flow Injection Analysis With In-line Solid Phase Extraction For The Spectrophotometric Determination Of Sulfonated And Unsulfonated Quinoline Yellow In Cologne"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 7 Pages 672-676
L. F. Capit&aacute;n-Vallvey, M. C. Valencia, E. Arana Nicolas

Abstract: An integrated solid-phase spectrophotometry/ FIA method is proposed for the determination of the synthetic colorant matter Quinoline Yellow (QYWS) in the presence of its unsulfonated derivative QYSS. The procedure is based on the retention and pre-concentration of the low level QYSS on a C-18 silica gel minicolumn, followed by sequential measurement of its absorbance at lambda = 410 nm after its elution with methanol. The applicable concentration range, the detection limit and the relative standard deviation were the following: for QYWS, from 0.10 to 30.0 mg L-1; 0.013 mg L-1; and 0.6%; and for QYSS, between 10 and 1,000 µg L-1; 2 µg L-1; and 1.3%, respectively. The method was applied to the determination of small amounts of QYSS present in QYWS in Colognes. Percentages of recovery between 98% and 99% were obtained in all instances. The method was also satisfactorily applied to the determination of these compounds in samples of commercial Colognes comparing the results for QYWS with those offered by an HPLC reference method and also validating the results chemometrically.

"On-line Complexation Of Zinc With 5-Br-PADAP And Preconcentration Using A Knotted Reactor For Inductively Coupled Plasma Atomic Emission Spectrometric Determination In River Water Samples"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 7 Pages 653-657
J. A. Salonia, R. G. Wuilloud, J. A. G&aacute;squez, R. A. Olsina, L. D.Martinez

Abstract: An on-line zinc pre-concentration and determination system implemented with inductively coupled plasma atomic emission spectrometry (ICP-AES) associated with flow injection (FI) was studied. The zinc was retained as zinc-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Zn-(5-Br-PADAP)) complex at pH 9.2. The zinc complex was removed from the knotted reactor (KR) with 30% v/v nitric acid. An enrichment factor of 42 was obtained for the KR system with respect to ICP-AES using pneumatic nebulization. The detection limit for the pre-concentration of 10 mL of aqueous solution was 0.09 µg/L. The precision for 10 replicate determinations at the 5 µg/L Zn level was 2.3% relative standard deviation (RSD), calculated with the peak heights obtained. The calibration graph using the pre-concentration system for zinc was linear with a correlation coefficient of 0.9997 at levels near the detection limits up to at least 100 µg/L. The method was succesfully applied to the determination of zinc in river water samples.

"Flow Injection Spectrophotometric Determination Of Ultra Trace Amounts Of Oxalic Acid"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 6 Pages 590-592
A. A. Ensafi, A. Kazemzadeh

Abstract: A new simple, sensitive and rapid catalytic-spectrophotometric method for the determination of oxalic acid has been described based on its catalytic effect on the redox reaction between dichromate and Brilliant cresyl blue in acidic media by means of a Row injection analysis method. The color change of Brilliant cresyl blue due to its oxidation was monitored spectrophotometrically at 625 nm. The calibration graph was linear in the range of 0.020-4.70 µg/mL oxalic acid with a limit of detection 0.005 µg/mL of oxalic acid. The relative standard deviation for ten replicate measurements of 0.020 µg/mL and 0.900 µg/mL was 2.2% and 1.7%, respectively. No serious interference was identified. Oxalic acid was determined in wastewater and in spinach by the proposed method with satisfactory results.

"Determination Of S-triazines With Copper And Glassy Carbon Electrodes. Flow Injection Analysis Of Aziprotryne In Water Samples"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 5 Pages 461-466
A. Zapardiel, E. Bermejo, J. A. P&eacute;rez, M. Chicharro

Abstract: The detection and determination of s-triazines, atrazine-desethyl and aziprotryne by cyclic voltammetry and an amperometric method using a metallic copper electrode and a glassy carbon electrode are described. The concentrations of atrazine-desethyl and aziprotryne in 0.1 M NaOH solutions were determined using the oxidation signal corresponding to the Cu(O)/Cu(I) redox process. The detection level calculated for these s-triazines were 0.3 and 0.5 µg/mL of analyte, respectively. The glassy carbon electrode was shown to give sensitive reduction response to aziprotryne in flow injection mode. No special activation was required for the glassy carbon electrode. A detection limit of 0.2 µg/mL (20 ng aziprotryne) was obtained for a sample loop of 0.1 mi at a fixed potential of -1.0 V (vs. Ag/AgCl) in 0.1 M HCl and a flow rate of 3.5 mL/min. Furthermore, the glassy carbon electrode showed stable response in such a system, and the relative standard deviation was only 2.7% using the same surface, and 6.3% using different surfaces. The method developed was applied to the determination of aziprotryne in environmental and tap water samples; using a prior solid-phase extraction step, aziprotryne concentrations lower than 1.0 ng/mL could be measured.

"Total Determination Of Metal-binding Carbohydrates In Plant Extracts By Using FIA With Electrochemical Detection"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 4 Pages 356-358
G. Weber, J. Messerschmidt

Abstract: FIA with pulsed amperometric detection (PAD) is used for the determination of metal-binding carbohydrates in plant extracts. Results of direct FIA measurements agree very well with those of corresponding HPLC-PAD analyzes. The proposed method is used to determine total carbohydrates in isolated low-molecular-weight fractions of plant roots, which have been obtained after extraction at different pH values. The results are compared with those obtained by corresponding metal determinations (Ca, Mg, Zn, Mn) by AAS and also with constant potential amperometric detection at a copper working electrode. The latter detection mode is more sensitive, but less selective for carbohydrates.

"Determination Of Cu, Pb, Cd, And Zn In River Sediment Extracts By Sequential Injection Anodic Stripping Voltammetry With Thin Mercury Film Electrode"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 3 Pages 284-290
C. L. da Silva, J. C. Masini

Abstract: Determination of Cu, Pb, Cd and Zn was performed in sediment extracts obtained according to the three steps sequential extraction procedure proposed by the European Community Standards, Measurements and Testing Program. The metal content was determined by anodic stripping voltammetry with a thin mercury film electrode controlled by a sequential injection (SIA) system. The proposed method improved the reproducibility of conventional anodic stripping voltammetry, as well as the sample throughput, allowing analysis of 30 to 45 samples per hour. The influence of flow rate and sample volume was studied to achieve an adequate sensitivity for the leachate studied. No interferences due to adsorption of organic matter, colloids, or complexes with slow rate of dissociation were observed. The intermetallic formation of Cu-Zn was avoided by forming the mercury film in presence of Ga(III) ions in the SIA system, resulting in low consumption of reagent in comparison to flow injection or continuous flow systems. Results were in good agreement with those obtained by Induced Coupled Plasma - Atomic Emission Spectroscopy (ICP- AES).
Dilution

"Flow Injection Spectrophotometric Determination Of Anionic Surfactants Using Methyl Orange As Chromogenic Reagent"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 3 Pages 270-274
Qiaohong He, Hengwu Chen

Abstract: A flow injection(FI) spectrophotometric method for the determination of anionic surfactants was developed on the basis of the competition for the cationic surfactant cetyl pyridine (CP+) chloride between the acidic dye methyl orange (MO) and anionic surfactants. In a pH 5.0 medium the cation of cetyl pyridine (CP+) reacts with dissociated methyl orange (MO-) to form an ion-associate complex, causing a blue shift of lambda(max) from 465 nm for MO- to 358 nm for the CP+ . MO- associate. The MO- in the ion-associate complex can be quantitatively substituted by such anionic surfactants as sodium dodecyl benzene sulfonate (DBS) or sodium lauryl sulfate (LS), leading to an increase in the absorbance measured at 465 nm. This increased absorbance value is proportional to the concentration of anionic surfactants. Various chemical and physical parameters for the FI spectrophotometric method were optimized, and interference-free levels were examined. At the optimized conditions, Beers law was obeyed in the range 1.4 similar to 25 mg/L sodium DBS for an injected sample volume of 180 µL, and a detection limit of 0.22 mg/L. fur sodium DBS was achieved at a sampling rate of 90 h-1. Eleven determinations of a 16 mg/L sodium DBS solution gave a RSD of 0.4%. The proposed method has successfully been applied to the determination of anionic surfactant concentration in waste water and in detergents.

"Preconcentration Of Trace Amounts Of Silver Ion In Aqueous Samples On Octadecyl Silica Membrane Disks Modified With Hexathia-18-crown-6 And Its Determination By Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 3 Pages 246-249
M. Shamsipur, M. H. Mashhadizadeh

Abstract: A simple and reliable method has been developed to selectively separate and concentrate trace amounts of silver ion from aqueous samples for the subsequent measurement by atomic absorption spectrometry. Ag+ ions are absorbed quantitatively during passage of aqueous samples through an octadecyl-bonded silica membrane disk modified by hexathia-18-crown-6. Almost all matrix elements will pass through the disk to drain. The retained Al ions are then stripped from the disk with a minimal amount of thiosulfate solution as eluent. The proposed method permitted large enrichment factors of about 200 and higher. The limit of detection of the proposed method is 50 ng Ag+ pel 1000 mL. The effects of various cationic interferences on the recovery of silver in binary mixtures were studied. The method was applied to the recovery of Ag+ ions from different synthetic and water samples.

"Amperometric Detection Studies Of Nafion/indium Hexacyanoferrate Film For The Determination Of Electroinactive Cations In Ion Chromatography"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 3 Pages 241-245
Q. Xu, S. Zhang, W. Zhang, L. Jin, K. Tanaka, H. Haraguchi, A. Itoh

Abstract: An amperometric detector based on the chemical modification of Nafion and indium (III) hexacyanoferrate (II, III) thin film (Nafion/In-CN-Fe) onto a glassy carbon (GC) electrode, was first successfully used for the determination of electroinactive cations (Li+, Na+, K+, Rb+, Cs+, NH4+) in single column ion chromatography (IC), A set of well-defined peaks of electroinactive cations was obtained. The detection limits of the cations are 8.9 x 10^-6 mol/L for Li+, 2.3 x 10^-6 mol/L for Na+, 5.2 x 10^-6 mol/L for K+, 4.8 x 10^-6 mol/L for Rb+, 4.0 x 10^-6 mol/L for Cs+ and 5.3 x 10^-6 mol/L for NH4+ at a single-to-noise ratio of 3. The proposed method was quick, sensitive and simple. The cations in rainwater and mineral water were successfully analyzed by this method.

"A Factorial Design For Optimizing A Flow Injection Analysis System"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 2 Pages 201-203
J. R. Luna, J. F. Ovalles, A. Le&oacute;n, M. Buchheister

Abstract: The use of a factorial design for the response exploration of a flow injection (FI) system is described and illustrated by Fl spectrophotometric determination of paraquat. Variable response (absorbance) is explored as a function of the factors flow rate and length of the reaction coil. The present study was found to be useful to detect and estimate any interaction among the factors that may affect the optimal conditions for the maximal response in the optimization of the FI system, which is not possible with a univariate design. Ln addition, this study showed that factorial experiments enable economy of experimentation and yield results of high precision due to the use of the whole data for calculating the effects.
Optimization

"Amperometric Biosensor Based On D-aminoacid Oxidase For The R-perindopril Assay"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 2 Pages 178-180
J. F. van Staden, R. -I. Stefan, H. Y. Aboul-Enein

Abstract: A new amperometric biosensor based on D-aminoacid oxidase is described for the assay of R-perindopril. R-perindopril can be determined in the 400-20 nmol/L concentration range; the detection limit is 10 nmol/L. The selectivity was checked with S-perindopril, D- and L-proline, and polyvinylpyrrolidone. The main interfering species was D-proline. An automated system for the assay of R-perindopril based on the concept of flow injection with an amperometric biosensor (based on D-aminoacid oxidase) as detector is also described. The system is suitable for the on-line monitoring of R-perindopril at a sampling rate of 72 samples/h, in the Linear range: 100 nmol/L -20 nmol/L with an RSD better than 0.09% (n = 10).

"Potentiometric Determination Of Acids And Bases Using A Silica Gel Based Carbon-epoxy Indicator Electrode"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 1 Pages 86-89
M. F. S. Teixeira, L. A. Ramos, E. Almeida Neves, O. Fatibello-Filho

Abstract: The construction and the application of a silica gel based carbon-epoxy indicator electrode for the potentiometric determination of acids and bases are described. The effect of composition of silica gel and carbon-epoxy, slope (mV/pH). linear response (pH range) and the use for acid-base titrations were investigated. The data obtained for the acid-base titrations were compared with those obtained using a glass electrode in the same conditions. The electrode showed a linear response in the pH 2 to 13 range with a slope of -40.5±0.4 mV/pH (at 25°C) and a response time of less than 15 s. The lifetime of the electrode was higher than one year (over 6000 determinations) with a decrease of only 5% of the initial potentiometric response. The silica gel based carbon-epoxy electrode showed excellent results in the end-point indication potentiometric titrations in determination of acids and bases. The miniaturization of the proposed electrode for flow injection analysis was investigated.

"Determination Of Zinc In Pharmaceutical Products Using An Electrodialyser Incorporated Into A Flow System"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 1 Pages 79-83
J. (Koos) F. van Staden, Cornelius J. Hattingh

Abstract: An electrodialyser unit has been designed, incorporated into the conduits of a flow injection (FI) system, and employed for the removal of interferences in the determination of zinc(II) in multivitamin tablets. The proposed system is fully computerised and is able to determine zinc(II) at a frequency of 18 samples/h with a sample interaction of 0.0015%. The calibration graph is linear between 1 and 20 mg/L. The detection limit is 0. 998 mg/L. The results obtained for zinc(II) in multivitamin tablets with the proposed system compared favourably with those obtained with the standard manual AAS method.

"Speciation Of As(III), As(V), MMA And DMA In Contaminated Soil Extracts By HPLC-ICP/MS"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 1 Pages 51-55
M. Bissen, F. H. Frimmel

Abstract: A method to separate and quantify two inorganic arsenic species As(III) and As(V) and two organic arsenic species, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), by HPLC-ICP/MS has been developed. The separation of arsenic species was achieved on the anionic exchange column IonPac(R)AS11 (Dionex) with NaOH as mobile phase. The technique was successfully applied to analyze extracts of two contaminated soils, sampled at a former tannery site (soil I) and a former paint production site (soil 2). The soils were extracted at pH values similar to the natural environment. Extractions were performed at different pH values with 0.3 M ammonium oxalate (pH = 3), milli-Q water (pH = 5.8), 0.3 M sodium carbonate (pH = 8) and 0.3 M sodium bicarbonate (pH = 11). No organically bound arsenic was found in the extracts. As(V) was the major component. Only up to 0.04% of the total arsenic contained in soil 1 were mobilized. The highest amount of extracted arsenic was found at the highest pH. In the milli-Q water extract of soil 1 As(III) and As(V) were found. High amounts of As(V) were found in the extracts of soil 2. Up to 20% of the total arsenic bound to soil 2 constituents were released. The results show that the mobilization of arsenic depended on the pH value of the extraction solution and the kind of extracted soil. Dramatic consequences have to be expected for pH changes in the environment especially in cases where soils contain high amounts of mobile arsenic.

"Flow Injection Atomic Absorption Spectrometric Determination Of Iodide Using An On-line Preconcentration Technique"
Fresenius J. Anal. Chem. 2000 Volume 367, Issue 1 Pages 24-28
M. C. Yebra, R. M. Cesp&oacute;n

Abstract: A continuous Row atomic absorption spectrometric system was used to develop an efficient on-line pre-concentration-elution procedure for the determination of iodide traces. Chromium (VI) is introduced into the flow system and is reduced to chromium (III) in acid medium proportionally to the iodide present in the sample. The Cr(III) reduced by iodide is retained on a minicolumn packed with a poly(aminophosphonic acid) chelating resin, while unreduced Cr(VI) is not retained. Reduced Cr(III) is pre-concentrated by passing the sample containing iodide through the system during 3 min, and is then eluted with 0.5 mol L-1 hydrochloric acid and determined by flame atomic absorption spectrometry (FAAS). The detection limit (3s) obtained is 2.5 µg L-1. Other ions typically present in waters do not interfere. The proposed method allows the determination of iodide in the range 6-220 µg L-1 with a relative standard deviation of 2.7% at a rate of 17 samples h-1. The method has been applied to the determination of iodide in tap and sea waters.
Precipitation Membrane

"Flow Injection Spectrophotometric Determination Of Ascorbic Acid In Soft Drinks And Beer"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 8 Pages 857-862
E. Luque-P&eacute;rez, A. R&iacute;os, M. Valc&aacute;rcel

Abstract: Two spectrophotometric methods, a photochemical and a non-photochemical, for the determination of ascorbic acid in soft drinks and beer using a flow injection system are proposed. The non-photochemical method is based on the redox reaction that takes place between ascorbic acid and Fe(III), yielding dehydroascorbic acid and Fe(II). Fe(II) reacts with 1,10-phenantroline, originating the reddish orange Fe(phen)(3)(2+) complex (ferroin). This complex is spectrophotometrically monitored at 512 nm, and the signal is directly related to the concentration of ascorbic acid in the sample. The photochemical method has the same basis, nevertheless, uses the irradiation with visible light to enhance the redox reaction and so achieve higher sensitivities in the analysis. The non-photochemical method shows a linear range between 5 and 80 µg mL-1 with a relative standard deviation of 1.6% (n = 11), a detection limit of 2.7 µg mL-1 and a sample throughput of 60 samples h-1. The photochemical method shows a linear range between 1 and 80 µg mL-1, with a relative standard deviation of 1.0% (n = 11), a detection limit of 0.5 µg mL-1 and a sample throughput of 40 samples h-1.
Reactor

"Rapid And Selective Determination Of Ammonium By Fluorimetric Flow Injection Analysis"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 8 Pages 825-829
H. Mana, U. Spohn

Abstract: Selective and sensitive procedures for the determination of ammonium in river water and diluted urine were developed by using flow injection analysis equipment. The methods are based on the derivatization of ammonia with o-phthaldehyde (OPA) and thioglycolate under alkaline conditions. The formed isoindole derivative is detected fluorimetrically at an excitation wavelength of 415 nm and an emission wavelength of 485 nm. The derivatization only takes 15 to 20 s at room temperature to achieve the maximum sensitivity. The optimized OPA reagent shows a surprisingly high selectivity for ammonium in the presence of many primary amines. With respect to the analysis of turbid and fluorescent sample solutions the selectivity can be improved by separating the ammonia through a microporous membrane from the OPA reagent. Without this separation step ammonia can be detected in the range between 0.05 and 100 µM with excellent linearity. After the insertion of an optimized membrane separation cell ammonia can be determined in the linear range between 0.2 µM and 20 mM.
Membrane Derivatization

"Synthesis Of Rhodanine-bonded Silica Gel And Its Application In The Preconcentration And Separation Of Noble Metals"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 8 Pages 816-820
P. Liu, Q. -S. Pu, Q. -Y. Sun, Z. -X. Su

Abstract: A silica gel based sorbent containing rhodanine as functional group (RDSG) was prepared. Its adsorption and separation characteristics for Ag(I), Au(III) and Pd(II) were studied by flow injection (FI) on-line pre-concentration. Influence of different experimental parameters such as acidity, eluent, co-existing ions were investigated. Trace amounts of Ag, Au and Pd could be efficiently adsorbed by rhodanine-bonded silica gel from acidic solution and eluted with thiourea solution. Common co-existing ions exhibited virtually no interference to the pre-concentration and determination. The adsorption capacity of RDSG was 0.0352, 0.107 and 0.122 mmol/g for Ag, Au and Pd, respectively. Detection limits of 0.004, 0.022 and 0.019 µg/mL for Ag, Au and Pd, respectively, were achieved with a sampling time of 60 s at a flow rate of 5.0 mL/min. The relative standard deviation were 0.5%, 0.9% and 1.7% for 0.040 µg/mL Ag, 0.200 µg/mL Au and 0.300 µg/ mt Pd. The sorption property did not change after 1000 cycles of sorption-desorption. The contents of Ag and Au in three national certified ore samples and Pd in a secondary nickel alloy, an anode slime and a CoCl2 electrolytic solution were determined. The results showed good agreement with the certified values.

"A New Procedure For The Construction Of Flow-through Optodes. Application To Determination Of Copper(II)"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 8 Pages 811-815
C. Sanchez-Pedre&ntilde;o, J. A. Ortu&ntilde;o, M. I. Albero, M. S. Garcia, J. C. Garcia de las Bayonas

Abstract: A new procedure for constructing an optical fiber reflectance, bulk optode membrane type, sensor is presented. The optode membrane consists of a plasticized poly (vinyl chloride) membrane in which the ionophore is dissolved, entrapped in a cellulose support. The new optode with the dye indicator 1-(2-pyridylazo)-2-naphthol (PAN) was incorporated in a new flow-through cell and the injection system was optimized to determine Cu (II) at 567 nm in the range 5 2 10 m5-10 m3 M. The response was reproducible and the optode can be regenerated using 10 m2 M EDTA followed by water. The method was applied to the determination of copper in real samples.

"Bio- And Chemiluminescence In Bioanalysis"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 6-7 Pages 752-759
A. Roda, P. Pasini, M. Guardigli, M. Baraldini, M. Musiani, M. Mirasoli

Abstract: Analytical chemiluminescence and bioluminescence represent a versatile, ultrasensitive tool with a wide range of applications in diverse fields such as biotechnology, pharmacology. molecular biology, clinical and environmental chemistry. Enzyme activities and enzyme substrates and inhibitors can be efficiently determined when directly involved in luminescent reactions, and also when chev take part in a reaction suitable for coupling to a final light-emitting reaction. Chemiluminescence detection has been exploited in the fields of flow injection analysis and column-liquid chromatographic and capillary-electrophoretic separative systems, due to its high sensitivity when compared with colorimetric detection. It has widely been used as an indicator of reactive oxygen species formation in cells and whole organs, thus allowing the study of a number of pathophysiological conditions related to oxidative stress. Chemiluminescence represents a sensitive and rapid alternative to radioactivity as a detection principle in immunoassays for the determination of a wide range of molecules (hormones, food additives, environmental pollutants) and in filter membrane biospecific reactions (Southern, Northern. Western, dot blot) for the determination of nucleic acids and proteins. Chemiluminescence has also been used for the sensitive and specific localization and quantitation of target analytes in tissue sections and single cells by immunohistochemistry and in situ hybridization techniques. A relatively recent application regards the use of luminescent reporter genes for the development of bioassays based on genetically engineered microorganisms or mammalian cells able to emit visible light in response to specific inorganic and organic compounds. Finally, the high detectability and rapidity of bio- and chemiluminescent detection make it suitable for the development of microarray-based high throughput screening assays, in which simultaneous, multianalyte detection is performed on multiple samples.

"Immunoanalytical Techniques For Pesticide Monitoring Based On Fluorescence Detection"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 6-7 Pages 646-658
U. Schobel, C. Barzen, G. Gauglitz

Abstract: In the field of environmental analysis there is still great potential for development and application of immunoanalytical techniques (IT). Heterogeneous and homogeneous immunoassays (IA), flow injection immunoanalysis (FIIA) and immunosensors (TS) with different detection principles have been developed. In this review we focus on fluorescence methods for pesticide monitoring published since 1992. These techniques offer a high degree of selectivity and, in principle, sensitivity. Restrictions on the limits of detection (LOD) due to background signals are minimized by development of solid-phase separation systems. new fluorescent probes, and new instrumentation.

"Immunochromatographic Techniques - A Critical Review"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 6-7 Pages 635-645
M. G. Weller

Abstract: Hyphenated techniques have become very popular during the last decade. Nevertheless, the use of biochemical methods, such as immunoassays, in conjunction with instrumental methods, such as chromatography, have not gained widespread acceptance. This review critically discusses many of the implemented and potential options for such coupled systems or components, which might be useful for such systems, including immunoaffinity extraction, immunoaffinity chromatography, immunochemical detectors, immunoblotting, receptor assays, enzyme inhibition assays, displacement assays, flow injection immunoassays, miniaturized techniques and stationary phases such as restricted access materials or molecularly imprinted polymers. The performance of immunochromatographic systems is discussed regarding their ability to solve highly complex and demanding analytical problems.

"A Low-cost Non Instrumental Method For Semiquantitative Determination Of Mercury In Fish"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 5 Pages 461-465
A. V. Yallouz, R. Calixto de Campos, S. Paciornik

Abstract: A non instrumental method for the semiquantitative determination of mercury in fish is described. The sample is acid digested and the mercury vapor released after chemical reduction with SnCl2. The mercury vapor is then collected on a detecting paper covered with an emulsion of Cu2I2, 3% carboxymethylcellulose and MgCl2 as moistener agent. The colored Cu-2[HgI4] complex is formed and the color intensity is proportional to the mercury concentration in the original sample. Parameters such as sample mass/digestion solution volume ratio, emulsion composition, paper covering technique, carrier gas flow were investigated. Comparative studies using CVAAS and digital color analysis after scanning the papers confirmed the applicability of the method to real samples.

"Gold Electrodes From Recordable CDs For Mercury Quautification By Flow Injection Analysis"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 5 Pages 444-448
E. M. Richter, M. A. Augelli, G. H. Kume, R. N. Mioshi, L. Angnes

Abstract: The development of a new methodology for the construction of very efficient flow cells for mercury detection by potentiometric stripping analysis, employing the thin gold layer of recordable CDs as working electrode is reported. This new source of electrodes (CDtrodes:) show very attractive performance, similar to that obtained with commercial gold electrodes, with superior versatility. The low cost of this new source of gold electrodes allows a frequent replacement of the electrode, avoiding cumbersome clean-up treatments. Various experimental parameters have been optimized to yield low detection limits (0.25 ng/mL of mercury for 5 min deposition at 0.3 V) and good precision (standard deviation of 1.9% was obtained for 15 repetitive measurements using 10 ng/mL of mercury). Standard curves were found to be linear over the range of 0.5-100 µg L-1 of mercury. The flow cells developed were used for the quantification of mercury in oceanic and tap water.

"Analysis And Stability Of Mercury Speciation In Petroleum Hydrocarbons"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 5 Pages 438-443
N. S. Bloom

Abstract: Raw petroleum and natural gas often contain high concentrations of mercury, which can be damaging to the metal components of production facilities, as well as to the environment. Various Hg species have different properties in terms of mobility, reactivity and bioavailability. Thus, for cost-effective decisions regarding plant design, Hg extraction. and pollution control, speciation information must be available at the production facility. In this paper, a simple, wet chemical speciation method, which provides data on Hg-o, dissolved and particulate total Hg, Hg(II), and methyl Hg is presented. The method incorporates species-specific extraction and separation procedures, followed by cold vapor atomic fluorescence spectrometry (CVAFS). For each species. detection limits of approximately 0.1 ng/g were obtained. Storage experiments in various containers showed that organo-mercury species were stable for at least 30 days in all containers except those made of polyethylene; and Hg-o was stable in all containers except those made of stainless steel or polyethylene. HS(II) was rapidly lost from all containers except those made of aluminum, which rapidly converted it to Hg-o, which was stable. In general, most of the total Hg in petroleum products was particulate Hg, Followed by dissolved Hg(II) and Hg-o. Sub ng/g concentrations of methyl-Hg were observed in most samples.
Extraction

"Clean Conditions For The Determination Of Ultra-low Levels Of Mercury In Ice And Snow Samples"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 5 Pages 433-437
C. P. Ferrari, A. L. Moreau, C. F. Boutron

Abstract: Laboratory facilities and methods are presented for the determination of ultra-low levels of mercury (Hg) in ice and snow samples originating from polar ice caps or temperate regions. Special emphasis will be given to the presentation of the clean laboratory and the cleaning procedures. The laboratory is pressurized with air filtered through high efficiency particle filters. This first filtration is not enough to get rid of contamination by Hg in air. Experiments are conducted in a clean bench, especially built for Hg analysis, equipped with both particle filter and activated charcoal filter. It allows to obtain very low levels of atmospheric Hg contamination. Ultrapure water is produced for cleaning all the plastic containers that will be used fur ice and snow samples and also for the dilution of the standards. Hg content in laboratory water is about 0.08±0.02 pg/g. A Teflon system has been developed for the determination of Hg in ice and snow samples based on Hg(II) reduction to Hg(0) with a SnCl2/HNO3 solution followed by the measurement of gaseous Hg(0) with a Hg analyzer GARDIS 1A+ based on the Cold Vapor Atomic Absorption Spectroscopy method. Blank determination is discussed.
Speciation

"Automized Procedures For The Determination Of Ozone And Ammonia Contents In Air By Using The Chromatomembrane Method For Gas-liquid Extraction"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 4 Pages 332-335
H. Erxleben, J. Simon, L. N. Moskvin, L. O. Vladimirovna, T. G. Nikitina

Abstract: Chromatomembrane cells (CMC) operate as unique manifolds for extraction and pre-concentration procedures in computer controlled now-injection-analysis (FIA). By coupling to an ion chromatograph and to a conductometer, respectively, instrumentation is obtained that allows the pretreatment and the detection of ozone- and ammonia-containing samples after absorption of the gaseous constituents of air inside a chromatomembrane cell. The analysis of air even in the presence of liquid aerosols is discussed.

"Evaluation Of Hydrogen Line Emission And Argon Plasma Electron Concentrations Resulting From The Gaseous Sample Injection Involved In Hydride Generation-ICP-atomic Emission Spectrometric Analysis"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 3 Pages 221-227
D. A. Batistoni, R. N. Garavaglia, R. E. Rodr&iacute;guez

Abstract: The simultaneous injection of volatile hydride species and hydrogen gas, originating in reagent decomposition, was monitored during the operation of a continuous hydride generation manifold employed for the determination of trace arsenic by HG-ICP-AES. Line and background intensities as well as the FWHM of the hydrogen H gamma and H delta lines were measured, and electron number densities (n(e)) estimated from Stark broadening of the line profiles. Results were compared with those obtained by conventional pneumatic injection of aqueous solutions. Overlapping with atomic nitrogen lines at 410 nm and 411 nm tends to distort the H-δ line profile for the hydrogen-seeded plasma, rendering unreliable results. The N I lines seem to be quenched by the presence of water aerosol. More consistent results were obtained with the H gamma line. When no solutions are pumped through the hydride generation manifold (dry plasma), the measured n(e) value was (1.57±0.22) x 10(15) cm(-3). Conversely, when the reducing reagent flow was replaced by pure water (corresponding to the injection of water vapor in equilibrium that is swept by the argon carrier gas passing through the phase separator), the electron concentration is 25% higher. In that case the n(e) value agrees between the experimental error with that obtained for a plasma in which a water aerosol is introduced at a flow rate of 1 mL/min. An enhancement of 52% relative is observed in n(e) when the system is operated under optimized conditions for arsine generation, employing sodium tetrahydroborate in acidic medium as reducing agent (i.e. hydrogen seeded plasma). It was also observed that the continuum emission near 410 nm for the hydrogen containing plasma correlates with the measured electron number density, suggesting that the background enhancement under hydride generation conditions may respond to the ion-electron recombination mechanism.
Speciation

"On-line Determination Of Mercury In River Water At The German Monitoring Station Schnackenburg/Elbe"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 2 Pages 196-199
Olaf Elsholz, Carsten Frank, Birgit Matyschok, Frank Steiner, Oliver Wurl, Burkhard Stachel, Heinrich Reincke, Manfred Schulze, Ralf Ebinghaus, Maximilian Hempel

Abstract: A monitor is described which provides the online determination of mercury in river water at concentrations from 20 to 1000 ng/L. The measurement includes an on-line digestion with Br-/BrO3- and UV-radiation. Each determination is controlled by an on-line addition of 50 and 100 ng/L mercury carried out by pre-dilution of a 500 and 1000 ng/L stock solution using sequential injection analysis (SIA). One cycle of analysis takes 20 min and results in nine signals. A five days stand-alone operation has been performed successfully. Details are also published at web page: http/www.rzbd.fh-hamburg.de/similar to prmercol.

"Monitoring Of Total Hg In The River Elbe: FIA-device For On-line Digestion"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 2 Pages 191-195
O. Wurl, O. Elsholz, J&ouml;rn Baasner

Abstract: The development of an apparatus for the online sampling, digestion and quantification of total mercury in surface water is described. Detection and quantification is done by flow injection cold vapor atomic absorption spectroscopy (FI-CVAAS). Three digestion methods were tested, chemical, microwave and UV, The influence of the digestion parameters (digestion method, digestion time, microwave power, concentration of oxidation solution) on the recovery of mercury in water of the river Elbe have been investigated. Mercury can be determined almost quantitatively (recovery rate > 85%) with some digestion procedures described. The best results were reached by UV digestion. The technique is fast, simple to handle and robust. Each complete analysis only take four minutes. The working range is 10 to 1000 ng/L, The measuring arrangement has been applied successfully in a governmental monitoring station at Schnackenburg/Elbe, Germany.

"Determination Of Cadmium By Flow Injection-chemical Vapor Generation-atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 2 Pages 182-190
C. Vargas-Razo, J. F. Tyson

Abstract: A method was developed for the generation of a cold vapor of cadmium by means of flow injection-chemical vapor generation from aqueous samples, the determination being conducted with an atomic absorption spectrometer (Pyrex glass T-cell). Several gas-liquid separator designs, atomizer designs, and the effect of several reagents previously reported as sensitivity enhancers (including cobalt, nickel, thiourea and didodecyl-dimethyl-ammonium bromide) were investigated. The limit of detection, calculated as the concentration giving a signal equal to three times the standard deviation of the blank, was 16 ng L-1. and the relative standard deviation was 1.4% for a concentration of 2 µg L-1 and 3.8% for 0.1 µg L-1 The addition of nickel and thiourea to the samples provided improved tolerance to the interference of coexisting ions. Two NIST certified reference materials, Montana Soil and Apple Leaves (respectively containing 41.7±0.25 mg kg-1 Cd and 0.013±0.002 mg kg-1 Cd) were accurately analyzed. The interference of lead was overcome by coprecipitation with barium sulfate, and the experimental values obtained were 41±1 mg kg-1 Cd and 0.013±0.002 mg kg-1 Cd, respectively.

"Laser Atomic Absorption Spectrometry Of Excited Hg In A Discharge Applying Sum Frequency Mixing Of Two Diode Lasers (preliminary Results)"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 2 Pages 156-158
R. Uhl, O. Wolff, J. Franzke, U. Haas

Abstract: Wavelength modulation diode laser atomic absorption spectrometry is applied to the detection of atomic mercury. Transitions from metastable energy levels highly populated in a radio-frequency discharge are induced with laser diodes by use of nonlinear techniques. The wavelength of one strong transition at 365.119 nm with a high oscillator strength is obtained by sum frequency generation of two diode lasers. The cold vapor technique is used to transfer ionic into atomic mercury. The mercury in the vapor phase is transported by an argon stream into the discharge tube. From the time-dependent absorption signals detection limits of 100 ng/L are achieved at this state of research.

"Spectrophotometric Flow Injection Determination Of Total Phosphorus In Beer Using On-line UV/thermal Induced Digestion"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 1 Pages 112-115
S. M. V. Fernandes, J. L. F. C. Lima, A. O. S. S. Rangel

Abstract: A flow injection system for the automatic determination of total phosphorus in beer is described. The developed manifold uses a two-stage photooxidation/thermal digestion procedure together with oxidizing and hydrolyzing reagents to convert all forms of phosphorus compounds to orthophosphate. Polyphosphates are hydrolyzed by acid and heat, and organo-phosphates are digested by UV-catalyzed peroxodisulfate oxidation. The orthophosphate formed is then spectrophotometrically determined by the phosphomolybdenum blue reaction, using stannous chloride as reducing agent. The results obtained for a set of 19 beer samples (with concentrations from 120 to 735 mg P/L) were in good agreement with the reference method, the maximum relative deviation found being 4.7%. Relative standard deviations for ten consecutive determinations were lower than 1.5%, and a detection limit of 1 mg P/L was achieved.

"Application Of Artificial Neural Networks In Multifactor Optimization Of An FIA System For The Determination Of Aluminum"
Fresenius J. Anal. Chem. 2000 Volume 366, Issue 1 Pages 17-21
Yongyao Zhou, Huaiwen Wang, Gang Sun, Yuquan Fan, Xingguo Chen, Zhide Hu

Abstract: A methodology based on the coupling of experimental design and artificial neural networks (ANNs) is proposed in the optimization of a new flow injection system for the spectrophotometric determination of Al(III) with Arsenate DBM, which has for the first time been used as chromogenic reagent in the quantitative analysis of aluminum. An orthogonal design is utilized to design the experimental protocol, in which three variables are varied simultaneously. Feedforward-type neural networks with faster back propagation (BP) algorithm are applied to model the system, and then optimization of the experimental conditions is carried out in the neural network with 3-7-1 structure, which have been confirmed to be able to provide the maximum performance. In contrast to traditional methods, the use of this methodology has advantages in terms of a reduction in analysis time and an improvement in the ability of optimization. The method has been applied to the determination of Al(III) in steel samples and provided satisfactory results.

"Oriented Antibody Immobilization For Atrazine Determination By A Flow-through Fluoroimmunosensor"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 8 Pages 658-662
E. Turiel, P. Fern&aacute;ndez, C. P&eacute;rez Conde, A. M. Guti&eacute;rrez, C. C&aacute;mara

Abstract: An atrazine flow-through fluoroimmunosensor was developed, based on an oriented antibody covalently bound to Protein-A (Prot-A) immobilized on Controlled Pore Glass (CPG). Atrazine was detected 'in-situ' by placing the immobilized antibody in the optical path of the flow cell. Immobilization of 30 wg of polyclonal anti-atrazine antibody on 0.5 g of Prot-A-CPG provided the highest sensitivity. The effect of several solvents on the covalently immobilized antibodies regeneration was evaluated, the optimum conditions being achieved by pumping 5% acetonitrile (pH = 3) at 0.15 mL/min for 100 s. The detection limit of the immunosensor was 0.7 wg/L and the reproducibility was 2% and 4% for 5 wg/L and 40 wg/L, respectively, in the optimum working concentration range (0.7-50 wg/L). This device allowed 12 samples per hour to be analyzed and had a life-time of 200 assays. Simazine and desisopropylatrazine (DIA) were not cross-reactive, desethylatrazine (DEA) has a cross-reactivity of 8% and propazine and prometryn of 44% and 27%, respectively. The immunosensor was applied to the determination of atrazine in tap and ground water samples spiked at the 10 and 30 µg/L concentration level.
Atrazine Ground Water Fluorescence Sensor Optimization Controlled pore glass

"Kinetic Spectrophotometric Determination Of Sulfide, Using In-cuvette Mixing And Titration Techniques With Computerized Data Acquisition"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 8 Pages 654-657
B. Haghighi, A. Safavi

Abstract: In-cuvette mixing and titration techniques have been used for the kinetic determination of sulfide based on its inhibition effect on the oxidation of indigo carmine with hexacyanoferrate(III) in the presence of silver. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of indigo carmine at 612 nm. Both initial rate and fixed-time methods were applied to the in-cuvette technique. Using in-cuvette mixing, sulfide up to 1800 ng was determined and detection limit and relative standard deviation for the determination of 120 ng of sulfide were calculated as 23.0 ng and 1.59%, respectively. On the basis of the titration technique, the upper limit of determination was 25 µg of sulfide and detection limit and average relative standard deviation for the determination of 1 µg of sulfide were 0.025 µg and 4.95%, respectively. The effect of foreign ions;on the sulfide determination was studied. The proposed methods were applied to the determination of sulfide in water.

"Copper Determination After FI Online Sorbent Preconcentration Using 1-nitroso-2-naphthol As A Complexing Reagent"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 8 Pages 642-646
A. Ali, Y. Ye, G. Xu, X. Yin

Abstract: The suitability of 1-nitroso-2-naphthol as a complexing agent for online pre-concentration of copper using RP-C-18 material in a microcolumn with flow injection coupled with flame atomic absorption spectrometry (FI-FAAS) has been tested. Various parameters affecting complex formation, such as pH, sample flow rate, etc, and its elution into the nebulizer of FAAS were optimized. A 5 x 10^-3 mol/L reagent was online mixed with aqueous sample solution acidified with 0.1% (v/v) nitric acid (pH 3-4) and flowed through the microcolumn for 30 s. The adsorbed complexes in the microcolumn were eluted with ethanol in 10 a into the nebulizer of FAAS. A good precision (1.7% for 50 µg/L copper, n = 12), high enrichment factor (19) with detection limit (3s) 2.0 µg/L, and sample throughput (90 h-1) were obtained. The method was applied to certified reference materials seawater, mussel (biological), NBS-362 and NBS-364 (special low alloy steel), for the determination of copper, and the results were in good agreement with the certified values.
Extraction

"A Simple Solid Phase Spectrofluorimetric Method Combined With Flow Analysis For The Rapid Determination Of Salicylamide And Salicylic Acid In Pharmaceutical Samples"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 7 Pages 619-624
A. Ruiz Medina, M. L. Fern&aacute;ndez de C&oacute;rdova, A. Molina D&iacute;az

Abstract: A new, sensitive and very simple spectrofluorimetric biparameter sensor is described for the determination of salicylamide and/or salicylic acid in pharmaceutical preparations. The method integrates the transitory retention and fluorescence detection of both compounds on Sephadex QAE A-25 resin packed into a conventional flow-through cell. A monochannel manifold with two alternative carriers is used. At pH 2.0 (first carrier) salicylic acid is selectively retained on the solid support and after developing the analytical signal it is desorbed. At pH 11.0 (second carrier) both salicylic acid and salicylamide are simultaneously and transitorily retained on the solid, the analytical signal now corresponding to both analytes. The monochromators were tuned at 260 (excitation) and 415 (emission) nm, respectively. The calibration graph for salicylamide is linear over the range 0.01 to 0.32 wg mL-1 and for salicylic acid from 0.04 to 1.0 wg mL-1 in the presence of each other. The relative standard deviation and the sampling frequency for the determination of salicylamide (0.20 wg mL-1) and salicylic acid (0.50 wg mL-1) were 1.1% and 35 h-1, and 0.9% and 45 h-1, respectively. Good results on application to individual determination or mixture resolution in pharmaceutical samples testify to the usefulness of the proposed sensor.
Salicylic acid Salicylamide Pharmaceutical Fluorescence Method comparison Optimization Sephadex Resin Solid phase extraction

"Photodissociation/gas-diffusion Separation And Fluorimetric Detection For The Analysis Of Total And Labile Cyanide In A Flow System"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 6 Pages 516-520
E. Miralles, R. Compa&ntilde;&oacute;, M. Granados, M. D. Prat

Abstract: Total cyanide species are determined in a flow injection system which includes UV-photodissociation, gas-diffusion separation and spectrofluorimetric detection. Without the irradiation step, only cyanide easily released in acid medium, i.e. labile cyanide, is determined. Cyanide diffuses through a microporous PTFE membrane from an acid donor stream to a sodium hydroxide acceptor stream. Then, the transferred cyanide reacts with o-phthalaldehyde and glycine to form a highly fluorescent isoindole derivative. Complete cyanide recoveries were obtained for the most important metal cyanide complexes found in environmental samples, excepting cobaltocyanide. The sampling frequency for total cyanide was 4 samples h-1 and the detection limit was 0.4 µg L-1. Recoveries of total cyanide from river water obtained with this method are about 90% of those obtained with APHA Method 4500-CN C for total cyanide.
Cyanide, total River Fluorescence Method comparison Gas diffusion Teflon membrane UV reactor

"A Novel Chemiluminescence Flow-through Sensor For The Determination Of Analgin"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 4 Pages 381-383
Yu-Ming Huang, Chao Zhang, Xin-Rong Zhang, Zhu-Jun Zhang

Abstract: A novel chemiluminescence (CL) flow-through sensor for the determination of analgin with flow injection analysis (FIA) based on the auto-oxidation of analgin in the presence of Tween 80 sensitized by Rhodamine 6G immobilized on a cation-exchange column is described. This sensor responds linearly to the analgin concentration in the range of 0.4 similar to 10 mg/L, with a detection limit (30) of 0.15 mg/L. A complete analysis, including sampling and washing, takes 1 min with a relative standard deviation of < 5%. The sensor is stable for over 200 determinations and has successfully been applied to the determination of analgin in pharmaceutical preparations.

"Sequential Determination Of Carbon Dioxide And Free Sulfur Dioxide In Wine By Flow Injection Pervaporation With In Series Potentiometric-photometric Detection"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 4 Pages 377-380
E. Mataix, M. D. Luque de Castro

Abstract: A method for the simultaneous determination of CO2 and free SO2 in wines based on the use of a continuous arrangement coupled to both a pervaporator and in series arranged potentiometric and photometric detectors is proposed. After pervaporation, both analytes give one common potentiometric signal and then the free SO2 is photometrically determined via the colored compound formed with p-rosaniline and formaldehyde. The CO2 content is determined by difference. The range of the method is linear between 2.0 and 20.0 mg/L for free SO2 and 50.0 and 600.0 mg/L for CO2, with a precision, expressed as relative standard deviation, of 7% in both cases. The method was applied to different Spanish wines and the results compare well with those obtained by the corresponding official methods.

"Indirect Atomic Absorption Spectrometric Determination Of Citric Acid By Continuous Precipitation"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 4 Pages 370-373
M. C. Yebra, R. M. Cesp&oacute;n

Abstract: A continuous precipitation and filtration flow system for the separation of citric acid by precipitation with lead and indirect flame atomic absorption spectrometry is proposed. The precipitate is formed by injecting the lead solution into a carrier containing the sample and is subsequently retained on a filter. By using this reversed precipitation flow injection configuration, citric acid was determined in the range 2-40 µg mL-1, with a relative standard deviation of 2.9% at a sampling frequency of 60 samples h-1. This method has been applied to the determination of citric acid in fruit juices. carbonated soft drinks and sweets.

"Preparation Of An Ion-selective Electrode By Chemical Treatment Of Copper Wire For The Measurement Of Copper(II) And Iodide By Batch And Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1999 Volume 365, Issue 4 Pages 314-319
D. Dobcnik, M. Kolar, J. Komljenovic, Nj. Radic

Abstract: The preparation of an ion-selective electrode by chemical treatment of copper wire and its application for the measurements of copper (II) and iodide ions is described. The proposed reaction mechanism at the sensing surface, which explains the response of the electrode to Cu2+ and iodide ions, is discussed. The prepared electrode was suitable for direct potentiometric measurements of iodide and copper (II) in batch experiments down to concentrations of 1 x 10^-5 mol L-1. A tubular electrode, prepared in the same way, may be used as a potentiometric sensor in a flow injection analysis for Cu (II) and/or iodide determinations.

"Application Of A Fractionary Factorial Design To The Determination Of Tin In Lubricating Oils By Continuous Flow Hydride Generation-atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 6 Pages 527-532
M. Bego&ntilde;a Mart&iacute;n-Garc&iacute;a, Dolores Bellido-Milla, Andr&eacute;s Jimenez-Jimenez, Mar&iacute;a Purificaci&oacute;n Hern&aacute;ndez-Artiga

Abstract: The determination of wear metals and metalloids in used lubricating oils allows the prediction of equipment failure. A number of procedures to determine wear metals in lubricating oils by atomic spectrometry has been published. Industry has lately shown a special interest in the determination of tin, since its appearance at certain levels in used oils indicates severe engine wear. Therefore, a method for the determination of the total tin content in used lubricating oils by hydride generation-atomic absorption spectrometry (HG-AAS) is described. Unused marine lubricating oils spiked with the analyte were digested in closed vessels in a microwave oven and the diluted product was used for continuous stannane generation. There are many factors that influence effective SnH4 generation; therefore, fractionary factorial design was used to obtain an adequate sensitivity and also to stabilize the signal. Six variables were taken into account and a 26-2IV design was used with spiked samples containing 30 ng g-1 Sn. The reproducibility, stability, calibration curve and limit of detection were established. The method was applied to different kinds of used lubricating oils. In all cases, the results were higher than those obtained in the industry by simple dilution.
Tin Oil Spectrophotometry Volatile generation Optimization Factorial design

"Precise Isotope Ratio Measurements For Uranium, Thorium And Plutonium By Quadrupole-based Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 5 Pages 482-488
J. S. Becker and Hans-Joachim Dietze

Abstract: Precise long-term measurements of uranium and thorium isotope ratios was carried out in 1 wg/L solutions using a quadrupole inductively coupled plasma mass spectrometer (ICP-QMS). The isotopic ratios of uranium (235U/ 238U = 1, 0.02 and 0.00725) were determined using a cross-flow nebulizer (CFN, at solution uptake rate of 1 mL/min) and a low-flow microconcentric nebulizer (MCN, at solution uptake rate of 0.2 mL/min) over 20 h. For 1 wg/L uranium solution (235U/238U = 1) relative external standard deviations (RESDs) of 0.05% and 0.044% using CFN and MCN, respectively, can be achieved. Additional short term isotope ratio measurements using a direct injection high-efficiency nebulizer (DIHEN) of 1 wg/L uranium solution (235U/238U = 1) at a solution uptake rate of 0.1 mL/min yielded an RSD of 0.06-0.08%. The sensitivity of solution introduction by DIHEN for uranium, thorium and plutonium (145 MHz/ppm, 150 MHz/ppm and 177 MHz/ppm, respectively) increased significantly compared to CFN and MCN and the solution uptake rate can be reduced to 1 wL/ min in DIHEN-ICP-MS. Isotope ratio measurements at an ultralow concentration level (e.g. determination of 240Pu/ 239Pu isotope ratio in a 10 ng/L Pu waste solution) were carried out for the characterization of radioactive waste and environmental samples.
Thorium-232 Uranium Waste Mass spectrometry Mass spectrometry Isotope ratio

"Determination Of Trace Impurities In High Purity Copper Using Sector-field ICP-MS: Continuous Nebulization, Flow Injection Analysis And Laser Ablation"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 5 Pages 410-416
S. Pattberg, R. Matschat

Abstract: High resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) was applied for multielement-determination in high-purity copper (~99.99%). The samples were introduced into the instrument by three different introduction systems, which were studied with respect to high accuracy, low detection limits and fast analysis: continuous nebulization (CN), flow injection analysis (FIA) and laser ablation (LA). The trueness of the applied method was checked by the analysis of high-purity copper reference material (BCR Cu074). All values obtained for this CRM using CN were in the range of the stated uncertainty for the 9 elements determined: Ag, As, Bi, Cr, Fe, Ni, Pb, Sb, and Sn with contents in the range of 0.5-13 µg/g. Another approach for checking the trueness of the method was to compare the results obtained by this method characterizing the purity of a 4N (99.99% copper content) copper material with those obtained by application of electrothermal atomic absorption spectrometry (ET-AAS) and inductively coupled plasma optical emission spectrometry (ICP-OES). For further characterizing, the concentrations of 49 elements were found in this material below detection limits of HR-ICP-MS in the range of low µg/kg and sub µg/kg. The combination of HR-ICP-MS and a flow injection analysis system (FIAS) improved the robustness of the system in regard to high matrix concentrations. Therefore, matrix concentrations up to 4 g/L could be used for liquid analysis and detection limits were lowered by a factor of 2-5. A calibration method for bulk analysis with laser ablation was developed with doped copper powder as pressed pellets for calibration standards. This method proved to be an excellent fast semi-quantitative method, which was less time consuming in comparison with the analysis of liquids. After application of correction factors the deviation between the results obtained by laser ablation and by analysis of liquids was approximate to 15% for most elements. The method offered the possibility to check for potential losses of analytes occurring during the wet chemical operations.

"Determination Of Glucose In Soft Drink And Sugar-cane Juice Employing A Multicommutation Approach In Flow System And Enzymatic Reaction"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 4 Pages 358-361
Elo&iacute;sa A. M. Kronka, Ana Paula S. Paim, B. F. Reis, Jos&eacute; L. F. Costa Lima, Rui A. Lapa

Abstract: A flow system based on a multicommutation approach was developed for the determination of glucose and sucrose employing enzymatic reactions. The determination was based on the reaction with D-glucose generating hydrogen peroxide catalyzed by glucose-oxidase (GOD). Subsequently, the H2O2 generated reacts with 4-aminefenazone plus phenol to form 4-(p-benzoquinone-mono-imine) fenazone detected at 510 nm. This reaction is catalyzed by the peroxidase enzyme (POD). The flow network comprised a set of three-way solenoid valves and was controlled by means of a microcomputer furnished with an electronic interface and running a software written in Quick BASIC 4.5. The flow network and control software were designed to implement the multicommutation approach providing facilities to handle sample and reagent solutions, so that, sample dilution could be easily performed on line. Accuracy was assessed by comparison with results obtained by known procedures and no significant difference at the 95% confidence level was observed. Other advantageous features were a linear response ranging from 0.05 to 0.20% (w/v) glucose without prior dilution, a reagent consumption of 336 µL per determination, an analytical throughput of 30 samples per hour.
Glucose Sucrose Soft drink Juice Spectrophotometry Multicommutation Immobilized enzyme Computer Method comparison

"Determination Of Total Nitrogen In Food By Flow Injection Analysis (FIA) With A Potentiometric Differential Detection System"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 4 Pages 353-357
Jos&eacute; L. F. C. Lima, M. C. B. S. M. Montenegro, Ana P. M. M. O. Pinto

Abstract: A flow injection set-up based on potentiometric detection and gas diffusion device for the determination of total nitrogen in food is described. The detection system consisted of two ammonium-sensitive electrodes placed sequentially and each alternately operating as reference electrode. Tubular electrodes without an inner reference solution were prepared with a PVC membrane composed of nonactin in Tris (2-ethylhexyl) phosphate and potassium tetrakis (4-chlorophenyl) berate to reduce the membrane resistance. The food sample digests were inserted into the system, and the ammonium present was converted into ammonia gas. The gas diffused through a gas-permeable membrane to a buffer acceptor stream with a pH that ensured transformation to the ammonium cation, which was potentiometrically detected. Good agreement between FIA results and those provided by the reference procedure was obtained, with relative deviation errors below 5%. Using the proposed system, low reagent consumption is possible, a sampling rate of about 30 samples/h was achieved, as well as a good reproducibility for consecutive injections of the same sample (variation coefficient < 2%).
Membrane

"Automated Continuous Monitoring Of Drug Dissolution Process Using A Flow Injection Online Dialysis Sampling -solvent Extraction Separation Spectrophotometric System"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 4 Pages 347-352
Qun Fang, Yu-Qing Sun, Zhao-Lun Fang

Abstract: A flow injection (FI) system was developed incorporating online solvent extraction separation and stopped-flow dialysis systems for automated continuous monitoring of multi-vessel drug dissolution processes. The system employed PTFE pump tubes for solvent delivery, and combined a coaxial phase segmentor, conical cavity gravitational phase separator with a microdialysis sampling system to produce a reliable extraction system capable of stable non-stop operation over extended period of time. The system was evaluated for continuous monitoring in multi-vessel drug dissolution testing of ethambutol hydrochloride tablets using bromocresol green as reagent and chloroform as extractant. With the six-vessel dissolution system used, a sampling frequency of 15/h for each dissolution vessel was achieved with a total of 90 determinations per hour, giving an average precision of 3.6% RSD (n = 11). Results showed good agreement with those obtained using the Chinese Pharmacopoeia standard method.

"Spectrofluorometric Determination Of Hesperidin By Manual And Flow Injection Methods"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 3 Pages 279-283
T. P&eacute;rez-Ru&iacute;z, C. Mart&iacute;nez-Lozano, V. Tom&aacute;s, J. Fenoll

Abstract: A reliable and highly sensitive method for the determination of hesperidin is described. It involves the formation of a highly fluorescent complex between hesperidin and aluminum (III) in a micellar medium. There is a linear relationship between fluorescence intensity (lambda(em) = 496 nm, lambda(ex), = 391 nm) and hesperidin concentration over the range 5 x 10^-7 -2 x 10^-5 mol L-1. The detection limit is 79 µg L-1. The method can easily be adapted to a flow system using a three-channel manifold, the peak height being proportional to the hesperidin concentration over the range 1 x 10^-6-1 x 10^-4 mol L-1. Manual and flow injection procedures have been successfully applied to the determination of hesperidin in orange peel and orange juice.

"Determination Of Citric Acid In Soft Drinks Using Flow Injection With Potentiometric Detection"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 3 Pages 266-269
Jos&eacute; L. F. C. Lima, C. Delerue-Matos, M. Carmo, M. C. V. F. Vaz, Jeanine Silva

Abstract: A flow injection analysis (FIA) system with potentiometric detection has been developed for the determination of citric acid in commercial fruit juices using a copper-selective tubular electrode. It consists of the complexation of citrate ion with copper(II) ion, monitoring the free copper (II) concentration. Linear relationships between the potential and log concentrations of citric acid in the range of 1 x 10^-3 mol/L -1 x 10^-2 mol/L were attained with samples injected in the system without prior treatment. Repeatability was determined by assessing the relative standard deviation for ten replicate injections of different juice samples which varied from 1.2% to 3.0%. The results provided by the automated system were compared with those of an enzymatic conventional method used for the analysis of citric acid in food and a relative deviation of less than 4.0% was found. Recovery trials resulted in values from 97.0% to 101.0%. The system allows a sampling frequency of 60 samples/h.

"Flow Injection Analysis Of Hydrogen Peroxide In Disinfectants"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 1-2 Pages 184-188
Diedrich Harms, Roberto Than, Bernt Krebs, U. Karst

Abstract: A flow injection analysis (FIA) method for the automated determination of hydrogen peroxide in the presence of even stronger oxidants is presented based on the immediate formation of a colored adduct between hydrogen peroxide and a dinuclear iron(III) complex.-A reagent stream with the complex and a carrier stream into which the sample is injected are combined in a low dead volume mixing tee. A reaction coil provides for a reaction time of 7 s, after which detection is performed using UV/vis spectroscopy at 575 nm. Major advantages of the method are the simple experimental setup and the high selectivity even towards stronger oxidants. Real samples have been investigated and the method has been validated using independent techniques including microplate spectrophotometry and HPLC.

"New Enzyme Sensors For Morphine And Codeine Based On Morphine Dehydrogenase And Laccase"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 1-2 Pages 179-183
Christian G. Bauer, Andrea K&uuml;hn, Nenad Gajovic, Olga Skorobogatko, Peter-John Holt, Neil C. Bruce, Alexander Makower, Christopher R. Lowe, Frieder W. Scheller

Abstract: Two new enzymatic methods have been developed to quantify morphine and codeine simultaneously in a flow injection system (FIA). The first enzyme sensor for morphine or codeine is based on immobilizing morphine dehydrogenase (MDH) and salicylate hydroxylase (SHL) on top of a Clark-type oxygen electrode. Morphine or codeine oxidation by MDH leads to a consumption of oxygen by SHL via the production of NADPH. This decreases the oxygen current of the Clark electrode. Concentrations of codeine and morphine are detected between 2 and 1000 µM and between 5 and 1000 µM, respectively. The second enzyme sensor for morphine is based on laccase (LACC) and PQQ-dependent glucose dehydrogenase (GDH) immobilized at a Clark oxygen electrode. Morphine is oxidized by laccase under consumption of oxygen and regenerated by glucose dehydrogenase. Since laccase cannot oxidize codeine, this sensor is selective for morphine. Morphine is detected between 32 nM and 100 µM. Both sensors can be operated simultaneously in one flow system (FIA) giving two signals without the requirement for a separation step. This rapid and technically simple method allows discrimination between morphine and codeine in less than 1 min after injection. The sampling rate for quantitative measurements is 20 h-1. The method has been applied to the quantitative analysis of codeine or morphine in drugs.

"Capillary Enzyme Immunoassay With Electrochemical Detection For Determining Indole-3-acetic Acid In Tomato Embryos"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 1-2 Pages 170-174
Hongying Gao, Tongbo Jiang, William R. Heineman, H. Brian Halsall, John L. Caruso

Abstract: An amperometric immunoassay for indole-3-acetic acid (IAA) in tomato embryos: was developed. The antibody against IAA was covalently bound to the chemically modified inner surface of a 22 µL silica capillary. The competitive binding of methylated IAA and an IAA alkaline phosphatase conjugate for alimited amount of antibody was accomplished in the silica capillary in 20 min. The enzymatic product p-aminophenol, produced from p-aminophenyl phosphate, was determined by flow injection analysis with amperometric detection. A detection limit for IAA of 3 pg µL was obtained. The average concentration of IAA in mature embryos measured by this method is 0.37±0.03 µg/g. Although isotope dilution GC-SIM-MS can achieve the same detection limit, the sample analysis is not feasible in such a complicated matrix and further purification and separation are required.

"An Enzymatic-fluorimetric Method For Monitoring Of Ethanol In Ambient Air"
Fresenius J. Anal. Chem. 1999 Volume 364, Issue 1-2 Pages 100-105
M. Schilling, G. Voigt, T. Tavares, D. Klockow

Abstract: A method is described for the continuous monitoring of ethanol in ambient air. The system consists of a scrubber coil for enrichment of the analyte from air in an aqueous solution and a directly connected, fluorescence detector. Because of using a reagent solution containing alcohol dehydrogenase (ADH) and nicotinamide adenine dinucleotide (NAD(+)) for absorption, ethanol can react directly with ADH and NAD(+) during air sampling, producing NADH, which can be measured by fluorescence detection. The influence of reagent concentrations, gas flow rate and scrubber solution flow rate on the performance of the. instrument was tested. Possible ozone interferences can be avoided by placing a KI coated filter in front of the scrubber inlet. The response time of the,system was found to be 2.3 min and the detection limit about 1 ppb(V). The applicability of the developed method was demonstrated during a field campaign in Brazil.

"Determination Of Arsenic Species In Human Urine Using HPLC With Online Photooxidation Or Microwave-assisted Oxidation Combined With Flow Injection HG-AAS"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 5-6 Pages 526-530
R. Sur, J. Begerow, L. Dunemann

Abstract: An improved analytical procedure is presented for the separation and simultaneous determination of hydride-forming (toxic) and not hydride-forming (non-toxic) arsenic species in human urine. Separation was performed by cation-exchange chromatography using a new solid phase type based on the continuous bed chromatography (CBC) technology. This column permits by a factor of ii higher now rates than conventional columns resulting in a drastical reduction of retention times without any loss of resolution. Using this type of column, arsenobetaine (AsBet), arsenocholine (AsChol), and dimethylarsinic acid (DMA) were separated from the more toxic arsenic species arsenous acid (As(III)), arsenic acid (As(V)), and methylarsonic acid (MA) within only 4 min. The HPLC system was coupled via a flow injection system and either a UV or a microwave (MW) reactor to the HG-AAS instrument. UV photolysis and MW digestion were used to transform AsBet and AsChol to hydride-forming species and to make them accessible to HG-AAS. UV photolysis turned out to be more suitable for this, application than MW digestion, because the latter technique led to peal; broadening and poorer performance. The described procedure was applied to the determination of arsenic species in urine samples of non-occupationally exposed persons before and 12 h after seafood consumption. Detection limits were about 1 µg/L for each arsenic species. After consumption, the AsBet and DMA excretion increased by at least a factor of 150 for AsBet and by a factor of 6 for DMA, respectively, while the excretion of the other species did not increase significantly. This invalidates the use of total urinary arsenic as well as total hydride-forming arsenic as an indicator for exposure to inorganic arsenic.
Speciation

"Flow Injection Electrochemical Hydride Generation Atomic Absorption Spectrometry (FI-EHG-AAS) As A Simple Device For The Speciation Of Inorganic Arsenic And Selenium"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 5-6 Pages 495-498
U. Pyell, A. Dworschak, F. Nitschke, B. Neidhart

Abstract: A flow injection system for the determination of inorganic arsenic [As(III)/As(V)] and selenium species [Se(IV)/ Se(VI)] by electrochemical hydride generation, cryogenic trapping and atomic absorption spectrometry is described. A simple and robust electrochemical flow-through cell with fibrous carbon as cathodic material has been developed for the speciation of arsenic. A cold-trap system makes possible to eliminate interferences from methylated arsenic species. Without pre-reduction the system is selective to As(III) and Se(IV). The selectivity obtained with fibrous carbon as cathode material is compared to the selectivity obtained with a second electrochemical flow-through cell using a lead foil as cathode.

"Possibilities For The Simultaneous Preconcentration And Flame Atomic Absorption Spectrometric Determination Of Cr(III) And Cr(VI) Using A C18 Column And Sorption Loop"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 5-6 Pages 480-483
A. G&aacute;sp&aacute;r, Csilla S&oacute;gor, J&oacute;zsef Posta

Abstract: The sorption loop as a pre-concentration unit used so far in the low-pressure flow injection (FI) system was combined with the hydraulic high-pressure nebulizer (HI-IPN) and a high-pressure liquid chromatographic (HPLC) column. Thus, the sorption pre-concentration of CI(VI) can be coupled to a powerful sample introduction method or pre-concentration techniques of Cr(III). The subsequent determination of the Cr(VI) content of the samples was carried out by flame atomic absorption (FAAS).

"Sensitive Reaction Rate Method For The Determination Of Low Levels Of Formaldehyde With Photometric Detection"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 4 Pages 376-379
A. A. Ensafi, S. Abassi

Abstract: A simple and rapid method is proposed for the determination of ultra trace amounts of formaldehyde. It is based on the catalytic effect of formaldehyde on the oxidation of Brilliant cresyl blue by bromate. The reaction is monitored photometrically by measuring the decrease in absorbance of the dye. Formaldehyde in the range of 0.005-2.300 µg/mL can be determined with a limit of detection of 0.003 µg/mL. The relative standard deviation for ten replicate measurements of 1.5 µg/mL formaldehyde is 0.1%. The method was used for the determination of formaldehyde in real samples with satisfactory results.

"The Influence Of An Anionic Additive On The Properties Of Cation-exchanger Based Calcium-selective Electrodes"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 4 Pages 369-375
A. Schwake, K. Cammann, A. L. Smirnova, S. S. Levitchev, V. L. Khitrova, A. L. Grekovich, Y. G. Vlasov

Abstract: Potentiometric and electrochemical impedance spectroscopic investigations of calcium-selective membranes containing poly(vinylchloride), dioctylphenylphosphonate, calcium (bis[4-(1,1,3,3-tetramethylbutyl)phenyl] phosphate) and different amounts of the lipophilic anionic additive tridodecylmethylammonium chloride were carried out. The addition of the lipophilic additive changes the properties of calcium-selective electrodes, e.g. slope and calcium selectivity. The selectivity for calcium in presence of H+, Na+, K+, NH4+, Mg2+, Ba2+, Sr2+ and (C2H5)(4)N+ was measured by three different methods, namely separate solution method, fixed interference method and matched potential method. Membranes with different concentration ratios between the calcium-exchanger and tridodecylmethylammonium chloride were investigated within half a year. The tendency of changing from cationic into anionic response for membranes containing nearly equivalent concentrations of cation-and anion-exchanger was shown. This inversion of the electrode response depends not only upon the concentration ratio of both ion-exchangers but also upon the total concentration of calcium-exchanger. Electrochemical impedance spectroscopy was used for monitoring the development of membrane resistances during a soaking period of one month. Based on these results dielectric constants for the calcium-selective membranes depending on the membrane composition were determined. Furthermore, the dependence of the membrane resistance on the membrane thickness and the concentration of tridodecylmethylammonium chloride was evaluated.

"FIA Determination Of Pyruvate In Serum Based On Direct Chemiluminescence Oxidation"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 3 Pages 320-322
Manliang Feng, Guofang Zhang, Zhujun Zhang

Abstract: Chemiluminescence was observed by mixing acidic potassium permanganate solution with pyruvate in the presence of quinine. A new simplified method for pyruvate determination based on this phenomenon was established. The chemiluminescence intensity is a linear function of the concentration of pyruvate in the range of 2 Å~ 10^-6 to 1 Å~ 10^-3 g/mL with a detection limit of 0.8 µg/mL and a relative standard deviation of less than 2.3%. The method has been successfully used to determine pyruvate in serum.

"Flow Injection Solid Phase Spectrofluorimetric Determination Of Pyridoxine In Presence Of Group B-vitamins"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 3 Pages 265-269
A. Ruiz-Medina, M. L. Fern&aacute;ndez-de C&oacute;rdova, A. Molina-D&iacute;az

Abstract: A flow-through optosensor has been prepared for the sensitive and selective determination of pyridoxine (vitamin Bg) in aqueous solutions. The sensor was developed in conjunction with a monochannel flow injection analysis system with fluorimetric detection using Sephadex SP-C25 resin as an active sorbent substrate. This method of determination is carried out without any derivatization. The wavelengths of excitation and emission were 295 and 385 nm, respectively. When a HCl (10^-3 mol L-1)/NaCl (3 x 10^-2 mol L-1) solution is used as carrier solution, the sensor responds linearly in the measuring range of 5-200, 10^-400 and 50-1800 ng mL-1 with detection limits of 0.33, 0.67, and 5.70 ng mL-1 for 2000, 1000 and 200 µL of sample volume, respectively. The relative standard deviation for ten independent determinations is less than 0.75% for 0.2 and 1.0 mt of sample volumes used, and 1.31% for 2.0 mi, of sample volume used. The method was satisfactorily applied to the determination of vitamin Bg in pharmaceutical preparations.

"Preconcentration Of Trace Elements In Sea Water With Poly (acrylaminophosphonic-dithiocarbamate) Chelating Fiber For Their Determination By Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 3 Pages 251-255
B. Wen, X.-Q. Shan, Rui-Xia Liu, Hong-Xiao Tang

Abstract: A new ion exchange chelating fiber with aminophosphonic and dithiocarbamate groups based on polyacrylonitrile was used for the simultaneous pre-concentration of beryllium, bismuth, cobalt, gallium, silver, lead, cadium, copper, manganese and indium in sea water. The optimum experimental parameters, such as fiber capacity, pH, sample flow rate and volume, eluant and effect of matrix ions on the pre-concentration were investigated. The separation of analytes can be achieved from sea water with a concentration factor of at least 200 times. The method has been applied for the determination of trace elements in coastal sea water. The data obtained by this method agreed well with certified values.
8-Hydroxyquinoline

"End-point Detection Of The Potentiometric Titration Of Anionic Polyelectrolytes Using An Anionic Surfactant-selective Plasticized Poly (vinyl Chloride) Membrane Electrode And An Anionic Surfactant As A Marker Ion"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 3 Pages 241-245
T. Masadome, Toshihiko Imato, Yasukazu Asano

Abstract: A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to dodecylbenzenesulfonate (DBS) ion is applied to the determination of anionic polyelectrolytes such as potassium poly (vinyl sulfate) (PVSK) by potentiometric titration, using a poly (diallyldimethylammonium chloride) (Cat-floc) solution as a titrant. The end-point of the titration is detected as the potential jump of the plasticized PVC membrane electrode caused by decrease in the concentration of DBS ion added to the sample solution as a marker ion, due to the ion association reaction between the DBS ion and Cat-floc. The effects of the concentration of DBS ion, coexisting surfactants and electrolytes in the sample solution and pH of the sample on the degree of the potential jump at the end-point were examined. A linear relationship between the concentration of anionic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2 x 10^-5 to 4 x 10^-4 N for PVSK, alginate, and carrageenan.

"Comparison Of Mu M And Mm Sized Disk Electrodes For End-column Electrochemical Detection In Capillary Electrophoresis"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 3 Pages 231-235
Frank-Michael Matysik, L. Nyholm, Karin E. Markides

Abstract: End-column electrochemical detection based on either the use of a 25 µm microdisk electrode or a 0.5 mm macrodisk electrode has been compared with respect to performance and influence on non-aqueous capillary electrophoretic separations. Despite the much higher coulometric efficiency obtained with the larger disk electrode, the microdisk electrode configuration offers comparable limits of detection (LOD) for the neutral and positively charged ferrocene compounds employed in conjunction with a non-aqueous acetonitrile-based buffer. The LODs for ferrocene were found to be 4.0 x 10^-8 M and 6.7 x 10^-8 M for the microdisk and macrodisk detector, respectively. In addition, both detector arrangements showed different relative responses for neutral and positively charged analytes. The macroelectrode-based detector introduced additional zone broadening while this was not found to be the case with the microelectrode arrangement. Using the microelectrode detector, the band broadening in an electro-osmotically driven flow system was compared to that in a gravity flow-based system. It was demonstrated that the zone broadening under gravity flow conditions was approximately twice as large as under electro-osmotic flow conditions for a typical set of experimental parameters.

"Ultra-trace Analysis Of Nitrite In Food Samples By Flow Injection With Spectrophotometric Detection"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 1 Pages 131-133
A. A. Ensafi, G. Bagherian Dehaghei

Abstract: A flow injection system with spectrophotometric detection is proposed for the determination of low levels of nitrite based on its catalytic effect on the oxidation of gallocyanine by bromate in acidic media. Various analytical parameters such as acidity, reagent concentration, flow rate, sample size, time, temperature, and interfering species were studied. The calibration graph was linear for 0.020-0.500 µg/mL of nitrite. The method is successfully applied to food samples. Up to 30±5 samples can be analyzed per hour.

"Flow Injection Chemiluminescence Determination Of Isoniazid With Electrogenerated Hypochlorite"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 1 Pages 126-128
Jiachu Huang, Chengxiao Zhang, Zhujun Zhang

Abstract: A flow injection chemiluminescence method for the determination of isoniazid based on the sensitizing effect of isoniazid on the chemiluminescence generating luminol-hypochlorite reaction is described. The hypochlorite was electrogenerated online by constant current electrolysis, thus, eliminating instability of hypochlorite solution prepared from commercially available sodium hypochlorite. The calibration graph is linear in the range 1 x 10^-8 to 1 x 10^-6 g mL-1, and the detection limit is 6 x 10^-9 mL-1. The relative standard deviation for determination of 5 x 10^-8 g mL-1 is 2.8%. The proposed method has been successfully applied to the determination of isoniazid in pharmaceutical preparations.

"FIA Spectrophotometric Determination Of Pd With DBOK-chlorophosphonazo"
Fresenius J. Anal. Chem. 1999 Volume 363, Issue 1 Pages 117-118
Jian Huang, Xingguo Chen, Zhide Hu, Zhengfeng Zhao, Martin Hooper

Abstract: A flow injection method was developed for the determination of palladium, based on the reaction of palladium with DBOK-chlorophosphonazo with a detection limit of 0.07 µg/mL and a linear calibration range from 0.1 to 3.2 µg/mL of palladium. The reaction product has a maximum absorption at 630 nm. The method was applied to determine Pd2+ in catalysts and in anode mud samples. The relative error is less than 3% and the recovery of palladium is in the range 95% to 105%.

"Flow Injection Analysis Of Zinc And Cobalt In Beverages, Biological, Environmental, And Pharmaceutical Samples"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 7-8 Pages 571-576
S. G. Aggarwal and K. S. Patel

Abstract: A new, simple, rapid, and selective flow injection analysis (FIA) method for the spectrophotometric quantification (speciation of inorganic and organic form) of Zn and Co with NH4SCN and malachite green (MG) in the presence of surfactants (CPC and TX-100) is described. The value of apparent molar absorptivity of the Zn- and Co-complexes are 1.23 x 104 and 8.67 x 103 L mol-1 cm-1 at absorption max., 635 nm, respectively. The detection limit (amt. causing a peak height >3 s) is 15 ppb Zn and 20 ppb Co, whereas their optimum working ranges for the quant. determinations are 0.05-2.0 ppm Zn and 0.07-2.5 ppm Co in the real samples. The sample throughput of the method is 120 samples/h at the flow rate of 5.0 mL/min with RSD of <1%. The method is free from interferences of almost all ions which are commonly associated with these metals in the complex materials. The composition of the complexes and their reaction mechanism involved are discussed. The effect of FIA and anal. variables for the determination of the metals are optimized. The method was applied to the quantification of Zn and Co in beverages, biol., environmental, and pharmaceutical samples.
Zinc Cobalt Urine Environmental Pharmaceutical Beer Spectrophotometry Speciation pH gradient Surfactant Interferences Complexation

"Chemiluminescence Determination Of Sulfite In Sugar And Of Sulfur Dioxide In Air Using The Tris(2,2 '-bipyridyl)ruthenium-KIO4 System"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 7-8 Pages 566-570
F. Wu, Zhike He, H. Meng, Liangjie Yuan, Xiaoyan Li, Yun'e Zeng

Abstract: The chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy)(3)(2+)(bipy=2,2'-bipyridyl)-SO32--KIO4 is described. The concentration of sulfite is proportional to the CL intensity from 1.0 x 10^-7 to 1.0 x 10^-4 mol/L. The limit of detection is 2.0 x 10^-8 mol/L and the relative standard deviation is 4.4% for a 2 x 10^-5 mol/L sulfite solution (n = 9). This method has successfully been applied to the determination of sulfite in powdered sugar (sucrose) and of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.
Sulfite Sulfur dioxide Food Wine Environmental Chemiluminescence

"Flow Injection Spectrofluorimetric Determination Of Ethylenethiourea"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 4 Pages 399-403
Tom&aacute;s P&eacute;rez-Ruiz, Carmen Mart&iacute;nez-Lozano, Virginia Tom&aacute;s, Antonio Sanz, Jes&uacute;s Mart&iacute;n

Abstract: A flow injection configuration is proposed for the fluorimetric determination of ethylenethiourea. The procedure is based on the inhibitory effect of ethyl-enethiourea on the oxidation of thiamine to thiochrome by Hg(II). A linear calibration graph was obtained between 0.1-2.0 µg mL-1, with a sampling rate of 40 samples/h and a relative standard deviation of 1.11%. The usefulness of the method was tested for the determination of ethylenethiourea residues in water, milk, potatoes, pear, grape, and apple.
Ethylenethiourea Water Cow Vegetable Fruit Fruit Fruit Fluorescence Indirect

"Optosensing Of Hydrochloric Acid Based On The Fluorescence Quenching Of A Flavone Copolymer"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 4 Pages 387-390
Wanhui Liu, Jianghong Tang, Ying Wang, Guoli Shen, R. Yu

Abstract: An optical fiber sensor for the continuous determination of HCl is presented. It is based on the fluorescence quenching of a flavone-containing copolymer membrane by HCl. The quenching efficiency is greatly enhanced in the presence of Fe(III). This enhancement is attributed to the primary inner filter effect, as well as the formation of a complex between the 4'-N,N-dimethylaminoflavone group in the copolymer and the Fe(III) species extd. from HCl solution The optical response is linear and reversible for 0.10-6.00 mol L-1 HCl with a response time of the order of a second. The standard deviations for repeated alternative measurements of 0.20 and 2.00 mol L-1 HCl are 0.32% and 0.46% (n = 10), respectively, indicating a good reproducibility. Because of the covalently bonding of the dye to polymer, the sensor exhibits also a good stability. Selectivity was also evaluated for some potential interferents. The sensor in conjunction with a flow injection system can be used for online determination of HCl.
Hydrochloric acid Fluorescence Sensor Optosensing Quenching Interferences

"Determination Of Total Iron In Groundwaters And Multivitamin Tablets Using A Solid Phase Reactor With Tiron Immobilized On Amberlite Ion-exchange Resin In A Flow Injection System"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 3 Pages 319-323
J. F. van Staden and L. G. Kluever

Abstract: A method is described for the flow injection determination of total Fe as Fe(III) (Fe(II) was oxidized before determination) using a solid phase reactor containing disodium-1,2-dihydroxybenzene-3,5-disulfonate (tiron) as substrate. The Fe(III) reacted with tiron and formed a complex which absorbed at 667 nm, where it was measured spectrophotometrically. The system has a linear range of 1-50 mg L-1 with a detection limit of 0.67 mg L-1. The method was applied to the determination of total Fe in multivitamin tablets and iron-rich ground waters, with a RSD <1.1%. The results agreed with certified values and results of a standard ICP-AES method.
Iron Ground Pharmaceutical Spectrophotometry Solid phase reagent Tiron Amberlite Complexation Method comparison Reference material

"Flow Injection Analysis Of Fluoride In Electroplating Baths With Potentiometric Detection"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 230-233
R. P&eacute;rez-Olmos, M. B. Etxebarria, J. L. F. C. Lima, M. C. B. S. M. Montenegro

Abstract: A high dispersion FIA system with a fluoride-selective and a double junction reference electrode in cascade arrangement was developed for the determination of F- in chromium electroplating baths. The analyzes of seven synthetic baths prepared in the laboratory and two samples provided by the industry gave results with a mean recovery value of 100.5% and a mean variation coefficient of 1.6%. These data are better than those obtained by the EDTA complexometric titration, the reference technique, with a mean recovery of 94.0% and a mean variation coefficient of 7.5%. The sampling rate for the FIA manifold was 20 samples per h.
Fluoride Chromium Electrode Potentiometry Dilution Dispersion Method comparison

"Flow-through Stripping Chronopotentiometry For The Monitoring Of Mercury In Waste Waters"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 201-204
E. Beinrohr A, J. Dzurov A, J. Annus A, J. A. C. Broekaert

Abstract: A simple method for the determination of total mercury in waste waters is described. It makes use of a flow system incorporating a wall-jet cell equipped with a gold working electrode. The untreated sample is mixed on-line with the acidic carrier electrolyte which contains potassium permanganate and transforms the various species of mercury, especially elementary Hg, to Hg(II). The pre-treated solution enters the cell where mercury is deposited on the gold electrode. In the next step the deposit is stripped at constant current and the time corresponding to the dissolution of the deposit is obtained from the chronopotentiometric signal. The method enables it to determine and monitor Hg in the concentration range of 1 to 1000 wg/L in 5 min intervals.
Mercury Waste Potentiometry Electrode

"Amperometric Determination Of Hydrogen Peroxide With A Manganese Dioxide Film-modified Screen Printed Carbon Electrode"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 194-200
Klemens Schachl, Hailemichael Alemu, K. Kalcher, Helmut Moderegger, Ivan Svancara, Karel Vytras

Abstract: A carbon thick film electrode modified with an MnO2-film was investigated as an amperometric detector for H2O2 in flow injection analysis (FIA). At an operating potential of +0.48 V vs. Ag/AgCl catalytic oxidation of the analyte was exploited for amperometric monitoring. Experimental parameters, such as pH of the carrier, working potential, flow rate, and injection volume were optimized. The amperometric signals were linearly proportional to the concentration. of H2O2 in the range from 0.005-10 mg/L, showing a detection limit (3s) of 2.3 µg/L. The method was applied to the determination of H2O2 in rainwater and to a simple assay to quantify glucose in human plasma.
Hydrogen peroxide Glucose Plasma Human Rain Amperometry Electrode Electrode Electrode Sensor Apparatus Detector Optimization

"Capillary Batch Injection Analysis And Capillary Flow Injection Analysis With Electrochemical Detection. A Comparative Study Of Both Methods"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 2 Pages 189-193
U. Backofen, F.-M. Matysik, W. Hoffmann, H.-J. Ache

Abstract: Capillary batch injection analysis (CBIA) and capillary flow injection analysis (CFIA) in combination with electrochemical or optical detection methods were studied and compared with respect to their performance. Despite the differences in tech. equipment both techniques share the same idea of reliable transport and washout of nanoliter samples over sensing surfaces. The amperometric and potentiometric CBIA responses were studied under various experimental conditions in order to optimize the CBIA set-up. The dispersion of the sample solution relative to that of the cell electrolyte had a remarkable effect on the hydrodynamic characteristics of CBIA. Dispersion in CFIA was investigated using on column UV-detection for electroosmotic flow (EOF) conditions as well as for gravity flow conditions. For a 75 µm capillary the relative band broadening of the sample plug under gravity flow was twice as large as under EOF. Dispersion in a system that involves a chemical reaction between the sample and the carrier solution, namely CrO72- and Fe2+ was investigated by amperometric detection and exploited for the determination of microsamples.
Iron(2+) Dichromate Amperometry Potentiometry Spectrophotometry Electrophoresis Capillary Electroosmotic flow

"Flow Injection Chemiluminescence Determination Of Medazepam"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 1 Pages 167-169
S. M. Sultan, Ala'ddin M. Almuaibed, A. Townshend

Abstract: A new flow injection chemiluminescence method for the assay of medazepam is explored. The method involves the use of permanganate in sulfuric acid for the oxidation of medazepam with the emission of chemiluminescence detected by a photomultiplier tube. A simplex procedure was employed for optimizing the conditions for high sensitivity detection, which were found to be 1.03 x 10^-3 mol L-1 permanganate, 0.153 mol L-1 sulfuric acid, and 3.43 mL min-1 flow rate. The linear calibration range was 3.7 x 10^-5 to 1.7 x 10^-3 mol L-1. The detection limit (3s) and the sample throughput were 1.85 x 10^-5 mol L-1 and 100 per h, respectively. The relative standard deviation for S replicate determinations of 1.9 x 10^-4 mol L-1 medazepam was 0.15%. Common excipients (starch, glucose, maltose, lactose) used in pharmaceutical preparations had no effect.
Medazepam Pharmaceutical Chemiluminescence Interferences Optimization

"A Rapid Automated Method For Wine Analysis Based Upon Sequential Injection (SI)-FTIR Spectrometry"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 1 Pages 130-136
R. Schindler, R. Vonach, B. Lendl, R. Kellner

Abstract: A new process control methodology for the simultaneous determination of sugars, alcohols, and organic acids in wine based on multivariate evaluation of mid-IR transmission spectra of wine samples is presented. In addition to EtOH several lower level wine components (glucose, fructose, glycerol, citric- , tartaric-, malic-, lactic-, and acetic acid) were determined To establish a multivariate calibration model a set of 72 calibration solutions was prepared and measured, using a novel, fully automated sequential injection (SI) system with Fourier transform IR (FTIR) detection. The resulting spectra were evaluated using a partial least square (PLS) model. The developed PLS model was then applied to the anal. of real wine samples containing 79-91 g L-1 EtOH, 5.9-8.1 g L-1 glycerol, 0.4-6.9 g L-1 glucose, 1.5-7.5 g L-1 fructose, 0.3-1.6 g L-1 citric acid, 1.0-1.7 g L-1 tartaric acid, 0.02-3.2 g L-1 malic acid, 0.4-2.8 g L-1 lactic acid, and 0.15-0.60 g L-1 acetic acid, yielding results which were in good agreement with those obtained by an external reference method (HPLC-IR). The short analysis time (<3 min) together with high reproducibility makes the newly developed method applicable to process control and screening purposes (av. of the standard deviations calculated from four repetitive measurements of 6 different real samples: EtOH: 0.55 g L-1, glycerol: 0.037 g L-1, glucose: 0.056 g L-1, fructose: 0.036 g L-1, citric acid: 0.020 g L-1, tartaric acid: 0.010 g L-1, malic acid: 0.052 g L-1, lactic acid: 0.012 g L-1, and acetic acid: 0.026 g L-1).
Sugars Alcohol Acids, organic Ethanol Glucose Glycerol Fructose Citric acid Tartaric acid l-Malic acid Lactic acid Acetic acid Wine Spectrophotometry Sequential injection Method comparison Simultaneous analysis Multivariate calibration Partial least squares

"The Effect Of Sample Preparation On Metal Determination In Soil By FAAS"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 1 Pages 125-129
Zofia Kowalewska A, E. Bulska A, A. Hulanicki

Abstract: Different methods for the determination of several metals in soils by flame atomic absorption spectrometry (FAAS) were investigated. Different procedures for total dissolution of soil: I - HF+HClO4, H3BO3, HCl digestion (conventional heating), II - HF+HClO4, H3BO3 digestion followed by fusion with LiBO2 (conventional heating) and III - HF+HCl+HNO3, H3BO3 digestion (microwave heating), as well as a leaching procedure with HNO3+HClO4, HCl were tested and compared. For quality assessment, the certified reference material S-1 soil was used. For most of the investigated metals, the best accuracy and precision were achieved when the procedure I or III were used. The developed procedure was applied to the analysis of soil samples from crude oil refinery and dump of petroleum origin wastes regions.
Environmental Spectrophotometry Sample preparation

"Flow Injection Microscopy As A Tool For Two-parameter Monitoring Of Cellular Responses"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 1 Pages 67-72
Ilkka L&auml;hdesm&auml;ki and J. Ruzicka

Abstract: Flow injection fluorescence microscopy (FIFM) was further developed to become a useful tool for a multiparametric study of the response of living cells to a biochemical stimulus. Rather than recording several parameters simultaneously, the multiparametric measurements are carried out in a sequential fashion: internal Ca concentration. and pH of Chinese hamster ovary cells were alternately monitored in subsequent runs where the cells were exposed to carbachol. Delivery of carbachol onto the cells was carried out by the flow injection app. in the FIFM setup. Fluorescent indicators fura-2 and BCECF were loaded into the cells to provide the Ca- and pH-dependent signals, respectively. The fluorescent signals were detected by the fluorescent microscope domain of the FIFM setup. Comparison of the temporal dependence of the response curves shows differences in the 2 responses. The experimental evidence is supported by a novel functional tracer test that is used to characterize the kinetics of cell-stimulation interaction.
Calcium pH Hamster Microscopy Kinetic

"Coupling Continuous-flow Systems To Instruments Based On Discrete Sample Introduction"
Fresenius J. Anal. Chem. 1998 Volume 362, Issue 1 Pages 58-66
M. Valc&aacute;rcel, Mercedes Gallego, Angel R&iacute;os

Abstract: The interfaces between low-pressure continuous sample treatment systems and high-level information instruments such as gas chromatographs, capillary electrophoresis equipment and graphite furnace atomic spectroscopic instruments, which are characterized by conventional discrete sample introduction devices, are presented. The present and future developments are discussed of (directly) linking real samples and those analytical equipments with the main objective of avoiding or minimizing manually implemented preliminary operations of the analytical process
GC Electrophoresis Spectrophotometry Interface Review

"Chemiluminescence Flow System For The Determination Of Sulfite"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 8 Pages 824-826
Wei Qin A, Z.-J. Zhang A, Cheng-Jie Zhang

Abstract: A novel chemiluminescence(CL) flow system for sulfite is described based on electrostatically immobilized luminol on an anion exchange column. Sulfite is detected by the CL reaction with luminol bleeding from the column by hydrolysis. The calibration graph is linear in the range 3 2 10^-7 to 1 2 10^-5 mol/L, and the detection limit is 1 2 10^-7 mol/L. Interfering metal ions co-existing in sample solutions could be effectively eliminated on-line by an upstream cation exchanger. A complete analysis could be performed in 1 min with a relative standard deviation of less than 5%. The system could be reused for over 50 h and has been applied successfully to the determination of sulfur dioxide in air.
Sulfite Chemiluminescence

"Mercury Speciation By Coupling Cold Vapor Atomic Absorption Spectrometry With Flow Injection Online Preconcentration And Liquid Chromatographic Separation"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 8 Pages 761-766
Xuefeng Yin, Wolfgang Frech, Erwin Hoffmann, C. L&uuml;dke, Jochen Skole

Abstract: A fully automated system for the direct determination of methylmercury (MeHg), ethylmercury (EtHg), phenylmercury (PhHg), and inorganic mercury (Hg(II)) at the ng/L level is described. It is based on solid phase extraction pre-concentration incorporated in a flow injection (FI) system, high performance liquid chromatography (HPLC) separation, reduction combined with thermolysis and determination by cold vapor atomic absorption spectrometry (CVAAS). For pre-concentration a microcolumn of bonded silica with octadecyl functional groups (C18 reversed phase material) was used as a sorbent for the Hg complexes formed online with ammonium pyrrolidine dithiocarbamate. Retained mercury species are eluted with a methanol-acetonitrile-water mixture and subjected to separation on an octadecyl silane (ODS) column before determination by CVAAS. The sensitivity of organo-mercury determination could be improved by NaBH4 as a reductant combined with a thermolysis step. To perform online measurements the pre-concentration microcolumn was mounted in a pressure-tight casing. Limits of detection for MeHg, EtHg, PhHg, and Hg(II) employing a sample volume of 58.5 mL were 9, 6, 10, and 5 ng/L, respectively. The RSD calculated from 9 repeated measurements was 3.6, 5.5, 10.4, and 7.6% for MeHg, EtHg, PhHg, and Hg(II), respectively. Finally, the application of this method for speciation of Hg in fish and human urine is described.
Mercury(II) Methylmercury ion Phenylmercury Ethylmercury Marine Urine Spectrophotometry HPLC Speciation Preconcentration Solid phase extraction Silica C18 Pyrrolidine dithiocarbamate Heated reaction Post-column derivatization

"Electrolytic Hydride Generation Electrothermal Atomic Absorption Spectrometry - In Situ Trapping Of As On Different Pre-conditioned End-heated Graphite Tubes"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 6-7 Pages 733-737
E. Denkhaus A, A. Golloch A, T. U. Kampen A, M. Nierfeld A, U. Telgheder

Abstract: An automated analytical system for the determination of As combining an electrolytic hydride generator and a graphite furnace atomic absorption spectrometer has been developed. To investigate the trapping efficiency of permanent modifiers, the end-heated graphite tubes have been impregnated with Ir and mixed Pd/Ir pre-reduced modifiers, respectively, or pre-coated with Ir by electron beam evaporation under high vacuum. Furthermore, the influence of the modifier mass on the shape of the absorption signal has been studied and the performance of the modifier has been discussed. Using the pre-coated graphite tube the calculated detection limit (3s criteria ) for As was 3 pg and 15 ng/L (200 wL sample volume, two pre-concentration steps) for the absolute mass and the concentration, respectively. The long-term stability of the permanent modifiers and their physical and or chemical changes during the lifetime of the tube have been observed.
Arsenic Spectrophotometry Electrochemical product generation

"Determination Of Chromium(III) In Urine, Blood Serum, And Hair Using Flow Injection Chemiluminescence Analysis"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 5 Pages 509-511
R. Escobar, M. S. Garc&iacute;a-Dom&iacute;nguez, A. Guira&uacute;m, F. F. de la Rosa

Abstract: A flow injection (FI) chemiluminescence method for the determination of Cr(III) in blood serum, urine, and hair samples is reported. It is based on the chromium-catalyzed light emission from the luminol oxidation by H2O2. The app. consists of an FI system with a flow cell formed by a coiled transparent tube suitable for chemiluminescence detection. The specificity of the method is achieved in presence of EDTA. The detection limit under optimum conditions is 0.01 µg/L of Cr(III). Precision and accuracy were evaluated by determining Cr(III) concentrations in urine standards from the National Institute of Standard and Technol. (NIST).
Chromium(III) Blood Serum Urine Hair Chemiluminescence Indirect EDTA Optimization Reference material

"Flow Injection Online Sorption Preconcentration Of Platinum In A Knotted Reactor Coupled With Electrothermal Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 5 Pages 445-450
E. Ivanova and F. Adams

Abstract: A flow injection online sorption pre-concentration method for the electrothermal AAS determination of Pt was developed. The pyrrolidine dithiocarbamate complexes of either Pt4+ or Pt2+, formed in 0.7 mol L-1 HNO3, are online adsorbed on the inner walls of a PTFE knotted reactor and subsequently eluted with MeOH. An enhancement factor of 112 and a detection limit (3s) of 10 ng L-1 along with a sampling frequency of 21 h-1 were achieved with a 90 s pre-concentration time at a sample flow rate of 8.8 mL min-1. The RSD is 2.5% for 0.4 µg L-1 Pt. The method was applied to the determination of Pt in blood samples.
Platinum Blood Spectrophotometry Preconcentration Pyrrolidine dithiocarbamate Complexation Knotted reactor Tube wall immobilization

"Sequential Determination Of Tin, Arsenic, Bismuth And Antimony In Marine Sediment Material By Inductively Coupled Plasma Atomic Emission Spectrometry Using A Small Concentric Hydride Generator And L-cysteine As Prereductant"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 2 Pages 155-157
Y.-L. Feng A, H.-Y. Chen A, H.-W. Chen A, Li-Ching Tian

Abstract: A hydride generation system using a small concentric hydride generator combined with inductively coupled plasma atomic emission spectrometry (ICP-AES) was established to determine tin, arsenic, bismuth and antimony in a marine sediment material with L-cysteine as a pre-reductant. Influences of concentrations of three kinds of acids (HCl, HNO3 and HClO4), L-cysteine, and sodium tetrahydroborate(III) as well as sodium hydroxide were investigated. The interferences from transition ions were found to be insignificant for determination of the four elements in presence of L-cysteine. Under optimized conditions the detection limits were 0.6 ng/mL for arsenic(III), 0.8 ng/mL for antimony(III), 1.7 ng/mL for tin(IV), and 1.2 ng/mL for bismuth(III). The method was applied to determine the four elements in standard marine sediment materials and the results were in agreement with certified values.
Tin Arsenic Bismuth Antimony Marine Mass spectrometry Phase separator Volatile generation Apparatus

"Determination Of H2O2 And Organic Peroxides By High-performance Liquid Chromatography With Post Column UV Irradiation, Derivatization And Fluorescence Detection"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 2 Pages 124-128
Jianguo Hong A, J. Maguhn A, Dieter Freitag A, Antonius Kettrup

Abstract: A method for the determination of hydrogen peroxide and several organic peroxides by high-performance liquid chromatography with post-column UV irradiation, derivatization and fluorescence detection is described. By means of post-column UV irradiation in the presence of water organic peroxides are converted into hydrogen peroxide and organic hydroperoxides, which react rapidly with the post-column derivatization agent p-hydroxyphenylacetic acid (PHPAA) under catalysis of horseradish peroxidase to yield the fluorescent PHPAA dimer that is detected at excitation and emission wavelengths of 285 and 400 nm, respectively. The detection limit for hydrogen peroxide is 14 ng/mL, for organic peroxides between 34 ng/mL and 5 wg/mL. No interference by other compounds was observed when their concentrations were below 10 mg/mL except ethers and phenols.
Hydrogen peroxide Peroxides, organic HPLC Fluorescence Post-column derivatization Photochemistry UV reactor

"The Effect Of Palladium Modifier On The Efficiency Of Antimony Hydride Trapping In Graphite Furnace Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1998 Volume 361, Issue 1 Pages 43-46
S?awomir Garbos, Ewa Bulska, Adam Hulanicki

Abstract: The performance of palladium as permanent chemical modifier electroplated on the surface of a graphite tube for the pre-concentration of antimony hydride was examined and compared with thermally formed Pd-coatings. The application of Pd-electroplated tubes allows to perform at least 75 determination cycles without any significant change in the efficiency of hydride collection. This is an advantage over the thermally formed palladium coating which must be obtained individually before each measurement. After the optimization of the system parameters a concentration detection limit of 48 ng/L and an absolute detection limit of 71 pg for a 1.48 mL sample were obtained. The procedure was applied to the determination of antimony at a concentration level of 0.2 wg/L in a tap water sample.
Antimony Spectrophotometry Optimization

"Selenium Determination Using Ethylation And Online Trapping/detection By Graphite Furnace Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 6 Pages 723-725
R. Allabashi A, J. Rendl A, M. Grasserbauer

Abstract: An on-line system for the continuous ethylation of selenium (IV) in combination with trapping and detection of the produced diethylselenide in the coated AAS graphite furnace was developed. Due to the slow kinetics of the ethylation the volume of the reaction coil and the reaction time had to be increased to 5.5 mL and 80 s, respectively. The sensitivity of the method was comparable with that of the hydride generation in the same system and the relative standard deviation was 6-10%. The determination of Se(IV) in real samples after the most widely used digestion with nitric acid could not be accomplished, because of the drastic signal depression caused by this acid.
Selenium Spectrophotometry

"Study And Application Of A Method For The Determination Of Metallic Elements By ICP-AES With Preconcentration On An Active Carbon-silica Gel Microcolumn In A FI System"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 6 Pages 721-723
Hongnian Ji, Zhenhuan Liao, Junmei Sun, Zucheng Jiang, Hongnian Ji, Zhenhuan Liao, Junmei Sun, Zucheng Jiang

Abstract: Using active carbon-silica gel as adsorbent and sodium diethyldithiocarbamate (NaDDTC) as chelating reagent in a flow injection system, an ICP-AES method was developed for pre-concentration and determination of trace metallic elements in high purity rare earth oxides. The experimental parameters such as pH, flow rate, amt. of adsorbent, length of reaction coil and eluent acidity were optimized. At pH 4.6 Al, Cr, Cu, Fe, Pb, V, Zn could be pre-concentrated, and subsequently determined by ICP-AES. This method can eliminate matrix effects. Its enrichment factors were 8.1-12.6 with detection limits in the ng/mL range and RSD of 2.3-5.0. This method was applied to the analysis of high purity of La2O3, and Eu2O3 with satisfactory results.
Aluminum Chromium Copper Iron Lead Vanadium Zinc High purity High purity Spectrophotometry Activated carbon Silica gel Preconcentration Chelation Diethyldithiocarbamate Optimization

"Determination Of Alkaline Phosphatase Activity In Human Sera By Mid-FTIR Spectroscopy"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 6 Pages 717-720
B. Lendl A, P. Krieg A, R. Kellner

Abstract: Fourier transform infrared spectroscopy is applied to the determination of alkaline phosphatase (ALP) activity in human sera. 4-nitrophenylphosphate was found to be an excellent ALP substrate for FT-IR spectroscopic detection. The developed method is based on the acquisition of two FT-IR spectra: one recorded immediately after mixing the sample and assay solution and the other after an incubation time of 10 min. Spectral changes in the mid IR range due to the enzymatic reaction could be correlated to the ALP activity in the sample. Experimental conditions were established such that the clinically relevant range for determination of ALP activity in human sera (50 to 900 U/L) was covered. The method was applied to the analysis of ALP activities in standard solutions as well as in human sera yielding results which agreed well with those obtained by a standard reference method.
Enzyme, alkaline phosphatase Serum Human Spectrophotometry

"Determination Of N-acetyl-L-cysteine By Flow Injection Potentiometry"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 6 Pages 675-678
Nj. Radi&#cacute; and J. Komljenovi&#cacute;

Abstract: A multi-purpose tubular flow-through sensor was constructed with an AgI-based membrane. The membrane was prepared by pressing silver salts (AgI, Ag2S) and powd. Teflon. This membrane was incorporated in the tubular flow-through sensor body. A 2-mm diameter hole was drilled through the center of the tubular sensor and the membrane, thus determining the active sensor volume of about 4 µL. The tubular sensor with reference electrode was placed into a complex flow injection system and used for the flow-through determination of N-acetyl-L-cysteine, (NAC), in perchloric acid medium, pH = 1. Linear dependence was established between the recorded signal height and the concentration of NAC in the injected sample. The recorded change in potential for a decade change in concentration, 62 mV {p (NAC)}-1, in the concentration range from 1 x 10^-4 to 1 x 10^-1 mol L-1, was based on the formation mechanism of the sparingly soluble deposit between silver and NAC on the surface of the sensitive part of the membrane.
N-Acetyl-L-cysteine Potentiometry Electrode Electrode Apparatus Detector

"Flow Injection Analysis Based On A Membrane Separation Module And A Bulk Acoustic Wave Impedance Sensor. Determination Of The Volatile Acidity Of Fermentation Products"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 272-274
Xiaoli Su, Lihua Nie, S. Yao

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid determination of the volatile acidity of some fermentation products like vinegars and juices. The proposed method is based on the diffusion of volatile acids, mainly acetic acid, across a PTFE gas-permeable membrane from an acid stream into an alkaline stream, and the acids trapped in the acceptor solution are determined online by a bulk acoustic wave impedance sensor based on changes in the conductivity of the solution It exhibited a linear frequency response up to 10 nmol L-1 acetic acid with a detection limit of 50 µmol L-1, and the precision was better than 1% (RSD) at a through-put of 72 hr-1. The effects of operating voltage for the detector, cell constant of the electrode, composition of acceptor stream, flow rates, and temperature on the FIA performance were also investigated.
Acidity, volatile Acetic acid Food Fruit Conductometry Sensor Sensor Teflon membrane Gas diffusion Optimization

"A Simple Procedure For The Chromatographic Analysis Of Nanoliter Samples"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 260-262
Rosanna Toniolo, Alan Valentino, G. Bontempelli, Gilberto Schiavon

Abstract: A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected as, for instance, in the case of several biological fluids and particularly in clinical chemistry a glass capillary associated to a micromanipulator is used to collect sub-microliter volumes which are partially transferred into transparent polymeric tubings with known internal diameters (120-178 µm), where the volumes sampled are measured by meniscus collimations with a collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings, so as to make them suitable for connection a the loop to a conventional high-pressure injection valve. The reliability of this procedure has been tested for the anal. of Na+, K+, and Ca2+ present in minute synthetic standard samples (10-200 nL) by a conventional ion-chromatography instrumentation. Relative standard deviations in peak area measurements (5-6%) are discussed in terms of the whole approximation affecting volume measurements, which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species present in very small samples, provided that their detection can be achieved by any chromatography approach or, more generally, by flow injection analysis.
Sodium Potassium Calcium Biological fluid Apparatus Droplet Small sample

"Determination Of Selenium In Soil By Hydride Generation AAS"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 225-229
V. Kos A, Marjan Veber A, Vida Hudnik

Abstract: Hydride generation AAS was applied for the determination of total selenium in soil. The influence of various anions and cations present in the sample solution on the generation of selenium hydride was investigated. Special attention was paid to the wet oxidation procedure for the sample dissolution. The proposed procedure involves microwave sample preparation by using a mixture of H2O2/HNO3/H2SO4. The accuracy of the procedure was checked by the analysis of the standard reference material Buffalo River Sediment (SRM-2704, NIST). Satisfactory agreement of the results obtained with the values reported was achieved. The detection limit of the procedure was 25 ng Se/g of soil. The relative standard deviation of the measurements varied from 5.5% for SRM-2704 up to 10% for the real soil samples.
Selenium Environmental Spectrophotometry Volatile generation

"Dual Stage Preconcentration System For Flame Atomic Absorption Spectrometry Using Flow Injection Online Ion-exchange Followed By Solvent Extraction"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 2 Pages 156-160
Guanhong Tao and Z. Fang

Abstract: A dual stage pre-concentration system based on flow injection online ion-exchange and solvent extraction was developed for flame atomic absorption spectrometry. Pb was taken as a model trace element. A column packed with Amberlite IRC-718 cation exchanger was incorporated into the FI manifold. The analyte was retained on the column by time-based sample loading and eluted by 1 mol/L HNO3. The eluate was subsequently merged with KI and tetrabutylammonium bromide. Pb was extd. online into iso-Bu Me ketone as the ion-pair formed between the iodo plumbate anion and tetrabutylammonium cation. The organic phase was separated from the aqueous phase by a gravity phase separator. 50 µL of concentrate was introduced into the nebulizer-burner system of the spectrometer. An enhancement factor of 550 was achieved with a 30 mL sample consumption at a sampling frequency of 30/h. The RSD was 2.4% at 10 µ/L level and the detection limit was 0.3 µg/L (3s). The method was successfully applied to the determination of Pb in water samples.
Lead Water Ion exchange Spectrophotometry Preconcentration Amberlite MIBK Ion pair extraction Phase separator

"Chemiluminescence Flow System For The Determination Of Iron(II) And Iron(III) In Water"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 1 Pages 130-132
W. Qin A, Z. J. Zhang A, F. C. Wang

Abstract: A novel chemiluminescence (CL) flow system has been developed for the sequential determination of Fe(II) and Fe(III) in water. Fe(II) was detected by its catalytic effect on the CL reaction between luminol immobilized on an anion exchange resin column and dissolved oxygen; Fe(III) was determined by difference measurement after on-line conversion to Fe(II) in a reducing mini-column packed with Cu plated Zn granules. For both ions, the calibration graph was linear in the range 1 2 10^-9 to 1 2 10^-6 g/mL, and the detection limit was 4 2 10^-10 g/mL. A complete analysis could be performed in 1.5 min with a relative standard deviation of less than 5%. The system could be reused for over 200 times and has been applied successfully to the determination of Fe(II) and Fe(III) in natural water samples.
Iron(2+) Iron(III) Water Chemiluminescence

"Monosegmented Flow-analysis Of Slow Enzymatic Reactions: Determination Of Triglycerides In Serum"
Fresenius J. Anal. Chem. 1998 Volume 360, Issue 1 Pages 100-103
A. N. Ara&uacute;jo A, Jos&eacute; A. M. Catita A, Jos&eacute; L. F. C. Lima A, Elias A. G. Zagatto

Abstract: A monosegmented flow system (MCFA) is proposed to achieve slow enzymatic spectrophotometric determinations, here applied to the determination of triglycerides in blood serum. The sample (4.5 µL), enzymatic reagent (150 µL) and an air plug (100 µL) are simultaneously inserted into a carrier stream buffered to pH 7.9 (Tris HCl). In order to avoid the cumbersome step of air removal, a relocating detector was used. This system handles about 60 samples/h, yielding precise results (RSD usually <2.5%). Sensitivity is 56 mAU L/mmol up to 6 mmol/L triglycerides. Accuracy was assessed by running 50 samples already analyzed by a conventional procedure yielding the equation CMCFA(mmol/L) = 1.00(±0.04) CRef(mmol/L) -0.03(±0.08); r=0.990.
Triglycerides Blood Serum Kinetic

"Determination Of Trace Inorganic Selenium In Organoselenium (selenosugar) Oral Nutrition Liquids By Graphite Furnace Atomic Absorption Spectrometry With Hydride Generation"
Fresenius J. Anal. Chem. 1997 Volume 359, Issue 6 Pages 492-496
Zhang De-qiang A, Sun Han-wen A, Yang Li-li

Abstract: A method has been proposed for the determination of trace levels of inorganic selenium in organoselenium (selenosugar) oral nutrition liquids using hydride generation-graphite furnace atomic absorption spectrometry (HG-GFAAS), taking advantage of the fact that this organic selenium compound did not generate volatile hydride upon reduction. K2S2O8 was selected for the decomposition of the compound in a boiling water bath. Selenium was found to give a sharp analytical signal upon reduction with NaBH4 in 1.0 mol L-1 HCl medium. The characteristic mass giving an integrated absorbance of 0.0044 s was 21 pg. An absolute detection limit (3s) of 36 pg was obtained. The recovery was in the range of 94.2-102.1%. Less than parts per million levels of inorganic Se in the presence of organic selenium can be determined.
Selenium, inorganic Selenium, organic Commercial product Spectrophotometry Speciation

"Screening-method For Organotins By Elimination Of The Inorganic Tin Matrix Using A Coupling Of Hydride Generation (HG) And Transversely Heated Graphite Atomizer-atomic Absorption Spectrometry (THGA-AAS)"
Fresenius J. Anal. Chem. 1997 Volume 359, Issue 3 Pages 239-243
H. G. Riepe A, D. Erber A, J. Bettmer A, K. Cammann

Abstract: A selective detection method for organotin compounds by elimination of the inorganic tin matrix has been worked out using a coupling of the hydride generation technique (HG) with transversely heated graphite atomizer-atomic absorption spectrometry (THGA-AAS). The suppression of the inorganic tin matrix bases on the utilization of kinetic interferences during the hydride generation step avoiding expensive chromatographic separation techniques. For the different organotins this method delivers detection limits in the range 0.9-1.2 wg/L using a 500 wL sample loop. In comparison with the fully automated determination system this modification represents an efficient screening-method for the determination of organotin in environmental samples allowing fast and inexpensive monitoring.
Tin, organic Spectrophotometry Interferences

"Highly Sensitive Chemiluminescence Flow Sensor For Ascorbic Acid"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 7-8 Pages 861-863
W. Qin A, Z. J. Zhang A, H. H. Chen

Abstract: A highly sensitive chemiluminescence(CL) flow sensor is proposed for the determination of ascorbic acid. The analytical reagents luminol and iron(II) are immobilized on anion-exchange and cation-exchange resins, respectively, and can be eluted by sodium sulphate. The calibration graphs are linear in the range 1 2 10^-9 to 1 2 10^-6 g mL-1 and the detection limit is 4.0 2 10^-10 g mL-1. The sensor has been applied successfully to the determination of ascorbic acid in vegetables.
Ascorbic acid Chemiluminescence Sensor

"A Novel Preconcentration Technique Using Crosslinked Chitosan For The Determination Of Mercury By CVAAS"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 7-8 Pages 856-858
Meilin Wang A, Ganquan Huang A, Shahua Qian A, Jianshen Jiang A, Yuting Wan A, Y. K. Chau

Abstract: A novel crosslinked chitosan (CCTS) has been synthesized by the reaction of water-soluble chitosan with epoxy chloropropane. In the presence of the chelating EDTA and in the pH range between 4-10, CCTS selectively adsorbed trace inorganic Hg in water samples with enrichment factors of 100. Inorganic Hg could be directly reduced using KBH4 without preceding elution and determined by CVAAS. Accordingly, the total mercury could be determined after all species of mercury in water samples were transformed into Hg2+. The detection limit (3σ) for mercury was 12 ng L-1 and the relative standard deviation less than 5% at the 50 ng L-1 level. Beer's law was obeyed over the range 30-400 ng L-1 of mercury and the pre-concentration method was applied to environmental water samples with the recoveries between 92-96%.
Mercury Spectrophotometry Preconcentration Chitosan Volatile generation Volatile generation

"Determination Of Total Arsenic In Urine By Hydride AAS After UV-digestion"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 7-8 Pages 838-843
R. Ritsema and E. van Heerde

Abstract: A method for analyzing arsenic in urine samples by Flow Injection Analysis-Atomic Absorption Spectrometry (FIA-AAS) after ultra-violet (UV) digestion is developed and validated. The validated method has the following performance characteristics: limit of detection (LOD) 0.5 µg L-1, repeatability and reproducibility better than 5% and 10% relative standard deviation (RSD) respectively for arsenic concentrations above 3 µg L-1, linear range 0.5-40 µg L-1. Validation of the method was performed by analyzing several certified reference materials. Results obtained were well within the certified intervals. Several urine samples analyzed by UV-FIA-AAS were also analyzed by Inductively Coupled Plasma-Mass Spectrometry after High Performance Liquid Chromatography (HPLC-ICP-MS) in order to investigate comparability. Again results were satisfactory, arsenic concentrations in urine samples did not differ from each other significantly. Storage conditions were also studied. Urine samples are best stored in polyethylene containers at 5 ± 4°C and are stable in arsenic content for at least 30 days.
Arsenic, total Urine Spectrophotometry Sample preparation UV reactor Photochemistry

"Application Of Factorial Designs And Simplex Optimisation In The Development Of Flow Injection Hydride Generation-graphite Furnace Atomic Absorption Spectrometry (FI-HG-GFAAS) Procedures As Demonstrated For The Determination Of Trace Levels Of Germanium"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 7-8 Pages 775-780
B. Hilligs&oslash;e A and E. H. Hansen

Abstract: The optimization of a volume-based FI-HG-GFAAS procedure is described for the trace determination of Ge, comprising in situ collection of the generated germane in the graphite furnace. The response function is the peak area readout (A 2 s). Based on a preliminary study, where factorial designs were used to identify significant factors and interactions, the procedure was optimized using both simplex and OVAT (one variable at a time) methods. The characteristics and merits of these methods are discussed. Under optimal experimental conditions, using a sample volume of 100 wL, Ge was determined at a sampling frequency of 22 h-1. The sensitivity, in terms of the characteristic mass, m0, was 26 pg/0.0044 A 2 s, with a detection limit of 0.21 wgL-1 (3σ). The precision (relative standard deviation) was 2.0% (n = 10) at the 1 wgL-1 level.
Germanium Spectrophotometry Simplex Optimization Factorial design

"Sequential Flow Analysis Coupled With ACSV For Online Monitoring Of Cobalt In The Marine Environment"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 6 Pages 703-710
Anne Daniel A, Alex R. Baker A, C. M. G. van den Berg

Abstract: The development of a compact instrument for on-line measurement of trace metals in seawater is described. The system is based on adsorptive cathodic stripping voltammetry (ACSV), and on the concept of sequential flow analysis, to perform on-line measurements with controlled perturbation of natural equilibria of the element. The design combines a low volume flow cell with a miniature solenoid pump and valves to achieve low power consumption. The flow segmentation is time-controlled and the detection step takes place in a well-defined part of the flow stream where reagent and sample occur mixed. The system was tested on the determination of cobalt in seawater but it is likely that the same technique can be used to determine other metals detectable by CSV. The determination range was 6-1050 pmol/L cobalt with a detection limit (3σ) of 6 pmol/L. The measurement rate was about 60 h-1. Comparative measurements were carried out using continuous flow analysis. The apparatus was used continuously on board a ship to determine the distribution pattern of cobalt in surface waters off the coast of California.
Cobalt Sea Voltammetry Voltammetry Sequential injection

"A New Concept For The Quasi Non-destructive Microsampling Of Historical Glasses"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 6 Pages 694-698
G. Schulze, I. Horn, H. Bronk

Abstract: A glass object was sampled by filing with a diamond-coated Cr file. For the determination of Si, the file was sonicated for 20 min in 5 mL 6% Na2CO3/K2CO3 (1:1) to remove the sample material, and was also washed with water. The slurry and washings were combined and evaporated to dryness, and then fused at 1000°C for 20 min. For other determinations, the file was immersed in 0.4 mL HF or HF/HClO4 (3:1), then rinsed with water. The combined solution and washings were evaporated to dryness and the residue was reconstituted prior to analysis. Digestion of the residue with Cl/H2O was used prior to the determination of Au. Si and P were determined by FIA with photometric detection (based on the molybdenum blue reaction). Other elements were determined by ion chromatography or GFAAS (details given).
Gold Silicon Phosphorus Commercial product Spectrophotometry Sample preparation Sample preparation

"Micro Flow Calorimeter For Thermoelectrical Detection Of Heat Of Reaction In Small Volumes"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 6 Pages 683-686
J. M. K&ouml;hler and M. Zieren

Abstract: A microchip element with an integrated flow channel and thin film thermopiles was developed in order to realize a microcalorimeter for small volumes in a flow arrangement. The flow channel consists of two inlets, a mixing region, a measurement region, and one outlet. Thermopiles of BiSb/Sb thermocouples were used as thermal transducers because of their extraordinary high thermopower. A thin film heater of a NiCr alloy was integrated in order to yield the possibility of internal electrical calibration. In addition, this heater can be used for thermal modulation of the whole measurement system. The calorimeter was prepared using vacuum evaporation, PECVD and magnetron sputtering for thin film deposition and photolithography as well as chemical wet etching for microstructuring. The function of the device was tested to neutralize 400 nmol, 100 nmol and 10 nmol NaOH by H2SO4.
Calorimetry Temperature

"A Flow System For Calibration Of Dissolved Oxygen Sensors"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 6 Pages 677-682
P. Jeroschewski A and D. zur Linden

Abstract: Well-defined oxygen standard solutions were obtained by the electrolysis of water in a coulometric oxygen generator. The generator was integrated into a flow system that includes the degassing of the carrier electrolyte, the generation of dissolved oxygen and the temperature control of the carrier electrolyte. The current efficiency of oxygen generation was found to be 100% by the Winkler titration method. Calibrations of a home made laboratory sensor and a WTW CellOx dissolved oxygen sensor have been made in a concentration range of 0.02 to 8 mg/L at temperatures from 5°C to 30°C. The calibration of the WTW sensor on water vapor saturated air was compared with the electrochemical calibration method. Both methods gave reliable results provided that the temperature equilibration between the sensor and the ambient air was successful.
Oxygen Sensor Calibration

"Flow Injection System With Gas Diffusion For The Sequential Determination Of Total Nitrogen And Phosphorus In Vegetables"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 5 Pages 657-662
Jos&eacute; L. F. C. Lima, Antonio O. S. S. Rangel, M. Renata S. Souto

Abstract: Dried, ground vegetables were digested with Se and H2SO4/salicylic acid/H2O2 and then diluted in 0.8 M H2SO4. A portion (180 µL) of the solution was injected into a stream of 0.8 M H2SO4, which merged with a stream of 2.5 M NaOH and passed through a gas diffusion unit. The NH3 diffused into a secondary stream of 0.01 M Tris hydrochloride of pH 7.5 which converted it to ammonium prior to detection with an ISE. The primary stream, now purged of NH3, passed through a stream splitter to reduce the total flow and then merged with a stream containing ammonium molybdate, stannous chloride and hydrazine sulfate in H2SO4. The primary stream then passed through a flow cell for determination of phosphate at 710 nm. The calibration graphs were linear from 0.34-2.4 mM phosphate and up to 0.11 M ammonium, the detection limits were 43 µM phosphate and 1.4 mM ammonium, and the RSD (n = 10) were <3.5%. The sampling rate was 40-60/h. The ammonium and phosphate levels were indicative of the total N and P contents of the vegetables analyzed.
Nitrogen Phosphorus Vegetable Electrode Sample preparation Spectrophotometry Dual detection Gas diffusion

"Gaseous Sample Introduction For The Determination Of Silicon By ICP-AES"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 5 Pages 599-603
A. Lopez Molinero, Alberto Morales, Anselmo Villareal, Juan R. Castillo

Abstract: A portion (150 µL) of Si solution was injected into a stream (1 ml/min) of 0.05 M NaF solution, which passed through a 5 cm mixing coil and a 25 cm reaction coil prior to nebulization. A portion (100 µL) of H2SO4 was injected into the flow 15 s after the injection of the Si solution; the second injector was positioned between the mixing and reaction coils. Nebulization was with Ar (1.3 l/min) and detection was by ICP-AES at 251.611 nm (instrumental settings given). The calibration graph was linear from 0.1-200 µg/ml Si, the detection limit was 4 ng/ml and the RSD was 2%. Alternatively, a portion (150 µL) of Si solution was injected into a stream (1 ml/min) of 0.01 M NaF, which passed through a 25 cm mixing coil and into a nebulization chamber via a Meinhard nebulizer with Ar as nebulization gas (500 ml/min). Simultaneously, a portion (100 µL) of H2SO4 was injected into a separate flow (1 ml/min) of 0.01 M NaF, which passed through a 25 cm mixing coil and into the same nebulization chamber via a cross-flow nebulizer with Ar at 1 l/min. The aerosols reacted in the chamber and passed into the ICP for detection as described above. The calibration graph was linear from 0.1-1000 µg/ml Si, the detection limit was 20 ng/ml and the RSD (n = 6) was 8%. The methods were applied to mineral- and tap water (results presented).
Silicon Water Mineral Spectrophotometry Gas phase reaction

"Determination Of Procaine Hydrochloride By Ion-pairing Flow Injection Analysis With Piezoelectric Detection"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 4 Pages 556-558
Z. Mo, J. Luo, Xiaohui Long, Ziling Xia

Abstract: The method was based on the formation of an ion pair with sodium dodecyl phenylsulfonate. Sample was injected in to 5 mM sodium dodecyl phenylsulfonate as carrier (2 ml/min) and mixed in a mixing coil (30 cm; total volume = 0.2 ml) with piezoelectric detection. The FIA system has been previously described (cf. Anal. Lett., in press). The calibration graph was linear from 0.02-2 mg/ml of procaine hydrochloride (I) with a detection limit of 0.01 mg/ml. The RSD (n = 10) was 0.3% and the sampling frequency was 120/h. The method was applied to the determination of I in pharmaceuticals.
Procaine hydrochloride Pharmaceutical Microbalance Sensor Ion pair formation Surfactant

"Sequential Flow Injection Spectrophotometric Determination Of Iron(II) And Iron(III) By Copper(II)-catalysed Reaction With Tiron"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 4 Pages 546-547
M. Endo and Shigeki Abe

Abstract: The method was based on the differential reaction kinetics of Fe(II) and Fe(III) with Tiron in a double-injection flow injection system (schematic of manifold given). Acetate buffer (0.1M) of pH 6 containing 6 mM Tiron was pumped into two reaction coils whilst 0.79 mM Cu(II)/6 mM Tiron/0.1 M acetate buffer of pH 6 flowed into a third reaction coil at 3.6 ml/min. Two sample solutions were injected into the reaction streams at the same time and the resulting absorbance of the Fe(III)-Tiron complex was measured at 560 nm. The oxidation of Fe(II) was increased by Tiron and Cu(II) catalyst. The first and second peaks at the detection cell corresponding to Fe(III) and total Fe, respectively. The calibration graph was linear from 18 µM to 0.18 M Fe(II) and Fe(III). The sample throughput was 30 injections/h.
Iron(2+) Iron(III) Spectrophotometry Catalysis Kinetic Tiron Speciation Buffer Complexation

"Flow Injection Determination Of Silver With Spectrophotometric Detection"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 4 Pages 475-479
A. A. Ensafi and K. Zarei

Abstract: Sample (170 µL) was injected into a stream (8 ml/h) of water which merged with streams (8 ml/h) of 0.8 M peroxodisulfate in 32 mM H2SO4 and of 18 mM 1,10-phenanthroline/0.42 mM gallocyanine and passed through a reaction coil (220 cm x 0.5 mm i.d.) before the absorbance was measured at 540 nm. The optimal temperature was 40°C. Tolerance limits for interfering ions are tabulated. Tolerance to bromide, chloride, iodide and thiosulfate was increased 1000-fold by digestion of sample with concentrated HNO3. The detection limit was 0.001 µg Ag and the analytical range was 0.002-0.7 µg. The RSD (n = 10) at 0.035 and 0.17 µg were 2.8% and 0.9%, respectively. The method was applied to river water after digestion with HNO3/H2SO4 and to panchromatic plates (photographic materials) after treatment with NaOH and digestion of the gelatinous film with HNO3. Results agreed with those obtained by AAS. Calibration graphs were linear.
Silver Plate River Sample preparation Spectrophotometry Detection limit Interferences Method comparison Heated reaction

"Certification Of Three Mussel Tissue Standard Reference Materials (SRM) For Methylmercury And Total Mercury Content"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 3 Pages 424-430
M. K. Donais, Rajananda Saraswati, Elizabeth Mackey, Rabia Demiralp, Barbara Porter, Mark Vangel, Mark Levenson, Vesna Mandic, Sabine Azemard, Milena Horvat, Karl May, Hendrik Emons, Stephen Wise

Abstract: Three mussel tissue SRM (SRM 1974a, SRM 2974 and SRM 2976) were certified for methylmercury and total Hg contents. The methylmercury contents were measured using three independent extraction and quantification procedures; (i) solid-liquid extraction under acidic conditions, clean-up by gel permeation chromatography and GC, (ii) saponification at 70°C, room temperature ethylation, pre-concentration, GC followed by pyrolysis cold vapor (CV)-AFS and (iii) steam distillation under acidic conditions, separation of inorganic Hg and organomercury by anion-exchange chromatography, UV irradiation and CV-AAS. The total Hg content was measured using four independent procedures; (1) microwave digestion and flow injection CV-AAS, (2) instrumental NAA, (3) acid digestion at 70°C, double Au trap amalgamation and CV-AFS and (4) acid digestion at 150°C, Au wire amalgamation and CV-AAS. The certified values (ng/g, dry-mass basis) for methylmercury (as Hg)/total Hg contents were 77.2/186 for SRM 1974a, 77.2/171 for SRM 2974 and 27.7/61 for SRM 2976.
Mercury Methylmercury ion NIST 1974 NIST 2974 NIST 2976 Mussel Spectrophotometry Fluorescence GPC Sample preparation Neutron activation analysis Amalgamation Preconcentration Reference material Speciation Volatile generation Volatile generation

"Flow Sorption Calorimetry, A Powerful Tool To Investigate The Acid-base Character Of Organic Polymer Surfaces"
Fresenius J. Anal. Chem. 1997 Volume 358, Issue 1-2 Pages 244-247
S. Schneider A, F. Simon A, D. Pleul A, H.-J. Jacobasch

Abstract: Flow sorption calorimetry (FSC) can be a useful tool to estimate the Lewis acid-base behavior of the surface of organic polymers with less than 1 m2/g surface area. Polyethylene powders grafted with different amounts of acrylic acid have been chosen as samples. The surface of the powders was investigated by means of X-ray photoelectron spectroscopy (XPS) at first and than brought into contact with the strong electron donor triethylamine in a special FSC measuring system. The heat of the displacement isotherm together with the surface excess isotherm of triethylamine adsorbed onto the powders was determined. The results obtained with FSC and XPS were well correlated and gave a comprehensive picture of the acidic surface character of modified polyethylene.
Acids Bases Polymers Calorimetry

"Sensitive Spectrophotometric Determination Of Ascorbic-acid In Fruit Juices And Pharmaceutical Formulations Using 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (br-padap)"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1174-1178
S&eacute;rgio L. C. Ferreira, Marcus L. S. F. Bandeira, Valfredo A. Lemos, Hilda C. dos Santos, A. C. Spinola Costa, Djane S. de Jesus

Abstract: A simple and very sensitive method has been developed for the determination of ascorbic acid based on the oxidation of ascorbic acid to dehydroascorbic acid by iron(III), followed by a complexation of iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol(Br-PADAP). The iron((II) complex is formed immediately, with absorption maxima at 560 and 748 nm and a molar absorptivity of 1.31 x 10(5) l mol-1 cm-1 and 5.69 x 10(4) l mol-1 cm-1, respectively. The ascorbic acid determination is possible with a linear range up to 2.4 µg mL-1, a calibration sensitivity of 0.744 mL µg-1 at 560 nm and 0.323 mL µg-1 at 748 nm, and a detection limit of 15 ng mL-1 and 44 ng mL-1, respectively. The procedure was used for the ascorbic acid determination in several fruit juices and pharmaceutical formulations. The results demonstrated a good precision (RSD < 1%) and are in agreement with those obtained with others methods. The Br-PADAP method proposed is six times more sensitive than the method using the iron(II)-1,10-phenanthroline system. 65 References
Ascorbic acid Fruit Pharmaceutical Spectrophotometry Complexation Detection limit Redox Sensitivity Method comparison

"Determination Of Acetaldehyde In Liquid, Solid And Semi-solid Food After Pervaporation-derivatization"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1168-1173
I. Papaefstathiou, U. Bilitewski, M. D. Luque de Castro

Abstract: A continuous-flow configuration was coupled to a pervaporation unit (details and diagram given). Liquid samples (e.g fruit juices) were injected into a water stream and led to the lower part of the thermostated laboratory-made pervaporation unit which has been described previously (Ibid., 1996, 354, 442). The volatile analyte evaporated and diffused through a hyrophobic PTFE membrane then was accepted by a stream of fuchsin in ethanol/H2SO4. The outlet of the upper acceptor chamber was merged with a stream of sodium sulfite solution. The resultant colored product (alkylsulfonic acid chromophore) was monitored spectrophotometrically. Procedures for analyzing semi-solids (e.g, yogurt) and solids (e.g, bread) are described. Sensitivity could be varied by altering the pervaporation temperature and the membrane thickness. Detection limits were 4.2 µg/ml; RSD were 1.2-3.6% (n=7-10)
Acetaldehyde Fruit Spectrophotometry Pervaporation Teflon membrane Gas diffusion Sensitivity

"Colorimetric Determination Of Iron In Infant Fortified Formulas By Sequential Injection Analysis"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1153-1156
A. N. Ara&uacute;jo, Joan Gracia, Jos&eacute; L. F. C. Lima, Manel Poch, M. L&uacute;cia M. F. S. Saraiva

Abstract: Commercial infant formulas (3-5 g) were heated at 550°C to constant wt. then treated with 50 mL 0.2 M HNO3 as described previously (AOAC, Official Methods of Analysis (15th ed.), 1990, 777). Sequential injection analysis was then carried out (details of system and diagram given). The digest (140 µL) was aspirated to a holding coil (200 cm x 0.8 mm i.d.) via a sampling tube (15 cm x 0.5 mm i.d.) and mixed with 70 µL 2 M potassium thiocyanate. The resultant mixture was propelled at a flow rate of 5 ml/min from the holding coil through a mixing coil (75 cm x 0.8 mm i.d.) to the detector. The detector was a Pye Unicam SP6-350 spectrophotometer with a Hellma 178. 712Q flow cell (18 µl). Calibration graphs were linear from 0.5-20 mg/l. The sampling rate was 100 samples/h; RSD was n=12).
Iron Baby Spectrophotometry Selectivity Sequential injection

"An Optosensor For Tryptophan With C18 Silica Gel As A Substrate"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1097-1100
Zhilong Gong and Z. Zhang

Abstract: C18 silica gel (15 µL) was loaded into one end of a Perkin-Elmer flow cell L225 1247 (10 x 1.8 mm i.d.) and the other end was kept free. The cell was then connected into the flow system of a simple optosensing FIA manifold (diagram given). Samples or standards (2 ml) were injected into the flow system at a flow rate of 1 ml/min. The carrier solution was 0.1 M NaH2PO4/0.1 M NaOH of pH 8. tryptophan passed into the flow cell where it was retained on the gel. Fluorescence was measured using a Perkin-Elmer LS-SO instrument with excitation and emission slits set at 5 and 15 nm, respectively. Calibration graphs were linear from 0.1-50 µg/ml tryptophan; detection limit was 25 ng/ml. RSD was 2.9% (n = 7) for 10 µg/ml tryptophan. Most common species did not interfere. The method was successfully applied to the analysis of a pharmaceutical preparation containing 18 amino-acids; composition results compared favourably with those reported by the manufacturer.
Tryptophan Pharmaceutical Fluorescence Sensor Detection limit Method comparison Optosensing Selectivity C18 Silica gel Interferences

"Cyclodextrin-based Optosensor For The Determination Of Quinine"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1093-1096
Zhilong Gong and Z. Zhang

Abstract: β-Cyclodextrin (β-CD) was immobilized on to silica gel (100-200 mesh) using a standard method; 20 µL was loaded into one end of a flow-cell (25 µL) and the other end was kept free. The cell was then connected into the flow system of a simple optosensing FIA manifold (diagram given). Samples of standards (2 ml) were injected via a valve and pumped through the flow system; quinine was complexed with the β-CD. The carrier solution used throughout was 0.1 M H2SO4 at a flow rate of 2 ml/min. The fluorescence of the complex on the β-CD immobilized gel was measured at 451 nm (excitation at 350 nm). Calibration graphs were linear from 3 x 10^-9 to 2 x 10^-5 M quinine. The detection limit was 0.2 ng/ml quinine; RSD was 2.1% (n = 7) for 0.05 µg/ml quinine. The method was successfully applied to the analysis of some pharmaceuticals (results tabulated); recoveries were 97-104%.
Quinine Pharmaceutical Fluorescence Sensor Detection limit Immobilized reagent Optosensing Silica gel Standard method Method comparison

"Inline Flow Injection Extraction-preconcentration Through A Passive Hydrophilic Membrane. Determination Of Total Phenols In Oil By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1066-1071
J. F. van Staden and H. E. Britz

Abstract: Phenols were extracted and pre-concentrated from a xylene donor solution, or oil sample, using a selective passive hydrophilic Spectrapor membrane (up to 6000-8000 Da mol. wt.). The extracted phenols were diffused to a basic acceptor stream and the pre-concentrated phenolate was injected into a carrier stream of 4-aminoantipyrine (4-AAP). The carrier stream was then merged with an oxidant stream of K2S2O8. Analysis was carried out using a Unicam 8625 spectrophotometer with a 80 µL flow-through cell; detection was at 500 nm. Optimal flow rates were 1 and 2.5 ml/min for the xylene and the buffered 4-AAP streams, respectively. The system was suitable for the determination of total phenols in oil. Calibration graphs were linear from 1-600 mg/l phenol; detection limits were 0.09, 0.18 and 0.02 mg/l phenol, o-cresol and m-cresol, respectively. RSD was n = 14). Sampling rate was 12 samples/h. The results compared favourably with those obtained using a standard manual 4-AAP and a standard GC method.
Phenols Phenol 4-Cresol 2-Cresol Oil Spectrophotometry Sample preparation Preconcentration Hydrophilic membrane Method comparison Optimization Extraction

"Simultaneous Determination Of Metal-ion Concentrations In Binary-mixtures With A Multi-LED Photometer"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1056-1060
P. C. Hauser and Thusitha W. T. Rupasinghe

Abstract: A compact photometer is based on up to seven different light-emitting diodes whose light is guided into a photometric cell by means of a fiber-optic coupler. The wavelength is selected by switching on the appropriate light source. The application of this multiwavelength photometer to the determination of binary metal ion samples is demonstrated using model mixtures. Solutions of Fe, Co, Cu, Ni, Cr and Mn were used in combination with several photometric reagents. It was found that the instrument yielded concentration measurements which were usually within a few percent of the correct concentration. These results are comparable to reported data obtained with conventional instruments for similar measurements. The application of the instrument for simultaneous determination in flow injection analysis employing rapid computer controlled switching of the light-emitting diodes is also demonstrated. A limitation in the use of light-emitting diodes for the simultaneous determination was found to arise from the fact that in some instances non-linear calibration curves are obtained when employing light-emitting diodes as light sources. This occurs when the absorptivity of the measured compound changes over the emission band of the diodes. Multiple regression analysis is then not easily possible. A compact photometer is used based on up to seven different LED (from blue to near-IR); the light is guided into a photometric cell via a fiber-optic coupler. Wavelength is selected by switching on the appropriate light source. The photometer was applied to the analysis of several model metal ion mixtures in combination with several photometric reagents (details given). Results obtained were comparable to those reported using conventional instruments. This instrument was also applied to simultaneous determination in flow injection analysis using rapid computer-controlled switching of the LED. 19 References
Cadmium Chromium Cobalt Copper Manganese Nickel Spectrophotometry Chemometrics Light emitting diode Multicomponent Optical fiber Computer

"Gas Permeation Continuous-flow Coulometric Analysis: Determination Of Sulfur Dioxide"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1045-1049
S. Liu, Han-xi Shen, Jian-xing Feng, Matthieu Tubino

Abstract: A gas permeation system is presented which has two gaseous streams on both sides of a membrane (schematic given). Ambient air was passed through silica-gel and activated C scrubbers then entered the acceptor side of the permeation cell. Sulfur dioxide samples entered directly on the donor side; flow rates were controlled using two adjusting valves. Measurements were carried out using a three-electrode dynamic coulometric detector. The effects of donor flow rates, gas pressure and membrane thickness on the signal are discussed. Calibration graphs were linear from 10^-6 up to 10^-3 mol/mol SO2/air; RSD was 1.3% (n = 7).
Sulfur dioxide Environmental Coulometry Gas diffusion Optimization

"Validation Of Three Atomic Absorption-spectrometric Methods For The Determination Of Selenium - A Comparative Evaluation Of Performance Characteristics"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 8 Pages 1024-1028
R. Allabashi, J. Rendl, M. Grasserbauer

Abstract: The methods used were: ET AAS (method A), flow injection hydride generation AAS (method B) and continuous-flow hydride generation AAS with ET atomization (method C). The analyzes were performed on a Perkin Elmer 4100-ZL instrument with an electrodeless discharge lamp as Se radiation source; detection was at 196 nm for all three methods. In method A, the sample (20 µL) and 5 µL modifier solution [palladium(II) nitrate/magnesium(II) nitrate (5:3)] were simultaneously injected then ashed and atomized according to the temperature program described previously (Allabashi, R, Thesis, 1996). For method B, 500 µL sample was channelled into a carrier flow of HCl (10 ml/min) and brought together with NaBH4 (5 ml/min); the gaseous products were carried by Ar gas for analysis. In method C, the acidified sample was continuously transported at 6 ml/min into the reaction cell where it was mixed with NaBH4 (3 ml/min). The continuously formed hydride was heated to 400°C for analysis as described previously (Int. J. Environ. Anal. Chem., 1996, submitted) and temperature programming as for method A was used. Each method performed well but has a typical optimal application along with specific advantages (details given).
Selenium Spectrophotometry Spectrophotometry Volatile generation Method comparison Optimization Volatile generation

"Spectrophotometric Flow Injection Determination Of Trace Iodide In Table Salt And Laver Through The Reaction Of Iodate With 3,5-Br2-PADAP And Thiocyanate"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 1002-1005
Junying Sun, Xingguo Chen, Zhide Hu

Abstract: Cleaned, dried laver (2 g) was mixed with 10 mL 2 M KOH, dried at 80-100°C for 1-2 h, charred for 2-3 h, ashed for 4-5 h and the residue was dissolved in water with heating. A portion (10 ml) of prepared solution of 0.4 mg/ml table salt solution was mixed with 1 mL H3PO4 solution and 1 mL saturated Br2 solution, the mixture was heated to remove Br2 and then diluted to 50 mL with water. Portions (100 µL) were injected into a water stream (0.8 ml/min) which merged with a stream (0.8 ml/min) of 0.004% 2-(3,5-dibromo-2-pyridylazo)-5-diethylamino-phenol (3,5-Br2-PADAP) in 4.5 M H2SO4, passed through a mixing coil (12 cm x 0.5 mm i.d.), merged with a stream (0.8 ml/min) of 10 mM KSCN and passed through a reaction coil (90 cm x 0.5 mm i.d.) prior to detection at 605 nm. Beer's law was obeyed from 1-24 µM-iodide, the detection limit was 0.5 µM and recoveries were 98-104%. RSD are not stated. The sample throughput was 80/h. The tolerance levels of various interferents were determined (results presented). The reaction mechanism is discussed.
Iodide Food Plant Spectrophotometry Interferences

"Flame Atomic Absorption Spectrometry Using A Microvolume Injection Technique For The Determination Of Cu, Zn, Ca, Mg And Fe In Whole Blood From Healthy Infant And Mother Ears"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 997-999
Sufen Shang, Wang Hong

Abstract: An FAAS method for the determination of Cu, Zn, Ca, Mg and Fe using a microvolume injection technique is described. The injection volume for the determination of each element is 10 wl and the calibration graphs are linear over the ranges 0.05-1.5, 0.1-3.0, 0.1-2.0, 0.1-2.0 and 1.0-6.0 mg/l for Cu, Zn, Ca, Mg and Fe, respectively. The relative standard deviations are 2.6%, 2.8%, 3.0%, 1.3% and 2.5%, the rates of recovery 98%, 100%, 99%, 99% and 97%. The method was successfully applied to the determination of these elements in whole blood from healthy infant and mother (lying-in) ears.

"Flow Injection Determination Of Anionic Polyelectrolytes Using An Anionic Surfactant-selective Plasticized Poly(vinyl Chloride) Membrane Electrode Detector"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 901-903
Takashi Masadome, T. Imato, Satoshi Itoh, Yasukazu Asano

Abstract: A portion (200 µL) of anionic polyelectrolyte solution was injected into a water stream (0.5 ml/min), which passed through a Dowex 50W-X4 cation-exchange column (19.5 cm x 2 mm i.d.), merged with a stream (0.5 ml/min) of NH3 buffer solution of pH 10 and passed through a mixing coil (1 m x 0.5 mm i.d.). A stream (0.5 ml/min) of 0.5 mM Cat-floc polymer (Wako Pure Chem. Co.) merged with a stream (0.5 ml/min) of 20 mM NaNO3 containing 0.6 mM sodium dodecylbenzenesulfonate, passed through a mixing coil (3 m x 0.5 mm i.d.), merged with the polyelectrolyte-containing stream and passed through a similar 1 m mixing coil prior to detection by a dodecylbenzenesulfonate-selective PVC-membrane electrode (cf. Anal. Sci., 1987, 3, 121). The calibration graph was linear from 0.1-1 mM potassium poly(vinyl sulfonate), the detection limit was 25 µM and the RSD (n = 5) was ~1.3%. The sampling rate was 10/h. Linear calibration graphs were also obtained for 0.1-1 mM sodium alginate and 0.1-1 mM carrageenan.
Electrolytes Polyvinyl sulfonate Alginate Carrageenan Potentiometry Electrode Dowex Buffer Surfactant

"Flow Analysis Preconcentration Of Magnesium And Zinc Using Emulsions For Flame Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 860-863
T. Yokoyama, Takashi Watarai, Takeo Uehara, Koh-ichi Mizuoka, Kenji Kohara, Masato Kido, Michio Zenki

Abstract: A pre-concentration method combining Water/Oil/Water (W/O/W) emulsions with flow injection manifolds has been developed for determinations of Mg and Zn. The system consists of a mixing coil filled with Span 80 as a surfactant, palmitic acid or di(2-ethylhexyl) phosphate as an extractant, kerosene as a solvent in the oil phase, and HCl in the inner aqueous phase to form W/O emulsions, an extraction coil for the sample solution to form W/O/W emulsions, a phase separator to waste the outer aqueous phase, a dry bath to demulsify W/O emulsions with 2-ethylhexanol, a phase separator to waste the oil phase, and an air pump to deliver the concentrated sample solution to the flame atomic absorption spectrophotometer. This method proved to be excellent regarding the reproducibility, the rapidity, and the small quantity of sample, compared with the W/O/W emulsions method without the flow injection manifolds. The signal of flame atomic absorption spectrometry (FAAS) after pre-concentration of Mg by this method was 2.4 times as large as that before pre-concentration. Also, this method suppressed some interferences. The system was applied to FAAS determinations of Mg and Zn in duralumin alloys and Zn in commercial reagents. 10 References Samples were injected into a stream (2.4 ml/min) of water, which merged with an emulsified stream of 0.55-1.1 M HCl and kerosene containing 0.4-0.5% Span 80 (Nacalai tesque, Kyoto, Japan) and 0.5-2% palmitic acid (details given) then passed through a PTFE extraction coil (10 m x 0.5 mm i.d.) and a phase separator. The emulsion then merged with a stream (0.4 ml) of 2-ethylhexanol (demulsifier), and passed through a dry bath at 130°C for demulsification (details given) and a second phase separator; the aqueous phase was carried in air (42 ml/min) to an AAS instrument for analysis. The detection limits using 1 mL samples were 20 ng/ml Mg and 100 ng/ml Zn. The calibration graphs were linear from 20-200 and 100-500 ng/ml, respectively. RSD and recoveries are not given. The method was applied to commercial reagents and duralumin alloys (results presented).
Magnesium Zinc Duralumin Alloy Inorganic compound Spectrophotometry Sample preparation Extraction Emulsion Phase separator Preconcentration Surfactant Interferences

"Selenium Determination By Hydride-generation ICP-AES: Elimination Of Iron Interferences By Means Of An Ion-exchange Resin In A Continuous-flow System"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 850-852
L. D. Martinez, M. Baucells, E. Pelfort, M. Roura, R. Olsina

Abstract: Sample solution prepared from geological materials (details given) was subjected to online SPE on a Dowex 50W-X8 cation-exchange column (5-10 cm x 3 mm i.d.) at 2 ml/min to remove Fe. A portion (500 µL) of the extract was injected into a water stream (6 ml/min), which merged with a stream (1 ml/min) of 6N-HCl and a stream (1 ml/min) of 0.6% NaBH4. The flow passed through a reaction coil (dimensions not given) and into a gas-liquid separator. Volatile hydrides were carried in Ar (90 ml/min) into a plasma torch for ICP-AES determination of Se (operating conditions given). The column eliminated interference from 2.5 mg/ml Fe in the determination of 20 ng/ml Se. The detection limit ws 0.4 ng/ml Se, recoveries were 98-99.5% and the RSD (n = 10) was 2%. Calibration details are not given. The method was applied to geological CRM. The results agreed with the certified values.
Selenium Geological Ion exchange Sample preparation Spectrophotometry Sample preparation Solid phase extraction Reference material Volatile generation Phase separator Interferences Dowex Resin Volatile generation

"Anionic Cartridge Preconcentrators For Inorganic Arsenic, Monomethylarsonate And Dimethylarsinate Determination By Online HPLC-HG-AAS"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 844-849
M. G&oacute;mez, C. C&aacute;mara, M. A. Palacios, A. L&oacute;pez-Gonz&aacute;lvez

Abstract: Preconcentration anionic cartridges in combination with hyphenated FI-HG-AAS and HPLC-HG-AAS have been evaluated for the pre-concentration and quantification of total toxic arsenic and of inorganic arsenic, monomethylarsonate and dimethylarsinate species, respectively. Optimum retention and elution parameters of the species on the anionic cartridges are evaluated and the quality parameters of the analysis are reported. The detection limits for the arsenic species under study range from 0.1 µg L-1 to 0.6 µg L-1. The proposed method was successfully applied to the determination of arsenic species in spiked fresh water.
Arsenic, inorganic monomethylarsonic acid Dimethylarsinic acid HPLC Ion exchange Spectrophotometry Column Resin Preconcentration Post-column derivatization Volatile generation Speciation Volatile generation

"Flow Injection Atomic Absorption Spectrometry For The Standardization Of Arsenic, Lead And Mercury In Environmental And Biological Standard Reference Materials"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 827-832
Gautam Samanta and D. Chakraborti

Abstract: Environmental and biological CRM were digested (details given). For the determination of Pb, prepared samples (50 µL) were injected into a carrier stream (1 ml/min) of 9% ammonium persulfate in 6% HNO3, which merged with a reducing stream (1 ml/min) of 8% NaBH4 in 1% NaOH then passed through a gas-liquid separator. A N2 flow (100 ml/min) carried hydrides to an AAS instrument for determination at 283.3 nm using an air-acetylene flame. For the determination of As, the carrier stream was 5 M HCl, the reducing stream was 1% NaBH4 containing 0.5% NaOH, the N2 flow rate was 200 ml/min and measurement was at 193.7 nm. For the determination of Hg, the carrier stream was 4% NaOH, the reducing stream was 0.5% SnCl2 and 0.035% L-cysteine in 1.5% H2SO4, the N2 flow rate was 50 ml/min and measurement was at 253.7 nm. A flame was not required for Hg determinations. The detection limits were 2 µg/l Pb, 1.8 µg/l As and 1.5 µg/l Hg, the quantitation limits were 7, 6 and 5 µg/l, respectively, and the corresponding RSD (n = 10) were 4%, 3% and 2%. Calibration ranges and recoveries are not stated. The sample throughput was 80/h in all cases. Results are tabulated for 12 CRM. The effects of interferents are also discussed. Results of a thorough study and application of flow injection atomic absorption spectrometry for the determination of As, Pb and Hg in parts per million to subparts per billion levels in environmental and biological samples have been described. Various standard reference materials from the National Bureau of Standards, USA, the National Institute of Standards and Technology, USA, the Community Bureau of Reference, Brussels, Belgium and the National Institute for Environmental Studies, Japan and Standard Chinese river sediment were used. By flow injection hydride generation AAS the standard reference materials were analyzed for As and Pb. Mercury was determined by cold vapor flow injection AAS from environmental and biological standard reference materials. The technique is fast, simple and highly sensitive. It takes only 30 s for each analysis from the digested solution. The detection limits of As, Pb and Hg are 1.8 µg L-1, 2.0 µg L-1 and 1.5 µg L-1, respectively. The results show good agreement with the certified values. 48 References
Arsenic Lead Mercury River Biological Water Ground Spectrophotometry Sample preparation Spectrophotometry Reference material Interferences PPB Volatile generation Volatile generation

"Semi-automatic Determination Of Tin In Marine Materials By Continuous-flow Hydride-generation Inductively Coupled Plasma Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 822-826
Yong-Lai Feng, H. Narasaki, Hong-Yuan Chen, Li-Ching Tian

Abstract: Sample (1.25 g) was equilibrated overnight with 15 mL 68% HNO3 and 2 mL 70% HClO4, then digested by heating with 0.5 mL concentrated H2SO4. The resulting solution was adjusted to pH 3.5 with 4 M NaOH and passed through a DIAION SA 10A anion-exchange resin column (15 cm x 8 mm i.d.; Mitsubishi Kasei Corp., Tokyo, Japan). The eluate was mixed with 3.5 mL 3 M H2SO4 and 2.5 mL 10% L-cysteine hydrochloride monohydrate, diluted to 25 mL and then analyzed for Sn by continuous-flow hydride-generation ICP-AES at 189.93 nm (operating conditions given). The detection limit was 0.4 ng/mL Sn and the RSD (n = 10) was 0.5%. The effects of varying the H2SO4, NaBH4 (hydride-generating reagent) and NaOH concentrations, Ar (carrier gas) and NaBH4 flow rates and the ratio of flow rates of sample solution and NaBH4 were investigated (results presented). The effects of interferents were also investigated, along with seven methods for masking interference (results tabulated). The method was applied to an environmental (marine) CRM. The result agreed with the certified value and the RSD (n = 6) was 0.95%.
Tin Environmental Marine Ion exchange Sample preparation Spectrophotometry Column Detection limit Interferences Reference material

"Comparison Of Sample Digestion Procedures For The Determination Of Arsenic In Certified Marine Samples Using The FI-HG-AAS-technique"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 7 Pages 817-821
G. Damkr&ouml;ger, M. Grote, E. Jan&szlig;en

Abstract: For dry ashing, 0.2 g CRM (cod and mussel) were homogenized with 3 g MgO and 40 mL 0.75 M magnesium nitrate, evaporated at 130°C for ~3 h to near-dryness and ashed at 550°C overnight. The ash was dissolved by the dropwise addition of 25 mL 32% HCl and the solutions were diluted to 100 mL with water. For high-pressure ashing, 0.2 g mussel CRM and 0.16 g cod CRM were each mixed with 2 mL 65% HNO3 and 4 mL 30% H2O2 and then ashed with temperature programming from 50-70°C in 30 min, to 120°C in 30 min, then to 300°C (held for 80 min) in 15 min. The resulting clear solutions were diluted to 20 mL with water. For microwave digestion, 0.25 g mussel CRM and 0.2 g cod CRM were each mixed with 3 mL 65% HNO3, and 2 mL 30% H2O2 and irradiated at 250 W for 1 min, left to stand for 1 min, then irradiated at 250 W for 1.5 min, 450 W for 3 min, 850 W for 5 min and 250 W for 1 min. The resulting solutions were diluted to 25 mL with water. The solutions were analyzed for As by flow injection hydride-generation AAS (details given). Mean recoveries of As from mussel and cod were 13% and 2%, respectively, by microwave digestion and 56% and 25%, respectively, by high-pressure ashing. The dry ashing method gave quantitative recoveries from both CRM. Nitrite interference was overcome by the addition of an amino sulfuric acid (350 mM).
Arsenic Muscle Liver NRCC DORM-1 NRCC NOAA-K Sample preparation Sample preparation Sample preparation Spectrophotometry Interferences Method comparison Reference material

"Enzymatic Interference-free Assay For Oxalate In Urine"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 6 Pages 777-781
P. Ca&ntilde;izares and M. D. Luque de Castro

Abstract: A potentiometric method for the determination of oxalate in urine is proposed. It is based on the biochemical reaction catalyzed by oxalate decarboxylase/pervaporation/stopped-flow. The method affords a linear determination range between 0.03 and 0.08 mmol/l and has been successfully applied to the determination of oxalate in urine with excellent agreement of the results with those obtained by the conventional method based on precipitation/dissolution and titration. The effectiveness of the pervaporation process makes sample pretreatment other than dilution unnecessary. 16 References
Oxalate Urine Potentiometry Stopped-flow Pervaporation Catalysis Method comparison Interferences Enzyme

"Determination Of Mercury(II) Traces In Drinking Water By Inhibition Of An Urease Reactor In A Flow Injection Analysis (FIA) System"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 6 Pages 752-755
Renbing Shi, K. Stein, Georg Schwedt

Abstract: The immobilization of urease on to polyacrylamide gel was carried out by a modification of a previous method (Stein and Schwedt, Vom Vasser, 1992, 79, 211). Acrylamide (50 mg) with 5% NN'-methylene bisacrylamide was dissolved in 0.5 mL phosphate buffer of pH 7 then 330 iu urease was dissolved in the resultant solution. Then 7 µL NNN'N'-tetramethylene diamine/ammonium peroxodisulfate (2:5) was added. This reaction mixture was poured on to a cellulose acetate membrane between two glass plates. After 30 min, the plates were separated and the enzymatic membrane was cut into pieces (1 cm diameter). A piece of membrane was rolled up and set in a glass column (45 x 2 mm i.d.). This urease reactor was integrated into an FIA system (schematic and details given). The measurement parameters are tabulated. Potentiometric measurements were made using an Ingold LOT 453 S-7 pH electrode. Calibration graphs were linear from 2-20 µg/l Hg(II); RSD was 1.4% (n = 5) for 2 µg/l Hg(II). A sample frequency of 7/h was achieved. The method was applied to the analysis of potable water; results were comparable with those obtained by a commercial system.
Mercury(II) Water Potentiometry Electrode Immobilized enzyme Method comparison Membrane Cellulose acetate

"Determination Of Copper By Anodic Stripping Voltammetry On A Glassy Carbon Electrode Using A Continuous-flow System"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 6 Pages 624-628
J. F. van Staden and M. Matoetoe

Abstract: Samples were analyzed using a continuous-flow voltammetric flow-through trace analyzer. system with a Perspex wall-jet flow cell (5 ml). Three electrodes were positioned in the cell; a 3 mm diameter glassy C disc working electrode, a glass C rod auxiliary electrode and a Ag/AgCl/KCl reference (schematic of cell given). The supporting electrolyte was 1 M HNO3 and the following conditions applied: 5 min deposition time, -400 mV deposition potential, -400 mV to +400 mV stripping range, 150 mV pulse amplitude, 5 s rest time, 1 ml/min flow rate (during deposition, otherwise O), 10 mV/s scan rate and ~10 min deaeration time. The detection limit was 0.56 µg/l Cu. An accuracy of 0.09±0.005% was obtained with analysis of a CRM of low alloy steel containing 0.09±0.004% Cu. The method was applied to various fresh water samples; RSD (n = 6) was
Copper Environmental Alloy Voltammetry Electrode Electrode Flowcell Reference material

"Coulometric Determination Of The Flow Rate Of Small Masses Of Substances. 2. Application To Online Measurement Of The EOX-parameter"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 6 Pages 582-588
M. Luitjens, H. Kupka, D. Gherban, E. Baumgarten

Abstract: A previously developed coulometric method (Ibid. 1993, 347, 87) has been coupled with a FIA system and applied to the analysis of the EOX-parameter extractable organic halogens (where X = Cl, Br and I). The titration curve was determined using the coulometric system for the determination of the adsorbable organic halogen (AOX) global parameter described in the previous paper (loc. cit.). The curve was then integrated into computer software which evaluated the time dependent signal. The flow rate can then be calculated (details given). For online analysis, water samples were mixed with hexane (1:40) with stirring for 1 h; flow rates were 1.4 and 0.1 ml/min for the aqueous and hexane phases, respectively. The phases were separated and hexane extracts were combusted at 700°C in Ar/O with a Pt/Pd catalyst (system details given). Recoveries were >70%; detection limit was 0.1 mg Cl/l. Applications include waste water and process water control.
Organics, halogenated Industrial Waste Coulometry Computer

"Online Dilution With Sequential Injection Analysis: A System For Monitoring Sulfate In Industrial Effluents"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 6 Pages 577-581
J. F. van Staden and R. E. Taljaard

Abstract: Two manifold sequential injection analysis systems were evaluated: one included a dilution step (system A) and one had a dilution coil in the manifold (system B). The components of each system are illustrated. Flow rates for both systems were 5 ml/min. Standard sulfate solutions were prepared from 1-5000 g/l. Barium chloride reagent solution was used, containing potassium hydrogen phthalate/HCl buffer of pH 2.5, filtered to 45 µm. The device sequences of the two systems are tabulated. For system A, dilution is carried out in the well defined water zone between the barium chloride reagent and the sample zone with a timing sequence from 0-15 S. In addition, 47g EDTA/ammonium chloride (40:7) and 57 mL ammonia were dissolved in 600 mL water, diluted to 1l and this buffer was introduced between samples at the start of each sequence. Calibration graphs were linear from 50-5000 mg/l sulfate for system B; RSD were n=10) for both systems. The merits of each system are discussed.
Sulfate Waste Industrial Turbidimetry Dilution Sequential injection

"Activated Platinum Electrodes As Transducer For A Glucose Sensor Using Glucose Oxidase In A Photopolymer Membrane"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 5 Pages 534-538
D. Wilke, H. M&uuml;ller, N. Kolytsheva

Abstract: Lyophilized glucose oxidase and 5 mg dodecyltrimethylammonium bromide (surfactant) were mixed with 121 mg poly(methyl methacrylate)/bisphenol A-bis (2-hydroxypropyl methacrylate/Michler's ketone/benzophenone (70:30:1:20) dissolved in 1 mL CHCl3 (photopolymer system). Dry planar Pt electrode surfaces (preparation details given) were spin-coated with this cocktail. After solvent evaporation for ~2 min, the electrodes were exposed to UV light for 60 s then conditioned in phosphate buffer for 12 h. Three- and two- electrode techniques were used for cyclic voltammetric and amperometric flow injection measurements, respectively, with a SCE reference and a Pt wire auxiliary electrode. Amperometric measurements were made in an H-form wall-jet cell where one part was the SCE. Glucose measurements were accelerated using a FIA system with a flow rate of 1 ml/min. Calibration graphs were linear from 0.05-10 mM glucose. Electrodes were maintainable for >20 days after coating with the enzyme membrane. The sensor was applied to determination of glucose in diluted serum; calibration graphs were linear from 3-15 mM and results agreed with those obtained using standard photometry.
Glucose Blood Serum Amperometry Electrode Electrode Sensor Voltammetry Method comparison

"Distillation, Online RP C18 Preconcentration And HPLC-UV-PCO-CVAAS As A New Combination For The Determination Of Methylmercury In Sediments And Fish Tissue"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 4 Pages 439-441
Ralf Eiden, Falf Falter, Barbara Augustin-Castro, Heinz Friedrich Scholer

Abstract: Distillation as a way of sample digestion has been combined with on-line RP C18 pre-concentration and HPLC-UV-PCO-CVAAS (high performance liquid chromatography - ultra violet - post column oxidation - cold vapor atomic absorption spectrometry) for the determination of methylmercury at background levels in sediments, soils and fish tissue. To prove the accuracy of this method, it was applied to sediment and fish tissue reference materials. The results correspond with the reference values within their error ranges. Excellent recoveries (92-95%) were obtained for the sediment samples by means of the standard addition method. The standard deviations of the sediment samples were within an acceptable range (7.2-12.5%), those of the fish samples were substantially lower (3.4-5.0%). The detection limit is 0.04 ng/g for 1 g sample weight.
Methylmercury ion Fish Tissue Environmental HPLC Spectrophotometry C18 UV reactor Preconcentration Volatile generation Speciation Volatile generation Photochemistry

"Two-step Solvent Extraction Flow Injection System For The Determination Of Anionic Surfactants By Spectrophotometry"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 4 Pages 416-419
Shihua Fan and Z. Fang

Abstract: An automated flow injection method is presented based on the official methylene blue (MB) method (Hein et al., Water and environmental analysis with the UV/Vis spectrometer Lambda 2 (Perkin-Elmer, 1992, Uberlingen). Samples (100 µL) were injected into the system manifold (diagram and details given) and transported by water carrier to merge downstream with buffered MB solution (preparation details given). CHCl3 was delivered by PTFE tubing (0.5 i.d. x 1 mm o.d.) and segmented with aqueous flow in a segmentor. The ion-pair formed in the aqueous phase was extracted into the organic phase whilst passing through an extraction coil. The organic phase was separated from the aqueous phase and merged with acid MB washing solution (preparation details given). Interferents were back-extracted into the aqueous phase which was then discarded. The CHCl3 phase was introduced into a flow cell and detection was at 652 nm. Calibration graphs were linear up to 6 mg/l SDS in aqueous solution; RSD were 4.6% (n = 7). Recoveries were 89-107% anionic surfactants. Results obtained for anionic surfactants in waste water samples agreed well with those obtained by the standard MB batch method.
Surfactants, anionic Waste Spectrophotometry Sample preparation Automation Interferences Method comparison Organic phase detection Ion pair extraction Solvent extraction

"Flow Injection Analysis With Amperometric Detection For Measurements Of Proton Activities In Solutions Of Strong Acids And Strong Bases"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 4 Pages 392-396
Anastas Dimitrov Dakashev

Abstract: Flow injection and reversed flow injection analysis with amperometric detection were used for the determination of the concentrations of strong acids and strong bases and the pH of the solutions. The amperometric detection was based on the reduction current of hydrogen ion or water molecules. A platinum indicator electrode cathodically polarized at a constant potential was employed, choosing the potential in the rising part of the current/potential curve. On the basis of the experimental data an equation was developed for the calculation of the concentrations of the strong acids and strong bases and the pH by a non-linear regression computer program. Analysis was carried out with an FIA system (schematic given) consisting of a peristaltic pump and an injection valve with a loop volume of ~100 µL. An electrochemical detector as described previously (Ilcheva and Dakashev, Analyst, 1990, 115, 1247) was adapted to amperometric determination using a Pt wire (4 x 0.5 mm diameter) placed axially in a cylindrical channel (2 mm diameter) as an indicator electrode. An OH 102 polarograph was also used. A buffer vessel (75 ml) was inserted between the peristaltic pump and the injector valve. Buffer solutions were aqueous solutions of 0.1 M HCl/glycine for acid buffers and 0.1 M NaOH/glycine for basic. An equation was developed, using the data obtained by this system, to calculate concentrations of strong acids and bases, and pH, by a non-linear regression computer program (details given).
Acids Bases pH Amperometry Electrode Chemometrics Buffer Activity

"Use Of Microwave Plasma Torch Atomic Emission Spectrometry For The Determination Of Silicon"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 4 Pages 384-388
Feng Liang, Hanqi Zhang, Q. Jin, Daxin Zhang, Y. Lei

Abstract: Standard steel samples were dissolved with 30% H2O2/HCl then mixed with 35 mL water. The resultant solution was heated until H2O2 was completely decomposed. Standard Al samples were digested similarly without H2O2. Mineral water was analyzed directly. A dual-pump flow injection system was used for online separation. Samples (300 µL) were carried with water or HCl into a nebulizer through a glass cation-exchange resin column (4 cm x 4 mm i.d.). A schematic of the flow injection system is given. The desolvation system was similar to one described previously (Zhang et al., J. Anal. Atom Spectrom., 1994, 9, 851). The sample was automatically carried into the microwave plasma torch. The operating conditions of the system are tabulated. Detection limit was 10.8 ng/ml silicon when Ar was both carrier and support gas; RSD was 4.2% (n=11) for determination of 1 µg/ml silicon.
Silicon Alloy Mineral Ion exchange Spectrophotometry Sample preparation Resin

"Improvement Of An Old Spectrophotometric Method For The Microdetermination Of Ascorbic Acid By The Use Of A Micellar Medium"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 3 Pages 317-320
P. B. Issopoulos A and Sofia E. Salta

Abstract: A long known indirect method for the spectrophotometric determination of the ascorbic acid (ASCA) has been improved. The initial method, as well as the improved one is based on the same coupled redox-complexation reaction between Fe(III) and ASCA, the resulting Fe(II) reacts with o-phenanthroline (o-Phen) to form the well-known orange-red colored ferroin chelate complex dFe(II)-(o-Phen)3]2+. Whereas the initial method is carried out in an aqueous solution, the improved one employs an aqueous micellar medium formed by the cationic surfactant cetylpyridinium bromide (CPBR). The λmax in both methods is the same, i.e. 510 nm. The mean apparent molar absorptivity (l) and Sandell's sensitivity (Ss) were calculated as l=2.102 x 10^4 L mol-1 cm-1 and Ss=8.37 ng cm-2 for the initial procedure, and l=2.622 x 10^4 L mol-1 cm-1 and Ss=6.72 ng cm-2 for the improved one. The regression line equation for the improved method was: A=1.4872 x 10^-1 C + 1.4152 x 10^-2 (r=0.9998). The accuracy and the precision of the improved method were investigated and the conclusions were satisfactory. The results obtained for ASCA by both the described method and an official one, were statistically compared by means of the Student's t-test and by the variance ratio F-test; and no significant difference was observed.
Ascorbic acid Spectrophotometry Micelle

"Analytical Chemical Laboratory Exercises On Basic And Advanced Level At The Technical University Budapest"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 2 Pages 227-228
E. Graf-Hars&aacute;nyi A, L&aacute;szl&oacute; Bez&uacute;r A, Zs&oacute;fia Feh&eacute;r

Abstract: An overview on the practical laboratory work done by the chemical engineering students is given at different levels of the curriculum of the Faculty of Chemical Engineering. Laboratory exercises and individual laboratory work is carried out at the following levels: Basic level. The different analytical chemical methods are acquisited by the students. Advanced level. A problem oriented project work is done with integrated use of the different analytical methods in the 8th semester. Thesis work. Specialized individual work on an elected research topic. Postgraduate courses. Organized for the understanding and practice of the latest methods and applications in the analytical chemistry. The programs of the different levels are detailed in the following.
Education

"Determination Of Antimony In Wine By Hydride Generation Graphite Furnace Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 1 Pages 92-96
Anne-Marie Wifladt A, Grethe Wibetoe A, W. Lund

Abstract: A method was developed for the determination of Sb in wine by electrothermal atomic absorption spectrometry, based on pre-concentration by hydride generation with collection directly in the graphite furnace. Thiourea was added for prereduction of Sb(V) to Sb(III). The hydride was directly generated from diluted wine. Palladium was used as modifier in the collection step; the overall efficiency of the hydride/trapping system was found to be 67%. Sb was determined in several samples of red wine; the concentrations found were in the range 0.6 to 5.7 µg/L Sb. The detection limit of the method was 39 pg Sb, corresponding to 0.13 µg/L Sb in wine when 0.3 mL wine was analyzed.
Antimony Wine Spectrophotometry Volatile generation Volatile generation

"Flow Injection Analysis Of Ascorbic Acid At A Methylene Green Chemically Modified Electrode"
Fresenius J. Anal. Chem. 1997 Volume 357, Issue 1 Pages 84-85
A.-M. Yu, Chun-Xiang He, J. Zhou, H.-Y. Chen

Abstract: A carbon paste electrode that had been chemically modified with methylene green (electron mediator) was used to determine ascorbic acid. The flow injection equipment and electrode construction were described previously (Chen et al., Anal. Lett., 19 95, 28, 1579). The optimum experimental parameters were investigated: the voltage was at 0.5 V; the mobile phase was at pH 7 and the flow rate was 1.5 ml/min. Calibration graphs were linear over three orders of magnitude; the detection limit was 0.25 pM-ascorbic acid. The electrode retained >80% of its initial response level after 7 h continuous use. There was no interference from myoglobin, haemoglobin, glucose, acetic acid, folacin, glycine, glutamic acid and amino acetic acid.
Ascorbic acid Electrode Electrode Potentiometry Interferences Optimization

"Automated High Performance Liquid Chromatographic Analysis And Post-column Photoderivatization Of Iotetrol¨ In Aqueous Solutions"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 7 Pages 456-460
M. Pfeffer and B. Wykhoff

Abstract: An automated procedure for sample work-up and preparation of calibration standards for HPLC analyzes is presented. The equipment consisting of a benchtop workstation and a conventional HPLC system was used to analyze aqueous solutions containing Iotetrol, a contrast medium. The four rotamers of the test compound were separated using the stationary phase Hypercarb S and by elution with tetrahydro-furan/water 3:97 (w/w). The analytical procedure was characterized with respect to sensitivity, selectivity, linearity of the detector response, accuracy, precision and carry-over effect. The use of the workstation yielded excellent data with respect to accuracy (102%) and precision (1%). At the stage of method development, the influence of post-column photoderivatization on the detectability of the analyte was investigated. As a result, a bathochromic shift of the UV absorbance maximum and the considerable intensification of the rudimentary fluorescence properties of the Iotetrol molecule were observed. The automatization saved a considerable amount of man-hours (ca. 25%).
Iotetrol HPLC Post-column derivatization Photochemistry

"Investigation Of The Automated Determination Of Arsenic, Antimony And Bismuth By Flow Injection Hydride Generation Using In Situ Trapping On Stable Coatings In Graphite-furnace Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 7 Pages 435-444
H. O. Haug and Y. -p. Liao

Abstract: The elements were determined in low-alloy steel reference materials, which were dissolved in aqua regia at 90°C over 3 h. Solutions were diluted to 100 mL with 1 M HNO3 and portions treated with 1% L-cysteine in 0.1 M HNO3 for flow injection hydride generation by reaction with alkaline 0.5% NaBH4 and use of 0.1 M HCl (2.8 ml/min) as carrier solution. The liberated hydrides were measured by GFAAS trapping adsorption in situ on to Zr-coated graphite tubes (or Ir-coated for Sb). Hydride introduction was at 700-750°C (As), 450°C (Sb) or 300-400°C (Bi) and atomization at 2100-2400°C (As) or 2100°C (Sb or Bi) and measurements were at 197.2 (As), 217.6 (Sb) or 223.1 nm (Bi) with Zeeman background correction (As and Sb) or with no correction or deuterium correction (Bi). Hydride generation efficiencies were >98% for Sb and >95% for Bi and respective trapping efficiencies were 91% and 56%. Detection limits were 0.015, 0.010 and 0.027 ng for As, Sb and Bi hydrides, respectively, and corresponding precisions of determination were
Arsenic Antimony Bismuth Alloy Sample preparation Spectrophotometry Volatile generation Reference material Volatile generation

"HPLC Analysis Of Carbohydrates On POLYSPHERCH¨OH Columns Using Pulsed Amperometric Detection (PAD) With Sodium Hydroxide As Post-column Detection Reagent"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 5 Pages 339-343
M. H. Gey, K. K. Unger and G. Battermann

Abstract: Carbohydrates have been separated on POLYSPHER®CH OH columns using pulsed amperometric detection (PAD) and UV detection ( =196 nm) in series and pure water as mobile phase. Nearly baseline separations have been obtained for the glycoprotein carbohydrates of sialic acid (N-acetylneuraminic acid, NANA), N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc). As carbohydrates dissolved and eluted with pure water are present in the neutral form they are not detectable with PAD in contrast to carbohydrate anions formed at high pH values. Therefore an additional NaOH post column reagent has been continuously pumped through a mixing chamber into the mobile phase to form carbohydrate anions resulting in improved detection limits. Monosaccharides as well as glycoprotein carbohydrates could be detected in the g/ml-range. This method has been applied successfully to the analysis of sugars in fruit juice. With only 2 l of juice per 50 mL water, the determination of the main constituents, sucrose, glucose and fructose, was possible in a few minutes without sample preparation.
Carbohydrates HPLC Amperometry Post-column derivatization

"Interferences By Transition Metals And Their Elimination By Cyanide As A Complexing Agent In The Determination Of Arsenic Using Continuous-flow Hydride-generation ICP-AES System"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 5 Pages 331-334
. Jamoussi, M. Zafzouf and B. Ben Hassine

Abstract: The suppressing effects of ppm amounts of Cu, Pb, Co, Au, Pd, and Ni in the determination of As by hydride-generation (HG) ICP-AES were eliminated by use of cyanide as masking agent. In the determination of As by continuous-flow HG ICP-AES, 0.1 M KCN (2.5 ml/min) was mixed with 2% NaBH4 in 1% NaOH (2.5 ml/min), and the mixture was combined with the sample stream (2.75 ml/min) in a V-shaped reaction vessel, and the resulting AsH3 was swept by Ar, via a water condenser, into the ICP source (operating conditions tabulated) and the intensity of the As emission was recorded at 279.55 nm. Under the cited conditions up to 100 µg/ml of the interfering elements could be tolerated. The limit of detection was 0.82 ng/ml of As, and for 50 ng/ml of As the RSD was 1.3% (n = 10).
Arsenic Spectrophotometry Interferences Volatile generation Volatile generation

"Amperometric Carbohydrate Detection In Flow Systems By Means Of A Bismuth Modified Platinum Electrode"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 274-278
A. Str&uuml;bing, G. Wittstock, R. Szargan and G. Werner

Abstract: Bismuth modified platinum electrodes are used for constant-potential amperometric determination of carbohydrates in flow systems. The monitored response is stable and reproducible over more than two days. An attempt is made to gain more detailed information about the characteristics of the modified layer by electrochemical methods and X-ray photoelectron spectroscopy. The response proved to be linear over the investigated concentration range (1.1-1200 mol/L) and detection limits for glucose and fructose were found to be 1.1 mol/L.
Carbohydrates Amperometry Electrode Electrode

"Determination Of Cyanide In Microsamples By Means Of Capillary Flow Injection Analysis With Amperometric Detection"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 271-273
Ulli Backofen, Frank-Michael Matysik and G. Werner

Abstract: A new approach for determining cyanide in microsamples is described. The method is based on capillary flow injection analysis (CFIA) with amperometric detection. The sensing electrode is a silver-plated micro-disk electrode, where cyanide can react under formation of a dicyanoargentate complex. A remarkably low mass detection limit of 231 fmol cyanide is obtained for an injection volume of 60 nl. The sample throughput of the CFIA-arrangement is comparable with a conventional sized FIA-system. A practical application is given by analyzing the cyanide (amygdalin) concentration in apple kernels. The experimental set-up was described in detail. The detector consisted of a Pt microdisc electrode covered with a thin layer of silver. Measurements were made at a potential of 0 V vs. a Ag/AgCl reference electrode. The sample solution (60 nl) of standard cyanide (I) solution were injected into the carrier solution (640 nl/min) consisting of 50 mM borate buffer of pH 10.8. The calibration graph was linear from 3.84-384 µM-I with a detection limit of 0.384 µM. The method was used for the determination of amygdalin (AMY) in apple kernel indirectly by measuring I produced by the enzymatic hydrolysis of AMY with β-glucosidase.
Cyanide Kernels Amperometry Electrode Indirect Capillary

"Calibrationless Determination Of Mercury By Flow-through Stripping Coulometry"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 253-258
E. Beinrohr, M. &#268;akrt, J. Dzurov, P. Kotta&#353; and E. Koz&aacute;kov&aacute;

Abstract: The system consisted of a flow-through cell equipped with a porous working electrode previously plated with a thin layer of gold by allowing a solution of 50 µM-HAuClO4 in 10 mM HCl to flow-through the cell and scanning the potential from -0.5 V to 0 V. A Ag/AgCl reference electrode and a Pt spiral counter electrode were used and these were separated from the working electrode by means of a cation-exchange membrane. The sample solution was then allowed to flow-through the cell and a deposition potential of +200 mV was applied. The cell was then washed by means of a flow of the electrolyte solution (3 ml/min) consisting of 0.1 M H2SO4 containing 4 mM HCl. Determination was carried out by monitoring the potential of the working electrode at a constant current of 200 µA. Detection limit was 0.1 ng/ml. The presence of interfering compounds was investigated and reported.
Mercury Coulometry Electrode Potentiometry Interferences

"Selective Detection Of Metal Species In HPLC And FIA By Means Of Pulsed Amperometric Detection"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 242-246
G&uuml;nther Weber

Abstract: Standard solutions of Sn(IV)/rutin or Pt(II)/glutathione complexes were prepared and analyzed by HPLC on a Spherisorb ODS II column (10 cm x 4.6 mm) with 0.1 M acetate buffer of pH 4.5/methanol (3:2) as mobile phase (1 ml/min) and triple-step pulsed amperometric detection at +800, +1000 and -500 and +250, +800 and -600 mV, respectively, for Sn(IV) and Pt(II). The optimum potentials, time intervals and time delays for each system were reported. Calibration graphs were linear up to 200 and 2000 ng/ml, respectively, for Sn(IV) and Pt and the corresponding detection limits were 8 and 20 ng/ml. The method was also applied for the analysis of fruit juice and grass extract.
Tin Platinum Plant Fruit Environmental HPLC Amperometry Sample preparation Optimization

"Reactive Electrode (reactrode) For The Voltammetric Determination Of Heavy Metals In Laboratories And For Use As A Passive Monitor In Remote Analysis"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 237-241
I. Helms and F. Scholz

Abstract: The electrode was prepared by heating a mixture of graphite powder (0.45 g), HYPHAN cellulose (0.25 g) and paraffin (0.45 g) and pressing the resulting paste into rods of diameter 0.5 mm. In the batch analysis technique, the metal ions were accumulated from a medium of pH 6 at open-circuit potential for 15 min. The electrode was transferred to an electrochemical cell containing 0.1 M KNO3/0.1 M acetic acid (20:1). A potential of -1.2 V (vs. Ag/AgCl) was applied for 250 s. Anodic stripping was effected by differential pulse voltammetry using a pulse amplitude of 50 mV. Detection limits for Pb, Hg and Cu were 0.11 µM, 50 nM and 0.24 µM, respectively. Of the cations investigated, only Fe(III) interfered. The method was also applied for FIA systems.
Metals, heavy Environmental Environmental Voltammetry Electrode Interferences Remote instrument

"Capillary Electrophoresis And Capillary Flow Injection Analysis With Electrochemical Detection"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 3-4 Pages 169-172
F.-M. Matysik and Ulli Backofen

Abstract: The use of novel electrodes, viz. a spherical Au and a dual-microdisc, as electrochemical detectors for both capillary electrophoresis (CE) and FIA is presented. The detector consisted of a glass body equipped with a voltammetric Pt or carbon disk microelectrode with a conically-shaped tip, a Pt counter electrode and a Ag/AgCl reference electrode. The system was used for the simultaneous detection of hexacyanoferrate and hexacyano-osmate or ferrocene and nickelocene, using the capillary FIA technique. Separation of serotonin from its precursors and metabolites was effected with CE.
Electrophoresis

"Immobilized 2-(4-hydrazinocarbonylphenyl)-4,5-diphenylimidazole As Solid-phase Luminophore In Peroxyoxalate Chemiluminescence"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 1 Pages 84-89
Einar Pont&eacute;n, Patrik Appelblad, Malin Stigbrand, K. Irgum and Kenichiro Nakashima

Abstract: A new luminophore for application in peroxyoxalate chemiluminescence is presented. An analogue of the well-known chemiluminescence compound lophine, i.e. 2-(4-hydrazinocarbonylphenyl)-4,5-diphenyl-imidazole (HCPI), has been covalently immobilized to controlled pore glass and a porous methacrylate resin. By using this reagent in a solid phase detection reactor, sensitive determinations of hydrogen peroxide have been demonstrated. In homogeneous solution HCPI emits poorly as a result of 1,1'-oxalyldiimidazole excitation, but when immobilized its efficiency is almost comparable to highly efficient luminophores such as 3-aminofluoranthene. Linearity extends in the single stream flow system over several orders of magnitude with both materials. The limit of detection was 1 nmol/l (10 fmol injected), when using the porous methacrylate support.
Hydrogen peroxide Chemiluminescence HPLC Solid phase reagent Controlled pore glass Resin Immobilized reagent Solid phase detection

"Determination Of Salicylate In Beverages And Cosmetics By Use Of An Amperometric Biosensor"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 1 Pages 75-79
M. Ehrendorfer, G. Sontag Contact Information and F. Pittner

Abstract: A fast and selective enzymatic method for the determination of sialicylate in beverages and cosmetics has been developed. The enzyme salicylate hydroxylase was immobilized covalently onto a glassy carbon working electrode of a wall-jet cell coupled with a flow injection analysis system. The salicylate is enzymatically converted to catechol, which can be detected amperometrically on the glassy carbon electrode at +0.45 V. The response of the biosensor is linearly proportional to the concentration of salicylate between 725 nmol/l and 700 µmol/l. A high sample throughput (60 h-1) is possible, and the biosensor is stable for more than three months. Sample pretreatment for beverages and hair lotions is easy and fast. For creams, an extraction of salicylate is necessary. Relative standard deviations are less than 5.5% and the recoveries are between 9 and 105%.
Salicylate Beverage Commercial product Commercial product Amperometry Sensor Electrode Electrode Enzyme

"Spectrophotometric Determination Of Nitrite In Foodstuffs By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 1 Pages 70-74
J. F. Van Staden and M. A. Makhafola

Abstract: Sample extracts of cured meat (0.1 ml) were injected into an water stream (2.9 ml/min), which was then mixed with the carrier buffer (60 g of NH4Cl plus 0.4 g of EDTA per l, with the pH adjusted to 6 with 25% NH3; 2.5 ml/min) in a Tygon coil (1 m x 0.76 mm i.d.), then further mixed the color reagent [40 g of sulfanilamide and 2 g of N-(1-naphthyl)ethylenediammonium dichloride in 200 mL of 80% H3PO4, diluted to 1 l; 0.42 ml/min] in a Tygon coil (4 m x 0.76 mm i.d.), and the absorbance was measured at 540 nm in a 1 cm 80 µL flow-through cell. To avoid loss of nitrite, the meat samples (40 g) were heated in a microwave oven with 200 mL of 1 M NH4Cl of pH 9 for 5 min under an N2 atmosphere and allowed to cool under N2. With these precautions, recovery of 160 ppm of NaNO2 from four samples of sausage averaged 94.3%, with RSD of 0.55%, if analyzed immediately and 83.47%, with RSD of 0.64%, if analyzed after 24 h. Cold extraction or extraction by heating on a hotplate (both with H2O) gave much lower recoveries, depending on the pH of the extract. If the sample volume was increased to 0.4 ml, the detection limit was 0.036 ppm.
Nitrite Meat Spectrophotometry

"Automatic Determination Of Total Aliphatic Amines By Online Photometric Liquid-liquid Microextraction"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 1 Pages 49-51
J. M. L&oacute;pez Fern&aacute;ndez, A. R&iacute;os and M. Valc&aacute;rcel

Abstract: An automatic flow method for the determination of total aliphatic amines has been developed. Using an integrated µextraction unit at the detection point that allows continuous on-line monitoring of small organic plug from which amines are extracted. It is based on the formation of ion-pairs between aliphatic amines and sodium 1,2-naphthoquinone-5-sulphonate that are subsequently extracted into chloroform. The gradual enrichment of the organic phase with the ion-pair is continuously monitored at 460 nm. Absorbance readings at a fixed time and the slopes of absorbance-time recordings are the measured parameters used for determination purposes. The proposed method has been applied to the determination of total aliphatic amines in both synthetic and real (food) samples.
Amines, aliphatic Spectrophotometry Sample preparation Extraction Automation

"Optimization Of ET-ICP-MS Conditions For The Determination Of Multi-elements In Semiconductor-grade Acids"
Fresenius J. Anal. Chem. 1996 Volume 356, Issue 1 Pages 31-36
L. Samuel Contact Information, Katsuhiro Nakagawa and Tetsuya Kimijima

Abstract: Sample solutions (1-50 µL) were placed in graphite cups held in a ring-shaped graphite holder. The ET heating cycles were optimized for the cations of Cr(III), Mn(II), Al(III) and Na(I) singly, with Ar (1.07 L/min) as carrier gas to the ICP-MS detector. The Ar plasma-gas flow rate was 0.5 l/min and the cooling gas flow rate was 15 L/min. Maximum intensity and minimum RSD were achieved at vaporization temperatures of 3000°C for Cr and Al, 2800°C for Mn and 2750°C for Na, with vaporization times of 6-15 s. Compromise conditions of 2950°C for 6 s were chosen for the simultaneous determination of all four metals. Calibration graphs (25 µL injections) were linear for 0.5-3 ng/ml of each. The method was applied to the analysis of concentrated HCl that had been used for cleaning silicon wafers. Recoveries of 1 and 2 ng/mL of the four metals added to HCl were 95.5-117.7%. The detection limits, calculated as the surface atom concentration x 10^10/cm2 ranged from 0.002-0.58 for the single-element conditions and 0.002-1.48 for the compromise multi-element conditions, which compared very favourably with the detection limits obtained by flow injection ICP-MS.
Chromium(III) Manganese(II) Aluminum(III) Sodium(I) Industrial High purity Mass spectrometry Method comparison Optimization

"Effect Of Slurry Mineralogy On Slurry ICP-AES"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 7-8 Pages 801-802
C. J. Walker, D. E. Davey, K. E. Turner Contact Information and I. C. Hamilton

Abstract: A sample (0.01-2 g) was ground with 20 mL water in a micronizing mill using sintered corundum rods. After dilution with water to 100 ml, the slurries were sonicated for 10 min and analyzed by FIA ICP-MS (Dickinson et al., BHP Research, Central Research Laboratories, 1990, CRL/S/18/90). The background noise was reduced by increasing grinding time, e.g., the peak area RSD for Cu in pyrite was reduced from 17% to 3% by increasing grinding time from 15 to 30 min. Sphalerite, pyrite, haematite, pyrrhotite, goethite and two types of coal slurries containing 2-176 mg/l Fe had the same linear calibration graph of Fe content vs. peak area; results were not affected by the slurry density or mineral hardness or density. The determination of Zn in ZnO, ZnS, sphalerite, pyrite and pyrrhotite was also unaffected by slurry mineralogy.
Copper Sphalerite Pyrite Pyrrhotite Coal Mass spectrometry Sample preparation Spectrophotometry Slurry

"Flow Injection Mini Column Technique With ICP-AES Detection For The Isolation And Preconcentration Of The Fast Reactive Aluminum Fraction In Waters"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 7-8 Pages 757-762
Ben Fairman and Alfredo Sanz-Medel

Abstract: A 1 mL sample was injected into water at a flow rate of 0.6 ml/min which was then mixed with 0.03 M sodium acetate/acetic acid buffer of pH 5 (buffer A) at a flow rate of 0.27 ml/min. Simultaneously, 1.5 mL of 0.5 mM 8-hydroxyquinoline (oxine) in 0.1 M buffer A was injected into water at a flow rate of 1.2 ml/min. After merging, the two streams were passed through a reaction coil (0.5 m long) then applied to a column (5 x 0.3 cm) of Amberlite XAD (0.08-0.16 mm). The oxine complexes of fast-reactive Al were backflushed from the column with water at a flow rate of 1.2 ml/min containing 0.3 mL 1 M HCl. Detection was by ICP-AES at 396.15 nm. Calibration graphs were linear up to 200 and 500 µg/l of fast-reactive Al with one and two HCl backflushes, respectively. The detection limit was 2 µg/l fast-reactive Al and up to 18-fold pre-concentration was possible. Injected samples with high organic C content may be passed through an XAD column in order to remove the organic compounds. The method was applied to tap water and a solution with an F- to Al3+ mol. ratio of 0.27:1 gave results comparable with those obtained by HPLC. The possibility of using the method for field sampling is discussed.
Aluminum Water Spectrophotometry Preconcentration 8-Hydroxyquinoline Amberlite

"Cr(III) And Cr(VI) Online Preconcentration And Determination With High Performance Flow Flame Emission Spectrometry In Natural Samples"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 719-720
J&oacute;zsef Posta, Attila G&aacute;sp&aacute;r, R&oacute;bert T&oacute;th and L&aacute;szl&oacute; Omb&oacute;di

Abstract: Methods for the on-line chromatographic pre-concentration of Cr(III) and Cr(VI) have been developed. Cr(VI) has been pre-concentrated on an RP C18 silica based column with tetrabutylammonium-bromide (TBABr) as ion-pairing agent. Specially for Cr(III) a new and effective pre-concentration technique based on the sorption of Cr(III)-ions in a C18 column in presence of KH-phthalate has been developed. The efficiency of sample introduction into the atomic emission spectrometer could be improved by hydraulic high pressure nebulization. For the detection of chromium the acetylene/N2O flame has been used as a powerful emission spectrometric source. Applying these steps the detection limit (3) could be improved to 25 pg/mL for Cr(III) and to 20 pg/mL for Cr(VI). The method has been applied for the chromium speciation in natural water samples.
Chromium(III) Chromium(VI) Environmental Spectrophotometry Preconcentration Speciation

"Near Melting Point Flow Injection: A Drastic Enhancement In FAAS Detection Limits"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 687-689
S. Walter and A. Aleboyeh

Abstract: The described technique is based on segregation phenomena taking place in solids near their melting point. High impurity concentration occurs in a liquid phase at the grain boundaries. A continuous flow of an adequate solvent is used in far from equilibrium conditions to reach high extraction efficiency of the analyte. As an example, the determination of trace amounts of caesium in metallic sodium is described. The 5 mg/kg detection limit of conventional FAAS is thus lowered to a few g/kg.
Spectrophotometry Temperature

"Online Column Preconcentration For The Determination Of Cobalt In Seawater By Flow Injection Chemiluminescence Detection"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 676-679
Shizuko Hirata, Yukimasa Hashimoto, Masato Aihara and G. Vitharana Mallika

Abstract: Seawater (100 ml) was adjusted to pH 3.6 with 0.5 mL formic acid/ammonium formate buffer then passed through a fluoride-containing metal alkoxide glass column (3 cm x 4 mm i.d.) of 8-quinolinol immobilized on silica gel for 2 min at a flow rate of 3 ml/min, with 0.05 M HCl as carrier stream at a flow rate of 1.7 ml/min. Most heavy metals were separated except Fe(III), but it did not interfere when the gallic acid/H2O2 method was used: water was passed through the column to remove alkali and alkaline earth metals, then the eluate was passed in the reverse direction at a flow rate of 1.7 ml/min and mixed with gallic acid and NaOH both flowing at 0.76 ml/min. The mixture was heated to 60°C in a 2 m reaction coil and the chemiluminescence intensity was measured. The calibration graph was linear from 0.6 ng/l to 1 µg/l Co. The detection limit was 0.62 ng/l Co for a 6 mL sample; RSD was 2.1% (n = 10) for 10 ng/l Co(II). Results from the analysis of reference seawater samples agreed with the certified values.
Cobalt Sea Environmental Chemiluminescence Interferences Reference material Preconcentration Silica gel Heated reaction

"A Microwave Plasma Cavity Assembly For Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 623-625
H. Matusiewicz

Abstract: Although inductively coupled plasmas (ICPs) are widely used for multielement analysis microwave induced plasma (MIP) offers a great potential for a variety of applications. Modifications to incorporate MIP into commercial ICP direct reading spectrometer systems have been developed. A direct reading echelle spectrometer is described which opens new possibilities for the successful construction of commercial MIP-AES systems with the potential to run all of the typical methods worked out for earlier ICP-AES applications. Use of flow injection techniques and automation to couple with in situ concentration will likely offer a further improvement in the analytical performance of this system. Due to the capabilities demonstrated by this spectrometer it appears that hybrid instruments will be increasingly important for future developments in optical spectrometry. This is particularly true for very demanding areas such as atomic emission spectrometry. The system could be readily commercialized.
Spectrophotometry Apparatus

"Determination Of Morphine In Process Streams By Sequential Injection Analysis With Chemiluminescence Detection"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 591-595
N. W. Barnett Contact Information, Simon W. Lewis and Daryl J. Tucker

Abstract: A manifold is described for the determination of morphine in process streams, based on its chemiluminescent reaction with 2 mM KMnO4 in 1% sodium hexametaphosphate of pH 3. A modular injection system was used in the sequential injection mode. The emission was monitored at 610 nm using a flow-through fiber-optic cell and a sensitive, low dark current photomultiplier tube. The calibration graph was not linear over the entire concentration range from 0.02 µM to 0.1 mM, but approximated linearity from 2.5-30 µM. The estimated detection limit was 25 nM-morphine; RSD was 1.4% (n = 15) at the 12.5 µM level. The structurally related compound codeine did not interfere significantly, but the results suggested that matrix effects could occur depending on the sampling location.
Morphine Industrial Chemiluminescence Sequential injection Optical fiber Interferences

"New Developments In Flow Injection Separation And Preconcentration Techniques For Electrothermal Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 576-580
Zhaolun Fang and Guanhong Tao

Abstract: A review is presented of flow injection sample pretreatment systems for ET AAS with emphasis on developments since 1990 and work by the authors. Systems for pre-concentration and separation using sorption columns, online coprecipitation, solvent extraction and hydride sequestration are described. The advantages and limitations of combining flow injection techniques with ET AAS are discussed. (34 references).
Spectrophotometry Sample preparation Spectrophotometry Review Preconcentration Coprecipitation Solvent extraction

"High Performance Flow Atomic Spectrometry: New Nebulization Techniques, Online Speciation And Online Sample Pretreatment"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 555-558
H. Berndt and J. Y&aacute;&ntilde;ez

Abstract: An interface-free combination of HPLC separation techniques and methods for element determination by atomic spectrometry can be achieved by hydraulic high-pressure nebulization (HHPN). With high-temperature HHPN (300°C) super heated liquids can be nebulized providing aerosol yields of up to 90% in flame AAS. This new nebulization method combines the advantages of HHPN and thermospray techniques (very small aerosol droplets, high aerosol yield, nebulization of saturated salt solutions).
Sample preparation Spectrophotometry Nebulizer Speciation Online digestion

"Preconcentration Of Chromium(III) And Total Chromium In Waters For Flame AAS In A Flow-through Electrochemical/sorption Cell"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 5-6 Pages 528-531
E. Beinrohr, Alena Manov&aacute; and J&aacute;n Dzurov

Abstract: Water was adjusted to pH 7 and ionic strength 0.02 M and passed through a flow-through electrochemical cell containing activated alumina, with the electrodes off-circuited. The adsorbed Cr(III) was eluted with 1 M HCl and injected online for analysis using flame AAS. The cell contained a porous glassy C electrode coated with Au, a layer of sorbent and a counter electrode in series. Total Cr was determined by pumping the water through the cell while a constant current of -5 to -10 mA was applied. This reduced Cr(VI) to Cr(III) which was adsorbed together with the Cr(III) already present and analyzed as above. The method was applied to the analysis of tap, river and synthetic sea waters; detection limits were 0.5 and 250 ng/ml for 500 and 1 mL samples, respectively. Calibration graphs were linear from 0.5 ng/ml to 7.5 µg/ml Cr; RSD were 3-10%. Fe(III) did not interfere at concentrations 5 mg/l.
Chromium(III) Chromium, total Water River Sea Electrode Spectrophotometry Sample preparation Preconcentration Interferences Speciation Activated alumina

"Differential Determination Of Arsenic(III) And Total Arsenic With L-cysteine As Prereductant Using A Flow Injection Non-dispersive Atomic Absorption Device"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 3-4 Pages 324-326
X. Yin, E. Hoffmann and C. L&uuml;dke

Abstract: The reduction of 2 µg/l As(V) to As(III) was complete within 60, 40 or 20 min at L-cysteine concentrations of 0.04, 0.08 or 0.16M, respectively, at room temperature in 0.029 M HNO3 or 0.024 M HCl. After flow injection hydride generation, the sample was atomized in a quartz tube at 800°C for analysis using a non-dispersive AAS device. As was determined at 1 sample/min with a detection limit of 0.01 µg/l for a 0.5 mL sample. Of the other elements tested, only Se(IV) and Bi(III) interfered at 150-fold excess. The RSD was 1.2% (n = 10). The method was applied to the speciation of As in river, tap and mineral waters. The As(III) was determined directly in 0.166 M acetic acid and the total As by the above technique.
Arsenic Mineral Water River Spectrophotometry Interferences Speciation

"Mercury Determination By CV-AAS In Wastewater And Sewage Sludge From A Stabilization Pond System"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 3-4 Pages 319-320
Katiuska Araujo, Marinela Colina, Rom&aacute;n Mazurek, Jos&eacute; Delgado, Hilda Ledo, Elizabeth Gutierrez and Len&iacute;n Herrera

Abstract: The mercury concentrations in wastewater and sewage sludge of a stabilization pond system have been evaluated. The system is built by three parallel facultative ponds followed by two systems of three maturation ponds in series. The samples of wastewater and sludge were digested using nitric acid and placed into a Parr-type bomb for 4 h at 110°C. Mercury was measured by Cold Vapour Atomic Absorption Spectrometry (CV-AAS) at 253.7 nm with sodium tetrahydroborate as reductant. The methodologies were checked with an USEPA quality control sample, a standard reference material from NIST and with another method of mineralization (cold mineralization) showing good results. Concentrations of mercury in wastewater between 1.47 ± 0.75 µg L-1 have been found at the entrance of the system and 0.74 ± 0.0 µg L-1 at the exit, while in sludge the results were between 0.29 ± 0.12 µg kg-1 in the facultative pond and 0.04 ± 0.02 µg kg-1 in the second maturation pond (exit).
Mercury Waste Sludge NIST 1646 Spectrophotometry Method comparison Reference material

"New Injection Technique For Flow Injection Atomic Absorption Spectrometry Using Tubing Clamp Valves"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 3-4 Pages 295-296
Olaf Elsholz

Abstract: A system of tubing clamp valves was used to simulate a six-port valve device for sample injection in flow injection AAS. Operation of the system was illustrated by the determination of Hg in suspended particulate matter by cold vapor AAS. The advantages and limitations of the system are discussed.
Mercury Spectrophotometry Injection technique Suspended particulate matter

"Determination Of 0.1 To 1000 .mu.g/ml Cadmium In A Hydrometallurgical Zinc Refining Process Stream By A Flow Injection Technique With Computer-controlled Injection Method"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 2 Pages 144-149
Yutaka Hayashibe, Yasumasa Sayama and Koichi Oguma

Abstract: The computer-controlled flow injection system for the determination of Cd involved the online separation of Cd from the Zn matrix by anion exchange and spectrophotometric detection with 1-(4-nitrophenyl)-3-(4-phenylazophenyl)triazine (Cadion) as chromogenic reagent. A sample of 0.56-350 µL was inserted into a 0.1 M KI carrier stream (1 ml/min) and passed through a Bio-Rad AG1-X8 column (100-200 mesh; 10 cm x 1 mm i.d.). The retained analyte was eluted with a 1 M HNO3 stream (1 ml/min) which was merged with a chromogenic reagent stream formed by mixing 0.006% Cadion/0.1 M KOH/0.1% Triton X-100 (1.5 ml/min) with 17 mM sodium citrate/8.8 mM potassium sodium tartrate/2 M KOH (1.5 ml/min). The flow was propelled to the spectrophotometric detector were the absorbance at 480 nm was recorded. Calibration graphs for Cd were linear for 20-1000 µg/ml (0.56 µm injected) and 0.05-2 µg/ml (350 µL injected). RSD were 6.2% (n = 100) for 0.56 µL of 850 µg/ml Cd and 5% (n = 5) for 350 µL of 0.14 µg/ml Cd. The sampling frequency was 5 samples/h.
Cadmium Spectrophotometry Chromogenic reagent Computer Triton X Surfactant

"Flow Injection Determination Of Lead By Hydride Generation And Conductometric Detection"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 2 Pages 141-143
P. C. Hauser and Zhi-Ping Zhang

Abstract: Plumbane produced from the lead analyte in a flow injection manifold by reaction with sodium borohydride is passed through a porous poly(tetrafluoroethylene) membrane in a gas diffusion cell. The hydride reacts with bromine in the acceptor stream resulting in ionization which is detected by conductivity measurement. Direct mixing of the carrier with a reagent stream yields a limit of detection of approximately 1 mg/L. An improved detection limit of about 200 µg/L can be achieved by the incorporation of an auxiliary stream containing persulfate as oxidizing agent. The application of the method to the determination of lead in road dust and soil samples is demonstrated. The flow injection method was based on the reaction of PbH4 with Br2 to yield bromide ions which were detected by conductivity measurement. A sample of 75 µL was injected into a 0.04 M HNO3 carrier stream which was merged with the reagent stream, 0.3% NaBH4 in 0.05% NaOH. After passing through a reaction coil (60 cm x 0.5 mm i.d.), the flow was propelled to the gas diffusion cell where the liberated PbH4 diffused through a PTFE membrane and was collected in a 0.6 mM Br2 acceptor stream. The acceptor stream was propelled to the conductivity detector where the ionization was detected. All flow-rates were 0.3 ml/min. The calibration graph for Pb was linear for 2-12 mg/l, the detection limit was 1 mg/l and RSD (n = 5) were 3%. The method was applied to the determination of Pb in urban road dust and soil following sample preparation by a standard acid digestion procedure. The results were in agreement with those obtained by AAS.
Lead Environmental Road Conductometry Sample preparation Spectrophotometry Gas diffusion Teflon membrane Method comparison

"Automatic Flow Injection System For The Determination Of Heavy Metals In Sewage Sludge By Microwave Digestion And Detection By Inductively Coupled Plasma Atomic-emission Spectrometry."
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 2 Pages 112-119
Luis Bordera, Vicente Hernandis and A. Canals

Abstract: An automated dual-channel flow injection manifold was used to determine heavy metal concentrations of 77.7-4059 µg/g in sewage sludge. A suspension of sewage sludge containing 0.5-0.75% of solids in 1.5 M HNO3 was loaded into a digestion coil (3 m x 0.8 mm i.d.) and subjected to microwave radiation at 662 W for 360 s. The digest (~e;6 ml) was inserted into a 1.5 M HNO3 carrier stream (1 ml/min) and propelled to the sequential ICP-AES spectrometer where signals for Zn (213.856 nm), Cu (324.756 nm), Pb (220.353 nm), Cr (283.563 nm), Cd (228.802 nm) and Ni (231.604 nm) were recorded. The method was validated by analyzing a certified reference material (BCR No. 146) and relative errors of -4.8 to +2% were obtained for all elements apart from Ni (-10.4%). The complete analysis took ~e;12 min.
Metals, heavy Zinc Copper Lead Chromium Cadmium Nickel Sludge BCR 146 Sample preparation Spectrophotometry Reference material Microwave Online digestion Slurry

"Determination Of Zinc By Flow Injection With Fluorimetric Detection In A Micellar Medium"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 1 Pages 88-91
N. Ga&ntilde;&aacute;n Guti&eacute;rrez, F. S&aacute;nchez Rojas and J. M. Cano Pav&oacute;n

Abstract: Sample was injected into a carrier stream (1.9 ml/min) of 0.02 M acetate buffer of pH 5, the carrier stream merged with a 3% Triton X-100 stream (1.9 ml/min) and the solutions were mixed in a mixing coil (150 cm x 0.5 mm i.d.). The resulting stream merged with a reagent stream (1.2 ml/min) of 5 mM salicylaldehyde thiocarbohydrazone in DMF, passed through a mixing coil (200 cm x 0.5 mm i.d.) and the fluorescent intensity was monitored at 462 nm (excitation at 410 nm). Calibration graphs were linear for 10^-1000 ng/ml of Zn with a detection limit of 5 ng/ml and a RSD (n = 10) of 1.8 and 2% for 50 ng/ml and 100 ng/ml Zn, respectively. The effects of foreign ions are discussed. The method was applied to the determination of Zn in drinking water and biological materials.
Zinc Biological material Water Fluorescence Triton X Micelle Surfactant

"Extending The Dynamic Range Of Flame Atomic Absorption Spectrometry: A Comparison Of Procedures For The Determination Of Several Elements In Milk And Mineral Waters Using Online Dilution"
Fresenius J. Anal. Chem. 1996 Volume 355, Issue 1 Pages 57-64
I. L&oacute;pez Garc&iacute;a, P. Vi&ntilde;as, N. Campillo and M. Hern&aacute;ndez C&oacute;rdoba

Abstract: Three previously described flow injection manifolds (Lopez Garcia et al., J. Anal. Atomic Spectrom., 1992, 7, 1291; Ibid., 1994, 9, 553; Ibid., 1994, 9, 1167) are described and evaluated for their abilities to extend the dynamic range of flame AAS. The systems were used for elemental determination in infant formulae, powdered milk and mineral water. The results obtained by using each manifold are tabulated and discussed. The continuous-flow method is shown to be a reliable alternative to dilution procedures and the systems can be automated or semi-automated.
Trace elements Mineral Baby Powder Spectrophotometry Method comparison Linear dynamic range Dilution

"A FIA System For Arsenic(III)/arsenic(V) Determination With Electrochemical Hydride Generation And AAS Detection"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 7-8 Pages 866-869
Dirk Schauml&ouml;ffel and B. Neidhart

Abstract: Total inorganic As in the carrier stream (1 M H2SO4, 5.4 ml/min) was determined by mixing with 10% L-cysteine solution (1 ml/min), heating in a water bath (95°C) for 40 s and then cooling in ice. The stream passed to the cathode channel of a flow-through cell (described) in which As was converted into AsH3, which was carried in a stream of Ar for determination by AAS. The response was linear for 5-50 µg/l of As(III), with a detection limit of 0.4 µg/l, for 1 mL samples.
Arsenic Arsenic(3+) Arsenic(5+) Spectrophotometry Electrochemical product generation Heated reaction

"Determination Of Low Amounts Of Platinum In Environmental And Biological Materials Using Thermospray Nebulization Inductively Coupled Plasma-mass Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 5-6 Pages 664-667
M. Parent, H. Vanhoe, L. Moens and R. Dams

Abstract: Freeze-dried urine (SRM 2670), plant tissue, and soil or dust (0.1 g) were decomposed with HNO3, HNO3/HClO4 or HNO3/HClO4/HF, respectively. The solutions were heated with aqua regia then HNO3 was removed by evaporation. SnCl2 was added to convert the Pt(IV) to Pt(II). The resulting bis(carboxymethyl)dithiocarbamate complex of Pt(II) was adsorbed on to XAD-4 resin, then back-eluted with ethanol (idem, Biol. Trace Elem. Res., 1994, 43-45, 109). The ethanol was evaporated and the residue was dissolved in 0.5 mL 0.14 M HNO3 containing IR as internal standard. This procedure separated Pt from most matrix elements including Hf. Portions (0.1 ml) were introduced by flow injection into a thermospray nebulizer and the Pt was determined by ICP-MS. Recoveries were variable (from 62-102%) so isotope dilution was carried out with a 194Pt-enriched Pt sponge before the decomposition. The detection limit was 1 pg absolute. The results compared well with those obtained by other methods, e.g., electrothermal AAS or NAA and the certified value.
Platinum Platinum-194 Urine Plant Environmental Environmental NIST 2670 Sample preparation Mass spectrometry Mass spectrometry Reference material Method comparison

"A New Pyrrolidinedithiocarbamate Screening Method For The Determination Of Methylmercury And Inorganic Mercury Relation In Hair Samples By HPLC-UV-PCO-CVAAS"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 4 Pages 492-493
R. Falter and H. F. Sch&ouml;ler

Abstract: A new analytical screening technique for the determination of methylmercury and inorganic mercury in hair samples by HPLC-PCO-CVAAS has been developed. It is based on the extraction of mercury compounds by a buffered sodium pyrrolidinedithiocarbamate solution, separation by reversed-phase HPLC, post column oxidation by UV-irradiation, reduction with alkaline sodium borohydride, and determination by cold vapor atomic absorption detection. The standard deviation was 7% and recoveries were 90% for both compounds. The limit of detection (S/N = 3) for both compounds was calculated to be about 4 ppb.
Mercury(II) Methylmercury ion Hair HPLC Spectrophotometry Photochemistry UV reactor

"Flow Injection Pervaporation Coupling For The Determination Of Sulfide In Kraft Liquors"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 4 Pages 442-446
I. Papaefstathiou, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: A sample that contained sulfide ions was injected or aspirated into a stream (1.3 ml/min) of 1 M TCA of pH 1.16 in advance of a coil (30 cm) and the mixture led into a pervaporation module at 60°C, with a PTFE membrane (5 µm pore) permeable to H2S. The latter was trapped in an upper stream (1.3 ml/min) of 1.92 mM p-diethylaminoaniline in 1 M TCA of pH 1.16 mixed with 3.73 mM ferric ammonium sulfate in 0.044% H2SO4 (0.7 ml/min) and the ethylene blue product monitored at 670 nm. Calibration graphs were linear for 1-15 µg/ml sulfide (injection) or 1-10 µg/ml sulfide (continuous aspiration). Detection limits were 0.68 µg/ml (RSD 5.46%) and 0.42 µg/ml (RSD 8.03%), respectively. Determination of 5 µg/ml sulfide was affected by 5 µg/ml Cd(II); Zn(II), Fe(III), sulfite, carbonate and thiosulfate ions interfered only at 50 orders of magnitude. Sulfide determinations in white and green bleaching liquors agreed quite well with a standard methylene blue procedure.
Sulfides Beverage Industrial Spectrophotometry Interferences Pervaporation Teflon membrane Heated reaction

"Trace Enrichment And Measurement Of Platinum By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 4 Pages 420-423
M. M. Hidalgo, M. M. G&oacute;mez Contact Information and M. A. Palacios

Abstract: Solutions of PdCl4 in 0.01 M HNO3 of pH ~2.3 were pumped (3 ml/min) via a manifold through 0.025 g activated Al2O3 (63-200 µm) in a Teflon tube (7 cm x 1.5 mm i.d.). The concentrated Pd ions were eluted (1 ml/min) with 50 µL 2 M NH4OH and nebulized with Ar (32 psi) into an ICP operated at 1150 W r.f. forward power and 27.12 MHz. Cooling and auxiliary Ar flows were 14.41 l/min. MS measurements were made in the platinum-193 peak-jumping mode at 8.3 x 10^-5 mbar and dwell time 1000 ms. A nominal pre-concentration factor of 600 was achievable. Calibration graphs (ion intensity of net peak height) displayed good linearity for 0-250 ng/l Pt. The RSD (n = 5) for 100 ng/l Pt, with a 5 min sampling time was 4%. Detection limits were 4 ng/l and 2 ng/l with 5 and 10 min sampling times, respectively. The procedure was assessed for Pt(IV) in natural waters, motor car exhaust and common analytical reagents.
Platinum Environmental Environmental Mass spectrometry Preconcentration Activated alumina

"Speciation Of Arsenic In Water Samples By High Performance Liquid Chromatography-hydride Generation-atomic Absorption Spectrometry At Trace Levels Using A Post-column Reaction System"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 3 Pages 344-351
J. Stummeyer, B. Harazim and T. Wippermann

Abstract: Anion-exchange HPLC has been combined with hydride generation - atomic absorption spectrometry (HG-AAS) for the routine speciation of arsenite, arsenate, monomethylarsenic acid and dimethylarsinic acid. The sensitivity of the AAS-detection was increased by a post-column reaction system to achieve complete formation of volatile arsines from the methylated species and arsenate. The system allows the quantitative determination of 0.5 g/l of each arsenic compound in water samples. The stability of synthetical and natural water containing arsenic at trace levels was investigated. To preserve stored water samples, a method for quantitative separation of arsenate at high pH-values with the basic anion-exchange resin Dowex 1 x 8 was developed.
Arsenic Water HPLC Spectrophotometry Post-column derivatization Volatile generation Speciation Volatile generation

"Direct Determination Of Copper And Iodine In Milk And Milk Powder In Alkaline Solution By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 3 Pages 323-326
S. St&uuml;rup and Arne B&uuml;chert

Abstract: Milk powder (0.2 g) was dissolved in 50 mL 0.05 M KOH/0.07 M tetramethylammonium hydroxide, or 0.5 mL raw milk was diluted with 9.5 mL of the alkaline mixture. Each sample was spiked twice with 5 and 10 µg/l I2 and Cu for standard-addition calibration to overcome matrix effects. Analysis was performed using a FIA system with a 500 µL injection loop, the alkaline mixture as carrier and ICP-MS detection. The analyte masses were monitored at m/z 63 and 127. The measurement time was 70 s/injection, which resulted in a high sample throughput. The detection limits were 0.45 and 0.94 µg/l for I2 and Cu, respectively. The method was applied to monitoring over 100 milk samples.
Copper Iodine Milk Powder Mass spectrometry Interferences Standard additions calibration

"Flow-through Sensor Based On Derivative Synchronous Fluorescence Spectrometry For The Simultaneous Determination Of Pyrene, Benzo(e)pyrene And Benzo(ghi)perylene In Water"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 3 Pages 291-295
P. Ca&ntilde;izares and M. D. Luque de Castro

Abstract: A flow-through/first derivative synchronous spectrofluorimetric sensor for the determination of PAH has been described. This sensor has been used for the simultaneous determination of PAH mixtures (pyrene, benzo(e)pyrene and benzo(ghi)perylene). Linear calibration ranges between 10 and 500 ng/ml with acceptable precision (repeatability, expressed as relative standard deviation, smaller than 4.6%, and sampling frequency of 12 h-1) have been obtained. The method has been applied to the determination of the target analytes in spiked water samples with excellent results (recoveries between 94 and 108%).
Benzo(e)pyrene Pyrene Benzo(ghi)perylene Water Fluorescence Sensor

"Flow Injection Analysis - Spectrophotometric Determination Of 8-hydroxyquinoline With P-aminophenol"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 216-220
B. A. Hasan A, K. D. Khalaf A, A. Morales-Rubio A, M. de la Guardia

Abstract: A 10 mL portion of 1 M NaOH was added to 8-hydroxyquinoline (quinolin-8-ol; I) prepared in HCl of pH 3, or in KCl/H3BO3/NaOH buffers of pH 8 or 10 and the total volume was diluted to 25 mL. Streams (3.2 ml/min) of p-aminophenol (PAP) (100 µg/ml) and 0.004 M KIO4 were mixed in a reactor coil (45 cm x 0.8 mm i.d.) and the benzoquinoneimine, formed in situ fed into a second reactor coil (400 cm x 0.8 mm i.d.) with 0.4 M NaOH (3.2 ml/min) into which a 500 µL portion of I in an appropriate buffer had been injected. The resultant indophenol dye (structure illustrated) was measured at 610 nm in a 50 µL flow cell (1 cm path). The calibration graph was linear from 2-8 µg/ml I and the detection limit was 7.6 ng/ml. The RSD (n = 4) was 0.06% for 4 µg/ml I. Recoveries of 98-102% were obtained at pH 3, 8 or 10. Sensitivity is lower (ε = 9500) for the reaction of I with PAP than reported for batch procedures which employ reactions of I with orthanilic acid (ε = 26 500) or diazotized 4-aminoacetophenone (ε = 33 700).
8-Quinolinol Water Environmental Spectrophotometry Buffer

"Kinetic Flow Injection Spectrofluorimetric Determination Of Aluminum(III) Using Eriochrome Red B, Sensitized By Traces Of Fluoride"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 204-207
F. Carrillo, C. P&eacute;rez-Conde, C. C&aacute;mara

Abstract: Samples (100 µL) containing 1000 µg/l Al were injected into a carrier stream of 0.01 M NaF (0.45 ml/min) and mixed with 1.5 M hexamethylenetetramine (HMTA) buffer of pH 6 in a stream of HClO4 (0.6 ml/min) in a reaction coil (50 cm). The mixed solution was subsequently mixed with a 0.1% Erichrome Red B solution (0.45 ml/min) in a second reaction coil (500 cm x 0.5 mm i.d.) at 80°C and cooled to 4°C in a third reaction coil. The fluorescence intensity of the resultant solution was measured in a 18 µL flow cell (10 mm light-path) at 595 nm (excitation at 470 nm). The calibration graph was linear up to 1000 µg/l of Al with RSD (n = 10) of 2.6, 2.2 and 2%, respectively, for 5, 20 and 50 µg/l of Al, respectively. The detection limit was 0.15 µg/l in the presence of fluoride. Potential interferent anions and cations (listed) were studied with 20 µg/l Al; FIA was more selective than a batch procedure and more tolerant of Fe(III). The procedure was used successfully to determine Al in tap water, mineral water or urine.
Aluminum(III) Mineral Water Urine Fluorescence Interferences Kinetic

"A Flow Injection Flame-atomic Absorption Spectrometry System For The Determination Of The Real Stoichiometry Of Small CuInSe2 Semiconductor Crystals"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 184-187
A. Matousek Abel de la Cruz, J. L. Burguera, M. Burguera, S. Wasim, C. Rivas

Abstract: A method for the rapid determination of the real stoichiometry of small CuInSe, semiconductor crystals is presented. The powdered crystal samples have been weighed and acid dissolved in a closed dissolution system connected to a FI manifold for flame atomic absorption spectrometry (AAS) determination. The accuracy has been assessed by comparing the results obtained with those by conventional AAS, and by analyzing CuInSe2 polycrystals of known stoichiometry. The results obtained with the proposed method are in a good agreement with the expected values. The method alloys the dissolution of the crystals without any detectable loss of selenium and has been applied to the analysis of small samples of CuInSe2 monocrystals as a method for routine monitoring during the development of synthesis methods and in homogeneity studies of the crystal ingots. Finely ground CuInSe2 (3 mg; I) were dissolved in 1 mL 65% HNO3 and the solution was diluted to 10 mL with water in a closed dissolution system connected to a flow injection manifold (illustrated). Portions (120 µL) were diluted (1:10) with water (5 ml/min) in a dispersion coil (48.5 cm x 1 cm i.d.) and transferred to an AAS operated with air-acetylene burner gas and a nebulizer aspiration rate of 6 ml/min. Cu, In and Se were determined with lamp currents of 4 mA at 324.8 nm, 5 mA at 303.9 nm and 10 mA at 196 nm and slit widths of 0.7, 0.7 and 2 nm, respectively. Calibration graphs were linear from 5-80, 25-400 and 20-400 mg/l, respectively, for Cu, In and Se. The method was compared with the conventional open dissolution and direct batch aspiration procedure. RSD were 1.8-2.9 and 2.2-3.6%, respectively, for Cu and In were similar for both procedures but the RSD for Se were lower, 2.9-3.2% vs. 4.5-5%.
Copper Indium Selenium Industrial Spectrophotometry Method comparison Process monitoring Stoichiometry

"A Flow Analysis System With An Amperometric Detector For The Determination Of Hydrogen Sulfide In Waters"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 169-172
Paul Jeroschewski and Sabine Braun

Abstract: Hydrogen sulfide (I) was liberated from aqueous samples with an acidic carrier solution and the mixed streams subsequently mixed with N2 (1.78 ml/min) prior to passage through a coiled glass capillary (60 cm x 2 mm i.d.) extraction unit. These dimensions were necessary to ensure an equilibrium exchange of I from the liquid phase to a series of N2 bubbles (28 µL) in accordance with Henry's law. The liquid stream and N2 bubbles passed into an electrochemical sensor (described and illustrated) constructed to ensure that only H2S in the gas phase was able to permeate through a microporous PTFE membrane into alkaline ferricyanide. The current necessary to re-oxidize the resultant ferrocyanide depended directly on the concentration of I. The dynamic range, under the above conditions, was 1-750 µM-I with an RSD of 3%.
Hydrogen sulfide Water Amperometry Teflon membrane Gas diffusion Indirect

"Assessment Of Analytical Quality In Automatic Flow Systems"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 2 Pages 140-149
Juliana Marcos, Angel R&iacute;os, Miguel Valc&aacute;rcel

Abstract: Flow systems employed most frequently for the automatic photometric determination of elementary parameters incorporate a single channel manifold, a dual channel manifold or a merging-zones manifold (illustrated). Each type of manifold was characterized in terms of precision, sensitivity and throughput with bromocresol green in 0.01 M sodium tetraborate buffer of pH 10 and the dual channel manifold was further studied with the reaction of Fe(II) as (NH4)2SO4 with 0.01 M 1,10-phenanthroline and 0.1 M hydroxylamine hydrochloride in 0.1 M sodium acetate. The uncertainty introduced by each flow unit in a manifold was assessed in standard deviation units. Systems were also tested for ruggedness of both flow injections and chemical variables. A number of papers in the literature were evaluated with the data obtained.
Spectrophotometry Quality Merging zones

"Removal Of Iron Interference In The Determination Of Selenium In Geological Samples By Continuous-flow Hydride Generation ICP-AES"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 1 Pages 126-127
L. D. Martinez, M. Baucells, E. Pelfort, M. Roura, R. Olsina

Abstract: Samples (0.5 g) were digested with 6 mL HCl and 2 mL HNO3, the mixture was cooled, 5 mL HClO4 and 10 mL HF were added and the mixture was left overnight. The solution was evaporated until fumes of HClO4 ceased. This step was repeated until complete solution was obtained, the liquid was treated with 4 mL water and 2 mL HNO3 and diluted to 20 mL with water. The pH was adjusted to 0.5-2 with NH3, 10 mL 2% aqueous ammonium pyrrolidine-1-yl-dithioformate was added and the Fe(III) complex formed was extracted into 10 mL CHCl3. This step was repeated until the extracts were colorless. The aqueous phase was heated with 1 mL HNO3, the Se(VI) was reduced to Se(IV) by heating in 6 M HCl at 60°C for 30 min and the solution was diluted to a suitable volume. In the flow system, 0.6% NaBH4 in 0.5% NaOH was pumped at 1 ml/min, 6 M HCl at 1 ml/min and the sample solution at 6 ml/min. After mixing in a reaction coil, the solution was transferred to a gas-liquid separator and the gas phase was transported into the ICP-AES with Ar (90 ml/min) for measurement. The detection limit was 0.15 ng/ml of Se. Recovery of 50 and 300 ng of Se averaged 96 ± 2.8% and 99 ± 1.1% respectively. Satisfactory results were obtained on three certified samples.
Selenium Geological Spectrophotometry Reference material Interferences

"Determination Of Lipase Activity In Porcine Pancreas And Clinical Analysis Of Lipase In Human Serum With Surface Acoustic Wave Enzyme Sensor System"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 1 Pages 118-121
Kai Ge, Dezhong Liu, Kang Chen, Lihua Nie, Shouzhuo Yao

Abstract: The 61 MHz surface acoustic wave generator was made from a Y,Z-cut lithium niobate piezoelectric crystal connected to a pair of parallel platinum electrodes mounted in the 6 mL detection cell. Changes in the conductivity of the solution caused by enzyme reactions produce a change in the frequency response of the sensor detected by a frequency counter and recorded. For the assay of lipase (I), a 6 mL portion of 41.3 mM triacetin in 5 mM Tris buffer of pH 8 was transferred to the cell and the temperature was maintained at 30°C by magnetic stirring. Portions of standard solutions of I were added and the change in frequency was recorded as a function of time. For calibration graphs the initial rate of change of frequency was plotted against the concentration of I. The calibration graph was linear up to 500 U/l of I and the detection limit was 0.3 U/l. This is more sensitive than colorimetric, turbidimetric or flow injection methods, but less sensitive than immunoassay. Results from the injection of serum samples, including those of pancreatitis patients, correlated well with those from direct conductivity measurements, but conductivity was less precise and more restricted by ionic strength. The method was also applied to study the effects of activators and inhibitors of I.
Enzyme, lipase Blood Serum Clinical analysis Sensor Sensor

"Limitations Of A Laboratory Robot For Extracting Available Nutrients From Soil"
Fresenius J. Anal. Chem. 1996 Volume 354, Issue 1 Pages 77-80
N. Brenes, A.M. Bunnell, P.A. Langan, M.N. Quigley, W.S. Reid

Abstract: Soil (2 ml) and 0.2 mL of activated charcoal were transferred to borosilicate glass test tubes (15 cm x 2.5 cm i.d.) by hand, placed in one of four racks of 40. The Zymate II weighed the samples, added 10 mL of acetate buffer of pH 4.8 (Morgan's reagent), vortex-mixed the tubes for 30 s at a setting of 100 units and centrifuged the mixtures. The supernatant liquids were analyzed for phosphate and nitrate by continuous-flow colorimetry and for Al, Ca, Fe, Mg, Mn, K and Zn by the sample volume to 3, 4, 5 and 6 ml, while maintaining the same sample/reagent ratio, were studied. The vortexing step was unchanged, but, for comparison, in another set, the solutions were mixed by hand with a glass rod during a pause. These procedures were applied to a reference soil sample. For all analytes, the maximum extraction by vortexing was obtained with the standard 2 mL sampling; with larger volumes, the amount extracted dropped to half or less. In theory, hand mixing should give results independent of sample volume and this was approximately the case for some analytes (nitrate, phosphate, Ca, K, Mg) but not all. The implications of these findings are discussed briefly.
Phosphate Nitrate Aluminum Calcium Iron Manganese Potassium Zinc Environmental Spectrophotometry Sample preparation Extraction Robot

"Spectrophotometric Determination Of Dopamine And Methyldopa With Metaperiodate By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 2 Pages 221-223
J. J. Berzas Nevado Contact Information, J. M. Lemus Gallego and P. Buitrago Laguna

Abstract: Tablets were dissolved in 0.02 M acetate buffer of pH 4.8 to give a concentration of 8 M dopamine or methyldopa with ultrasonication followed by filtration. Aqueous formulations of dopamine and methyldopa were diluted with the above buffer to give a concentration of 20-200 µM. The resulting solutions were analyzed by FIA as previously described (Anal. Chim. Acta, 1995, 300, 293) with reactor set at 45°C for methyldopa and at 65°C for dopamine and detection at 473 nm. Calibration graphs were linear up to 20 mM catecholamines with a detection limit of 0.59 µM-dopamine and 0.32 µM-methyldopa; RSD (n = 10) were 0.402 and 0.463%, respectively.
Methyl dopa Dopamine Pharmaceutical Spectrophotometry Heated reaction

"Determination Of Cadmium And Bismuth In High-purity Zinc Metal By Inductively Coupled Plasma Mass Spectrometry With Online Matrix Separation"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 2 Pages 162-166
Yasumasa Sayama, Yutaka Hayashibe and Masamitsu Fukuda

Abstract: High-purity Zn metal was dissolved in 7 M HNO3 and evaporated to near dryness. The residue was dissolved in 0.5 M HNO3 and injected into a carrier stream 1 ml/min) of 0.1 M KI. The resulting solution passed through an anion-exchange mini-column (10 cm x 1 mm i.d.) which adsorbed Cd and Bi as the iodide complex. After 3.3 min, the column was washed with 0.1 M HNO3 for 20 min at 0.4 ml/min, the ICP-MS instrument was cleaned with 0.4 M HNO3 (0.4 ml/min), Cd and Bi were eluted from the column with 2 M HNO3 and the eluate was introduced directly into the ICP-MS instrument. The ICP-MS instrumental parameters are tabulated. Calibration graphs were obtained for up to 10 ng/ml of Bi and Cd with detection limits of 0.075 and 0.81 ng/g, respectively, for single injections and 0.014 and 0.16 ng/g. respectively, for multiple injections. Recoveries were 109% Cd and 92% Bi at 10 ng levels.
Bismuth Cadmium High purity Mass spectrometry Sample preparation Resin Preconcentration Complexation

"Selective Determination Of Antimony(III) And Antimony(V) In Liver Tissue By Microwave-assisted Mineralization And Hydride Generation Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 2 Pages 133-136
C. Rond&oacute;n, J. L. Burguera, M. Burguera, M. R. Brunetto, M. Gallignani and Y. Petit de Pe&ntilde;a

Abstract: Antimony(III) and antimony(V) species have been selectively determined in liver tissues by optimizing the acidic conditions for the evolution of stibine using the reduction with sodium borohydride. The results show that a response for Sb(III) of 0.5 to 20 g l-1 was selectively obtained from samples in a 1 mol l-1 acetic acid medium. The best response for total antimony from 1 to 20 g l-1 is obtained after sample treatment with a 0.5 mol l-1 sulfuric acid and 10% w/v potassium iodide. Microwave digestion has been necessary to release quantitatively antimony species from sample slurries. The amount of Sb(V) was calculated from the difference between the value for total antimony and Sb(III) concentrations. A relative standard deviation from 2.9 to 3.1% and a detection limit of 0.15 and 0.10 g l-1 for Sb(III) and total Sb has been obtained. The average accuracy exceeded 95% in all cases comparing the results obtained from recovery studies, electrothermal atomic absorption spectrometry and the analysis of certified reference materials.
Antimony(3+) Antimony(5+) Liver Sample preparation Spectrophotometry Speciation Volatile generation Volatile generation

"Antimony(III) And Antimony(V) Separation And Analytical Speciation By A Continuous Tandem Online Separation Device In Connection With Inductively Coupled Plasma Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 2 Pages 128-132
A. Men&eacute;ndez Garc&iacute;a, M. C. P&eacute;rez Rodr&iacute;guez, J. E. S&aacute;nchez Uria and A. Sanz-Medel

Abstract: For Sb(III) determination a stream of sample (0.75 ml/min) mixed with 0.2 M ammonium citrate/NaOH buffer solution of pH 6 was merged with a stream (0.7 ml/min) of 0.1% pyrrolidine-1-dithiocarboxylic acid ammonium salt and the resulting stream (1.45 ml/min) then merged with IBMK (0.5 ml/min) at a solvent segmenter. Extraction took place in an extraction coil (270 cm x 0.7 mm i.d.) and the consecutive organic and aqueous segments were separated at a membrane phase separator. The aqueous phase as collected for Sb(V) determinations and the organic phase was mixed with glacial acetic acid (1 ml/min) and 2% sodium tetrahydroborate in DMF (0.5 ml/min) for stibine generation. The stibine formed was transferred to the ICP torch by Ar (0.3 l/min) and Sb was monitored at 217.58 nm. For Sb(V) determination the aqueous phase collected above was acidified with HCl to give a final concentration of 3 M HCl and mixed with 2% KI. The resulting solution was used for hydride generation ICP-AES with 1% NaBH4. The calibration graph was linear up to 100 µg/ml with detection limits of 3 ng/ml of Sb(III) and 8 ng/ml of Sb(V). RSD (n = 10) were 4% for 100 ng/ml Sb(III) and 5% for 100 ng/ml Sb(V). Interferences by ions found in sea and estuarine water was tabulated and discussed. The method was applied to Sb determination in seawater.
Antimony(3+) Antimony(5+) Sea Spectrophotometry Speciation Interferences Volatile generation MIBK Phase separator Volatile generation

"Ion Exchange Micro Columns For Online Preconcentration Of Heavy Metals. 2. Online Break-through Test For Zinc, Cadmium And Lead"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 2 Pages 119-122
O. Elsholz, and G. Schulze

Abstract: An on-line break-through test for zinc, cadmium and lead has been carried out by means of a flow-through cell and computerized potentiometric stripping analysis. This test has been applied to seventeen ion-exchange materials and enabled within a short time a predecision about the suitability of a resin for a special precon-centration problem. For the determination of the three trace elements in drinking water five ion exchangers are found to be appropriate without restriction and eight resins with some restrictions (not suitable for all three elements, weak matrix influences).
Cadmium Lead Zinc Ion exchange Column Preconcentration

"Polar Organic Compounds In The River Elbe - Development Of Optimized Concentration Methods Using Substance-specific Detection Techniques"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 1 Pages 93-97
Horst Friedrich Schr&ouml;der

Abstract: Water was extracted by SPE on cartridges containing C18 or LiChrolut EN material with elution by methanol or selective elution with mixtures of organic solvents, or on XAD columns with desorption by hot steam extraction with methanol and ethyl acetate. The extracts were analyzed by LC-MS or FIA with thermospray ionization. LC was performed on a 5 µm nucleosil C18 column (25 cm x 4.6 mm i.d.) with gradient elution (1 ml/min) with acetonitrile and aqueous 20% methanol (details given) and thermospray ionization MS. For FIA by-passing the analytical column a mobile phase of aqueous 60% methanol and aqueous 0.1 M ammonium acetate (overall flow rate 1.5 ml/min) was used. The different extraction methods were compared and the results are discussed. There were little differences between the extraction methods for the adsorption of polar organic compounds.
Organic compounds River LC Mass spectrometry

"Determination Of Mercury Species In Natural Waters At Picogram Level With Online RP C18 Preconcentration And HPLC-UV-PCO-CVAAS"
Fresenius J. Anal. Chem. 1995 Volume 353, Issue 1 Pages 34-38
R. Falter and H. F. Sch&ouml;ler

Abstract: A new technique has been developed for the determination of methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury in natural water samples. The mercury compounds have been complexed for the pre-concentration on RP C18 columns by sodium pyrrolidinedithiocarbamate (SPDC), sodium diethyldithiocarbamate (SDDC) and hexamethyleneammonium (HMA) - hexamethylenedithiocarbamate (HMDC), separated by HPLC and determined by UV-PCO-CVAAS (ultra violet, post column oxidation, cold vapor atomic absorption spectrometry). The standard deviations are in the range of 6.9 to 11.8%. The recoveries amount to 86%, 78%, 88%, 83%, 79% and 84% for methyl-, ethyl-, methoxyethyl-, ethoxyethyl-, phenyl- and inorganic mercury for the enrichment from 300 mL water samples. The detection limit for methyl mercury is 0.5 ppt. This new on-line pre-concentration procedure has been tested with rain, drinking, surface and process water samples.
Mercury Environmental HPLC Spectrophotometry Preconcentration C18 Photochemistry UV reactor Speciation

"Development Of An Automated Flow Injection Chemiluminescence Immunoassay For Human Immunoglobulin G"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 7-8 Pages 793-796
Andrea Hacker, Martin Hinterleitner, Curt Shellum and Gerald G&uuml;bitz

Abstract: An immunoreactor flow cell was constructed comprising a transparent PTFE tube (2 cm x 1.5 mm i.d.) packed with anti-human IgG immobilized on Affi-prep 10 support (details given). The immunoreactor was equilibrated with assay buffer of 0.01 mM sodium phosphate buffer/0.14 M NaCl/0.05% NaN3 of pH 7 at 0.3 ml/min, serum sample was injected at 0.03 ml/min and, after 1 min, the buffer was changed to the elution buffer of 32 mM 85% phosphoric acid of pH 1.8 (0.3 ml/min) and H2O2/NaOH solution was injected. Detection was by chemiluminescence. The detection limit was 7 fmol/injection of IgG in serum with intra-assay RSD (n = 7) of 1-3% and inter-assay RSD (n = 21) of 1.4%. Recoveries of 15.6 and 31.2 µM-IgG from serum were 102.2 and 103.4%, respectively.
Immunoglobulin G Serum Human Chemiluminescence Immunoassay Column Immobilized antibody

"Online Preconcentration And Determination Of Mercury In Biological Samples By Flow Injection Vapor Generation Inductively Coupled Plasma Atomic-emission Spectrometry"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 6 Pages 615-617
Pedro Ca&ntilde;ada Rudner, Jos&eacute; Manuel Cano Pav&oacute;n, Amparo Garc&iacute;a de Torres and Fuensanta S&aacute;nchez Rojas

Abstract: Hair was digested with 65% nitric acid for 30 min followed by microwave digestion at 360 W for 4 min and 180 W for 10 min. After cooling for 14 min, the digests were concentrated by evaporation, neutralized with NaOH and diluted with water. Pig kidney and dogfish muscle were prepared by the method of Niazi et al. (Analyst, 1993, 118, 821). The extracts (1.4 ml/min) were mixed with 0.2 M HCl/0.2 M glycine buffer of pH 3.6 (0.4 ml/min) in a FIA system. The flow merged with a stream of 1,5-bis(di-2-pyridyl)methylene thiocarbonohydrazide in IBMK (0.5 ml/min) at a solvent segmentor. The stream passed through an extraction coil (200 cm x 0.5 mm i.d.) to a membrane phase separator and the aqueous phase went to waste. The organic phase filled a sample loop (500 mL volume) and the excess went to waste. The sample was injected into a carrier stream (3.3 ml/min) of IBMF/DMF (1:1) and merged with a reagent stream (0.5 ml/min) of SnCl2 in DMF. The resulting stream passed through a mixing coil (100 cm x 0.8 mm i.d.) for the generation of Hg vapor. The gas and solvent passed to a gas-liquid separator and to Hg vapor was swept to a ICP torch by Ar. The Hg was determined by ICP-AES (operating details tabulated). The calibration graph was linear for 10^-2500 ng/ml of Hg(II) with a detection limit of 4 ng/ml and RSD (n = 10) of 1% at 100 ng/ml. The effects of foreign ions are discussed.
Mercury Hair Kidney Muscle Sample preparation Spectrophotometry Sample preparation Extraction Preconcentration Interferences Phase separator Volatile generation MIBK Volatile generation

"Flow Procedure For Ion-exchange Preconcentration And Online Spectrophotometric Determination Of Iron(III) As Its Thiocyanate Complex"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 6 Pages 601-602
Ala'ddin M. Almuaibed and Alan Townshend

Abstract: Sample was pumped via a 3-way valve at 1.5 ml/min for 4 min through a Dowex-50 W cation exchange column (25 cm x 0.25 mm i.d.). The value was switched and 1.2 M H2SO4 containing 0.082 M KSCN was pumped through the system to elute Fe(III) retained on the column. The resulting stream was monitored at 465 nm. The calibration graph was linear for 0.01-0.2 µg/ml of Fe(III) with a detection limit of 6 ng/ml and RSD (n = 4) of 3% at 0.08 µg/ml of Fe(III). The effect of foreign ions are discussed.
Iron(III) Ion exchange Spectrophotometry Column Interferences Preconcentration

"Spectrophotometric Simultaneous Determination Of Creatinine And Creatine By Flow Injection With Reagent Injection"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 6 Pages 557-561
Gloria del Campo, Ana Irastorza and J. Alfonso Casado

Abstract: Stock cubes (meat and fish) were dissolved in water by heating at 60°C with agitation and the resulting solution was cooled and filtered. After dilution with water a 220 µL portion was injected into the carrier stream of 2 g/l picric acid in 20 g/l NaOH in a FIA system. The system passed through a reaction coil (600 cm x 0.7 mm i.d.) and merged with 0.2 g/l of biacetyl and 25 g/l of 1-naphthol in 20 g/l of NaOH. The resulting stream passed through a second reaction coil (500 cm x 0.7 mm i.d.) to a spectrophotometer where the absorbance was measured at 520 nm. All flow rates were 0.9 ml/min and all reactions took place at 40°C. Calibration graphs were linear up to 30 mg/l of creatinine and creatine. RSD (n = 3) were 0.3-1.65% for 2-20 mg/l of creatinine and 0.34-0.67% for 2-30 mg/l of creatine. Recoveries were 99.6-102.9% for creatinine and 96.5-100.4% for creatine from meat and fish stock cubes.
Creatine Creatinine Cube Cube Spectrophotometry Heated reaction Reverse

"Membrane Separation In Flow Injection Systems. 1. Dialysis"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 3-4 Pages 271-302
J. F. van Staden

Abstract: A review is presented of membranes for online separations in flow-through dialysers. The historical perspectives are outlined and the fundamental aspects of dialysis are discussed. The theoretical principles and experimental parameters are described. The use of dialysis in sample preparation for chromatography and reactor systems, for FIA, pre-concentration and multicomponent analyzes is evaluated. (224 references).
Review Dialysis Membrane Preconcentration Multicomponent

"The Determination Of Lead In Blood Using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 1-2 Pages 203-208
K. E. Murphy and P. J. Paulsen

Abstract: Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) was applied to the certification of Pb in four levels of NIST blood SRM, 955a. This standard reference material (SRM) represents a significant improvement over the previous blood reference material and will greatly aid method development. The lowest level, 47.76 ng/g Pb was determined with analysis uncertainty (95% CI, ID-ICP-MS uncertainties) of less than 1% and the highest level, 517.9 ng/g Pb to 0.3%. Uncertainty in the lowest level was due to sample inhomogeneity and variability in the analytical blank as the RSD on ratio measurements was typically better than 0.2%. Properly applied isotope dilution coupled with careful isotope ratio measurements on the ICP-MS offers precision and accuracy for blood Pb analyzes beyond what is currently obtainable with routine methods.
Lead Blood Mass spectrometry Mass spectrometry

"Certification Of A New NIST Fly Ash Standard Reference Material"
Fresenius J. Anal. Chem. 1995 Volume 352, Issue 1-2 Pages 193-196
Robert R. Greenberg, Jean S. Kane and Thomas E. Gills

Abstract: A new fly ash standard reference material was prepared from the burning of mixed Appalachian range coals in a single coal-fired power plant. The material was certified by a number of different analytical methods including isotope-dilution MS, NAA, XRF, ICP-AES, ETAAS, cold vapor AAS, flow injection AAS and flame emission spectrometry. The homogeneity of the sample was determined by NAA and XRF. Results are discussed.
Mercury NIST 1633 Coal Fly ash Spectrophotometry Spectrophotometry Reference material

"Separation And Determination Of Cadmium In Biological Materials By Continuous-flow Fluid Extraction Coupled To Flow Injection ICP-AES"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 802-804
E. Vereda Alonso, M. T. Siles Cordero, A. Garc&iacute;a de Torres and J. M. Cano Pav&oacute;n

Abstract: Biological reference materials was dried, powdered and mineralized by heating under reflux with 65% nitric acid. H2O2 was added, the mixture was concentrated to remove the nitric acid and NaClO4 was added to give an ionic strength of 0.1 and the pH was adjusted to 3.6. The aqueous sample stream (0.68 ml/min) was merged with a carrier stream (0.22 ml/min) of 1,5-bis(di-2-pyridyl)methylene thiocarbohydrazide in IBMK at a solvent segmentor. The stream passed through an extraction coil (100 cm x 0.35 mm i.d.) to a membrane phase separator. The organic phase filled an injection loop and was carried to the ICP-AES instrument by a carrier stream (1.2 ml/min) of IBMK/DMF and the solution was analyzed. The operating conditions were plasma flow rate of 12 l/min, r.f. generator frequency of 40 MHz and a wavelength of 228.802 nm. The calibration graph was linear for 10^-2000 ng/ml with a detection limit of 8.7 ng/ml and RSD (n = 7) of 3.4% for 100 ng/ml of Cd.
Cadmium Biological Sample preparation Spectrophotometry Sample preparation Reference material MIBK Solvent extraction Phase separator Organic phase detection

"Simultaneous Flow Injection Determination Of Ammoniacal Nitrogen And Chloride In Industrial Effluent Water With A Combined Online Gas Diffusion/dialyser Unit"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 758-761
Jacobus F. van Staden, Cornelius J. Hattingh and Daniel Malan

Abstract: Industrial effluent was injected into a carrier stream (2.5 ml/min) of water, the stream was mixed with a stream (1.2 ml/min) of 0.1 M NaOH in a mixing coil (100 cm x 0.76 mm i.d.). The resulting stream passed into a gas diffusion/dialyser unit. The unit has two recipient channels; the top channel is separated from the donar channel with a PTFE membrane and contains ammoniacal indicator mixture (2.5 ml/min). The bottom channel is separated from the donar channel with a dialysis membrane and contains water (2.5 ml/min). The ammonical nitrogen stream passed through a coil (200 cm x 0.76 mm i.d.) and the absorbance was measured at 590 nm. The water dialysic stream was merged with a color stream (1.2 ml/min) containing mercury(II) thiocyanate in methanol, concentrated nitric acid and iron(III) nitrate in water. The resulting mixture passed through a coil (200 cm x 0.76 mm i.d.) and the absorbance of the chloride was measured at 480 nm. Calibration graphs were linear for 0.1 g/l ammonical nitrogen and 0-2.531 g/l chloride with RSD (n = 15) of 0.16-0.98% and 0.16-0.45%, respectively.
Ammonia, nitrogen Chloride Industrial Spectrophotometry Dialysis Gas diffusion Simultaneous analysis Teflon membrane

"Multielement Determinations In Ground Water Ultrafiltrates Using Inductively Coupled Plasma Mass Spectrometry And Monostandard Neutron-activation Analysis"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 745-751
T. Probst, P. Zeh and J. -I. Kim

Abstract: Twelve ultrafiltrates of two ground waters rich in humic substances (up to 97.8 mg CL-1) and in salinity (up to: cations 44.3 meq L-1, anions 44.9 meq L-1) were investigated with ICP-MS and with NAA in parallel. With both techniques 22 elements were analyzed in a wide concentration range (mg/L to ng/L). Ultrafiltration at pore sizes from 1000 nm down to 1 nm lowers the humic colloid content as well as the concentration of the colloidborne polyvalent cations. Carbon interferences were studied in detail using artificially prepared model waters. The detection limits of ICP-MS in the ultrafiltrates (0.01 g/L-10 g/L) and in pure analyte solutions (5 ng/L-600 ng/L) are compared with those of NAA for pure water analysis (0.004 ng/L-50 ng/L).
Metals Environmental Mass spectrometry Neutron activation analysis

"Flow Injection Near-infrared Determination Of Ethanol In Chloroform"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 724-728
Emilio L&oacute;pez-Anreus, Salvador Garrigues and Migue de la Guardia

Abstract: Chloroform (300 µL) was injected into a carrier stream (1.35 ml/min) of CHCl3 stabilized with pentene and the absorbance was measured by NIR spectrometry at 2272 nm. A reference sample of CHCl3 stabilized with pentene was used. The dynamic range of the method was upto 10% ethanol with a detection limit of 0.0045%. The RSD was 0.4% for 1% ethanol.
Ethanol Organic compound Spectrophotometry

"Development And Optimization Of A Multichannel FIA-cell Allowing The Simultaneous Determination With A Multiwavelength Photometric Device Based On Light Emitting Diodes"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 8 Pages 701-707
H. P. Beck and C. Wiegand

Abstract: A FIA cell is described comprising a PVC block with engraved channels (1 x1 mm2) containing a γ-mixing point for carrier and reagent or sample streams, a meandric reactor line and many detection points (schematic diagram given). Each detector channel was closed with a PMMA-waveguide (not defined) protruding out of the block. A long waveguide conducts light from a LED of the detector unit to the cell and another one back onto the signal photodiode. The flow cell is closed with PVC foil and an Al plate. The detection unit comprised six electronic circuits with a LED, a signal and a reference photodiode. The PMMA waveguides from the flow cell were attached to the LED and signal diodes. The LED have wavelengths of 470, 560, 585, 630, 660 and 850 nm. The system was used for the simultaneous measurement of the absorbances of metal complexes with xylenol orange and EDTA.
Metals Spectrophotometry Complexation Flowcell Light emitting diode Optimization Simultaneous analysis Multichannel Photodiode

"Digestion-free Determination Of Heavy Metals In Honey Using Anodic-stripping Differential Pulse Voltammetry And Potentiometric-stripping Analysis"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 7 Pages 678-682
Yingjian Li, Faramarz Wahdat and Rolf Neeb

Abstract: Experiments have been carried out to assess the potential of differential pulse voltammetry and potential stripping analysis for determining Pb, Cu and Cd directly in dissolved honey samples using a flow-through cell. With the hanging mercury drop electrode Pb alone can be determined only if the electrode is first modified in-situ with Triton X 100 to increase the separation between the Pb peak and a broad, interfering adsorption peak which overlaps the Cu peak. If the (more sensitive) thin film mercury electrode is used the interference encountered is less so also Cu and Cd can be determined. With potentiometric stripping analysis Cu and Pb can be determined using normal procedures. The determination of Cd, however, can only be carried out if the concentration of the oxidizing agent [Hg(II)] in solution is decreased. A good agreement has been obtained between the values found and those obtained after high pressure digestion of the samples.
Cadmium Copper Lead Metals, heavy Food Potentiometric stripping analysis Voltammetry Voltammetry

"Flow Injection Analysis Of High Chloride Levels In Electroplating Baths Using Online Dialysis And Potentiometric Detection"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 7 Pages 614-617
A. N. Ara&uacute;jo, M. B. Etxebarria, J. L. F. C. Lima, M. C. B. S. M. Montenegro and R. P&eacute;rez Olmos

Abstract: Electroplating bath solution (80 µL) was injected into a carrier stream (0.5 ml/min) of water which merged with a stream (2 ml/min) of 2 M Na2SO4 in a mixing coil (56 cm x 0.8 mm i.d.). The stream passed to a dialysis unit (3.5 cm long) with an acceptor stream (2 ml/min) of 0.8 mM HNO3/0.1 M KNO3 to a tabular chloride electrode with a homogeneous crystalline membrane as previously described (Ferreira et al., Ibid., 1993, 347, 314) for potentiometric measurement. The calibration graph was linear for 1.4-2.5 M chloride. Sample throughput was 30/h.
Chloride Industrial Electrode Potentiometry Dialysis Membrane

"Studies On The Elimination Of Sulfide Interference In The Potentiometric Determination Of Chloride Using Ion Selective Electrodes In A Flow Injection System"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 7 Pages 593-598
Tahir Altunbulduk, Heinz Meier zu K&ouml;cker and Wolfgang Frenzel

Abstract: Detailed investigations have been reported on the application of a common procedure using bromate in nitric acid for the removal of the interference of sulfide in the direct potentiometric determination of chloride using silver-based ion selective electrodes in a flow injection system. It is shown that this procedure is not very efficient and carries a high risk of chloride underestimation. With increasing levels of sulfide the oxidation of chloride to elemental chlorine becomes progressively significant and under certain circumstances virtually no chloride is left irrespective of its initial concentration. Hydrogen peroxide in alkaline medium is proposed as a suitable alternative for the efficient removal of sulfide without any adverse effects on the potentiometric method.
Chloride Electrode Potentiometry Interferences

"Microcolumn Preconcentration And Gas Chromatography-microwave Induced Plasma-atomic Emission Spectrometry (GC-MIP-AES) For Mercury Speciation In Waters"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 4-5 Pages 456-460
M. L. Mena, C. W. McLeod , P. Jones, A. Withers, V. Minganti, R. Capelli and P. Quevauviller

Abstract: A novel method for the direct determination of mercury species at the ng L-1 level in natural waters is described. Methyl-, ethyl- and inorganic mercury are pre-concentrated on a sulphhydryl cotton microcolumn incorporated in a flow injection system. Retained mercury species are then eluted with hydrochloric acid solution (3 mol/l) and subjected to phenylation before determination by gas chromatography-microwave induced plasma-atomic emission spectrometry. Limits of detection for mercury species are 10 ng L-1 for methyl- and ethyl-mercury and 16 ng L-1 for inorganic mercury based on processing 200 mL of sample. Application of the methodology to waters of the Manchester Ship Canal revealed elevated levels of methylmercury and inorganic mercury.

"On Line Speciation Of Selenium(VI), Selenium(IV), And Trimethylselenium By HPLC-microwave Oven-hydride Generation-atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 4-5 Pages 438-442
M. G. Cobo-Fern&aacute;ndez, M. A. Palacios, D. Chakraborti, P. Quevauviller and C. C&aacute;mara

Abstract: An on-line system is proposed consisting of an anion-exchange chromatographic column, microwave-induced thermooxidation of trimethylselenium in the presence of persulphate, and microwave-induced thermoreduction of Se(VI) to Se(IV) in HCl medium, followed by hydride generation and atomic absorption for the determination of trimethylselenium (TMeSe), Se(IV) and Se(VI). Trimethylselenium is eluted in the dead volume of an anion-exchange column (Hamilton PRP-X-100), before elution of Se(IV) and Se(VI). Optimum chromatographic conditions have been obtained using 100 mmol L-1 phosphate buffer (pH=6.8) H2PO 4 - /HPO 4 2- as the mobile phase. Recoveries were around 100%, absolute detection limits were 1.1, 1.4 and 2.2 ng for TMeSe, Se(IV) and Se(VI), respectively. Precision was lower than 10% in all cases. The method has been applied to tap water.
Selenium(IV) Selenium(VI) Trimethylselenium HPLC Spectrophotometry Microwave Speciation Volatile generation Volatile generation

"Sequential Speciation Of Selenium By Flow Injection Cathodic-stripping Voltammetry"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 4-5 Pages 433-437
D. W. Bryce, A. Izquierdo and M. D. Luque de Castro

Abstract: A schematic is given of the flow injection manifold used. For Se(IV), the sample loop was filled with sample and deposited onto a vitreous C electrode at 0.0 V for 3.5 min. After stopping the flow for 15 s, a cathodic scan was applied from 0.0 to -0.9 V and Se was stripped at -0.54 V; the current being proportional to the concentration of Se(IV). For Se(VI), the Se must be reduced to Se(IV) for measurement. Sample (5 ml) was mixed with 10 mL 6 M HCl in a covered beaker and heated at 70°C for 1 h. After cooling, the solution was diluted to 50 mL with water and then again with 0.1 M HCl. Se(IV) was then determined as above and Se(VI) was calculated from the difference of the resulting currents between the reduced and non-reduced samples. Calibration graphs were linear from 0.5-30 ng/ml of Se(IV) and Se(VI). Ag/AgCl was used as the reference electrode together with a Au auxiliary electrode. The effects of interfering species are discussed. The method was applied to Se speciation in natural waters.
Selenium(IV) Selenium(VI) Environmental Voltammetry Electrode Heated reaction Interferences Sequential injection Speciation Stopped-flow

"Separation Techniques In Speciation Analysis For Organometallic Species"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 4-5 Pages 351-377
Joanna Szpunar-obiska, Claudia Witte, Ryszard &#321;obinski and Freddy C. Adams

Abstract: A comprehensive review of the state-of-the-art of the separation of various organically-bound metals and metalloids for speciation analysis is presented. Recent developments in chromatographic (gas, liquid and supercritical fluid), electrophoretic (free-flow and gel) and fractionation techniques are discussed, followed by a survey of pertinent applications to speciation analysis for organometals and metalloids. The required sample characteristics for a given separation technique are specified and appropriate derivatization procedures are characterized. Methods applicable to the speciation of organic species of a particular element in various matrices are critically evaluated.
Organometallic compounds Speciation

"Flow Injection Spectrophotometric Determination Of Residual Free Chlorine And Chloramine"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 2-3 Pages 335-337
Anupama Chaurasia and Krishna K. Verma

Abstract: Reagent (2,4-dinitrophenylhydrazine in H2SO4 and HCl or acetic acid; preparation details given) was injected into a carrier stream (0.36 ml/min) of 0.2 M KCl adjusted to pH 1 with 0.2 M HCl and the carrier stream merged with the sample stream (0.93 ml/min). The merged stream passed through a reaction coil (105 cm x 0.5 mm i.d.) and the absorbance was measured at 360 nm. Beer's law was obeyed for 0.1-10 mg/l chlorine with a detection limit of 0.05 mg/l. The effects of foreign ions are tabulated. The method was applied to the analysis of natural and drinking water with RSD of 2.3% for chlorine and chloramine.
Chlorine, residual, free Chloramide Water Environmental Spectrophotometry Interferences Speciation

"Aqueous Ethylation Of Organotin Compounds In Simple Solution For Speciation Analysis By Cryofocussing And Detection By Atomic Absorption Spectrometry - Comparison With Hydride Generation"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 2-3 Pages 230-236
F. M. Martin and O. F. X. Donard

Abstract: A 23 factorial experimental design has been used to determine the optimum reaction conditions for organotin ethylation in simple aqueous solutions for speciation by Cryogenic Trapping/ Gas Chromatography/Atomic Absorption Spectrometry (CT/GC/AAS). The factors chosen and their levels of variation (- and +) were the pH of the solution (levels 3 and 5), the amount of NaBEt4 added (levels 1 and 9 mg) to the organotins and the time of ethylation reaction (levels 10 and 20 min). Optimum conditions were investigated for monomethyltin (MMT), diethyltin (DET) and dibutyltin (DBT) in mixed solution at a concentration of 10 ng of each Sn compound in 50 mL of solution (200 ng L-1). The influence of the different factors on the yield of the ethylation reaction in the ranges investigated depends on the degree of substitution and the nature of the alkyl groups of the organotins. The ethylation reaction for DET and DBT is more efficient at high pH levels, MMT gives higher yields at lower pH. Both MMT and DET require a high amount of reagent, while reagent concentration has no real influence on the DBT signal. Comparison of hydride generation and ethylation as derivatization procedures for organotin speciation has been performed in simple solutions. Under these analytical conditions, hydride generation is shown to be slightly more sensitive than ethylation by a factor of 1.4 for MMT and DET and 2 for DBT. However derivatization using ethylation provides more reproducible results and is not affected by inorganic interferents.
Tin Spectrophotometry Method comparison Volatile generation Speciation Volatile generation

"Tandem Online Dialysis With A Double And Single Dialyser In Flow Injection Dialysis-simultaneous Determination Of Calcium And High Chloride In Industrial Effluents"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 2-3 Pages 181-185
Jacobus F. van Staden

Abstract: A previously described online double membrane dialyser (cf. Ibid., 1993, 346, 723) was coupled in series with a single dialyser in the tandem mode in a flow injection manifold for the cited analysis (diagram given). The double online dialyser separated the analytes from interferents by dialysing a single sample plug into two different recipient streams. The resulting Ca plug was channelled to the detector immediately; the chloride plug was dialysed, and the dialysate was channelled to the detector. Details of the chromogenic reagents used are given. Detection was performed at 480 and 580 nm for chloride and Ca, respectively. A sampling rate of 90 samples/h was achieved with RSD of 1.0% for free Ca and 0.8% for high concentrations of chloride, respectively. The method was used for the analysis of industrial effluents containing 5-60 g/l of chloride and 100-1500 mg/l of Ca. Results are discussed.
Calcium Chloride Industrial Spectrophotometry Dialysis Dual membrane Interferences Chromogenic reagent

"Flow-through Voltammetry (FTV) With The Hanging Mercury Drop Electrode (HMDE)"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 2-3 Pages 154-157
D. Saur and E. Spahn

Abstract: A flow-through cell with integrated hanging mercury drop electrode for voltammetric, inverse voltammetric, adsorptive voltammetric, and chronoamperometric methods is described. HMDE droplets are automatically formed and renewed. By optimizing the flow-channel the sensitivity could be increased approximately five times in comparison with batch methods using the same deposition conditions.
Voltammetry Electrode

"A Continuous-flow Instrument With Flow Regulation And Automatic Sensitivity Range Adaptation For The Determination Of Atmospheric Hydrogen Sulfide"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 27-32
W. Jaeschke Contact Information, H. Schunn and W. Haunold

Abstract: A continuous-flow instrument (schematic of experimental set-up given) was developed for atmospheric H2S concentrations from 0.138-17.5 µg/m3. The flows were regulated by flow sensors connected to pumps via a feedback circuit. The instrument operates in two sensitivity ranges, viz., high and low. In the presence of low H2S concentrations (1.75 µg/m3) the instrument runs with low flow rate (0.37 ml/min) in high H2S concentrations (1.75 µg/m3) the pumps switch to a higher flow rate (1.13 ml/min) ensuring a linear quenching signal. The instrument was tested during field measurement in the tropics.
Hydrogen sulfide Environmental Gas phase detection Quenching

"Evaluation Of A Diffusive Sampling Method For The Determination Of Atmospheric Ammonia"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 19-26
Wolfgang Frenzel, Ewald Grimm and Gesa Gruetzmacher

Abstract: NH3 was collected in H3PO4 coated bottoms of glass phials followed by FIA. The samplers (3 at each site) were covered with a hydrophobic microporous membrane (PTFE tape) and hung upside down. After exposure, the tube-type samplers were opened under NH3-free air and 1 mL water was pipetted into each phial. After shaking, a 320 µL portion of the solution was pipetted into FIA system. Sample was mixed with a water carrier stream (1.4 ml/min) via an FIA manifold (schematic given) and 10 g/l NaCl in 1 M NaOH (0.4 ml/min) in a mixing coil. The resulting stream was mixed with an acceptor stream of 0.1 g/l bromocresol purple (0.6 ml/min) in a gas diffusion unit comprising channels (33 cm x 3 mm width x 0.1 mm depth). Detection was spectrophotometrically at 585 nm. The calibration range was linear from 0.5-100 µg/l (as NH3) and RSD were 1-3%. The standard deviation (n = 30) of the method was 0.33 ng and the sampling frequency was 20 samples/h. The detection limit under optimized conditions was 2.3 x 103:m3 s. The method was applied to outdoor and indoor measurements.
Ammonia Indoor Outdoor Spectrophotometry Gas diffusion Optimization

"Applicability Of Microwave Induced Plasma Optical Emission Spectrometry (MIP-OES) For Continuous Monitoring Of Mercury In Flue Gases"
Fresenius J. Anal. Chem. 1995 Volume 351, Issue 1 Pages 11-18
V. Siemens, T. Harju, T. Laitinen, K. Larjava and J. A. C. Broekaert

Abstract: The applicability of microwave-induced plasma optical emission spectrometry (MIP-OES) for continuous monitoring of the environmentally hazardous element mercury in flue gases has been studied. Microwave induced plasmas have been sustained using both a TM010 cavity (Beenakker resonator) and a so-called Surfatron. The analytical figures of merit for mercury in argon and helium discharges with both types of low-power micro-wave discharges have been examined. To determine mercury in artificial stack gases non-mixed argon/nitrogen discharges have been tested using a tangential flow torch design which allows to introduce a metal-loaded nitrogen gas flow as external gas and argon as internal gas. The addition of main flue gas components such as water vapor (concentration <6 g/m3), oxygen (<4% v/v) and carbon dioxide (<15% v/v) decrease the mercury line intensities to a considerable extent. Trace gases (CO, HCl, SO2, NO) in concentrations typical to waste incineration processes have been found to have no effect on the mercury and the argon line intensities. The detection limit of mercury in nitrogen is 8 g/m3 using the TM010 MIP and 10 g/m3 using the Surfatron. As such low detection limits are below the emission limit values of present-day environmental legislation MIP-OES is useful for on-line monitoring of mercury.
Mercury Waste Spectrophotometry Process monitoring

"Preconcentration Of Inorganic Selenium Species (selenium(IV) And Selenium(VI)) In An Alumina Filled Micocolumn And Online Determination By Hydride Generation Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 12 Pages 667-670
A. Larraya, M. G. Cobo-Fern&aacute;ndez, M. A. Palacios and C. C&aacute;mara

Abstract: A flow injection system has been developed consisting of on-line pre-concentration of selenium species in a microcolumn filled with activated alumina, reduction of Se(VI) to Se(IV) and determination by HG-AAS. When 0.01 mol/L HNO3 is used both as carrier and activation reagent for the alumina microcolumn, up to 150 ng of Se(IV) and Se(VI) can be pre-concentrated and quantitatively eluted by 500 L of 2 mol/L NH3. The pre-concentration factor is 50 when 25 mL of sample is used. The detection limit is about 6 ng/L, the precision is 5% for low concentrations such as 150 ng/L and 3% at high concentrations such as 120 ng/mL. The proposed method is suitable for natural water samples and inorganic Se speciation can be performed by determining Se(IV) and total selenium [Se(VI) is evaluated from the difference].
Selenium(IV) Selenium(VI) Spectrophotometry Column Alumina Volatile generation Preconcentration Volatile generation

"Continuous-flow Hydride Generation For The Preconcentrationand Determination Of Arsenic And Antimony By GFAAS"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 12 Pages 662-666
Maciej Walcerz, Slawomir Garbo, Ewa Bulska and Adam Hulanicki

Abstract: A method has been developed for the determination of arsenic and antimony at sub-ppb level using hydride pre-concentration inside the graphite furnace. The influence of the quality of the graphite surface, of its modification with palladium coating and of the ways of introducing hydride into the furnace on the analytical signal is discussed. After optimization of system parameters, detection limits of 25 and 36 pg were obtained for arsenic and antimony. Characteristic masses (for arsenic and antimony, respectively) were 31 and 33 pg/0.0044 A s for direct injection GFAAS and 69 and 57 pg/0.0044 A s for hydride in situ pre-concentration and atomization in the palladium coated graphite tube. Therefore the overall efficiency of the hydride generation and trapping was estimated to be 45 and 58% for arsenic and antimony, respectively
Antimony Arsenic Spectrophotometry Preconcentration Volatile generation Volatile generation

"Application Of The Photoionization Detector For Single Determinations Of Hydride Forming Elements"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 12 Pages 659-661
Steffen Mergemeier and Fritz Scholz

Abstract: The application of a photoionization detector in conjunction with a flow-through system is described for the determination of arsenic, antimony, selenium, tellurium, bismuth, tin, sulfide and ammonia. The analytical procedure is based upon a preliminary generation of the hydride compounds, their subsequent transfer to the gas phase and finally their detection in the photoionization detector. Linear calibration curves were obtained over three to four orders of magnitude with the following 3s-detection limits: 4 ng/ml As, 0.3 ng/ml Sb, 0.5 ng/ml Se, 3.0 ng/ml Te, 0.1 g/ml Bi, 0.5 g/ml Sn, 10.0 ng/ml S2-, 0.5 g/ml NH3.
Photoionization Volatile generation Volatile generation

"Gran's Plot Titration And Flow Injection Titration Of Sulfate In Ground And Drinking Water With A Barium Ion-selective Electrode"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 10-11 Pages 630-632
O. Lutze, B. Ro&szlig; and K. Cammann

Abstract: The application of a barium ion-selective electrode for the determination of sulfate is reported. Titrations in the batch mode using the Gran's plot method [1] have been carried out. In the presence of a lithium acetate buffer and after the addition of isopropanol it has been possible to determine sulfate with a relative standard deviation (RSD) of 1.5%. The concentration range of the samples was 5-400 mg sulfate/l. Interfering ions were separated by cation-exchange. This indirect titration constituted the basis of a flow injection titration (FIA titration) system for the continuous determination of sulfate. By plotting the peakwidth vs. the logarithm of the sulfate concentration of the injected samples, linear calibration graphs in the range of 50-200 mg sulfate/l were obtained. In this system, the sample stream was pumped through an ion-exchange column, mixed with a buffer stream of lithium acetate and injected in a reagent stream of a BaCl2 solution. The resulting free Ba(II) concentration was monitored with a barium ion-selective electrode. The content of sulfate in ground and drinking water samples has been determined with a RSD between 1.2% and 1.3%.
Sulfate Water Ground Electrode Indirect Precipitation Titrations

"High Performance Flow Flame Atomic Absorption Spectrometry For Interference-free Trace Determination"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 7-9 Pages 481-486
G. Schaldach and H. Berndt

Abstract: In High Performance Flow Atomic Spectrometry (HPF-AS), the aerosol is generated by injecting the sample solution into the gas mixing chamber with the aid of an HPLC pump (Hydraulic High Pressure Nebulization, HHPN, working pressure about 200 bar). Using an additional analytical HPLC column, between sample injection valve and nebulization nozzle, the elements under investigation can be separated from interfering elemental traces or major components (High Performance/Pressure Flow System, HPF). The elements to be determined and the interfering substances reach the flame at different times. This means, for example, that traces of Mg in solutions containing aluminum can be determined without interference. Compared to pneumatic nebulization, there is a 20 fold increase in the detection power when determining calcium in a saturated NaCl solution. HPF-AS is a rapid and sensitive method which allows separation of the calcium from the matrix with subsequent determination in less than 90 s.
Spectrophotometry Interferences

"Flow Injection Flame Atomic Absorption Spectrometry For Slurry Atomization: Determination Of Manganese, Lead, Zinc, Calcium, Magnesium, Iron, Sodium And Potassium In Cements"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 6 Pages 359-364
M. A. Bautista, C. P&eacute;rez Sirvent, I. L&oacute;pez Garc&iacute;a and M. Hern&aacute;ndez C&oacute;rdoba

Abstract: Cements of varying silica content (details given) were made in to a slurry in the 0.05-0.25% (m/v) range, by weighing appropriate amounts and adding 50 mL of a 30% glycerol/2% HNO3/2% HF solution. The suspensions were submitted to ultrasound for 10 min and stirred for a further 50 min. Portions (50-200 µL) were taken for analysis, while the suspension was being stirred, and fed straight into one of the two flow injection manifolds, (i) for direct injection and (ii) for on line dilution of the slurries (details given). The carrier was water (5 ml/min). For those instances where the online device was used, 0.1% suspensions were prepared in a similar way, but the suspension medium also contained 0.5 g solid lanthanum nitrate. The carrier was 5% glycerol and 1% lanthanum nitrate solution (4 ml/min). Calibration was performed using aqueous standard solutions under the same experimental conditions. Results are tabulated and agreed with those obtained by conventional procedures.
Manganese Lead Zinc Calcium Magnesium Iron Sodium Potassium Commercial product Sample preparation Spectrophotometry Slurry Suspension Method comparison

"Elimination Of Interferences From Copper, Lead, Silver, Gold, Platinum, Palladium And Selenium In The Determination Of Mercury By CVAAS Using Sodium Tetrahydroborate(III) Reduction In Copper Concentrates"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 3 Pages 178-180
Ewa Szmyd and Irena Baranowska

Abstract: The determination of mercury in the presence of Cu, Pb, Ag, Au, Pt, Pd, Se and As by cold vapor atomic absorption spectrometry was studied. Sodium tetrahydroborate(III) was used as a reducing agent. All the elements examined except arsenic exhibited strong interferences. A solution of 1,10-phenanthroline and thiosemicarbazide in 1.5% HCl solution was used as a masking agent. A highly effective reduction of interference by Cu, Ag, Au, Pt, Pd and Se was achieved. The results obtained were applied to the determination of mercury in a copper concentrate.
Mercury Copper concentrates Spectrophotometry Interferences Volatile generation Volatile generation

"Development Of An Automated Technique For The Speciation Of Arsenic Using Flow Injection Hydride-generation Atomic Absorption Spectrometry (FI-HG-AAS)"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 1-2 Pages 44-48
T. R. R&uuml;de and H. Puchelt

Abstract: Sample solution (0.5 ml) was injected into a HCl carrier stream (10 ml/min) which then merged with a reagent stream (6 ml/min) containing 37 mM KBH4 in 5 mM NaOH. The mixture passed through a stripping coil to a gas-liquid separator and the AsH3 was measured by AAS at 193.7 nm. With a carrier of 4 M HCl, only As(III) reacted. Using a carrier of 0.165 M HCl, containing 1 mg/l of KMnO4, As(III) was oxidized to As(V), and hence the sum of monomethylarsonic acid (I) and dimethylarsinic acid (II) was obtained. Using a carrier of 0.025 M HCl containing 1 mg/l of KMnO4, the sum of (I) and (II) was also obtained. The individual concentrations of (I) and (II) were calculated from their different sensitivities under the two sets of conditions. Using a carrier containing 0.85 mM tartaric acid and 1 mg/l of KMnO4, all four species were determined. Detection limits were 0.2-0.5 ng/ml.
Arsenic(3+) Arsenic(5+) Dimethylarsenic Monomethylarsine Environmental Spectrophotometry Speciation Volatile generation Volatile generation

"Speciation Of Mercury In Soils And Sediments By Thermal Evaporation And Cold Vapor Atomic Absorption"
Fresenius J. Anal. Chem. 1994 Volume 350, Issue 1-2 Pages 18-20
G. Bombach, K. Bombach and W. Klemm

Abstract: Evaporation studies of mercury in several chemical compounds, soils, and sediments with a high content of organic matter indicate that a quantitative release is possible at temperatures as low as 400°C. The desorption behavior from a gold column is not influenced. Only from samples with a thermal prehistory, such as brown coal ash, did mercury evaporate at higher temperatures. Qualitative conclusions can be derived about the content of metallic mercury as well as mercury associated with organic matter or sulfide. A comparison of the analytical results obtained by using the evaporation technique or by dissolving using a mixture of concentrated HCl and HNO3 shows good agreement; the advantages of the evaporation technique are obvious at very low mercury concentrations.
Mercury Environmental Environmental Sample preparation Spectrophotometry Volatile generation Heated reaction Speciation Volatile generation

"Individual And Simultaneous Determination Of Ephedrine And Phenylephrine By The Use Of Kinetic Methodology"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 12 Pages 824-828
B. Gala, A. G&oacute;mez-Hens and D. P&eacute;rez-Bendito

Abstract: A 0.1 mL portion of 0.2 mM NaIO4 and 0.5 mL 1 M KHCO3 were added to a solution of ephedrine (I) and phenylephrine (II) (140 µg/ml of I and or II in a final volume of 10 ml); after 5 min 0.75 mL 0.4 mM NaAsO2 was added and the mixture diluted to 10 mL (Solution A). One of the two 2 mL reservoir syringes of a stopped-flow module was filled with a solution containing 0.8 mM HCl, 1.2 mM 2-methylbenzothiazole-2-one hydrazone and a volume of A containing aldehydes corresponding to 0.7-70 µg/ml of I or II. The other was filled with a solution that contained 0.14 mM FeCl3 and 0.64 mM sulfamic acid. A 0.15 mL portion from each was transferred to a mixing chamber at 50°C. Absorbance was measured at 620 nm for 2 min and data processed by linear regression program. Reaction rates were measured from 30-90 s after the start of the reaction. Calibration graphs were linear for 0.7-70 µg/ml of I and 1.2-70 µg/ml of II, respectively. The mean recovery of I was 103.2% and synthetic mixtures containing I/II ratios between 3:1 and 1:5 were resolved.
Ephedrine Phenylephrine Spectrophotometry Stopped-flow Heated reaction Kinetic Simultaneous analysis

"Kinetic Fluorimetric Determination Of Aminoglycoside Antibiotics By Use Of OPA And N-acetylcysteine As Reagents"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 12 Pages 820-823
P. Izquierdo, P. Pav&oacute;n, A. G&oacute;mez-Hens and D. P&eacute;rez-Bendito

Abstract: One of the two 5 mL reservoir syringes of a stopped-flow module of a fluorescence spectrometer was filled with a solution containing 0.15 mM borate buffer of pH 9.2, 2 mM o-phthaldialdehyde (OPA) and 3 mM N-acetylcysteine and the other with 0.15 mM borate buffer and an aminoglycoside antibiotic, amikacin (I), kanamicin (II) or tobramycin (III) at a final concentration of 0.05-30 µg/ml. A 0.15 mL portion from each syringe was transferred to a mixing chamber (1 cm path length) at 25°C and the fluorescence measured at 455 nm (excitation at 335 nm) throughout the reaction. The initial-rate procedure, based on the measurement of the slope of the kinetic curve fluorescence intensity vs. time, which is proportional to the analyte concentration was applied. Calibration graphs were linear for 0.05-30 µg/ml of I. Three equations were required to cover the concentration ranges 0.05-1 µg/ml, 1-10 µg/ml and 10^-30 µg/ml. The detection limit was 0.02 µg/ml. RSD (n = 11) were 1.8 and 0.9% for 0.5 and 12 µg/ml of I. I/interferent ratios of 1:50 and 1:4 were tolerated for penicillins and tetracyclines respectively. The mean recovery was 98.7%.
Aminoglycosides Amikacin Kanamycin Tobramycin Biological Fluorescence Kinetic Interferences Stopped-flow

"Labile Complexes Of Trace Metals In Aquatic Humic Substances: Investigations By Means Of An Ion Exchange-based Flow Procedure"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 12 Pages 800-807
P. Burba, J. Rocha and D. Klockow

Abstract: The lability/inertness of heavy metals bound in aquatic humic substances (HS) has been characterized by means of ligand exchange with cellulose-immobilized triethylenetetramine-pentaacetic acid (TETPA) applying a flow system. On the basis of high metal distribution coefficients, Kd of 103 to 104 (ml/g) on cellulose TETPA even in slightly acidic HS solutions, labile and inert metal fractions in HS are characterized by their different kinetics and degree of phase exchange in small TETPA columns. For traces of metals bound to dissolved HS, the lability order Cd Mn(II)>Zn>Pb>Co>Ni>Cu is revealed. Systematic variation of environmentally relevant parameters shows the strong influence of the pH value and the ratio of metal loading/complexing capacity on the metal lability in HS. Surprisingly, in the case of freshly formed HS/Ni and HS/Cu complexes, slow transformation processes occur which lower their initial lability by one order of magnitude and supposedly increase their thermodynamic stability.
Metals, trace Ion exchange

"Sensitive Detection Of Ionic Organolead Compounds By Coupling Hydride Generation With Transversely Heated Graphite Atomizer-atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 10-11 Pages 738-742
D. Erber, J. Bettmer and K. Cammann

Abstract: Ionic alkyl-lead compounds were determined using a FIA system having an Ar flow rate of 75 ml/min, 2.5% tartaric acid for HG, 4% H2O2 for mobilization of the hydride products and 0.5% NaBH4 reducing agent. The furnace temperature was 350°C for injection, 600°C for pre-treatment, 1600°C for atomization and 2400°C for glow-out and AAS peak heights were measured at 283.3 nm using a Perkin-Elmer Model 4100 ZL spectrometer. For di- and trimethyl-lead and di- and triethyl-lead in the concentration range 0.1-5 µg/l (as Pb), a sample loop of 1.5 mL gave linear calibration graphs except for trimethyl-lead which showed linearity from 0.1-2 µg/l. The detection limits of the four compounds were 19, 7, 25 and 21 ng/l, respectively, with RSD of 2.6-5.8%. Increasing the sample volume to 6 mL gave a detection limit of 1.5 ng/l for trimethyl-lead; use of a continuous-flow system with enrichment of a 50 mL sample gave detection limits 1 ng/l.
Trimethyllead Dimethyllead Triethyllead Diethyllead Spectrophotometry Volatile generation Preconcentration Volatile generation

"Advances In Photolithographically Fabricated ENFET Membranes"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 8-9 Pages 666-669
Astrid Z&uuml;rn, Beatrice Rabolt, Manfred Gr&auml;fe and Helmut M&uuml;ller

Abstract: ENFET (enzyme FET) biosensors were constructed by coating an n-channel depletion mode ISFET (1.2 x 4.2 mm) with a solution of acrylamide, Michler's ketone, benzophenone, bisacrylamide and urease in aqueous 50% ethanol. The coated chip, which contained two ISFET gates (16 x 400 µm) with SiO2/Si3N4 gate insulator, was exposed to UV radiation through a mask and the crosslinked membrane was developed by washing with water. When used in a flow injection system a biosensor obtained from a coating solution containing 40 mg/ml of urease showed a high sensitivity to urea with a linear calibration range from 1-500 mM and a response time (95%) of 20 s. The response was not inhibited by exposure for 5 min to 10 mg/l of Cu(II) at 1.8 ml/min. The biosensors were stable for 30 days either dry or immersed in buffer solution. Compounds present in serum or waste water from urea production did not interfere. Biosensors obtained from coating solution containing 7 mg/ml of urease were used to detect pesticides, e.g., down to 0.1 µg/l of Carbofuran, by monitoring the inhibition by the pesticides of the biosensor urea response. These biosensors should be useful in screening for pesticides in drinking water.
Urea Pesticides Blood Serum Waste Water Sensor Spectrophotometry Field effect transistor Interferences

"Analytical Possibilities Of Microelectrode Use For Stripping Voltammetry"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 8-9 Pages 646-649
Frank-Michael Matysik Contact Information, Petra Gl&auml;ser and Gerhard Werner

Abstract: A microelectrode capillary flow injection system (cf Matysik and Werner, Analyst (London), 1993, 118, 1523) was used to determine Pb2+ in 1.3 µL of water giving a linear calibration range of 10^-95 µg/l, a detection limit of 6 µg/l, and an RSD (n = 8) for 20 µg/l of Pb2+ of 3.2%. The use of hemispherical or disc Pt/Hg electrodes in anodic differential pulse stripping-voltammetric determination of 1 mg/l of Pb2+ in 1 mM HNO3 with deposition for 2 min at -1 V vs. Ag/AgCl, scan rate 10 mV/s and pulse amplitude 40 mV was studied. For 25-60 µm diameter disc micro-electrodes the RSD obtained without stirring during accumulation (0.38-0.76%) were lower than those obtained with stirring at 1000 or 2000 rpm (0.72-1.67%). The peak heights obtained using quiescent accumulation were significantly less than those obtained with stirring for larger electrodes but for micro-electrodes with diameter 30 µm these peak height differences were slight. The use of micro-electrodes to determine low µg/l levels of Cu2+ in whisky and Cd2+ and Pb2+ in drinking water is also described.
Cadmium(2+) Copper(II) Lead(2+) Whisky Water Voltammetry Electrode

"Amperometric Method For Online Cyanide Detection"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 8-9 Pages 597-602
H. D. Suschke, H. Kaden and U. Enseleit

Abstract: An amperometric method for the detection of cyanide has been developed based on the anodic dissolution of gold in solutions containing cyanide. The method is characterized by a cyclic regeneration of the electrode surface. During the regeneration, the surface layers on the electrode are dissolved. By selection of suitable measuring potentials for the cyanide, linearity can be shown to exist between current and cyanide concentration over the concentration ranges from 0 to 10 mg/l and 10 to 100 mg/l. The lowest detection level is about 0.05 mg CN-/l. Determinations in the concentration range investigated are possible at a measuring potential of E=270 mV. The method is suitable for detecting the end point during the decontamination of cyanide-containing sewage. The influence on the results of pH, temperature, flow rate, heavy metal content, type of decontamination agent and the presence of brighteners is discussed.
Cyanide Amperometry Process control

"The Wickbold Combustion Method For The Determination Of Mercury Under Statistical Aspects"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 7 Pages 502-509
D. Erber, L. Quick, F. Winter, J. Roth and K. Cammann

Abstract: The Wickbold combustion method was used in the decomposition of environmental materials for the determination of Hg with use of a Perkin Elmer flow injection - cold vapor AAS analysis system. The method was applied to eight standard reference materials and the data were analyzed using a range of statistical procedures that are recommended for equality assurance purposes. For sample portions containing 1000 µg of Hg it was possible to decompose organic and inorganic samples quantitatively. The limit of detection was 2 µg/kg of Hg with a sample portion of 10 g.
Mercury Environmental Spectrophotometry Sample preparation Reference material

"Electrochemically Prepared Glucose Biosensors: Kinetic And Faradaic Processes Involving Ascorbic Acid And Role Of The Electropolymerized Film In Preventing Electrode-fouling"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 7 Pages 497-501
D. Centonze, A. Guerrieri, F. Palmisano, L. Torsi and Pier G. Zambonin

Abstract: A systematic study is presented of the influence of ascorbic acid on the response of glucose biosensors based on glucose oxidase (I) immobilized in electropolymerized poly(o-phenylenediamine) (PPD), or overoxidized poly(pyrrole) films on a Pt electrode. The homogeneous reaction between ascorbic acid and enzymatically generated H2O2 is too slow to influence the response of a I-PPD sensor or other sensors with similar response times (~1 s). Electrode fouling by electro-oxidation products of ascorbic acid may present problems when working in continuous-flow or batch mode but is of no significance in flow injection arrangements. Electrode fouling can be avoided by use of a membrane e.g. overoxidized poly(pyrrole) which is highly impermeable towards ascorbic acid.
Glucose Electrode Electrode Sensor Interferences Kinetic

"Elimination Of Parasitic Signals Caused By Gas Bubbles By Integrating Separation And Detection In Continuous-flow Systems"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 7 Pages 483-486
M. T. Tena, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: A systematic study was made of the influence of gas bubbles, either injected into or generated in situ by chemical reaction, on the signal responses obtained with various designs of flow-through photometric detectors employed in continuous-flow systems. Parasitic signals caused by gas bubbles could be eliminated by use of a flow cell packed with C8-bonded silica beads (60-100 µm) or SP Sephadex (40-120 µm) particles.
Carbon dioxide Environmental Sephadex C18 Debubbler

"Flow Injection Analysis Of Cationic Disinfectants In Pharmaceuticals Using Ion Associates Formed Between Sulfonaphthalein Dyes And Quinidine"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 6 Pages 475-476
T. Sakai, H. Ohta, N. Ohno and H. Sasaki

Abstract: The extraction - flow injection apparatus was as previously described (cf. Analyst, 1992, 177, 295). Sample solution (0.18 ml) were injected into a carrier steam (0.95 ml/min) of buffer of pH 7.8. The reagent solution contained 0.1 mM quinidine and 40 µM-bromochlorophenol blue in 1,2-dichloroethane and was also pumped at 0.95 ml/min. A 4 m extraction coil was used, with back-pressure tubing (2.5-5 m x 0.25 mm i.d.) to ensure good recovery (80%) of the organic phase. Absorbances of the blue ternary complex were measured at 605 nm. Calibration graphs were linear for 5-50 µM-benzethonium chloride or berberine hydrochloride (ε = 61 000). Among 12 amines tested, only sparteine, acrinol and neostigmine interfered seriously. Similar results were obtained with a reagent solution containing 50 µM-quinidine and 40 µM-bromophenol blue and a carrier of pH 6.8. The method was tested on four drug samples and gave results in good agreement with the labelled values.
Disinfectants, cationic Benzethonium Berberine hydrochloride Pharmaceutical Spectrophotometry Interferences

"Determination Of Sulfite In Wine By Flow Injection Analysis With Indirect Electrochemical Detection"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 6 Pages 469-472
N. T. K. Thanh, L. G. Decnop-Weever and W. T. Kok

Abstract: Wine was diluted 50-100-fold with 0.1 M H2SO4 in 10% ethanol. A 0.13 l portion was injected into a carrier of the same composition as the diluent. The carrier flowed over a 45 µm thick permeable PTFE membrane and the SO2 diffused into an acceptor stream of acetate buffer of pH 4.7. This merged with a reagent stream, containing 5 mM KI, which was oxidized electrochemically at 5 or 25 µA, to provide an iodine solution All streams were pumped at 0.5 ml/min; this gave an iodine concentration of 0.78 or 3.9 µM. After the reaction with SO2, the unconsumed iodine was detected amperometrically. With the 5 µA generating current, the linear range was 0.05-2 ppm; at 0.9 ppm, the RSD was 1.6%. The results compared well with those obtained by titrimetry.
Sulfite Wine Amperometry Indirect Method comparison Teflon membrane Gas diffusion Electrochemical product conversion

"Determination Of Lead In Natural Waters Using Flow Injection With Online Preconcentration And Flame AAS Detection"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 6 Pages 442-446
D. Rodr&iacute;guez, P. Fern&aacute;ndez, C. P&eacute;rez-Conde, A. Guti&eacute;rrez and C. C&aacute;mara

Abstract: Silica gel (0.063-0.2 mm) was coated with a chloroformic extract of the ion pair formed from Aliquat 336 (methyltricaprylammonium chloride) and nitroso-R-salt and the solvent was evaporated in vacuo. The product (118.3 mg) was packed in a glass column (5.5 cm x 3 mm i.d.). Water samples (5-30 ml) were mixed with 5% 0.1 M acetate buffer of pH 5.5 and were passed through the column at 1 ml/min. The retained Pb(II) was eluted with 0.15 mL of 0.1 M HCl at 2 ml/min directly to the nebulizer for analysis by AAS at 217 nm, with deuterium background correction. Calibration graphs were linear for 10^-100 ng/ml of Pb(II). Detection limits were 10, 6 and 4 ng/ml for 5, 10 and 30 mL samples, respectively. At 10 and 100 ng/ml of Pb(II), the RSD (n = 10) were 12 and 6%. The pre-concentration efficiency for 5 and 30 mL samples decreased from 100 to 50%; concentration factors were 37 and 100 times, respectively. Serious interferences were caused by Ni(II) and fluoride but these were not significant for natural waters. The results on samples of tap, ground and river water were similar to those obtained by electrothermal AAS.
Lead Ground River Water Spectrophotometry Interferences Preconcentration Silica gel Immobilized reagent

"Comparison Of The Efficiencies Of Online And High-pressure Closed Vessel Approaches To Microwave Heated Sample Decomposition"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 6 Pages 428-433
Henryk Matusiewicz and Ralph E. Sturgeon

Abstract: Two microwave heated digestion techniques have been tested with a view to the evaluation of the effectiveness of wet decomposition procedures: a high-pressure/temperature focused microwave heated and an on-line microwave heated system. The efficiency of decomposition was studied using a number of biological reference materials as well as urine and sewage plant effluent. Oxidation reagents included mixtures of nitric acid, nitric acid/hydrogen peroxide and peroxodisulphate (Oxisolv). The residual carbon content of the digestate was determined coulometrically. Pressurised decomposition of a TFM-Teflon vessel is the most effective procedure (organic material is totally oxidized with nitric acid in a single-step procedure), whereas urine and sewage plant effluent are incompletely decomposed with on-line microwave heated digestion.
Sample preparation Online digestion Microwave

"Optimized Layer Systems For Immunosensors Based On The RIFS Transducer"
Fresenius J. Anal. Chem. 1994 Volume 349, Issue 5 Pages 360-366
A. Brecht and G. Gauglitz

Abstract: As one approach to direct affinity sensing, a study was made of the use of a transducer, based on thin dielectric films, for reflectometric interference spectroscopy. The transducer system includes a 20-W tungsten white-light source, a sorted bundle of 100 µm optical fibers (17 illuminating, 8 collecting) and a Zeiss-Jena MCS diode-array spectrometer (350-780 nm). For FIA detection film-coated glass substrates are mounted in a 0.3 µL PTFE flow-cell (4.5 x 1.5 mm x 50 µm). Methods to improve the modest detection limits achieved are discussed. Detection of protein coverage down to 10 pg/mm2 was achieved. Applications for direct monitoring of immuno-reactions are being sought.
Protein Biological Spectrophotometry Sensor Interferences