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

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Solid phase extraction

Classification: Manifold process -> Solid phase extraction

Citations 100

"Fluorimetric Determination Of Fluoride In A Flow Assembly Integrated On-line To An Open/closed FIA System To Remove Interference By Solid Phase Extraction"
Talanta 2002 Volume 58, Issue 5 Pages 849-853
M. Garrido, A. G. Lista, M. Palomeque and B. S. Fernández Band

Abstract: A simple flow injection fluorimetric method for fluoride determination is proposed. The method is based on the enhanced fluorescence of quercitin-Zr(IV) complex when fluoride ion is present in the sample. An open/closed FIA manifold with a mini-column of Dowex 50W X8 resin was used to remove the most important interference (aluminum). The two FIA assemblies were integrated on-line to automate the pretreatment of the water sample and fluoride determination. The calibration graph was linear over the range 0.1-3.0 µg mL-1 of fluoride with a correlation coefficient of 0.999 and LOD 0.06 µg mL-1. The relative standard deviation was 2.5% and the sample throughput was 52 h-1 without pretreatment and 10 h-1 with pretreatment of the sample. The method was applied to the determination of fluoride in water samples. (C) 2002 Elsevier Science B.V. All rights reserved.

"Determination Of Sulfur Dioxide And Ascorbic Acid In Beverages Using A Dual Channel Flow Injection Electrochemical Detection System"
Anal. Chim. Acta 2000 Volume 416, Issue 1 Pages 105-110
Terence J. Cardwell and Melinda J. Christophersen

Abstract: A new flow injection method is described for the simultaneous determination of ascorbic acid (AA) and sulfur dioxide in red and white wines and various fruit juices. The flow injection manifold consists of a dual channel amperometric detection system, where AA is detected at a glassy carbon electrode set at +0.42 V (versus Ag/AgCl) and sulfur dioxide is detected at a platinum electrode at +0.90 V (versus Ag/AgCl) after separation by a gas diffusion unit. In the application of this method to the analysis of both analytes in wines and fruit juices, the results for white wines, fruit juices and juice concentrates agree well with data obtained by ion-exclusion chromatography. However, in the case of red wines and a sweet white wine, it is necessary to extract the analytes using solid phase extraction on a quaternary amine SAX cartridge before acceptable results are achieved by the new flow injection method. The linear dynamic range for AA is 3-50 mg/l with a detection limit of 1.5 mg/l and for sulfur dioxide the linear range is 0.25-15 mg/l with a detection limit of 0.05 mg/l. The sampling frequency for both analytes is 30/h.
Ascorbic acid Sulfur dioxide Wine Red Wine White Amperometry Electrode Electrode

"Sequential Injection Spectrophotometric Analysis Of Nitrite In Natural Waters Using An On-line Solid-phase Extraction And Preconcentration Method"
Analyst 2000 Volume 125, Issue 5 Pages 943-948
Manuel Miró, Andreu Cladera, José Manuel Estela and Víctor Cerdà

Abstract: An automatic sequential injection analysis (SIA) set-up for the isolation, pre-concentration and spectrophotometric determination of nitrite in waters based on the Shinn reaction was designed and evaluated. The system performs the on-line azo dye formation and its subsequent extraction on a solid phase (monofunctional C-18), which is held inside a glass column incorporated into the system. A large sample volume (maximum, 10 mL) is sequentially segmented with sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride by using an iterative method. The azo dye collected is eluted with a small volume of 80% methanol and conducted to a diode-array spectrophotometer for quantitative analysis. It has been proved that the retention efficiency is maintained for up to 45 sample injections of 10 mL in spite of the high chromogenic reagent acidity. Nitrite has been determined within the 13.4-160 ng mL-1 and 0.83-20 ng mL-1 ranges for 1 and 10 mL of sample, respectively. For these volumes, the detection limits are 5.9 and 0.32 ng mL-1, the enhancement factors 17 and 170 and the sample throughput 15 and 3 h-1, respectively. A maximum RSD of 4.0% was achieved in all determinations. It is an advantage of this approach that it is possible to use the same mass calibration graph for any sample volume.
Nitrite Rain Water Spectrophotometry

"Determination Of Ultratraces Of Nitrite By Solid-phase Preconcentration Using A Novel Flow-through Spectrophotometric Optrode"
Anal. Chim. Acta 2001 Volume 437, Issue 1 Pages 55-65
Manuel Miró, Wolfgang Frenzel, Víctor Cerdà and José Manuel Estela

Abstract: A novel sorbent-packed planar wall microcolumn-based optosensor coupled to a flow injection analysis system (FIA) for the determination of traces of nitrite by solid-phase spectrophotometry is presented. The methodology is based on the on-line nitrite derivatization with a modified Griess reagent to form an aze-dye whose retention onto octadecyl-covalently bonded silica gel by physical adsorption and partitioning is continuously monitored. After the analytical signal has been recorded, the sorbed compound is eluted with 80% methanol/water (v/v), rendering the system ready for the next extraction. Selection of the solid support and the suitable flow-through cell configuration are discussed in detail. By minimization of the blank signal, a concentration of nitrite as low as 1 ng/ml can be easily determined using 2.5 mi of sample. Detection limit (3s blank) of 0.46 ng/ml of nitrite, relative standard deviation better than 4%, sample throughput of 12 h-1 and an enrichment factor of 93 in relation to the conventional spectrophotometric method were obtained. The utility of the present optosensing system, wherein a mass calibration is also feasible, was testified by the satisfactory results obtained in its application to tap, rain and aquarium water samples.
Nitrite Water Rain Water Spectrophotometry Optrode

"Determination Of Pseudoephedrine In Human Plasma Using Capillary Zone Electrophoresis Coupled By Flow Injection Online Solid Phase Extraction"
Gaodeng Xuexiao Huaxue Xuebao 1999 Volume 20, Issue 11 Pages 1688-1691
Chen Hengwu Fang Zhaolun

Abstract: The previously developed hyphenated system of flow injection online solid phase extraction-capillary zone electrophoresis (FI-SPE-CZE) was adapted to the determination of trace pseudoephedrine in human plasma. Interference from the coexisting species was eliminated by off-line and online sample cleaning-up, and by optimization of CZE separation conditions. The sensitivity of hyphenated system was improved by increasing of loaded sample volume and strengthening of field-amplified stacking effect. Thus, plasma samples, after deproteinized by off-line precipitation, could be consecutively loaded onto the FI-SPE-CZE system, and trace amounts of pseudoephedrine be automatically pre-concentrated, separated and determined by the system. The adapted FI-SPE-CZE system was successfully applied to determination of trace pseudoephedrine in volunteers plasma samples for pharmacokinetic studies after administration of the drug with normal dosage.

"Flow Injection Solid Phase Extraction With Chromosorb 102: Determination Of Lead In Soil And Waters By Flame Atomic Absorption Spectrometry"
Spectrochim. Acta B 2000 Volume 55, Issue 7 Pages 1107-1114
Latif Elçi, Zikri Arslan and Julian F. Tyson

Abstract: A flow injection, solid-phase extraction, pre-concentration method was developed for the determination of lead in soil and water samples by flame atomic absorption spectrometry. Lead, in the form of the diethyldithiocarbamate complex, was retained on a miniature column of Chromosorb 102 from buffered sample solutions. Several parameters governing the efficiency and throughput of the method were evaluated including pH, eluent composition, volume and flow rate. The complex retained from pH 9.0 (ammonium acetate) solutions was eluted with 176 µl of ethanol, at 4.2 mL min-1 into the nebulizer-burner system of the spectrometer. The detection limit was 2 µg L-1 for pre-concentration at 2.2 mL min-1 for 120 s. The relative standard deviation (R.S.D) was less than 4% for concentrations down to 400 µg L-1 The procedure was validated by the analysis of NIST standard reference material 2711 (Montana Soil) which contains lead at a concentration of 1162 µg g-1. Recoveries of spike additions (100-400 µg 1-1) to artificial sea water and tap water were quantitative.

"Preconcentration Of Trace Amounts Of Platinum In Water On Different Sorbents"
Int. J. Environ. Anal. Chem. 1999 Volume 75, Issue 1-2 Pages 71-81
Godlewska Zylkiewicz, B.;Lesniewska, B.;Michalowski, J.;Hulanicki, A.

Abstract: Three different sorbents for platinum pre-concentration in water were investigated: alumina, silica gel with bonded aminopropyl groups and Cellex-T. The sorbents were tested in a microcolumn at the flow rate 3 ml/min. Elution was performed with 2.0 mol/l ammonia, 2.0 mol/l hydrochloric acid and 1.2 mol/l thiourea solution, respectively. The optimal enrichment factor was 400 for the alumina column, when the eluent volume was 25 µL Satisfactory precision was obtained for all sorbents. As the detection technique was used either FAAS or GFAAS, depending on the concentration of platinum in the eluate.

"Determination Of Cadmium, Cobalt, Chromium, Copper, Iron, Manganese, Nickel And Lead In Natural Waters, Alkali And Alkaline Earth Salts By Electrothermal Atomic Absorption Spectrometry After Preconcentration By Column Solid Phase Extraction"
Microchim. Acta 1999 Volume 130, Issue 3 Pages 185-190
Irina Karadjova

Abstract: Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and pre-concentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates -Na-DDTC (sodium diethyldithiocarbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of pre-concentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed pre-concentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 µg L-1 Cd, 0.1 µg L-1 Cr, Cu, and Mn and 0.3 µg L-1 Co, Fe, Ni and Pb in natural waters and 1.10^-7% Cd, 3.10^-7% Cr and Mn, 7.10^-7% Co, Ni and Pb and 2.10^-6% Cu and Fe in alkali and alkaline earth salts.

"Online Solid-phase Extraction Liquid Chromatography-continuous Flow Frit Fast Atom Bombardment Mass Spectrometric And Tandem Mass Spectrometric Determination Of Hydrolysis Products Of Nerve Agents Alkyl Methylphosphonic Acids By P-bromophenacyl Derivatization"
J. Chromatogr. A 1999 Volume 833, Issue 2 Pages 169-179
M. Katagi, M. Tatsuno, M. Nishikawa and H. Tsuchihashi

Abstract: For proof of the presence of chemical warfare agents sarin, soman and VX, a rapid, accurate and sensitive method which allows us to determine their hydrolysis products ethyl methylphosphonic acid, isopropyl methylphosphonic acid and pinacolyl methyl phosphonic acid was explored by using continuous flow frit fast atom bombardment (FAB) LC-MS and LC-MS-MS. After derivatization of analytes with p-bromophenacyl bromide, LC-MS-MS analyzes for screening were performed by a flow injection method. The three alkyl methylphosphonic acids (AMPAs) were eluted within 5 min, and the detection limits for the three AMPAs ranged from 1 to 5 ng/ml. For confirmation of the screening results, LC-MS-MS analysis with chromatographic separation was conducted by using a narrow bore column. The three AMPAs were all eluted with excellent separation within 25 min, and the detection limits ranged from 1 to 20 ng/ml. Quantitative measurement was performed by LC-MS in selected ion monitoring (SIM) mode with chromatogaphic separation. Linear calibration curves were obtained for the three AMPAs and the detection limits ranged from 0.5 to 3 ng/ml. The relative standard deviation for peak area ranged from 3.4 to 6.0% at 50 ng/ml for the three AMPAs.

"Determination Of Nano-molar Levels Of Formaldehyde In Drinking Water Using Flow Injection System With Immobilized Formaldehyde Dehydrogenase After Off-line Solid-phase Extraction"
Anal. Chim. Acta 1999 Volume 378, Issue 1-3 Pages 169-175
Nobutoshi Kiba, Limin Sun, Shinya Yokose, Masaki Tachibana Kazue and Tani Takashi Suzuki

Abstract: Low levels of formaldehyde were determined by pre-concentration with poly(allylamine) beads and analysis by flow injection system with immobilized formaldehyde dehydrogenase. Formaldehyde dehydrogenase was immobilized on tresylate-poly(vinyl alcohol) beads and packed into a stainless-steel column (5 cm x 4 mm). The column was incorporated in a flow injection system with fluorimetic detection. The calibration graph was linear from 0.5 to 10 µM (15-300 µg l-1). The poly(allylamine) beads (0.5 g) were used to adsorb formaldehyde present at 20-400 nM (0.6-12 µg l-1) from drinking water (11). Formaldehyde was eluted with 1 M HCl (10 ml). The solution (50 µl) adjusted to pH 9 was injected into the flow injection system. Concentration factor was 25-fold. Recovery of formaldehyde spiked into purified water was >96% with a relative standard deviation of <3.0%.
Formaldehyde Water Spectrophotometry

"High Performance Liquid Chromatographic Determination Of Phenolic Compounds In Seed Exudates Of Festuca Arundinacea And F-pratense"
Phytochem. Anal. 2000 Volume 11, Issue 6 Pages 375-379
Borivoj Klejdus, Vlastimil Kub&aacute;n

Abstract: Derivatives of benzoic and cinnamic (caffeic, protocatechuic, vanillic, ferulic, p-coumaric, p-hydroxybenzoic and syringic) acids and 3,4-dihydroxybenzaldehyde in seed exudates of Festuca arundinacea cv, Kora and F. pratense cv. Otava have been separated and quantified on a Zorbax SE C-18 Rapid Resolution™ column with linear gradient elution using a mobile phase containing acetonitrile and 0.5 % acetic acid. The USP tailing factors were less than 1.15 for all peaks. Strictly linear calibration curves (r > 0.9997) with limits of detection of 90-880 nM were obtained for all analytes in the concentration ranges from units or tenths up to 600 µM. RP 105 and OASIS™ HLB polymeric sorbents have been shown to be the best of the tested sorbents for the separation and pre-concentration of phenolic compounds from both plant materials. The solid-phase extraction procedures have been compared with classical liquid-liquid extractions and consistent results were obtained.

"Sequential Injection Fourier Transform Infrared Spectroscopy For The Simultaneous Determination Of Organic Acids And Sugars In Soft Drinks Employing Automated Solid Phase Extraction"
Anal. Chim. Acta 2000 Volume 422, Issue 1 Pages 63-69
Hai LeThanh and Bernhard Lendl

Abstract: A fully automated method for the rapid determination of organic acids (citric-, malic- and tartaric acid) and sugars (glucose, fructose, and sucrose) in soft drinks by sequential injection Fourier transform infrared (FTIR) spectroscopy is presented. A convective interaction media (CIM) disc carrying quaternary amino moieties was added as a solid phase extraction column to the flow system. Upon injection of a sample the organic acids were completely retained on the CIM disc whereas sugars passed to the flow cell. The organic acids were subsequently eluted by injection of an alkaline (pH 8.5) 1 M sodium chloride solution and recorded in their fully deprotonated form as a second flow injection peak. In both cases, the FTIR spectra corresponding to the peak maxima were selected for data evaluation. Two partial least squares models, one for sugars and the other for organic acids, were constructed based on the analysis of standards containing all six analytes. The developed method was applied to natural samples yielding results which were in good agreement with those obtained by an external reference method (enzymatic test kits). Deviations in the results were 3.4. and 4.1% for citric and malic acid and ranged from 4.7-5.1% for the sugars. The developed method is characterized by its short analysis time, experimental simplicity and its potential applications in routine analysis and process control.
Citric acid l-Malic acid Tartaric acid Glucose Fructose Sucrose Soft drink Spectrophotometry

"Selective Pre-concentration And Solid Phase Extraction Of Mercury(II) From Natural Water By Silica Gel-loaded Dithizone Phases"
Anal. Chim. Acta 2000 Volume 415, Issue 1-2 Pages 33-40
Mohamed E. Mahmoud, Maher M. Osman and Mohamed E. Amer

Abstract: Two silica gel phases loaded with dithizone were synthesized based on chemical binding and physical adsorption approaches. The stability of a chemically modified dithizone phase (I) was found to be more superior than that of a physically adsorbed one (II), especially in concentrated hydrochloric acid which was then used as a recycling and pre-concentration reagent for further uses of phase (I). The application of these two silica gel phases for sorption of a series of metal ions was performed by using different controlling factors such as the pH of metal ion solution and the equilibration shaking time by the static technique. For most metal ions, the determined metal capacity values (µmol g-1) were found to be higher in the case of phase (I) as compared to phase (II). This difference was interpreted on the basis of selectivity incorporated in these sulfur containing silica gel phases. Hg(II) was found to exhibit the highest affinity towards extraction by these silica gel phases. The pronounced selectivity was also confirmed from the determined distribution coefficient (K-d) of all the metal ions, showing the highest value reported for mercury(II) to occur by phase (I). The potential applications of phase (I) for selective extraction of mercury(II) to occur from aqueous solution were successfully accomplished as well as pre-concentration of low concentration of Hg(II) (20 pg ml-1) from natural tap water with a pre-concentration factor of 200 for Hg(II) off-line analysis by cold vapor atomic absorption analysis.
Mercury(II) Water Sea Spectrophotometry

"The Retention Of Metal Species By Different Solid Sorbents - Mechanisms For Heavy Metal Speciation By Sequential Three Column Uptake"
Anal. Chim. Acta 2000 Volume 411, Issue 1-2 Pages 223-237
O. Abollino, M. Aceto, C. Sarzanini and E. Mentasti

Abstract: An apparatus consisting of three columns packed with different substrates, namely an anion exchange resin, a reversed phase sorbent and a chelating ion exchange resin, was developed. The retention of cadmium, copper and lead onto the substrates at different pH conditions was investigated, first by considering each column separately, then by connecting them in series. The aim of the study is to distinguish among species with different charge or chemical behaviour. Experiments were performed with the free metal ions, their anionic complexes with EDTA and 8-hydroxyquinoline-5-sulphonic acid, and their neutral complexes with 8-hydroxyquinoline. The results obtained were compared with those computed according to the theoretical species distribution of all species as a function of pH. The applicability of the technique to seawater was demonstrated.
Cadmium Copper Lead Sea Spectrophotometry

"Minimization Of Lead And Copper Interferences On Spectrophotometric Determination Of Cadmium Using Electrolytic Deposition And Ion-exchange In Multi-commutation Flow System"
Talanta 2000 Volume 53, Issue 3 Pages 497-503
Jos&eacute; A. Gomes Neto, Adriana P. Oliveira, Gian P. G. Freshi, Carolina S. Dakuzaku and Mercedes de Moraes

Abstract: A new strategy for minimization of Cu2+ and Pb2+ interferences on the spectrophotometric determination of Cd2+ by the Malachite green (MG)-iodide reaction using electrolytic deposition of interfering species and solid phase extraction of Cd2+ in flow system is proposed. The electrolytic cell comprises two coiled Pt electrodes concentrically assembled. When the sample solution is electrolyzed in a mixed solution containing 5% (v/v) HNO3, 0.1% (v/v) H2SO4 and 0.5 M NaCl, Cu2+ is deposited as Cu on the cathode, Pb2+ is deposited as PbO2 on the anode while Cd2+ is kept in solution. After electrolysis, the remaining solution passes through an AG1-X8 resin (chloride form) packed minicolumn in which Cd2+ is extracted as CdCl42. Electrolyte compositions, flow rates, timing, applied current, and electrolysis time was investigated. With 60 s electrolysis time, 0.25 A applied current, Pb2+ and Cu2+ levels up to 50 and 250 mg L-1, respectively, can be tolerated without interference. For 90 s resin loading time, a linear relationship between absorbance and analyte concentration in the 5.00-50.0 µg Cd L-1 range(r2 = 0.9996) is obtained. A throughput of 20 samples per h is achieved, corresponding to about 0.7 mg MG and 500 mg KI and 5 mi sample consumed per determination. The detection limit is 0.23 mg Cd L-1. The accuracy was checked for cadmium determination in standard reference materials, vegetables and tap water. Results were in agreement with certified values of standard reference materials and with those Obtained by graphite furnace atomic absorption spectrometry at 95% confidence level. The RSD for plant digests and water containing 13.0 mg Cd L-1 was 3.85% (n = 12). The recoveries of analyte spikes added to the water and vegetable samples ranged from 94 to 104%.

"Determination Of Trace Bismuth By Solid Phase Extraction And Anodic Stripping Voltammetry In Non-aqueous Media"
Anal. Chim. Acta 2001 Volume 437, Issue 2 Pages 217-224
M. H. Pournaghi-Azar, Dj. Djozan and H. Abdolmohammad zadeh

Abstract: The voltammetric characteristics of BL(III) oxinate at the mercury electrode in chloroform are investigated. Anodic stripping voltammetry (ASV) for the determination of trace bismuth was developed in chloroform, using the differential pulse technique to strip the amalgamated bismuth from hanging mercury drop electrode (HMDE). The experimental variables such as scan rate of electrode potential, deposition potential, deposition time and stirring speed were optimized. The linear range of calibration graph and the detection Limit were 5 x 10^-8 to 5 x 10^-6,d 3.5 x 10^-9 M for Bi(III), respectively. Preceded by a pre-concentration stage by solid phase extraction using octylsilane (RP-8) cartridge and subsequent elution by chloroform, the detection limit of the method is improved in 4.5 x 10^-10 M. The suitability of the proposed method for determination of trace bismuth in real sample was established by the analysis of a metallic aluminum sample.

"An Online Solid Phase Extraction System Using Polyurethane Foam For The Spectrophotometric Determination Of Nickel In Silicates And Alloys"
Anal. Chim. Acta 1999 Volume 378, Issue 1-3 Pages 287-292
S&eacute;rgio Luis Costa Ferreira, Djane Santiago de Jesus, Ricardo Jorgensen Cassella, Antonio Celso Spinola Costa, Marcelo Souza de Carvalho and Ricardo Erthal Santelli

Abstract: The present paper describes the use of a solid phase extraction system using a polyurethane foam (PUF) minicolumn, in order to separate nickel from interferences due to other elements and determine it by flow injection analysis with spectrophotometric detection. Separation is based on the retention of thiocyanate complexes of interferent ions in the PUF minicolumn. Nickel does not form complex with thiocyanate and pass through the minicolumn and then it can be determined by using 4-(2-pyridylazo)-resorcinol (PAR) as chromogenic reagent. So, parameters such as thiocyanate concentration and pH effects on the separation efficiency, sorption capacity of the polyurethane foam minicolumn, influence of the flow rates, PAR concentration, pH effect on the chromogenic reaction, minicolumn regeneration, analytical features and others were investigated. The results demonstrated that nickel (at concentration of 0.5 mg/ml) can be quantitatively separated from iron and copper (200 mg/ml), zinc and cobalt (100 mg/ml) by using a minicolumn containing 0.125 g of polyurethane foam. Nickel can be determined with great selectivity and sensitivity and the procedure was applied for nickel determination in brass, bronze, steel and rock certified reference materials. The results showed satisfactory accuracy and precision. The limit of detection was 77 ng/ml and the RSD was 2.63%. A dynamic range from 0.25 up to 5.00 µg/ml and a sample throughput of 24 samples per hour were achieved.
Nickel Alloy Alloy Alloy Alloy Geological Spectrophotometry

"Flow Injection Determination Of Cobalt After Its Sorption Onto Polyurethane Foam Loaded With 2-(2-thiazolylazo)-p-cresol (TAC)"
Talanta 2001 Volume 54, Issue 1 Pages 61-67
Ricardo Jorgensen Cassella, Veronica A. Salim, Luciene S. Jesu&iacute;no, Ricardo E. Santelli, S&eacute;rgio L. C. Ferreira and Marcelo S. de Carvalho

Abstract: This paper reports the development of a new methodology for determination of cobalt in water samples by using a flow injection system with loaded PUF as solid phase to pre-concentrate analytes. Procedure is based on on-line retention of Co(III) ions (generated in alkaline medium by Co(II) oxidation) in a minicolumn packed with a polyether type polyurethane foam loaded with TAC (2-(2-thiazolylazo)-p-cresol) and elution with 2 mol L-1 HCl directly to the flame atomic absorption spectrometer nebulizer. Several chemical and flow variables that could affect the performance of this system were investigated as well as the possible interferents. For 2 min of pre-concentration time (10.0 mi of sample volume) the system achieved a detection limit 3.2 µg L-1 , a RSD 5% at 20 µg L-1 and an analytical throughput 24 h-1. Whereas: for 3 min of pre-concentration time (15.0 mL of sample volume) a detection limit 2.4 µg L-1, a RSD under 8% at 10 µg L-1 and a sampling frequency 17 h-1 were reported. (C) 2001 Elsevier Science B.V. All rights reserved.

"Using On-line Solid Phase Extraction For Flow Injection Spectrophotometric Determination Of Salbutamol"
Anal. Chim. Acta 2002 Volume 455, Issue 1 Pages 103-109
Dalibor &Scaron;at&iacute;nsk&yacute;, Rolf Karl&iacute;&#269;ek and Anton&iacute;n Svoboda

Abstract: In the proposed procedure, the determination of salbutamol with Folin-Ciocalteau reagent (FC) using a flow injection analysis technique (FIA) with spectrophotometric detection at 750 nm is described. The lab-made FIA system consisted of a peristaltic pump Gilson Minipulse 3 equipped with Tygon tubes, double 6-port external Vici Valco sample injector and S 2000/SAD500 fiber optic spectrophotometer. It was controlled by a PC with use of originally compiled LabVIEW(R)- supported software containing the mathematical library with various statistical functions for off-line data evaluation. Concentration, volume of reagents and flow rate were optimized by a simplex method. The proposed system was used for the direct determination of salbutamol sulfate in the tablets and the human urine without preliminary pre-treatment of the sample. The negative effect of interfering substances (excipients of the tablets and matrix of the urine) is overcome by a solid phase extraction (SPE), when salbutamol is adsorbed on the solid phase in the microcolumn, which is integrated directly into the flow system. Pre-treatment of the sample takes place directly in the flowing stream. The sample throughput without carryover of on-line SPE was 60-80 samples per hour. With the SPE column (Baker-carboxylic acid), salbutamol was determined in the linear range from 1 to 15 µg mL-1 (RSD = 1.2%), with detection limit (3s) 0.1 µg mL-1 and a frequency of 40-60 samples per hour in the water solutions. The salbutamol was determined in the linear range from 2 to 20 µg mL-1 (RSD = 1.7%), with detection limit (3s) 1 µg mL-1 and a frequency of 30 samples per hour in the samples of the human urine.

"Determination Of The Pesticide Naptalam, At The Ppb Level, By FIA With Fluorimetric Detection And Online Preconcentration By Solid-phase Extraction On C-18 Modified Silica"
Anal. Chim. Acta 1999 Volume 384, Issue 2 Pages 185-191
T. Galeano D&iacute;az, M. I. Acedo Valenzuela and F. Salinas

Abstract: The paper describes a method of flow injection analysis for the determination of the pesticide Naptalam based on its hydrolysis, in an acidic medium, to 1-naphthylamine and the measurement of fluorescence due to this product in an alkaline medium. By direct injection of Naptalam in a carrier of HCl 1.0 M, subsequent heating at 100°C in the reactor and change of the pH with a flow of NH4OH 1.5 M, concentrations >3 x 10^-6 M can be analyzed. The sensitivity of the procedure is greatly increased by using online, a column (10 cm length x 0.3 cm i.d.) filled with a C-18 modified silica packing to retain a large volume of Naptalam. The injection of a very small volume of acetonitrile is enough to elute the pesticide, thus increasing the concentration in the sample zone to a great extent. The method has been successfully applied to the analysis of Naptalam, at the ppb level, in river-water samples.
Naptalam River Fluorescence

"Stability Of Parathion-methyl, Methiocarb, DDT And 2,4-D In Solid-phase Extraction Precolumns Packed With A Polymeric Reversed Phase"
Int. J. Environ. Anal. Chem. 2000 Volume 77, Issue 4 Pages 255-268
Vera Avila, L.E.;Vazquez Lira, J.C.;Covarrubias Herrera, R.;Garcia Camacho, M.P.;Nunez Gaytan, A.M.

Abstract: The stability of parathion-methyl, methiocarb, DDT and 2,4-D, adsorbed on the polymeric PLRP-S phase packed in small stainless steel precolumns was examined, with a view to propose the use of these precolumns as alternative means for the transport of water samples. First, water samples spiked with the studied pesticide at low µg/l concentration levels were extracted and pre-concentrated in the precolumns, using appropriate conditions for a total recovery. Then, the precolumns were stored at room temperature (15-20°C) or at 35°C for different time periods. At the end of the respective period each precolumn was coupled to an HPLC column via a switching valve and was on-line analyzed by reversed phase chromatography with UV detection. The four pesticide recoveries after one week in the precolumn at room temperature were higher than 90%. The same was true at 35°C except for DDT, which suffered a 30% degradation in one week. Further studies showed that DDT and parathion-methyl were stable at least for five weeks in precolumns stored at room temperature. Methiocarb also was stable for this period but storing the precolumns at 4°C.

"Determination Of Actinide Elements At Femtogram Per Gram Levels In Environmental Samples By On-line Solid Phase Extraction And Sector-field-inductively Coupled Plasma-mass Spectrometry"
Anal. Chim. Acta 2001 Volume 433, Issue 2 Pages 245-253
Jason B. Truscott, Phil Jones, Ben E. Fairman and E. Hywel Evans

Abstract: An on-line solid phase extraction method has been developed for the determination of 232Th, 237Np, 238U, 239Pu, 240Pu, 241Am and 243Am in biological certified reference material using a column containing TRU-Spec™ resin coupled with sector-field inductively coupled plasma-mass spectrometry. Absolute detection limits were 0.7, 0.85, 0.6, and 0.65 fg for 237Np, 239Pu, 241Am and 243Am, respectively. The 239Pu was determined in NIST Human Liver (963±297 fg g-1 compared with a certified value of 848±161 fg g-1) using a dry and wet ashing sample preparation method, and in a spiked cabbage reference material (394±54 fg g-1 compared to an indicative value of 467 fg g-1) using microwave digestion. Sequential separation of Pu and U was achieved by on-column reduction of Pu with titanium(III) chloride and elution in 4 M HCl to facilitate the determination of 239Pu in samples containing high levels of 238U, thereby eliminating the interference of 238U1H+ at m/z 239. The sequential elution procedure was used to determine 239Pu in NIST human lung (814±55 fg g-1 compared with a certified range of 227-951 fg g-1) and NIST Rocky Flats Soil (2423±137 fg g-1 compared with a certified value of 3307±248 fg g-1).
Actinides Thorium-232 Neptunium-237 Americium-241 Americium-243 Plutonium-239 Plutonium-240 Uranium-238 NIST 4253 NIST 4350b NIST 4351 NIST 4352 Mass spectrometry

"On-line Preconcentration System For Lead Determination In Seafood Samples By Flame Atomic Absorption Spectrometry Using Polyurethane Foam Loaded With 2-(2-benzothiazolylazo)-2-p-cresol"
Anal. Chim. Acta 2001 Volume 441, Issue 2 Pages 281-289
Valfredo A. Lemos and S&eacute;rgio L. C. Ferreira

Abstract: In the present paper, an on-line system for enrichment and determination of lead is proposed. It is based on the chemical sorption of lead(II) ions on a minicolumn packed with polyurethane foam loaded with 2-(2-benzothiazolylazo)-2-p-cresol (BTAC) reagent. After pre-concentration, lead(II) ions are eluted by 0.10 mol L-1 hydrochloric acid solution and determined directly by flame atomic absorption spectrometry (FAAS). Chemical and flow variables as well as effect of other ions were studied. The results demonstrated that lead could be determinate with an enrichment factor of 26 for a sample volume of 7.0 mL and pre-concentration time of 1 min. The detection limit (3 s) was 1.0 µg L-1 and the precision (assessed as the relative standard deviation) reached values of 6.0-0.7% in lead solutions of 10^-500 µg L-1 concentration, respectively. The enrichment factor and the detection limit can be further improved by increasing pre-concentration time without degradation in the efficiency due to the favorable kinetics and low hydrodynamic impedance of the present system. Achieved sampling frequency was 48 samples per hour. The effect of another ions in concentrations agreeing with biological samples was studied. It was found that the proposed procedure has necessary selectivity for lead determination in seafood and other biological samples. The accuracy was confirmed by analysis of the followings certified reference materials: fish tissue IAEA, lobster hepatopancreas NRCC TORT-1 and citrus leaves NIST 1572. Recoveries of spike additions (0.2 or 1.0 µg g-1) to several seafood samples were quantitative (90-107%). These results proved also that the procedure is not affected by matrix interferences and can be applied satisfactorily for lead determination in samples of shrimp, oyster, crab, fish and mussel contaminated by it.
Lead NRCC TORT-1 NIST 1572 Crab Shrimp Oyster Mussel Marine IAEA MA-B-3/TM Spectrophotometry

"Sorbent Extraction In Flow Injection Analysis And Its Application To Enhancement Of Atomic Spectrometry"
Anal. Chim. Acta 1989 Volume 216, Issue 1-2 Pages 243-255
J. Ruzicka and A. Arndal

Abstract: Standard Cu(II) and Pb(II) solution were prepared from the respective nitrates in 0.1 M HNO3. A time-based injection and a fixed-volume system are described and illustrated. The sample was mixed with a 0.05% solution of Na diethyldithiocarbamate (I) in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) containing 0.1% of Na2S2O4, and the solution was passed through a column (6.5 mm x 5 mm) containing 100 mg of Bond-Elut C18, with methanol as eluent. Lead and Cu were determined by AAS at 283.3 and 324.8 nm, respectively. Alternatively, saturated quinolin-8-ol (II) solution in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) was used as reagent solution and the eluent was ethanol. Complexation with 1-(2-pyridylazo)-2-naphthol and 4-(2-pyridylazo)resorcinol was also possible. Detection limits were 0.01 mg L-1 for Pb and 4 µg L-1 for Cu by using I and II, respectively. Standard Cu(II) and Pb(II) solution were prepared from the respective nitrates in 0.1 M HNO3. A time-based injection and a fixed-volume system are described and illustrated. The sample was mixed with a 0.05% solution of Na diethyldithiocarbamate (I) in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) containing 0.1% of Na2S2O4, and the solution was passed through a column (6.5 mm x 5 mm) containing 100 mg of Bond-Elut C18, with methanol as eluent. Lead and Cu were determined by AAS at 283.3 and 324.8 nm, respectively. Alternatively, saturated quinolin-8-ol (II) solution in 0.01 M acetic acid - aqueous 0.02 M NH3 (pH 9.2) was used as reagent solution and the eluent was ethanol. Complexation with 1-(2-pyridylazo)-2-naphthol and 4-(2-pyridylazo)resorcinol was also possible. Detection limits were 0.01 mg L-1 for Pb and 4 µg L-1 for Cu by using I and II, respectively.
Copper Lead Spectrophotometry Sample preparation

"Direct Automatic Determination Of Bitterness In Virgin Olive Oil By Use Of A Flow Injection - Sorbent Extraction System"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 367-374
J. A. Gar&iacute;a-Mesa, M. D. Luque de Castro* and M. Valc&aacute;rcel*

Abstract: In the manifold shown, 20 µL of the oil was injected into a hexane carrier stream and passed through a column of C18-bonded silica to remove the sample matrix. With use of methanol as intermediate solvent, the bitter substances were carried by aqueous 50% methanol to a flow cell for spectrophotometry at 225 nm. The column was washed in the reverse direction with methanol, hexane and methanol and then reconditioned with aqueous methanol between samples. Results, expressed as absorbance at 255 nm divided by the oil concentration. (g dl-1), agreed with those obtained by a manual batch method; analysis times by the respective methods were 5 and 50 min. An automated version of an existing batch method for the determination of bitterness in virgin olive oil was developed. The automatic method is based on flow injection analysis (FIA) principles and is implemented by coupling an FIA manifold to a solid-liq. retention unit in which the sample matrix is retained on a C18-bonded silica-packed minicolumn, the analytes being monitored by UV spectrophotometry and the retained matrix being eluted in the opposite direction to detection, so it never reaches the detector. The automatic method clearly surpasses its manual counterpart in terms of solvent savings, anal. time (5 vs. 50 min) and labor requirements (none of the tedious preliminary steps of the manual method need be implemented). The relative standard deviation was 1.26% for K225 (absorbance at 225 nm/oil concentration. in g/100 mL) = 0.55.
Bittering compounds Oil Spectrophotometry Sample preparation

"Time-based And Volume-based Sampling For Flow Injection Online Sorbent-extraction Graphite-furnace Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 477-487
Bernhard Welz*, Xuefeng Yin and Michael Sperling

Abstract: Separation of the analyte from the sample matrix, and its pre-concentration, were achieved by use of a Perkin-Elmer model FIAS-200 flow injection accessory having its sample loop replaced by a conical micro-column (Eppendorf pipette tip) packed with 15 µL of RP-C18 solid-phase sorbent. The flow injection manifold was connected to the sample-introduction capillary of a Perkin-Elmer model Zeeman/3030 AAS instrument equipped with an HGA-600 graphite tube furnace and an AS-60 furnace autosampler. Details and diagrams are given of the sequence of operations for pre-concentration, involving volume-based sub-sampling; the system was more sensitive than one involving time-based sub-sampling. The system was applied in the determination of Cd, Cu, Pb and Ni. The acidified sample was mixed with a pre-purified 0.05% solution of Na diethyldithiocarbamate (I) in 0.06 M NH3 - 0.03 M acetic acid buffer (pH 9), and the metal - I complex was adsorbed on the micro-column. The column was then washed in the reverse direction with 0.02% (v/v) HNO3 before elution of the complex with ethanol and transfer of only 40 µL of the eluate to the graphite tube; furnace operating parameters are specified. With 60-s pre-concentration. of the analyte, the detection limits for Cd, Cu, Ni and Pb were 0.6, 8.5, 21 and 4 ng l-1, respectively. The method was used to determine the cited metals in standard reference seawater (open-ocean and coastal), estuarine water and river water; results agreed well with reference values. Flow injection online pre-concentration. systems for graphite furnace atomic absorption spectrometry are complicated by the low eluate volume of typically less than 50 µL which can be accommodated in a graphite tube or on a graphite platform. Even when a column with an extra small capacity of 15 µL was used, it was found impossible to elute the sorbed analyte completely with an eluate volume that was compatible with the capacity of the graphite furnace. Two approaches for introducing only the most concentrated fraction of the eluate into the graphite tube while discarding the rest were investigated and compared: controlling the time interval for collection and introduction of the eluate fraction into the furnace tube (time-based sampling), and collection of the eluate fraction of interest in thin tubing of fixed volume, followed by introduction of this fraction into the tube using a low flow of air (volume-based sampling). Cadmium, copper, lead and nickel were the analyte elements investigated. A 15-30% greater enhancement factor was obtained for volume-based sampling because dispersion was interrupted during sample injection by air segmentation. The short- and long-term reproducibility were also better for volume-based sampling because variations in the pump tubing had no influence on the eluate volume introduced. These combined effects resulted in an improvement in detection limits of the four elements by factors of 1.3-2.0. Sample throughput (23 h-1), sample consumption (3 mL min-1) and reagent consumption were the same for both approaches. There were no significant differences in the accuracy and precision of the two techniques in the anal. of seawater, estuarine water and river water standard reference materials.
Cadmium Copper Lead Nickel Estuarine Sea River Spectrophotometry Sample preparation

"Comparison Of Three Propulsion Systems For Application In Flow Injection Zone Penetration Dilution And Sorbent Extraction Preconcentration For Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 9-19
Zhao-Lun Fang, Michael Sperling and Bernhard Welz*

Abstract: The zone penetration technique (Zagatto, Ibid., 1985, 173, 289) was evaluated using a peristaltic pump, a reciprocating piston pump and a sinusoidal syringe pump as propulsion systems in conjunction with an online sorbent extraction system. The efficiency of the dilution and the performance of pre-concentration with flame AAS detection were examined. Performance of the peristaltic pump was equal or better than that of the others which only showed superiority in improved long-term stability. Better precision can be achieved in flow injection online dilution for flame atomic absorption spectrometry by zone penetration using knotted reactor sample loops and transport conduits than with straight conduits. About a 2% relative standard deviation (RSD) was obtained for a dilution factor of 20 using the valley between 2 peaks with a peristaltic and a reciprocating piston pump. A sinusoidal syringe pump gave an inferior precision of 8% RSD under the same conditions owing to a lack of proper interfacing between such pumps and the atomic absorption spectrometer. Online sorbent extraction column pre-concentration. is feasible using sinusoidal and reciprocating pump systems, which obviated the need for solvent-proof pump tubes. However, both systems had to be supplemented by peristaltic pumps. Air segmentation between sample and eluent is effective in preventing dispersion at the interface when sample loading and elution were performed in 1 piston stroke of the sinusoidal pump. The concentration. efficiency (15-18 min-1) and short-term precision (~2% RSD) of both pre-concentration. systems were generally comparable to those of previously reported systems for sorbent extraction pre-concentration. with time-based sampling, but the long-term precision of the piston and syringe pump systems (4-5% RSD) was better than that of the time-based peristaltic pump system (10-20% RSD).
Spectrophotometry Sample preparation

"Online Monitoring Of Flowing Samples Using Solid-phase Micro-extraction Gas Chromatography"
Anal. Chim. Acta 1993 Volume 284, Issue 2 Pages 265-273
Safa Motlagh and Janusz Pawliszyn*

Abstract: The solid-phase micro-extraction (SPME) device was constructed by replacing the metal wire plunger assembly of a Hamilton 7105-N syringe with a poly(dimethylsiloxane)-coated fiber (6 cm x 253 µm o.d.) with a silica core (141 µm o.d.) partially inserted into a 30 gauge, 15 cm-long stainless-steel sheath. The SPME was supported in a solution of toluene (0.1 ppm) which was agitated by magnetic mixing, intrusive mixing or sonication (details given). After the extraction period, the SPME fiber was inserted into the injector of a Varian 6000 gas chromatograph for analysis of the adsorbed material on a SPB-1 column (15 m x 0.53 mm i.d.; 0.5 µm) operated with temperature programming from 0-211°C (held for 1.25 min) at 25°C/min, He as carrier gas (4.2 ml/min) and FID. Cryogenic focusing was used to cool the column below room temperature to trap the volatiles in a narrow band at the head of the column. Sonication was the most efficient and convenient agitation method (toluene equilibrated in 1 min) and was applied to continuous-flow (16 ml/min) experiments (details given); magnetic stirring was not efficient and intrusive mixing caused sample heating. The method allows GC to be incorporated into a FIA system.
GC Sample preparation

"Determination Of Cadmium, Copper And Lead In Environmental Samples. An Evaluation Of Flow Injection Online Sorbent Extraction For Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1994 Volume 285, Issue 1 Pages 33-43
Renli Ma, Willy Van Mol and Freddy Adams*

Abstract: Lake, estuarine or river sediment, calcareous loam soil or coal fly ash were digested in a PTFE bomb with concentrated HF and HNO3 by heating until fuming. After cooling HClO4 was added, the bomb was sealed and heated for 8 h at 150°C. Silicates were removed by repeated addition of HF and HNO3 and evaporation to dryness and the residue was dissolved in HNO3, HCl and water. The solution was injected into a FIA system and mixed with 0.2% ammonium diethyldithiophosphate in 0.1 M citric acid adjusted to pH 1 with HNO3. Following pH dependent complexion with 0.1% diethylammonium-NN-diethyldithiocarbamate in 0.1 M acetic acid (described), 50 mM citric acid was added to mask Fe(III) and Mn(II). The complexes were sorbed onto C18 bonded silica gel (40-63 µm) in a conical extraction column, eluted with methanol and analyzed by AAS; elution rates and AAS nebulizer uptake rates are discussed. Calibration graphs of peak height were linear up to 50 µg/l of Cd, 300 µg/l of Cu and 1 mg/l of Pb with detection limits of 0.8, 1.4 and 10 µg/l, respectively, with a 20 s sample loading at 8.7 ml/min.
Cadmium Copper Lead Estuarine Lake River Loam Coal Fly ash Sample preparation Spectrophotometry Sample preparation

"Selective Flow Injection Sorbent-extraction For Determination Of Cadmium, Copper And Lead In Biological And Environmental Samples By Graphite-furnace Atomic Absorption Spectrometry"
Anal. Chim. Acta 1994 Volume 293, Issue 3 Pages 251-260
Renli Ma, Willy Van Mol and Freddy Adams*

Abstract: Biological material was heated with HNO3 to fuming, cooled, HClO4 was added, heated at 150°C for 8 h in a sealed bomb and the contents diluted for analysis. Geological material was digested with HF and HNO3 to fuming, digested as above, the bomb contents were evaporated to dryness and the residue dissolved in HNO3. Seawater of pH 1.5 and estuarine water of pH 2 were filtered. Samples were transferred to the FIA system, the stream (8.7 ml/min) was merged with an ammonium diethyldithiophosphate/0.1 M citric acid stream (2.2 ml/min; 0.01% for Cu, 0.1% for Pb and 0.2% or 0.5% for Cd in digests and seawater, respectively) and passed through the ODS sorbent extraction column (40-63 µm) for 20-80 s. After rinsing, elution was effected with ethanol at 5.7 ml/min for 2 s. The eluate was analyzed by GFAAS at 228.8, 324.8 and 283.3 nm and charring/atomization temperature of 400/1500, 1100/2500 and 1100/2300°C for Cd, Cu and Pb, respectively. Calibration graphs were linear up to 0.1, 5 and 4 µg/l with detection limits of 0.003, 0.05 and 0.04 µg/l of Cd, Cu and Pb, respectively. The recoveries for 25-50 ng/l of Cd, 0.5-1 µg/l of Cu and 50 ng/l of Pb from sea and estuarine waters were >87.6%.
Cadmium Copper Lead Biological Geological Sea Spectrophotometry Sample preparation

"Flow Injection Sorbent Extraction With Dialkyldithiophosphates As Chelating Agent For The Determination Of Zinc By Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1995 Volume 309, Issue 1-3 Pages 395-403
Renli Ma, Willy Van Mol and Freddy Adams*

Abstract: Biological and environmental samples (100 mg) were digested as previously described (Ibid., 1994, 293, 251) and diluted to 50 mL with water. Portions were injected over 20 s at 8.7 ml/min into a carrier stream (~2 ml/min) of 0.5% di-sec-butyldiothiophosphate in 100 mM citrate buffer of pH 3 and the Zn chelate retained on a reverse-phase column (Ibid., 1994, 285, 33). The chelate was eluted with methanol and Zn determined by AAS using a spray chamber flow spoiler. Calibration graphs were linear up to 50 µg/l of Zn with RSD (n = 5) of better than 3% and a detection limit of 0.5 µg/l. The presence of 100 mg/l of Fe and Ni interfered. Fe did not however interfere when present at 10 mg/l.
Zinc Biological Environmental Spectrophotometry Sample preparation

"Solid Phase Preconcentration-Fourier Transform Infrared Spectrometric Determination Of Carbaryl And 1-naphthol"
Anal. Chim. Acta 1995 Volume 314, Issue 3 Pages 203-212
Yasmina Daghbouche, Salvador Garrigues and Miguel de la Guardia

Abstract: An analytical procedure has been developed for the simultaneous determination of carbaryl and 1-naphthol in water samples by means of in-field sampling and pre-concentration on C18 solid phase cartridges which, after drying are eluted on-line with a carrier flow of chloroform; carbaryl and 1-naphthol are determined by Fourier transform infrared spectrometry. Carbaryl is determined directly from the peak area of the flow injection absorbance versus time recordings, measured at 1741 cm-1 with a baseline correction established at 1875 cm-1. For 1-naphthol the peak area values were measured from the first order derivative peak, obtained between the peak at 1280 cm-1 and the valley at 1272 cm-1 which correspond to the derivative spectrum of the absorbance band at 1276 cm-1. Measurements carried out by batch elution of the pre-concentrated solutions provided detection limits of 0.36 mg 1-1 for carbaryl and 1.6 mg 1-1 for 1-naphthol for a sample volume of 100 ml.
Carbaryl 1-Naphthol Environmental Spectrophotometry

"Flow Injection Sorbent Extraction With Dialkyldithiophosphates As Chelating Agent For Nickel, Cobalt, And Manganese Determination By Atomic Absorption Spectrometry"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 215-222
Renli Ma and Freddy Adams*

Abstract: Using octadecyl functional group (C18) bonded silica gel as sorbent and methanol or ethanol as eluent, the extractability of nickel, cobalt and manganese with diethyl-, di-n-propyl-, di-2-propyl-, di-n-butyl-, di-isobutyl-, di-2-butyl-, di-n-pentyl- and di-n-hexyldithiophosphates, (RO)2P(S)S-, was investigated in respect of the effects of pH, alkyl substituent group, reagent concentration and masking agent by flame atomic absorption spectrometry. The extractability increases with the chain length of the substituent groups in the reagents and is quantitative for alkyl groups larger than butyl at pH ~3. At a high concentration of di-n-pentyldithiophosphate, the metals are selectively extracted from coexisting cadmium, copper, lead and iron. As an analytical demonstration, di-n-pentyldithiophosphate was used for the determination of ultra-trace concentrations of nickel in two certified reference saline water samples (sea water and estuarine water) by graphite furnace atomic absorption spectrometry. Results were in good agreement with the certified values. The detection limit (3s) of peak area measurement was 0.07 µg L-1 with an enrichment factor of 10 for nickel with 20-s sample loading at 8.7 mL min-1 and 20 µL eluate injection.
Nickel Cobalt Manganese Spectrophotometry Sample preparation

"Determination Of Uranium By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
Anal. Chim. Acta 1996 Volume 319, Issue 1-2 Pages 135-143
Joseph H. Aldstadt*, Jacqueline M. Kuo, Lesa L. Smith and Mitchell D. Erickson

Abstract: The computer-controlled flow injection system for the determination of 238U in environmental samples by ICP-MS following separation/pre-concentration by SPE. The SPE column (5 cm x 5 mm i.d.) was packed with 20-50 µm TRU resin, a commercial extraction resin based on a bifunctional organophosphorus extractant. The retained lanthanides and actinides were eluted together with 0.1 M ammonium hydrogen oxalate or sequentially using 4 M HCl to elute the lanthanides and Am, 0.1 M tetrahydrofuran 2,3,4,5-tetracarboxylic acid to elute Pu and Th and then 0.1 M ammonium hydrogen oxalate to elute U. The eluate was injected (2.6 ml/min) into a FIA manifold (schematic shown) and mixed with a stream of 5% HNO3 (1 ml/min) before entering the pneumatic nebulizer of the ICP-MS. The performance of the SPE-ICP-MS system was evaluated for the determination of U in ground water. A pre-concentration factor of 30-fold was achieved with a 5 mL sample. The detection limit was 0.3 ng/l. The method was verified by analyzing EPA certified groundwater samples. A second FI-ICP-MD system which minimized the influence of polyatomic ions (eg. 238UH+) on the determination of minor actinides (eg. 239Pu+) was described briefly.
Uranium-238 Ground Mass spectrometry Sample preparation

"Solid Phase Extraction And Determination Of Ultra Trace Amounts Of Mercury(II) Using Octadecyl Silica Membrane Disks Modified By Hexathia-18-crown-6-tetraone And Cold Vapor Atomic Absorption Spectrometry"
Anal. Chim. Acta 1997 Volume 355, Issue 1 Pages 69-74
Yadollah Yamini, Naader Alizadeh and Mojtaba Shamsipur*

Abstract: A simple method for rapid extraction and determination of ultra trace amounts of mercury(II) ions using octadecyl-bonded silica membrane disks modified with hexathia-18-crown-6-tetraone and cold vapor atomic absorption spectrometry (CVAAS) is presented. Extraction efficiency and the influence of flow rates, pH, and type and smallest amount of stripping acid were evaluated. Maximum capacity of the membrane disks modified by 10 mg of the crown ether was found to be 241 µg Hg2+ ions. The limit of detection of the proposed method is 6 ng per 1000 mL. The method was applied to the recovery of Hg2+ ions from synthetic samples and four different water samples.
Mercury(II) Spectrophotometry Sample preparation

"Combination Of Flow Injection With Capillary Electrophoresis. 3. Online Sorption Column Preconcentration Capillary Electrophoresis System"
Anal. Chim. Acta 1997 Volume 355, Issue 2-3 Pages 135-143
Heng-Wu Chen and Zhao-Lun Fang*

Abstract: A combined flow injection (FI)-capillary electrophoresis (CE) system with a split-flow interface reported previously was used for online pre-concentration of pseudoephedrine by solid phase extraction on a micro-column packed with C-18. Aqueous samples were loaded on the column at 1.0 mi min-1 for 90 s and eluted by a mixed eluent of 40% 62.5 mM acetate buffer (pH 4.0) and 60% acetonitrile at 0.2 mi min-1. A zone-sampling approach was employed to sample 45 µl of the most concentrated zone of the eluate, which was injected into the FI-CE split-flow interface using a phosphate buffer carrier, with a 25 µl water zone preceding the sampled eluate zone to achieve enhanced field amplification effects. Sensitivity enhancements of 60 fold (180 fold with 4 min sample loading) were thus achieved with a sample throughput of 9 h-1 and 4.7% relative standard deviations (n = 10, 2 µg mL-1 pseudoephedrine) for peak area evaluation, without significant degradation of column efficiency. 16 References
Pseudoephedrine Electrophoresis Sample preparation

"Determination Of Trans-resveratrol And Other Polyphenols In Wines By A Continuous-flow Sample Clean-up System Followed By A Capillary Electrophoresis Separation"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 27-38
Lourdes Arce, Mar&iacute;a Teresa Tena, Angel Rios and Miguel Valc&aacute;rcel*

Abstract: A new method coupling flow injection (FI) with capillary electrophoresis (CE) was developed using diode array detection to measure the concentration. of trans-resveratrol in wines, in particular because of the interest in its biological properties and cancer prevention. A FI system furnished with a C-18 mini-column was used to clean up the wines by solid phase extraction prior to CE. The analytes were eluted from C-18 by using methanol and then driven from the FI system to the auto-sampler of the CE equipment by a programmable arm. The 3s detection limit ranged from 0.05 mg/L (trans-resveratrol) to 0.36 mg/L [(-)epicatechin]. The recoveries of added trans-resveratrol and other polyphenols from synthetic wines were between 92 to 110%, (mean of 99%). The method is faster and simpler than those previously reported which used liq.-liq. extraction and liquid chromatography
Polyphenols Trans-resveratrol Wine Electrophoresis Spectrophotometry

"Continuous-flow Determination Of Natural And Synthetic Antioxidants In Foods By Gas Chromatography"
Anal. Chim. Acta 1998 Volume 359, Issue 1-2 Pages 47-55
M. Gonz&aacute;lez, E. Ballesteros, M. Gallego and M. Valc&aacute;rcel*

Abstract: A simple, rapid continuous-flow method with gas chromatography detection for the simultaneous determination of natural and synthetic antioxidants (α-tocopherol, α-tocopheryl acetate, 2,6-di-tert-butyl-p-hydroxytoluene, tert-butyl-4-hydroxyanisole and tert-Bu hydroquinone) is proposed. A solid phase extractor is coupled to the flow system to isolate antioxidants from the sample matrix. During extraction, analytes are released from ~70% of the triglycerides present in fats and oils by using XAD-7 sorbent; after selective elution with 400 µL of 2-propanol, only ~0.7-0.8% of total triglycerides originally present in the sample remain in the final ext. XAD-7 adsorbs 70-95% of the antioxidants except BHT of which only ~30% is adsorbed. The proposed method is considered an effective alternative to earlier procedures.
Antioxidants tert-Butylhydroxytoluene Food GC

"Speciation Of Copper And Manganese In Milk By Solid Phase Extraction/inductively Coupled Plasma-atomic Emission Spectrometry"
Anal. Chim. Acta 1998 Volume 375, Issue 3 Pages 299-306
O. Abollino, M. Aceto*, M. C. Bruzzoniti, E. Mentasti and C. Sarzanini

Abstract: A speciation method was developed to study distribution of Cu and Mn species in cow milk. The method is based upon solid phase extraction of selective fractions of the analytes, followed by elution and determination by inductively coupled plasma-at. emission spectrometry (ICP-AES), using it as a flow injection detector. Fractions detected were cationic, anionic, neutral and casein-bound. A different behavior is observed for the 2 metals.
Copper Manganese Milk Cow Spectrophotometry

"Flow Injection And Solvent Extraction With Intelligent Segment Separation. Determination Of Quaternary Ammonium Ions By Ion-pairing"
Talanta 1992 Volume 39, Issue 2 Pages 101-111
Cherryleen C. Lindgren and Purnendu K. Dasgupta*,

Abstract: Details are given of a system in which segments of organic solvent are introduced at regular intervals in to a pre-mixed stream of sample solution and an ion-pairing dye. Extraction takes place in a coiled conduit internally coated with heat-embedded Amberlite XAD-2 powder, by which the ion pair is adsorbed and is subsequently eluted by the organic solvent. The organic segment is then isolated in the loop of a six-port valve fitted with a pair of conductivity sensors (to detect loop contents) and injected into the pure solvent for passage to a photometric detector. The circuit diagram of the valve controller and a diagram of the manifold are presented. The system was applied to tetrabutylammonium ion as analyte, with aqueous bromothymol blue (pH 8.5 to 8.8) as dye and CHCl3 as extractant. The best of three variants of the basic manifold design afforded a detection limit of 0.1 µM. Organic solvent segments are introduced into a premixed stream of the sample and an ion-pairing dye by a 3-way valve at regular intervals. The major mechanism of 'extraction' in such a system appears to be the adsorption of the ion-pair on conduit walls and subsequent elution by the organic solvent. Following passage through the conduit, the immiscible organic segment is isolated in the loop of a 6-port valve; loop filling is sensed by a pair of conductivity sensors located respectively at the fill and drain ports of the loop and appropriate logic circuitry. The isolated segment is then injected into a purely organic carrier and detected by a suitable optical detector. Results are reported for a number of parametric studies that characterize this system. With immobilized adsorbents on conduit walls for pre-concentration, a limit of detection of <10-7 M tetrabutylammonium ion can be obtained with bromothymol blue as the ion-pairing agent.
Quaternary Ammonium Ion Conductometry Sample preparation

"Solid Interfaces As Analytical Problem Solvers In Flow Injection Analysis"
Talanta 1993 Volume 40, Issue 1 Pages 21-36
M. D. Luque de Castro and M. T. Tena,

Abstract: The advantages of using solid interfaces in flow injection systems are illustrated by selected examples. The interfaces are classified according to whether they provide enhanced sensitivity, increased selectivity, decreased sample and reagent consumption or ease of automation of the preliminary steps of the analytical process. Some also allow the implementation of multi-determination methods or indirect determinations. Other problems that are solved by using solid interfaces include the generation of unstable reagents, minimization of heat losses, simultaneous sample and matrix measurements and sequential development of the different steps of a process.
Sample preparation

"Online Sorbent Extraction, Preconcentration And Determination Of Lead By Atomic Absorption Spectrometry"
Talanta 1995 Volume 42, Issue 2 Pages 211-218
Yaneira Petit de Pe&ntilde;a*, Mercedes Gallego and Miguel Valc&aacute;rcel*,

Abstract: Skimmed milk powder and mineral reference samples were dried to a constant weight and mineralized by mixing with 14.4 M HNO3 with or without 11.2 M HCl (details given) and heating at 180-200°C until the samples dissolved and N2O fumes were given off. After cooling, the process was repeated until no N2O was evolved and a clear solution remained. The solutions were diluted with water and the mineral samples were adjusted to pH 1 with 2 M HNO3. The sample (3 ml/min) was introduced into a FIA manifold where it merged with a chelating reagent stream (0.3 ml/min) of 0.1% ammonium pyrrolidine dithiocarbamate or saturated dithizone in 0.2 M ammonia. The chelate was retained on an activated carbon minicolumn (2.5 cm x 3 mm i.d.) and the sample matrix was flushed to waste. The injection valve was switched and the column was desorbed with IBMK. The Pb was determined by AAS at 283.2 nm. Linear calibration graphs were obtained in ng/ml range (details tabulated) with detection limits of 10^-15 ng/ml for a 2 min sampling time and RSD of 2.3-3%. The effects of interferences on the method are discussed.
Lead Powder Geological Sample preparation Spectrophotometry Sample preparation

"Flame AAS Determination Of Lead In Water With Flow Injection Preconcentration And Speciation Using Functionalized Cellulose Sorbent"
Talanta 1995 Volume 42, Issue 6 Pages 851-860
Abdulmagid M. Naghmush, Krystyna Pyrzyska and Marek Trojanowicz*,

Abstract: The online SPE of trace amounts of Pb in a flow injection system with flame AAS detection (schematic diagram given) was investigated using cellulose sorbents with phosphoric acid and carboxymethyl groups, C18 sorbent non-modified and modified with Pyrocatechol Violet or 8-quinolinol, commercial chelating sorbents Chelex 100 and Spheron Oxin 1000, Amberlite XAD-2 modified with Pyrocatechol Violet and several cation-exchange resins. The best dynamic characteristics of retention were observed for functionalised cellulose sorbents. For Cellex P as optimum sorbent, elution with separate fractions of HNO3 and ethanol allowed the differentiation between tetra-alkyllead, other organolead species and inorganic lead. The detection limit for the determination of inorganic Pb(II) was 0.17 µg/l at pre-concentration from a 50 mL sample at a flow rate of 7 ml/min. RSD at the 10 µg/l level was 5.9% (n = 10).
Lead tetraalkyllead Environmental Spectrophotometry Sample preparation

"Amberlite XAD Resin Solid-phase Extraction Coupled Online To A Flow Injection Approach For The Rapid Enrichment And Determination Of Phenols In Waters And Waste Waters"
Talanta 1997 Volume 44, Issue 8 Pages 1423-1433
Wen-lu Song, Zheng-liang Zhi* and Lian-sheng Wang

Abstract: Filtered water was adjusted to pH 2 with 12 M HCl and a portion (4.4 ml) was injected in to a carrier stream (1.8 ml/min) of HCl of pH 2 and applied to a column (3 cm x 3 mm i.d.) of Amberlite XAD-4 resin (80-120 mesh). The phenols were eluted from the column with 0.1 M NaOH of pH 13 by activating a switching value. The eluate was mixed with a stream (0.22 ml/min) of 0.1% 4-aminoantipyrine in NH4Cl/NaOH buffer of pH 8.5 in a mixing coil (30 cm x 0.8 mm i.d.) and then with a stream (0.22 ml/min) of 0.2% potassium ferricyanide in water adjusted to pH 11 with NaOH in a reaction coil (60 cm x 0.8 mm i.d.). The absorbance was measured at 510 nm. The manifold incorporated two pre-concentration columns operated alternatively; sample throughput was 12 per h. The calibration graph was linear for 0.01-1 µg/ml phenol and the detection limit was 4 ng/ml. The RSD at 0.2 µg/ml was 2.4%. (n = 11). Results agreed with those obtained by a FIA and a manual method. A novel and expeditious approach for direct determination of phenols in water and waste waters based on solid-phase extraction coupled online to a flow injection analysis (FIA) manifold is described. The method employs online pre-concentration of the phenols in an acidified sample (pH = 2.0) onto a 3 cm x 3 mm column packed with Amberlite XAD-4 resin. The phenols are subsequently eluted from the resin into a flowing system with an alkaline solution (pH = 13) by actuating a switching valve; the eluted analytes were then quantified spectrophotometrically as the products of reaction with 4-aminoantipyrine (4-AAP) and potassium ferricyanide on passing through the flow-cell of a detector. The proposed method has a linear calibration range 0.01-1 µg mL-1 of phenol, with a detection limit of 0.004 µg mL-1 (S/N = 3) and a sample throughput of 12 hr-1, investigated with a 4.4 mi sample volume. The relative standard deviation is 2.4% for 0.2 µg mL-1 of the analyte. The sensitivity offered by the procedure was higher by a factor of 13 than that provided by a conventional flow injection analysis method. The analytical scheme of the proposed system is much simpler than its conventional manual counterpart due to the fact that it combines trace enrichment, sample clean-up, derivation and detection in one analytical set-up. The high speed, ease of use and automation, selectivity, and relative freedom from random contamination by sample handling make this method ideal for the phenols monitoring in water and waste waters. (C) 1997 Elsevier Science B.V. 27 References
Phenols Environmental Waste Spectrophotometry Sample preparation

"Low Pressure Chromatographic Separation Of Inorganic Arsenic Species Using Solid Phase Extraction Cartridges"
Talanta 1998 Volume 47, Issue 3 Pages 787-796
Serife Yal&ccedil;in and X. Chris Le*

Abstract: Routine water analysis of arsenic species requires simple, inexpensive, rapid and sensitive methods. To this end, we have developed two methods, which are based on the use of inexpensive solid phase extraction (SPE) cartridges as low pressure chromatographic columns for separation and hydride generation atomic absorption spectrometry (HGAAS) and hydride generation atomic fluorescence spectrometry (HGAFS) for detection of arsenic. Both anion exchange and reverse phase cartridges were successfully used to separate arsenite [As(III)] and arsenate [As(V)]. The composition, concentration, and pH of eluting buffers and the effect of flow rate were systematically investigated. Speciation of inorganic As(III) and As(V) were achieved within 1.5 min, with detection limits of 0.2 and 0.4 ng/ml, respectively. Both isocratic and step gradient elution techniques were suitable for the baseline resolution of As(III) and As(V) using anion exchange cartridges. Application of the methods to the speciation of As(III) and As(V) in untreated water, tap water, and bottled water samples were demonstrated. Results from the speciation of arsenic in a standard reference material water sample using these methods were in good agreement with the certified value and with inter-laboratory comparison results obtained using HPLC separation and inductively coupled plasma mass spectrometric detection (HPLC-ICPMS).
Arsenate ion Arsenic(3+) Arsenic(5+) Arsenite Environmental Waste Water Mineral Sample preparation Fluorescence

"Differential Determination Of Chromium(VI) And Total Chromium In Natural Waters Using Flow Injection Online Separation And Preconcentration Electrothermal Atomic Absorption Spectrometry"
Analyst 1992 Volume 117, Issue 3 Pages 629-635
Michael Sperling, Xuefeng Yin and Bernhard Welz

Abstract: Samples were introduced into the FIA manifold and mixed with 4% HNO3 (to adjust the pH to 1.3 to 1.8) and 0.05% Na diethyldithiocarbamate solution (as complexing agent). The solution was applied to a column of RP-C18 and Cr(VI) was eluted with ethanol before determination with graphite-furnace AAS. Total Cr was determined after oxidation of Cr(III) to Cr(VI) by K peroxydisulfate and Cr(III) was calculated by difference. Detection limits for Cr(VI) and total Cr were 16 and 18 ng 1-1, respectively. The results for six reference samples agreed well with the certified values, with a coefficient of variation of 10%. A rapid, sensitive, and selective method for the differential determination of Cr(III) and Cr(VI) in natural waters is described. Cr(VI) can be determined directly by flow injection online sorbent extraction pre-concentration coupled with electrothermal atomic absorption spectrometry using Na diethyldithiocarbamate as the complexing agent and C18 bonded SiO2 reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of Cr(III) to C(VI) by potassium peroxydisulfate. Cr(III) can be calculated by difference. The optimum conditions for sorbent extraction of Cr(VI) and oxidation of Cr(III) to Cr(VI) are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 µL samples was achieved after pre-concentration for 60 s, giving detection limits of 16 ng/L for Cr(VI) and 18 ng/L for total Cr. Results obtained for seawater and river water reference materials were all within the certified range for total Cr with a precision of >10% relative standard deviation at 100-200 ng/L. The selectivity of the determination of Cr(VI) was evaluated by analyzing spiked reference materials in the presence of Cr(III) resulting in quant. recovery of Cr(VI).
Chromium(VI) Chromium, total River Sea Spectrophotometry Sample preparation

"Flow Injection Determination Of Triton X-100 With Online Solid-phase Extraction"
Analyst 1992 Volume 117, Issue 4 Pages 767-771
Charles Moeder, Nelu Grinberg, Holly J. Perpall, Gary Bicker and Patricia Tway

Abstract: Triton X-100 was determined in the presence of a quinoline derivative in a carrier solution comprising 5 mM KH2PO4 (pH 2.0) and isobutanol - 50% acetonitrile (13:7) on a column (25 cm x 4.6 mm) of Partisil 10 SCX with detection at 276 nm. The detection limit was 0.005 mg mL-1 with a coefficient of variation of ~0.2% (n = 8) for 16.73 mg mL-1. A simple and rapid method for the determination of Triton X-100 in the presence of quinoline derivatives is described. The method involves flow injection with online cation-exchange solid-phase extraction The carrier consists of a mixture of 5 mmol L-1 aqueous KH2PO4 (pH 2.0) and 1:1 volume iso-BuOH-MeCN in the proportion 65 + 35, v/v Under these conditions, Triton X-100 elutes unretained, while the quinoline derivatives are retained on the extractor. Authentic samples are analyzed by this method, with good precision and reproducibility.
Triton X-100 Ion exchange Spectrophotometry Sample preparation

"Trace Metal Atomic Absorption-spectrometric Analysis Utilizing Sorbent Extraction On Polymeric-based Supports And Renewable Reagents"
Analyst 1994 Volume 119, Issue 7 Pages 1459-1465
Herbert L. Lancaster, Graham D. Marshall, Encarnacion R. Gonzalo, Jaromir Ruzicka and Gary D. Christian

Abstract: The analyte was pre-concentrated by extracting it on to a silica-based C18 support (RP-18; Varian) on which the chelating agents quinolin-8-ol or diethyldithiocarbamate were adsorbed. Two different column designs were used. The metal-chelate complexes were eluted by changing the polarity of the carrier stream. Cu and Pb chelates were studied and some other chelates were also investigated. A Perkin-Elmer Model 2380 atomic absorption spectrometer was used and the flow system featured peristaltic pumps and PTFE tubing. Sample throughput was 20/h (2 mL samples for pre-concentration). Detection limits were low ppb, with enhancement factors of 50-100.
Copper Lead Metals, trace Spectrophotometry Sample preparation

"Continuous-flow Method For The Determination Of Phenols At Low Levels In Water And Soil Leachates Using Solid-phase Extraction For Simultaneous Preconcentration And Separation"
Analyst 1996 Volume 121, Issue 1 Pages 1-6
Zheng-liang Zhi, Angel R&iacute;os and Miguel Valc&aacute;rcel

Abstract: Soil was extracted with water and filtered. Water (tap, river) was filtered. The filtrates were adjusted to pH 2 with 12 M HCl and the ionic strength was brought to 0.34 M with NaCl. The sample was pumped continuously (4.8 ml/min) for 5 min through a column (4 cm x 2.5 mm i.d.) of Amberlite XAD-4, previously conditioned with 0.01 M HCl. The column was then washed with water at pH 2 for 30 s. Elution of the analytes was effected by continuously passing a stream (1 ml/min) of 0.1 M NaOH through the column. The eluate was merged with a stream (0.4 ml/min) of 1% 4-aminoantipyrine in borate buffer of pH 9-10, then with a stream (1 ml/min) of 4% K2S2O8 of pH 11 and finally with a stream (1 ml/min) of CHCl3 propelled from a displacement bottle. The mixture was passed through a 2 m extraction coil and the aqueous and organic phases were separated by means of a membrane phase separator. The absorbance of the organic phase was measured at 460 nm. The calibration graph was linear for 0.5-60 ng/ml phenol, the detection limit was 0.2 ng/ml and the RSD (n value not given) was 2.7%. The throughput was 8 samples/h. Recoveries of phenol were 91.6-108.3%.
Phenols Environmental Water River Spectrophotometry Sample preparation

"Determination Of Lead In Soil Samples By In-valve Solid-phase Extraction - Flow Injection Flame Atomic Absorption Spectrometry"
Analyst 1996 Volume 121, Issue 10 Pages 1413-1417
Ponlayuth Sooksamiti, Horst Geckeis and Kate Grudpan

Abstract: Soil (0.3 g) was digested with 5 mL concentrated HNO3 and 1 mL 30% H2O2 in a microwave digester at 250-650 W for 20 min. The digest was filtered and diluted to 100 mL with 1 M HNO3. A portion of the resulting solution was loaded (4 ml/min) onto a column (2.5 cm x 3 mm i.d.) of Sr. Spec SPS resin (Eichrom), which was incorporated in a flow injection system. Elution of Pb from the column was effected with 0.05 M ammonium oxalate (4 ml/min). The eluate was analyzed for Pb by flame AAS at 217 nm. The calibration graph was linear up to 5 µg Pb, the detection liwas 0.08 µg and the RSD (n = 15) was 4.1%. The recovery of Pb was 95-98%. The results obtained agreed with those obtained by ETAAS.
Lead Environmental Environmental Sample preparation Spectrophotometry Sample preparation

"Solid-phase Extraction Coupled With Electrochemical Detection For The Determination Of The Herbicide Bromofenoxim In Water Samples At Low- And Sub-micro G 1-1 Levels"
Analyst 1996 Volume 121, Issue 12 Pages 1839-1843
Irena Grabec vegl, Boidar Ogorevc, Milko Novi and Emilio Benfenati

Abstract: A sample (100-250 ml) was adjusted to pH 3 with HClO4 and pumped through a C18 Polar Plus silica gel SPE cartridge, previously conditioned with acetonitrile/H2O then dried. For square-wave voltammetric detection, bromofenoxim (I) was eluted with 10 mL acetonitrile containing 0.1 M LiClO4. The eluate was analyzed directly at a static Hg drop electrode by applying a depoon potential of -0.1 V vs. Ag/AgCl for 10 s followed by a potential scan to -0.8 V, at 175 Hz, a pulse amplitude of 30 mV and a potential step of 10 mV. For FI amperometric detection, I was eluted with 10 mL 20% aqueous acetonitrile containing 0.1 M LiClO4 (solution A). A portion of eluate (40 µL) was injected into a carrier stream of solution A at a flow rate of 0.5 ml/min. Detection was at an in situ prepared Hg-film eous C electrode at -0.7 V vs. Ag/AgCl. For square-wave voltammetric detection, the calibration graph was linear from 0.2-12 µg/l I; the detection limit was 0.05 µg/l. Recovery was 92% and RSD was 6% (n = 6). For FI amperometric detection, the calibration graph was linear from 3-120 µg/l I; the detection limit was 1.5 µg/l. The recovery was 121% and RSD was 9% (n = 7). The methods were applied to tap water.
Bromofenoxim Water Environmental Amperometry Sample preparation

"Stability Of Bromate Species Immobilized On Microcolumns Of Activated Alumina"
Analyst 1998 Volume 123, Issue 5 Pages 981-982
A. R. Elwaer, C. W. McLeod and K. C. Thompson

Abstract: Microcolumns of activated alumina (n = 30) were charged with bromate standard solution (0.5 mL, 6.0 µg L-1) and stored at 4°C in a light-tight container. Microcolumns were removed at regular time intervals (1 hour, 2 and 3 days and 1, 2, 3, 4 and 8 weeks) and bromate species were eluted and quantified by flow injection ICP-MS, Analyte recoveries were found to be quantitative (96-101%) and reproducible over the eight week period, These results indicate that for trace level determinations (µg L-1) of bromate, a microcolumn format may provide a convenient and reliable route for delivery of external calibrants and reference materials. (15 References)
Bromate Mass spectrometry

"Flow Injection Online Sorbent Extraction Preconcentration For Graphite Furnace Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1990 Volume 5, Issue 7 Pages 639-646
Zhaolun Fang, Michael Sperling and Bernhard Welz

Abstract: A micro-flow injection online sorbent extraction pre-concentration system was developed to improve the performance of flame and graphite-furnace AAS. Lead was determined as a test element. A Perkin-Elmer Model 2100 spectrometer was used at 283.3 nm. A 26-fold enhancement in peak area compared with 50 µL direct introduction was obtained with pre-concentration. for 60 s while achieving a coefficient of variation of 1.9% (n = 11) for 0.1 µg L-1 of Pb and a detection limit of 3 ng l-1. Determination of Pb in seawater revealed that the interfering matrix had been almost completely removed during pre-concentration. Results obtained for some National Research Council of Canada Standard Reference Materials agreed well with certified values.
Lead Sea Spectrophotometry Sample preparation

"Critical Evaluation Of The Efficiency And Synergistic Effects Of Flow Injection Techniques For Sensitivity Enhancement In Flame Atomic Absorption Spectrometry"
J. Anal. At. Spectrom. 1992 Volume 7, Issue 2 Pages 293-300
Zhaolun Fang, Liping Dong and Shukun Xu

Abstract: A mathematical model for evaluating sensitivity enhancement effects of batch offline and flow injection online pre-concentration. in flame AAS is proposed. Preconcentration by column ion exchange, C18 column sorbent extraction and co-precipitation with Fe(II) hexamethylenedithiocarbamate (with and without slotted-tube atom trap) was investigated. The validity of the model was tested in the determination of Pb by flame AAS with flow injection precipitation with a slotted-tube atom trap. A 135-fold sensitivity enhancement was achieved at a sampling frequency of 72 h-1. Math. models for evaluating sensitivity enhancement effects of batch off-line and flow injection (FI) online pre-concentration. systems for flame atomic absorption spectrometry (FAS) are proposed. The performance of four different FI pre-concentration. systems, including pre-concentration. by ion exchange, sorbent extraction and coprecipitation, with additional enhancement effects from organic solvents and slotted-tube atom traps, are critically evaluated in terms of apparent enrichment factors, enhancement factors, concentration. efficiency and consumptive index. The experimental results show good agreement with calculated results based on equations of the math. model. The synergistic effects of different enhancement approaches are illustrated by the determination of lead by FAAS using an FI coprecipitation pre-concentration. system equipped with a slotted-tube atom trap. A 135-fold sensitivity enhancement was achieved at a sampling frequency of 72 h-1 and with the consumption of 2.7 mL of sample solution
Lead Ion exchange Spectrophotometry Sample preparation

"Application Of Multielement Time-resolved Analysis To A Rapid Online Matrix Separation System For Inductively-coupled Plasma-mass Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 11 Pages 929-933
Simon M. Nelms, Gillian M. Greenway and Robert C. Hutton

Abstract: A rapid online matrix separation system for ICP-MS, using multi-element time-resolved analysis, was developed for the determination of several trace elements in complex matrix samples, A flow injection manifold was constructed consisting of a mini-column of 8-hydroxyquinoline covalently immobilized on to controlled pore glass, Analytes retained on the column were eluted using 0.1 mi of 2.0 mol L-1 nitric acid, Sample volumes of 0.5 mi were analyzed, yielding a pre-concentration factor of 5 in addition to matrix separation, The system was optimized with respect to the variables of buffer concentration, buffer pH and eluent acid volume and concentration, Calibrations from both pure water and synthetic seawater compared well and showed good linearity, with correlation coefficients of 0.988-0.999 for a range of analytes, The method showed good within-run reproducibility with precisions (s(r)) at the 1 ng mL-1 level of typically <3%, In general, recoveries between 89 and 104% were obtained, with the exception of Ni, which showed a recovery of 78% under the compromise conditions used. The method was validated by the analysis of estuarine (SLEW-1) and coastal (CASS-2) certified reference materials, Good agreement with the certified values was obtained for both of these materials. (17 references)
Metals, trace Sea Estuarine NRCC CASS-2 NRCC SLEW-1 Mass spectrometry Sample preparation

"Online Solid-phase Chelation For The Determination Of Eight Metals In Environmental Waters By Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1996 Volume 11, Issue 3 Pages 187-191
Daniel B. Taylor, H. M. Kingston, Donald J. Nogay, Dagmar Koller and Robert Hutton

Abstract: Seawater was mixed with 4 M ammonium acetate buffer, the pH was adjusted to 5.5 and diluted with water. The prepared seawater or natural water was loaded into a flow injection system at 2.4 ml/min and the sample merged with a buffer solution (2 ml/min) of 4 M ammonium acetate of pH 5.8 which had passed through a clean up Al-clad PEEK column (7.5 cm x 4.6 mm i.d.) packed with Muromac A-1 (50-100 mesh). The resulting solution was loaded on to a PEEK column (5 cm x 4 mm i.d.) and the column was washed with water. Weakly retained matrix components were eluted with buffer and the buffer was washed off the column with water. The metal analyzes were eluted with 1 M HNO3 and the eluate passed to the ICP-MS instrument via a V groove nebulizer. Eight metals (14 isotopes) were determined with detection limits of 0.5-60 ng/l for a 10 mL sample to 0.11-12 ng/l for a 50 mL sample (results tabulated). The results for the analysis of water reference materials are tabulated and discussed.
Metals Sea NIST 1643 NRCC CASS-2 NRCC NASS-4 Mass spectrometry Sample preparation

"Determination Of Selenium In Geochemical Samples By Flow Injection Hydride-generation Inductively Coupled Plasma Atomic-emission Spectrometry Following Online Removal Of Iron Interference By Anion Exchange"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 4 Pages 487-490
L. D. MARTINEZ, E. SAIDMAN, E. MARCHEVSKY and R. OLSINA

Abstract: A 0.5 g sample was acid-digested by the method of Subramanian (Fresenius' Z. Anal. Chem., 1981, 305, 382), the product was heated with HCl at 90°C for 1 h to reduce Se(VI) to Se(IV), and the resulting solution was diluted to 25 mL. This solution was pumped into the manifold illustrated for retention of the Fe on a microcolumn of Dowex 1-X8, and then passed to an injection valve for injection of a 0.7 mL portion into a carrier stream of water that subsequently merged with streams of 6 M HCl and 0.6% NaBH4 solution. The hydride was then generated in a reaction coil and passed via a gas-liquid separator to the plasma in a stream of Ar. The calibration graph was linear up to 30 ng/ml of Se with a detection limit of 0.3 ng/ml. The RSD (n = 10) was 2% at 20 ng/ml of Se. The results for geochemical standard reference materials agreed well with the certified values.
Selenium Geological Ion exchange Sample preparation Spectrophotometry Sample preparation

"Flow Injection Online Sorption Separation And Preconcentration With A Knotted Reactor For Electrothermal Atomic Absorption Spectrometric Determination Of Lead In Biological And Environmental Samples"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 4 Pages 459-464
XIU-PING YAN and FREDDY ADAMS

Abstract: Fish muscle was digested with 65% (w/w) HNO3, the digest was heated with 70% (w/w) HClO4 in a PTFE pressure vessel, the product was evaporated to near-dryness, and the residue was dissolved in water. Soil or sediment was digested with 40% (w/w) HF plus 65% HNO3, the digest was heated with 70% HClO4 in a PTFE pressure vessel, and the product was diluted with water. Diagrams of the flow injection manifold are presented; it incorporated a laboratory-made PTFE knotted reactor (100 cm x 0.5 mm i.d.) on the walls of which the Pb - diethyl phosphorodithioate complex was sorbed at pH 0.5-3.5 before elution with 35 µL of ethanol and transport to a pyrolytically coated GF without platform. The determination was carried out at the same time as the subsequent pre-concentration cycle. An enhancement factor of 125 was achieved, and the detection limit for Pb was 4.8 ng/l. The RSD (n = 11) at 0.5 µg/l of Pb was 2.1%. The results for standard reference materials agreed well with the certified values.
Lead Environmental Marine Environmental Sample preparation Spectrophotometry Sample preparation

"Flow Injection Manifold For Matrix Removal In Inductively Coupled Plasma Mass Spectrometry By Solid Phase Extraction: Determination Of Al, Be, Li And Mg In A Uranium Matrix"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 12 Pages 1327-1331
Paul Becotte-Haigh, Julian F. Tyson and Eric Denoyer

Abstract: A flow injection manifold, incorporating two pumps and an 8-port rotary valve, was developed for the automation of a procedure for the removal of the matrix suppression of uranium on light elements. The procedure was based on the selective retention of the uranium on a column of TRU.Spec.RTM. resin (a support material impregnated with a liquid ion-exchanger). The light elements were not retained. The uranium was removed by 0.2 mol/L ammonium oxalate solution and the column reconditioned by the passage of 25% (v/v) nitric acid. The interference of uranium, 5000 mg/L, was removed, allowing the determination of aluminum, beryllium, lithium and magnesium at concentrations. down to a few µg/L in 100 µL of sample. The sample acidity was 20% and the carrier stream was 5% with respect to nitric acid. Although higher acid concentrations. could have improved the retention of uranium, the acid concentration. was not increased to avoid degrdn. of the nickel sampling and skimmer cones. A complete anal. cycle took 4 min, including the regeneration of the column.
Aluminum Beryllium Lithium Magnesium Metal Mass spectrometry

"Enhancement Of Flow Injection Optosensing By Sorbent Extraction And Reaction Rate Measurement"
Anal. Chem. 1990 Volume 62, Issue 14 Pages 1482-1490
Nathan Lacy, Gary D. Christian, and Jaromir Ruzicka

Abstract: The molybdenum blue reaction for the determination of phosphate was used as a model to illustrate the extension of the use of hydrophobic sorbents in flow injection analysis for the pre-concentration. of an anion and for on-column detection. Optosensing provides for real-time monitoring of the rate of signal change so that the rate of color development during the reduction step of the analysis can be measured. The synergistic relationship between the rates of formation of the phosphate and silicate heteropoly complexes was examined. A kinetic optosensing method was developed in which the difference in reduction rate for the heteropoly complexes allowed simultaneous determination of phosphate in the ppb range, and silicate in the ppm range. The system used an inexpensive minispec-20 spectrophotometer with a net path length through the sorbent of 2 mm. Partial least-squares analysis was used to analyze the data, and prediction errors of ~10% were obtained for both components.
Phosphate Silicate Spectrophotometry Sample preparation

"Online Preconcentration Of Silver On Activated Alumina And Determination In Borehole Water By Flow Injection Atomic Absorption Spectrophotometry"
Fresenius J. Anal. Chem. 1990 Volume 336, Issue 3 Pages 201-204
P. P. Coetzee, I. Taljaard and H. de Beer

Abstract: Silver in borehole water is pre-concentrated on a polyethylene micro-column (3 cm x 1 mm) of activated alumina (basic form) connected to a flame AAS instrument (schematic diagram given). Sample (pH 4.0) is passed through the column for 3 to 6 min at 5 mL min-1 with water as carrier stream, elution is with 0.5 mL of 2 M HNO3 and regeneration is with 0.15 M NH4OH (2 min at 5 mL min-1). The effluent is directed to a nebulizer and analyzed by AAS at 328.1 nm. The calibration graph is rectilinear for up to 100 µg mL-1 of Ag, with coefficient of variation (n = 10) of ±5 and 18% for >10 and 5 µg l-1, respectively. The detection limit is 4 µg l-1. Sodium, Mg and Ca salts at 0.1 M to 0.5 M decrease the Ag signal by 10%.
Silver Borehole Spectrophotometry Sample preparation

"Flow Injection Online Sorbent-extraction Preconcentration - Graphite-furnace Atomic Absorption Spectrometry: Trace-element Determination In The Ng L.minus.1 Range"
Fresenius J. Anal. Chem. 1990 Volume 337, Issue 1 Pages 135-136
Bernhard Welz, Michael Sperling, Zhaolun Fang

Abstract: A pre-concentration. system has been developed for graphite-furnace AAS and applied in the determination of Pb. It involves online formation of Pb diethyldithiocarbamate and its retention on a 15 µL conical column of C18-bonded silica. The detection limit was 3 ng L-1 of Pb, and the coefficient of variation (n = 11) at 0.1 µg L-1 was 1.9%. The method gave a 26-fold increase in peak area as compared with direct injection of the same volume of sample solution Results for sea- and river water standard reference materials agreed with the certified values.
Lead River Sea Spectrophotometry Sample preparation

"Literature Survey Of The Online Preconcentration In Flow Injection Atomic-spectrometric Analysis"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 7 Pages 529-537
V. Carbonell, A. Salvador and M. de la Guardia

Abstract: A review is presented in which are discussed the three main online pre-concentration procedures - liquid - liquid extraction, column methods and precipitation before analysis by flame or electrothermal AAS or ICP-AES. Examples of applications of each are tabulated (82 references). A review with 82 references. The literature on the use of 'online' pre-concentration in flow injection atomic spectrometric anal. is reviewed, taking into account its application both in flame and electrothermal atomic absorption methods as well as in plasma emission spectrometry. The basis of the different pre-concentration approaches, such as liq.-liq. extraction, column pre-concentration and 'online' precipitation are discussed. The literature survey reveals the anal. performance of the developed methodologies.
Spectrophotometry Spectrophotometry Spectrophotometry Sample preparation

"Determination Of Ultratrace Concentrations Of Elements By Means Of Online Solid Sorbent Extraction Graphite Furnace Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1992 Volume 343, Issue 9-10 Pages 754-755
Michael Sperling, Xuefeng Yin and Bernhard Welz

Abstract: Solid sorbent extraction using a microcolumn in an automated system was successfully coupled with a graphite furnace for atomic absorption spectrometry. Bonded silica with octadecyl functional groups (C-18 reversed phase material) was used in a 15 µL conically shaped microcolumn as a sorbent for the metal complexes formed online with Na diethyldithiocarbamate. Column elution was performed with an EtOH eluent into a PTFE capillary used for eluate storage and transfer into the graphite tube. With a sample loading time of 60 s and direct introduction of the eluate portion containing the highest analyte concentration. into the graphite tube, an enrichment factor of ~20 was realized. Effective elimination of contamination by the closed system and online purifn. of the complexing agent together with highly selective separation of trace metals from alkaline and earth alkaline elements allowed the determination of ultratrace metals in seawater and deionized water. Using only 3 mL of sample, detection limits for Cd, Co, Cu, Pb, and Ni of 0.8, 12, 17, 6.5, and 36 ng/L, respectively, was achieved.
Cadmium Cobalt Copper Lead Nickel Sea Water Spectrophotometry Sample preparation

"Flame Atomic Absorption Spectrometric Determination Of Cadmium And Copper In Biological Reference Materials Using Online Sorbent Extraction Preconcentration"
Fresenius J. Anal. Chem. 1992 Volume 344, Issue 12 Pages 535-540
Shukun Xu, Michael Sperling and Bernhard Welz

Abstract: Animal or plant tissue reference material (0.5 g) was subjected to acid digestion and the residue was diluted with HNO3. Urine samples for analysis were diluted with water before addition of HNO3. The solution was loaded into a flow injection manifold where it was merged with a stream of 0.05% diethylammonium-NN-diethyldithiocarbamate. The complex formed was extracted online on a conical 100 µL micro-column of RP-C 18 sorbent and the chelates were eluted with methanol directly into the nebulizer - burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased sensitivity. A sampling frequency of 85 h-1 was achieved, with a sample loading time of 30 s at a flow rate of 4.0 mL min-1. The enrichment factor for Cd and Cu was 20 and the detection limits were 0.15 and 0.2 µg L-1 for Cd and Cu, respectively. The coefficient of variation were 2.3% for 10 µL L-1 of Cd and 1.4% for 45 µg L-1 of Cu (n = 11). The procedure was suitable for the determination of Cu in biological materials and for Cd in urine. Low recoveries were obtained for Cd in samples containing high levels of Cu and/or Fe. Cadmium and copper at the µg/g to ng/g level in plant and animal tissue reference materials, and at the µg/L level in urine were determined by flame atomic absorption spectrometry using online sorbent extraction pre-concentration based on flow injection techniques. Bonded silica reversed phase sorbent with octadecyl functional groups (RP-C 18), packed in a 100 µL column, was used to collect the diethylammonium-N,N-diethyldithiocarbamate (DDTC) complex formed online in the sample digests at low pH. Methanol was used to elute the analyte chelates directly into the nebulizer-burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased the sensitivity. A sampling frequency of 85/h could be obtained with a sample loading time of 30 s at a flow rate of 4.0 mL/min. The enrichment factor for both elements was 20 and the enhancement factors, including the effect of the organic solvent and with the flow spoiler removed, were 126 and 114 for cadmium and copper, respectively. The detection limits (3s) were 0.15 µg/L for cadmium and 0.2 µg/L for copper. The precision was 2.3% and 1.4% RSD for 10 µg/L Cd and 45 µg/L Cu, respectively. (n = 11). Results for the determination of cadmium and copper in various biological reference materials were typically in good agreement with certified values. Low recoveries were observed, however, for cadmium in samples containing high levels of copper and/or iron, such as bovine liver.
Cadmium Copper NIST 1577 Liver Plant Urine Sample preparation Spectrophotometry Sample preparation

"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

"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

"Flow Injection Online Sorbent Extraction Preconcentration And Separation For Flame And Graphite-furnace Atomic Absorption Spectrometry"
Microchem. J. 1992 Volume 45, Issue 2 Pages 163-177
Bernhard Welz

Abstract: A review with 33 references is presented that includes diagrams of the relevant systems. Significant progress has been made recently in online pre-concentration of trace elements for flame (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) by the use of solid sorbents. The use of microcolumns which were eluted in a direction opposite to the direction of sample loading, and an overall optimization of the system made it possible to increase efficiency and sampling rate substantially. Enrichment factors of 20-25 could be achieved with only 20 s loading time so that the sampling frequency could be increased to 120/h, a value which is compatible with routine FAAS operation. Online coupling of sorbent extraction pre-concentration with GFAAS was found to provide a number of important advantages. A 20 to 25-fold increase in sensitivity was typically obtained with 1 min pre-concentration, using eluate zone sampling for the most efficient analyte transfer into the graphite tube. An effective separation of the analyte element from interfering matrix components could be achieved using carefully designed wash steps between sample loading and elution. This resulted in detection limits for a number of trace elements which were essentially identical for pure solutions and samples with a high total salt content such as seawater. Finally, sorbent extraction could be used to pre-concentrate selectively one oxidation state of elements occurring in more than one valency, providing a means of speciation which is particularly attractive because of its speed of operation. Total analyte element concentrations could be determined after online or off-line reduction or oxidation of the other valency states. A review with 33 references.
Sea Spectrophotometry Spectrophotometry Sample preparation

"Flow Injection Analysis Of Human Serum Albumin Using A Stabilized, Immobilized Cibacron Blue Support"
Anal. Lett. 1992 Volume 25, Issue 9 Pages 1721-1739
Narinesingh, D.;Pope, A.;Ngo, T.T.

Abstract: A diagram of the flow injection manifold is given. The affinity column, operated at 25°C, consisted of a 1 mL cartridge packed with Blue Avid Gel P previously conditioned with 20 mM Tris containing 150 mM NaCl of pH 7.5 (TBS). Portions (160 µL) of human serum albumin (HSA) were injected into the system, and unbound material was washed out with the TBS. Once the absorbance (280 nm) had returned to the baseline, the albumin bound to the gel was eluted with TBS containing 2 M KCl (1 mL min-1), and the absorbance at 280 nm was measured. The method was applied to standard solution of HSA containing 2.5 mg mL-1, serum samples treated with HSA standard solution, and patients' serum. The calibration graph was rectilinear, with a mean recovery of 98% and a coefficient of variation of 4.3%. This paper reports on the development of a simple, accurate method which combines low pressure liquid affinity chromatography and flow injection analysis for the quantitation of albumin in human serum. The pseudo-affinity matrix consists of Cibacron Blue covalently linked to a 2-fluoro-1-methylpyridinium salt activated Fractogel support. The albumin can be readily eluted at pH 7.5 using a Tris buffer (20 mM) containing 2 M KCl. Linear calibration curves are obtained (r = 0.999) at albumin concentrations up to at least 250 mg dL-1. Recovery yields in the range 95% to 103% (mean = 98%) are obtained. The within day as well as the day to day relative standard deviation is less than 4.3%. Comparison of the albumin concentrations in serum samples analyzed for by the title method with those obtained for the samples analyzed for by the hospital method (bromocresol green method) gave good correlations (r = 0.999).
Albumin Serum Human Spectrophotometry Sample preparation

"Identification Of Pesticides By Liquid Chromatography Particle Beam Mass Spectrometry Using Electron Ionization And Chemical Ionization"
J. Chromatogr. A 1998 Volume 805, Issue 1-2 Pages 127-135
C. Aguilar*, F. Borrull and R. M. Marc&eacute;

Abstract: Liquid chromatography-mass spectrometry (LC-MS) with a particle beam (PB) interface is used to separate and identify a group of pesticides. The mass spectra obtained under the different ionization modes, electron ionization (EI) and positive and negative chemical ionization (PCI and NCI) are compared. The operating conditions under each mode, determined by studying the influence on the ion abundance of the ion source temperature of the EI mode, and the gas pressure and ion source temperature in the methane CI were optimized. EI was more sensitive than PCI and NCI and of the latter two modes, NCI gave higher responses, especially for organophosphorus compounds. When online solid-phase extraction-LC-PB-MS was applied to real samples, limits of detection in full scan mode were in the range of 0.5 and 10 µg L-1 for EI. The analysis of real samples by online solid-phase extraction-LC-PB-MS enabled EI detection of one of the pesticides studied and confirmation by PCI and NCI. The combined EI/CI information also enabled the detection of some non-target compounds.
Pesticides Mass spectrometry HPLC

"Flow Injection Sorbent Extraction With Dialkyl Dithiophosphates As Chelating Agent For The Determination Of Cadmium, Copper And Lead By Flame Atomic Absorption Spectrometry"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1917-1923
Renli Ma and Freddy Adams*

Abstract: Of the OO-dialkyl phosphorodithioates evaluated for retention of the cited heavy metals on a Perkin-Elmer B050-4047 C18 column containing 20 mg of ODS silica gel (cf. Anal. Chim. Acta, 1994, 285, 33), the best was diethyl phosphorodithioate in the presence of 0.1 M citrate at pH 3 (buffered with ammonium acetate). With loading for 20 s at 8.7 ml/min the enhancement factors for the cited metals were 35, 35 and 26 and the detection limits were 0.8, 1.4 and 10 µg/l, respectively. The method is applicable to digests of environmental, biological and industrial materials.
Cadmium Copper Lead Environmental Biological Industrial Sample preparation Spectrophotometry Sample preparation

"Online Sorption Preconcentration And Inductively Coupled Plasma Atomic Emission Spectrometry Determination Of Rare-earth Elements"
Spectrochim. Acta B 1996 Volume 51, Issue 11 Pages 1417-1423
O. N. Grebnevaa, Corresponding Author Contact Information, N. M. Kuz'mina, G. I. Tsysinb and Yu. A. Zolotov

Abstract: The system for online microcolumn sorption pre-concentration and inductively coupled plasma atomic emission spectrometry determination of 14 rare earth elements (REEs) is described. Aminocarboxylic sorbents of different structure are used. Preconcentration of REEs from the 20 mL of sample solution and elution with 210 µl of 1 mol L-1 HCl results in an enrichment factor of 99. The detection limit of REEs is about nx 0.1 µg L-1 (RSD 3-5%). The possibility of simultaneous REE determination in complicated solutions is demonstrated.
Metals, rare earth Geological Spectrophotometry Sample preparation

"Automated Solid Phase Extraction Of Theophylline By Sequential Injection On Renewable Column"
Anal. Commun. 1998 Volume 35, Issue 11 Pages 357-359
Brian Dockendorff, David A. Holman, Gary D. Christian and Jaromir Ruzicka

Abstract: A miniaturized and fully automated solid phase extraction system was developed based on sequential injection onto a renewable microcolumn of an ion exchanger. Extraction of theophylline from caffeine solutions was used as an example of sample preparation An important feature, compared to commercial sorbent extraction systems, was the elimination of prepackaged sorbent cartridges by using an automatically renewable microcolumn. The method has evolved from recent innovations in sequential injection analysis using a jet ring cell that entraps ion exchanger beads and discards them after completion of the monitoring cycle.
Theophylline Ion exchange

"Online FIA Atomic Spectrometry For The Analysis Of Metal Traces"
Ann. Chim. 1995 Volume 85, Issue 7-8 Pages 443-454
MENTASTI E

Abstract: A review is presented, with 28 references. It is concluded that the practical blank-limited detection limit obtainable by flow injection pre-concentration online with atomic spectrometry has nearly been reached, and that the only further possibility (apart from the impractical use of a larger sample volume) is the development of flow injection ICP-MS. Sensitivity of the pre-concentration to the chemical state of the metal indicates the possibility of using flow injection atomic spectrometry for speciation. Online flow injection analysis (online FIA) for the determination of metal traces by atomic spectrometry is reviewed and discussed with reference to environmental applications. The FIA manifold comprises a microcolumn packed with XAD-2 resin which retains the analytes in form of metal complexes. Successive elution enables the achievement of an enrichment step with which very low detection limits can be reached. (28 references)
Cadmium Copper Iron Manganese Nickel Zinc Sea Mass spectrometry Sample preparation

"Application Of Solid-phase Separation To Sensitivity Enhancement And Flow Injection Methods"
Bunseki 1992 Volume 1992, Issue 5 Pages 385-388
Motomizu, S.

Abstract: A review is presented, with 31 references. The principles of the technique are discussed.
Sample preparation

"Amberlite XAD-2 Resin Microcolumn Coupled Online To A Flow Injection Approach For The Preconcentration, Cleanup And Determination Of Trace Phenols In Waters"
Gaodeng Xuexiao Huaxue Xuebao 1997 Volume 18, Issue 10 Pages 1621-1623
Song, W.L.;Wang, L.S.;Zhi, Z.L.

Abstract: A novel and expeditious approach for direct determination of phenols in water and waste water based on solid-phase extraction coupled to a flow injection analysis (FIA) manifold is described. The method employs online pre-concentration of phenols using a 3 cm X 3 mm column packed with Amberlite XAD-2 resin. The phenols are subsequently eluted from the resin into a flowing system with an alkaline solution and quantified spectrophotometrically as the products of reaction with 4-aminoantipyrine (4-AAP) system. The sensitivity offered by the procedure was higher by a factor of pH=13 than that provided by a conventional FIA method. 5 References
Phenols Waste Spectrophotometry Sample preparation

"Studies On Adsorption Properties Of Chromium(VI) On The Nanometer-size TiO2 Powder Surfaces Using Online Flow Injection Analysis"
Gaodeng Xuexiao Huaxue Xuebao 1998 Volume 19, Issue 10 Pages 1566-1569
Ma, W.H.;Cai, R.X.;Lin, Z.X.

Abstract: Various nanometer-size TiO2 samples are prepared from TiCl4 under different hydrolysis and calcining treatment conditions, such as pH, surfactants, stabilizers and temperature It has been found that powders heat-treated at the temperature below 450°C are of anatase crystal structure with average grain size of less than 20 nm. Adsorption behavior of Cr(VI) ion on as prepared powders, adsorption kinetics, pH curves, adsorption isotherms and adsorption capacity are studied by flow injection microcolumn system for pre-concentration using spectrophotometric detection method. The results demonstrated that nanometer-size TiO2 possesses a significant capacity and exchange rate for adsorption of Cr(VI) ion (~3080 µg/g and 8.6 x 10^3 s-1).
Chromium(VI) Spectrophotometry

"Analytical Application Of FIA-AAS Combination For The Determination Of Heavy Metals In Environmental Samples"
Chem. Listy 1998 Volume 92, Issue 12 Pages 978-987
M. Foltin and T. Prochackova

Abstract: The examples of application of online FIA-AAS combination are presented for the trace heavy metals anal. of environmental and biological samples. The influence of various parts of flow injection system, e.g. type of flow, injection mode, separation and or pre-concentration cartridge, and detection mode on anal. signal is discussed.
Metals, heavy Silicate Spectrophotometry Spectrophotometry

"Design Of A Manifold For Online Solid-phase Extraction And Investigation Of Its Analytical Performance"
Fenxi Huaxue 1995 Volume 23, Issue 7 Pages 835-838
Lin, S.L.;Zheng, Q.X.;Zhu, H.J.;Yin, G.Z.

Abstract: The design and construction of the cited double-column FIA system have been described. For application, concentration factors of up to 145 for Pd (by adsorptive pre-concentration) and 78 for Sr (by coprecipitative pre-concentration) were achieved, and their corresponding concentration efficiencies were 36 and 26. The calibration graph was linear up to 100 ng/ml for Pd and Sr and the corresponding detection limits were 0.3 and 0.5 ng/ml. Sampling frequencies were 15-20 and 20-30 runs/h, respectively, for Pd and Sr.
Palladium Strontium Spectrophotometry Sample preparation

"Speciation Analysis Of Mercury By Liquid Chromatography Coupled With Online Sorbent Extraction Preconcentration And Cold Vapor Atomic Absorption Spectrometry"
Fenxi Huaxue 1996 Volume 24, Issue 11 Pages 1248-1252
Yin, X.F.;Liu, M.

Abstract: A mixture of methyl-, ethyl- and phenylmercury (I, II and III, respectively) and Hg(II) was injected into a flow injection HPLC - cold vapor AAS integrated manifold (diagram given) for pre-concentration for 9 min then speciation. A 5 µm Zorbax ODS column (25 cm x 4.6 mm i.d.) was used with methanol/acetonitrile/H2O (50:22:28) containing 3 mM dithiocarbamate as mobile phase (1 ml/min). Online reduction with 1% NaBH4 in the presence of 75% HNO3 was carried out with combined thermolysis and detection at 254 nm. All components were well separated. Calibration graphs were linear. Detection limits for I, II, III and Hg(II) were 0.86, 1.94, 1.06 and 1.92 ng/l, respectively. Recoveries were 92-106% with RSD of 3.8-7%. Most foreign species were either removed during pre-concentration or did not interfere. The method was applied to the analysis of urine.
Mercury Urine LC Spectrophotometry Sample preparation

"Application Of Flow Injection Analysis In The Analysis Of Pharmaceuticals And Biologically Active Compounds"
Folia Pharm. Univ. Carol. 1998 Volume 21-22, Issue 1 Pages 53-64
Petr Solich

Abstract: A review with 19 references. The author's research in the development and application of flow injection analysis (FIA) of pharmaceuticals and biological active compounds is summarized. The review includes applications of FIA for the determination of active ingredients in mass-produced pharmaceutical preparations, determination of the total drug content, determination of the active ingredient content uniformity in individual tablets, etc. Future FIA methods will take advantage of flow fluorimetric detection, immobilized enzymes, pre-concentration, absorption on a solid phase, and biosensors.
Drugs Organic compounds Pharmaceutical Fluorescence Sensor

"Determination Of Nickel, Copper, And Mercury By Flow Injection Preconcentration Coupled With HPLC"
Gaodeng Xuexiao Huaxue Xuebao 1998 Volume 19, Issue 11 Pages 1746-1748
Akbar, A.;Shen, H.;Xu, G.M.;Yin, X.F.

Abstract: A home designed pressure tight pre-concentration column combined with an HPLC six-port valve was used to interface the FI sorbent extraction pre-concentration system and HPLC. Based on this system, a method for determination of trace amt. of Ni, Cu and Hg in water samples after online derivatization and pre-concentration as their diethyldithiocarbamate complexes has been developed. The sensitivity and selectivity can be further improved by using time programming for absorption measurement. The detection limit 0.16 µg/L, 0.41 µg/L and 1.1 µg/L, and the relativity standard deviation, 3.6%, 4.5% and 3.9%, were found for Ni (II), Cu(II) and Hg(II), respectively.
Nickel Copper Mercury Water Spectrophotometry HPLC

"Application Of Flow Injection Analysis With An Amperometric Detector. 2. Analysis Of Trace Free Cyanide In Surface Water By Flow Injection Analysis"
Huanjing Huaxue 1983 Volume 2, Issue 4 Pages 58-65
Ma, Huichang; Jin, Li; Yan, Huiyu

Abstract: Trace cyanide in surface water was determined by amperometry using a gold-tube electrode detector and the flow injection analysis technique with NaOH solution as the carrier fluid. A Pb-granule (20-50 mesh) column (0.35 x 5 cm) treatment can eliminate S2- interference. The cyanide detection limit and relative standard deviation is 1 ppb and <3%, respectively. The measurement frequency using the method is 60-70 times/h.
Cyanide, free Surface Amperometry

"Continuous-flow Determination Of Organophosphorus Pesticides Using Solid-phase Extraction Coupled Online With High Performance Liquid Chromatography"
Int. J. Environ. Anal. Chem. 1992 Volume 46, Issue 4 Pages 245-253
Farran, A.;De Pablo, J.;Hernandez, S.

Abstract: A column (5 cm x 3 mm) of Amberlite XAD-2 resin was used for trace enrichment of diazinon (I), azinphos-methyl (II) and fenthion (III) in a low-pressure continuous-flow system (described) with methanol as mobile phase (1.6 mL min-1). HPLC was carried out on an RP-18 column (22 cm x 4 mm) with aqueous 80% methanol as mobile phase (1 mL min-1) and detection at 220 nm. Optimization of conditions is discussed, including pre-concentration. time, flow rate and pH. Calibration graphs (peak heights) were rectilinear in the range 0.07 to 2 mg L-1 for all three pesticides; the limits of detection were 90 µg L-1 for I and III and 40 µg L-1 for II. Recoveries were >95%. Interference from other pesticides and related compounds could be eliminated by using aqueous 70% methanol as the HPLC mobile phase. The method was successfully used for the determination of I, II and III in river water samples. A XAD-2 resin is used for trace enrichment of 3 organophosphorus pesticides (diazinon, azinphosmethyl, and fenthion) on an unsegmented-flow solid-phase pre-concentration. system, coupled online with a HPLC with UV detection at 220 nm. The influence of different parameters (e.g. pesticides water concentrations., water pH, pre-column characteristics, pre-concentration. and elution times and solvent flow rates) on the retention and recovery of the pesticides was studied. Recoveries >95%, were obtained for the pesticides, except for diazinon at sample volumes >500 mL. Calibration graphs are linear in the range of 0.07-2 mg/L for each pesticide under standard conditions, although concentrations. down to 5 µg/L can be measured. The method was been successfully applied to spiked river water samples.
Pesticides, organophosphorus River HPLC Sample preparation

"Fast Screening For Drugs Of Abuse By Solid Phase Extraction Combined With Flow Injection Ionspray-tandem Mass Spectrometry"
J. Anal. Toxicol. 1998 Volume 22, Issue 4 Pages 319-328
W. Weinmann (Wolfgang) and M. Svoboda

Abstract: A fast anal. approach for the simultaneous quant. screening for illicit drugs in serum and urine without tedious chromatography separation steps was developed by combining solid phase extraction (SPE) followed by flow injection analysis (FIA) with ion spray-ionization and tandem mass spectrometry (MS-MS) detection using a PE Sciex API 300 triple-quadrupole MS. MS-MS anal. was performed by sequentially isolating the precursor ions of the analytes and their deuterated standards with subsequent fragmentation and monitoring of one fragment ion for each substance. A multiple-reaction monitoring experiment was set up for morphine (MO), codeine (COD), amphetamine (AMP), benzoylecgonine (BZE), and their deuterated analogs. For method evaluation, serum samples spiked with 2-1000 ng of each drug and deuterated standards were extd. by mixed-mode SPE, redissolved in MeCN-NH4OAc-buffer, and directly injected by flow injection into the ion spray source. The specificity of this new method was demonstrated by testing compounds with similar chemical structure for interferences from the analytes of interest (e.g., hydromorphone, morphine glucuronide, and 6-monoacetylmorphine with MO; dihydrocodeine and hydrocodone with COD; cocaine [COC] and ecgonine methylester with BZE; methamphetamine with AMP). The possibility of interferences of such compounds with the FIA-ion spray-MS-MS screening method is discussed. Spiked serum samples and serum and urine samples from drug addicts and victims of drug abuse were analyzed with FIA-MS-MS and, after derivatization, with gas chromatography-mass spectrometry (GC-MS). Comparable quant. results were obtained with both methods; no interferences with metabolites or other compounds were found. The FIA-ionspray-MS-MS method is a fast, quant., sensitive, and highly specific alternative method to drug-screening by immunoassays, high-performance liquid chromatography, and GC-MS. It can be used for the simultaneous detection of different drugs and metabolites such as opiates, COC, AMP derivatives, and many other drugs.
Drugs Morphine Codeine Amphetamine Benzoylecgonine Serum Human Urine Mass spectrometry Mass spectrometry

"Solid-phase Extraction Cleanup For Determining Ascorbic-acid And Dehydroascorbic Acid By Titration With 2,6-dichlorophenolindophenol"
J. AOAC Int. 1996 Volume 79, Issue 5 Pages 1236-1243
Krishna K. Verma, Archana Jain, Bhushan Sahasrabuddhey, Kalpana Gupta and Sanjeev Mishra

Abstract: Ascorbic acid is frequently determined by titration with 2,6-dichlorophenolindophenol. The determination is rapid, but the method is neither specific for ascorbic acid nor very sensitive. The coloring matter in the assay solution interferes with the visual endpoint, and iron(II), copper(I), sulfite, and sulfhydryl substances such as cysteine and glutathione interfere with the color reaction. Sample cleanup by solid-phase extraction with C-18 bonded silica was developed to remove the coloring matter. Extraction sorbent impregnated with 2,2'-bipyridyl, 2,9-dimethyl-1,10-phenanthroline (neocuproine) acid N-ethylmaleimide removes Fe(II), Cu(I), and sulfhydryl compounds, respectively. The procedure was applied to highly colored multivitamin pharmaceuticals, soft drinks, and fruit and vegetable juices. In contrast to the results from the original method, which is not applicable to such samples, the results obtained by the method incorporating cleanup were accurate and selective for ascorbic acid. The sample cleanup also permitted determination of dehydroascorbic acid by reducing it to ascorbic acid with cysteine and titrating the ascorbic acid formed with indophenol. As little as 3 µg ascorbic acid was determined by the method incorporating cleanup.
Ascorbic acid dehydroascorbic acid Soft drink Pharmaceutical Vegetable Fruit Sample preparation Spectrophotometry HPLC

"Flow Injection Spectrophotometric Determination Of Salicylate Using Online Solid-phase Extraction"
J. Flow Injection Anal. 1996 Volume 13, Issue 1 Pages 45-52
Karlicek, R.;Gargos, M.;Solich, P.

Abstract: Sample solution (200 µL) was injected into a carrier stream of water (0.55 ml/min) of a flow injection system (schematic shown) and carried to a SPE column (0.5 cm x 2 mm i.d.) packed with quaternary ammonium-modified silica gel. The adsorbed salicylate (I) was eluted from the column with 50 µL 0.05 M HNO3 and injected into the carrier solution. The analyte-containing carrier stream was mixed with a reagent stream of iron(III) nitrate solution in 20 mM HNO3 at 0.25 ml/min in a reaction coil (150 cm x 0.5 mm i.d.) before detection at 540 nm. The calibration graph was linear from 1-20 µg/ml of I. The RSD (n = 10) was 0.44% for 10 µg/ml of I. All interfering substances were removed by the SPE process. The method was applied to the analysis of urine and blood serum, with recoveries of 98-101.4 and 98-102%, respectively, for 10^-200 and 10^-50 µg/ml of added I. Sampling rate of 30-60 runs per h could be achieved. There was no need for pretreatment.
Salicylate Urine Blood Serum Spectrophotometry Sample preparation

"Flow Injection In-valve Solid Phase Extraction Spectrophotometric Determination Of Uranium In Geological Samples"
Lab. Rob. Autom. 1998 Volume 10, Issue 1 Pages 25-31
Kate Grudpan *, Jaroon Jakmunee, Ponlayuth Sooksamiti

Abstract: Flow injection analysis (FIA) system incorporating in-valve solid phase extraction microcolumn for online separation and pre-concentration using a new resin, U/TEVA-Spec, is proposed for the spectrophotometric determination of U in geological samples using 4-(2-pyridylazo)resorcinol (PAR) as a color agent. Optimization of the condition involved in the system was studied. Possibility of a single standard calibration is discussed.
Uranium Geological Spectrophotometry

"Sample Preparation Perspectives. New Approaches To Sample Preparation"
LC-GC 1995 Volume 13, Issue 2 Pages 82-94
Ron E. Majors

Abstract: Four techniques that are on the verge of widespread acceptance are summarized. The microwave-assisted processes of microwave digestion, microwave-assisted solvent extraction and microwave heating for gas-phase extraction are presented which use microwave heating of the samples. SPE disc technology uses discs resembling membrane filters usually 1 mm thick and 4-96 mm diameter. The discs permit high flow rates but the number of stationary phases available is limited. Solid-phase µextraction uses a small diameter, polymer-coated, fused-silica optical fiber mounted in a microsyringe. Organic solvents are sorbed onto the fiber then thermally desorbed in the injection port of a gas chromatograph. The final technique is the direct analysis of small molecules in serum and plasma using internal-surface reversed-phase supports allowing large biomolecules to be eluted quickly at or near the column void volume whilst retaining small volumes beyond the void volume.
Sample preparation Sample preparation

"Determination Of Iron In Seawater By Flow Injection Analysis Using Inline Preconcentration And Spectrophotometric Detection"
Mar. Chem. 1995 Volume 50, Issue 1-4 Pages 3-12
C. I. Measures, J. Yuan and J. A. Resing

Abstract: The method was based upon one described previously by Hirayama and Unohara (cf. Anal. Chem., 60, 2573-2577). Seawater acidified with 6 M HCl (2.5 ml/min) was pumped into the manifold (diagram given) and mixed via a knitted coil with 2 M ammonium acetate buffer to pH 5.2 (0.32 ml/min). The resulting mixture was passed onto a concentration column of resin immobilized 8-hydroxyquinoline where Fe was retained. After loading (~e;1 min), the carrier stream comprising sub-boiled 6 M HCl was passed through the column in the opposite direction to the sample, Fe was released and mixed with 2 M ammonium acetate buffer containing 68.9 µmol of triethylamine and 15% Brij-35 (0.32 ml/min), 3.5 mM NN-dimethyl-p-phenylenediamine (0.06 ml/min) and 0.18 M H2O2 (0.1 ml/min). In the reaction coil, oxidation occurred and the resulting semi-quinone derivatives were detected spectrophotometrically at 514 nm. The detection limit was 0.025 nM-Fe. The RSD (n = 6) was ~e;2.5% at the 0.35 nM level. The method was used to determine Fe in open ocean water and hydrothermal plume samples.
Iron Sea Spectrophotometry Sample preparation

"Flow Injection Spectrophotometric Determination Of Captopril Using Online Solid Phase Extraction"
Pharmazie 1998 Volume 53, Issue 8 Pages 549-551
Karlicek, R.; Solich, P.

Abstract: In the proposed procedure, the determination of captopril with Folin-Ciocalteau reagent using a flow injection analysis technique (FIA) with spectrophotometric detection at 740 nm is described. The negative effect of interfering substances is overcome by a solid phase extraction (SPE), when captopril is adsorbed on the solid phase in the microcolumn, which is integrated directly into the flow system. Pretreatment of the sample takes place directly in the flowing stream. With the SPE column (quaternary ammonium), captopril was determined from 2-50 µg/mL with a frequency of 30-60 samples per h.
Captopril Spectrophotometry

"Solid-phase Reactors In Flow Injection Analysis"
Trends Anal. Chem. 1992 Volume 11, Issue 4 Pages 149-155
M. D. Luque de Castro

Abstract: A review is presented, with 49 references, with discussion on the use of solid-phase reactors coupled to the flow injection manifold. A review with 49 references. The use of a solid-phase reactor coupled online to a flow injector manifold can significantly expand the potential of flow injection analysis by enhancing such basic anal. parameters as sensitivity and selectivity, and allowing implementation of specific reactions. Typically, solid reactors involve chemical reactions (whether enzymatic, immunoassay, ion-exchange or redox) or act as sorbent extractants or reagent releasers. These aspects and major trends in their use in conjunction with flow injection manifolds are examined
Sample preparation

"Automated System For Rapid Flow Injection Extraction - Atomic Absorption Spectrometric Analysis Of Heavy Metals In Solutions"
Zavod. Lab. 1996 Volume 62, Issue 12 Pages 26-28
Kirko, E.V.;Sorokina, N.M.;Galdina, N.N.;Tsizin, G.I.;Zolotov, Y.A.

Abstract: The apparatus consisted of a peristaltic pump, two injection valves, an extraction column and an AAS instrument controlled by a computer. Samples were applied to the extraction column, the heavy metals were eluted with 2 M HNO3 and the eluate was analyzed by AAS. The column was regenerated periodically with 1 M ammonium acetate buffer. The extraction column, of ~0.1 mL capacity, contained a weak cross-linked polystyrene resin with diethylenetriaminetetra-acetate groups. The flow-through the column was 2-10 ml/min. The limits of detection of Cd, Co, Cu, Mn, Ni, Pb and Zn using the system described were 20-50 times lower than the limits obtained by direct AAS determination. The RSD were Up to 40 samples/h could be analyzed.
Metals, heavy Cadmium Cobalt Copper Manganese Nickel Lead Zinc Spectrophotometry Sample preparation

"Preconcentration And Determination Of Inorganic Arsenic Using A Multisyringe Flow Injection System And Hydride Generation-atomic Fluorescence Spectrometry"
Talanta 2004 Volume 64, Issue 5 Pages 1335-1342
L. O. Leal, N. V. Semenova, R. Forteza and V. Cerd&agrave;

Abstract: A new multisyringe flow injection system for inorganic arsenic determination at trace levels by hydride generation-atomic fluorescence spectrometry (HGAFS) is presented. Preconcentration on a solid-phase was carried out using a column packed with an anion-exchange resin (Amberlite IRA-410). The reagents are dispensed to the system using a multisyringe burette coupled with two multi-port selection valves. Different parameters were changing in order to make the system as effective as possible. An analytical curve was obtained for arsenic determination between 50 and 2000 ng l-1. This new approach improved five times the sensitivity over a MSFIA-HGAFS technique developed previously by the authors. Detection limit of the proposed technique was (3sb/S) of 30 ng l-1. The relative standard deviation (RSD) of As at 1 µg L-1 was 4.8% (n=7). A sample throughput of 10 h-1 has been achieved. The proposed method has been applied to different reference solid and water materials with satisfactory results.
Arsenic, inorganic NRCC DOLT-1 NRCC DORM-1 LGC 6010 Fluorescence

"Use Of Solid-phase Extraction To Eliminate Interferences In The Determination Of Mercury By Flow-injection CV AAS"
Anal. Bioanal. Chem. 2003 Volume 377, Issue 4 Pages 735-739
Agnieszka Krata, Krystyna Pyrzy&#324;ska and Ewa Bulska

Abstract: Solid-phase extraction with two-step elution has been developed for effective elimination of copper and iron interference with mercury determination by flow-injection cold vapor atomic absorption spectrometry (CV AAS). Sodium tetrahydroborate(III) was used as reducing agent. Cation-exchanger Dowex 50Wx4 was applied for the sorption of mercury and both interfering ions. In the first step elution of Cu(II) and Fe(III) was performed using 0.5 mol L-1 KF solution. Then mercury was eluted with 0.1% thiourea in 8% HCl. The detection limit (3s) for Hg(II) was 27 ng L-1. The expanded uncertainty estimated for the whole procedure was about 6%. The accuracy of the proposed method was evaluated by determination of the recovery of known amount of mercury added to mineral, spring, and tap waters, and by analysis of a certified reference material BCR-144R (sewage sludge).
Mercury BCR 144 Mineral Spring Water Spectrophotometry

"Fluorimetric Determination Of Aluminium In Water By Sequential Injection Through Column Extraction"
Anal. Bioanal. Chem. 2004 Volume 378, Issue 6 Pages 1652-1658
C. Brach-Papa, B. Coulomb, C. Branger, A. Margaillan, F. Th&eacute;raulaz, P. Van Loot and J.-L. Boudenne

Abstract: A fluorimetric procedure for the determination of aluminium with matrix removal in drinking water is proposed. The system is based both on the solid phase extraction of aluminium on a new chelating resin (XAD-4 modified by grafting salicylic acid) and the fluorimetric detection of a complex formed between 8-hydroxyquinoline-5-sulfonic acid (HQS) and Al(III), after elution of the resin by hydrochloric acid. The sorption and elution of aluminium were studied in both competitive and noncompetitive conditions, varying pH, flow-rates, volume and concentration of reagents, as well as time contact. The optimized procedure allows determination of Al(III) at the sub-ppb level (LOD: 0.2 µg L-1 for 1 mL of sample) within a working range of 0.2-500 µg L-1. The analytical procedure was successfully employed for the determination of aluminium in drinking water during and after flocculation/coagulation treatment processes.
Aluminum(III) Water Fluorescence

"Time-based On-line Preconcentration Cold Vapour Generation Procedure For Ultra-trace Mercury Determination With Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Bioanal. Chem. 2004 Volume 379, Issue 5-6 Pages 764-769
Aristidis N. Anthemidis, George A. Zachariadis, Christos E. Michos and John A. Stratis

Abstract: A time-based sequential dispensing on-line column pre-concentration procedure for mercury determination at trace levels by cold vapor generation inductively coupled plasma atomic emission spectrometry (CV-ICP-AES), by means of a unified module of a pre-concentration column and a gas-liquid separator (PCGLS) is described. The complex of mercury formed on-line with ammonium pyrrolidine dithiocarbamate (APDC) is retained on the surface of the hydrophobic poly(tetrafluoroethylene) (PTFE) turnings, which are packed into the lower compartment of the PCGLS. Subsequently, mercury vapor is generated directly on the PTFE turnings by reductant SnCl2 and separated from the liquid mixture via the PCGLS by argon purge gas. The outlet of the PCGLS is connected directly to the torch adapter of the plasma without the normal spray chamber and nebulizer. With 60-s pre-concentration time and 12.0 mL min-1 sample flow rate, the sampling frequency is 30 h-1. The calibration curve is linear over the concentration range 0.02-5.0 µg L-1, the detection limit (cL) is 0.01 µg L-1 and the relative standard deviation (sr) is 3.1% at the 1.0 µg L-1 level. The proposed method was evaluated by analysis of BCR CRM 278 (Mytilus Edulis) reference material and applied to the determination of total mercury in digested urine, blood and hair samples.
Mercury Blood Urine Hair Spectrophotometry

"The Use Of Anion-exchange Disks In An Optrode Coupled To A Multi-syringe Flow-injection System For The Determination And Speciation Analysis Of Iron In Natural Water Samples"
Talanta 2005 Volume 66, Issue 1 Pages 210-217
Carmen Pons, Rafael Forteza and V&iacute;ctor Cerd&agrave;

Abstract: A combination of multi-syringe flow-injection analysis (MSFIA) technique with an optical fiber reflectance sensor for the determination of iron in water samples has been developed in this work. Anion-exchange solid phase extraction (SPE) disks have been used as solid phase. Ammonium thiocyanate has been chosen as chromogenic reagent for Fe(III). The complex Fe[SCN]63-; is retained onto the SPE disk and spectrophotometrically detected at 480 nm. The complex is eluted with 0.25 mol l-;1 hydrochloric acid in 75% ethanol. Total iron can be determined by oxidising Fe(II) to Fe(III) with hydrogen peroxide. A mass calibration was run within the range of 0.4-37.5 ng. The detection limit (3sb/S) was 0.4 ng. The repeatability (RSD), calculated from 9 replicates using 0.5 mL injections of a 25 µg l-;1 concentration, was 3.6%. The repeatability between five anion-exchange disks was 5.4%. An injection throughput of 7 injections per hour for a sampling volume of 1 mL has been achieved. The applicability of the proposed methodology in natural water samples has been proved. The properties of anion-exchange and chelating SPE disks have been studied and compared.
Iron(2+) Iron(III) NWRI TMDA-54.3 Sensor Spectrophotometry

"Multi-pumping Flow System For The Determination, Solid-phase Extraction And Speciation Analysis Of Iron"
Anal. Chim. Acta 2005 Volume 550, Issue 1-2 Pages 33-39
Carmen Pons, Rafael Forteza and V&iacute;ctor Cerd&agrave;

Abstract: A multi-pumping flow system (MPFS) for the spectrophotometric determination, solid-phase extraction (SPE) and speciation analysis of iron at a wide range of concentrations is proposed. Chelating (iminodiacetic groups) disks have been used as solid phase. A solenoid valve allows the deviation of the flow towards the chelating disk to carry out SPE procedures. The possibility to combine solenoid micro-pumps with solenoid valves increases the versatility of MPFS. Ammonium thiocyanate has been chosen as chromogenic reagent for Fe(III). The determination of total iron is achieved by the on-line oxidation of iron(II) to iron(III) with a hydrogen peroxide stream. A mass calibration was run within the range 0.01-1.75 µg. The detection limit (3sb/S) was 0.01 µg. The repeatability (RSD) was estimated as 1.6% after 10-fold processing of 2 mL of 0.5 mg L-;1 Fe solution. When SPE was not required, two linear calibration graph within the ranges 0.05-10 and 0.2-15 mg L-;1 for the determination of iron(III) and total iron, respectively, were obtained. The proposed procedure was validated by analysis of certified reference materials. The analytical features were compared with those obtained exploiting MSFIA.
Iron(2+) Iron(III) NRCC DORM-2 Sea NRCC SLRS-4 Spectrophotometry

"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