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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Environmental

Classification: Environmental -> water

Citations 490

"Chemiluminescence-based (bio)sensors - An Overview"
Crit. Rev. Anal. Chem. 1999 Volume 29, Issue 4 Pages 323-331
Hassan Y. Aboul-Enein, Raluca-Ioana Stefan and Jacobus F. van Staden

Abstract: This review discusses the advances in the design of chemiluminescence-based sensors and biosensors with particular emphasis on their classification. Several up-to-date applications are presented.
Chemiluminescence Sensor Review Immobilized reagent

"Selective Preconcentration Of Phenyl-mercury By Living Escherichia Coli And Its Determination By Cold Vapor Atomic Absorption Spectrometry"
Anal. Chim. Acta 2000 Volume 423, Issue 2 Pages 255-263
L. C. Robles, J. C. Feo and A. J. Aller

Abstract: A method is proposed for speciation of phenyl-mercury (Ph-Hg) in waters based on the retention of analyte by a living Escherichia coli strain (K-15) grown in the aqueous sample solution containing glucose as a nutrient. In the general procedure, equilibrium between the analyte in the sample and the living bacterial cells is allowed to be established. However, a theoretical model of the retention process, based on a rate-determining step in reaching the adsorption equilibrium, illustrates the feasibility of quantifying the analyte before equilibrium is reached. The Ph-Hg-biomass is separated from the solution by centrifugation and the amount of organo-mercury retained is determined directly in the biomass slurry by cold vapor atomic absorption spectrometry (CVAAS). Speciation of Ph-Hg from matrices containing other mercury species (ethyl-mercury, methyl-mercury, Hg2+, Hg(I)) and the CVAAS determination of Ph-Hg can be carried out with relative standard deviations of 2.2-5.3%. The detection limit for Ph-Hg under optimum conditions is 0.05 ng ml-1.
Phenylmercury Spectrophotometry Speciation Slurry Optimization

"Integrated Biological And Chemical Monitoring: In Situ Physiological Responses Of Freshwater Crayfish To Fluctuations In Environmental Ammonia Concentrations"
Ecotoxicology 1999 Volume 8, Issue 3 Pages 225-237
M. J. Bloxham, P. J. Worsfold, M. H. Depledge

Abstract: A portable, computer-aided physiological monitoring system (CAPMON) has been integrated with an automated, flow injection (FI) based chemical monitor to enable continuous, long-term recording of cardiac activity in selected aquatic organisms, and total ammonia concentration in the surrounding environment. Heart rate of the freshwater crayfish Pacifastacus leniusculus was recorded using non-invasive infrared emitter/detectors to transduce heart beat from 4 animals simultaneously. Data were collected continuously and stored on a laptop computer. The chemical monitor incorporated a gas diffusion unit and a solid state photometric detector. Remote control and data processing were accomplished using an in-house designed microcomputer. The instrumentation was fully evaluated in the laboratory and the field and was shown to be capable of operating unattended for periods of at least 1 week. An exposure-response experiment showed that 4 h exposures to concentrations of ammonia greater than 5 mg L-1 had a significant stimulatory effect on heart rate (ANOVA F = 7.6; df = 5; P < 0.0005). The feasibility of using the system in situ was demonstrated in a 2 week field trial in which the integrated monitors were successfully deployed at a landfill leachate lagoon.
Ammonia, total Spectrophotometry Remote instrument

"Detection Limits In Classical Multivariate Calibration Models"
Anal. Chim. Acta 2000 Volume 423, Issue 1 Pages 41-49
Ricard Boqu&eacute;, Nicolaas (Klaas) M. Faber and F. Xavier Rius

Abstract: This work presents a new approach for calculating multivariate detection limits for the commonly used classical or direct calibration models. The derived estimator, which is in accordance with latest IUPAC recommendations, accounts for the different sources of error related to the calibration and prediction steps. Since the multivariate detection limit for a given analyte is influenced by the presence of other components in the sample, a different detection limit is calculated for each analyte and analyzed sample, at the chosen significance levels α and beta. The proposed methodology has been experimentally validated by determining four pesticides in water using a FIA method with diode-array detection. The results compare favourably with the ones obtained using previously proposed estimators.
Pesticides Spectrophotometry Detection limit Multivariate calibration Selectivity

"Sequential Injection Analysis System For Total Inorganic Arsenic Determination By Hydride Generation-atomic Fluorescence Spectrometry"
Anal. Chim. Acta 2000 Volume 412, Issue 1-2 Pages 169-175
N. V. Semenova, F. M. Bauz&aacute; de Mirab&oacute;, R. Forteza and V. Cerd&aacute;

Abstract: A sequential injection analysis system is proposed for total inorganic arsenic determination by hydride generation-atomic fluorescence spectrometry. The sample, a reducing sodium tetrahydroborate solution and a blank solution containing HCl, ascorbic acid and potassium iodide are sequentially aspirated and then dispensed into a gas-liquid separation cell. An Ar flow sweeps the arsine into the flame of an atomic fluorescence spectrometer. An auxiliary H-2 flow was necessary to support the flame. Linear calibration graphs were obtained for arsenic concentrations between 2.5 and 50 µg L-1, the detection limit (3s(b)/S) being 0.67 µg L-1. The relative standard deviation of the method was 1.8% (n=9) when 0.5 mL of a 20 µg L-1 As standard solution was aspirated. The sample throughput was 33 samples per hour. The proposed method has been validated by means of reference materials and the results obtained were in good agreement with the certified values.
Arsenic, inorganic Fluorescence Sequential injection Reference material Phase separator Speciation

"Fluorimetric Sequential Injection Determination Of Magnesium Using 8-hydroxiquinoline-5-sulfonic Acid In A Micellar Medium"
Talanta 2000 Volume 52, Issue 1 Pages 77-82
G. de Armas, A. Cladera, E. Becerra, J. M. Estela and V. Cerd&agrave;

Abstract: A fluorimetric sequential injection method for the determination of magnesium is proposed. The system is based on the complex formation between Mg(II) and 8-hydroxyquinoline-5-sulfonic acid (HQS). The reaction was carried out in the presence of ethylene glycol-bis(β-aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA) as a masking agent. Cetyltrimethylammonium chloride (HTAC) was employed as a fluorescence enhancer. The influence of several variables, such as reagent concentration, volumes and pH has been investigated. The reagent was prepared in a 0.1 M Tris-HCl buffer solution (pH 9). A detection limit of 12 µg L-1 magnesium was obtained. The proposed method was applied to the determination of magnesium in natural waters.
Magnesium Fluorescence 8-hydroxyquinoline-5-sulfonic acid Sequential injection EGTA Optimization Complexation

"A New Flow Injection System For Spectrophotometric Determination Of Phosphate Ions"
Rev. Roum. Chim. 1999 Volume 44, Issue 8 Pages 771-777
Cheregi, M.C.;Danet, A.F.

Abstract: A flow injection system for determining the phosphate ions in natural, drinking, and residual waters was assembled. It contained an injection device with several mono-channel valves which can be either opened or shut simultaneously. Determination of PO43- ion with this FIA system is done by using the method based on the formation of phosphomolybdenum blue and spectrophotometric detection at 660 nm of the reaction product. The influence of different operational parameters was investigated. The calibration curve was linear over the 1-30 µg PO43- mL-1 domain, the relative standard deviation was 1.8% (n = 10) and the number of samples that could be analyzed was 30 h-1. A study on possibly interfering ions was also carried out. (SFS)
Phosphate Spectrophotometry Interferences Optimization

"Simultaneous Determination Of Nitrite And Nitrate In Various Samples Using Flow Injection With Spectrophotometric Detection"
Anal. Chim. Acta 1999 Volume 382, Issue 1-2 Pages 15-21
Ali A. Ensafi and A. Kazemzadeh

Abstract: A direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow injection analysis has been developed. The method is based on catalytic effect of nitrite on the oxidation of gallocyanine by bromate in acidic media and the decrease in absorbance of the system at 530 nm. The injected sample is split into two segments. One of the streams was directly treated with the above reagents and passed to the sample how cell of the spectrophotometer. The decrease in absorbance at 530 nm is due to the nitrite. The other stream was passed through a reductor minicolumn containing copperized-cadmium, where reduction of nitrate to nitrite occurs, and then the sample was treated with the mixed reagents and was passed through the same cell of the spectrophotometer. The total nitrite concentration initially plus that produced was determined. The influences of reagent concentration and manifold parameters were studied. The effect of potential interfering ions was examined. Nitrite and nitrate can be determined for the range of 0.010-2.500 µg mL-1 and 0.020-3.500 µg mL-1, respectively. The sampling rate of analysis was 20±3 hr-1, with 3s detection limits of 0.001 and 0.002 µg mL-1 for nitrite and nitrate, respectively. Nitrite and nitrate were determined in food and water samples by the proposed method with satisfactory results.
Nitrate Nitrite Spectrophotometry Catalysis Indirect Reduction column Simultaneous analysis Optimization Interferences

"Performance Characteristics For Flow Injection Immunoassay Using Monoclonal Antibodies Against S-triazine And 2,4-D Herbicides"
Anal. Chim. Acta 2000 Volume 412, Issue 1-2 Pages 19-27
Milan Fr&aacute;nek, Anping Deng and Vladim&iacute;r Kol&aacute;&#345;

Abstract: A sequential injection instrument (ALITEA, USA) with a photometric and fluorometric detection unit S2000 (Ocean Optics) was employed for the development of flow injection immunoanalysis (FIIA). The monoclonal antibodies against atrazine, simazine and 2,4-D were immobilized on aminopropyl glass particles by means of avidin/biotin system and packed in plexiglass column of 18 µl volume. Assay characteristics for individual antibody-reactors and regeneration effectivities for acid and alkaline solutions are described. An attempt to prepare a functional mixed antibody-reactor has not achieved success since regeneration conditions found for individual reactors were not compatible with one performance protocol.
Atrazine Simazine 2,4-Dichlorophenoxyacetic acid Spectrophotometry Fluorescence Calibration Automation Column Immobilized antibody

"Selective Inhibition-based Biosensing System For The Determination Of Pesticides In Environmental Samples Using Analytical Pervaporation Coupled With Enzymatic Derivatisation"
Anal. Chim. Acta 2000 Volume 408, Issue 1-2 Pages 209-216
F. Delgado Reyes, J. M. Fern&aacute;ndez Romero and M. D. Luque de Castro

Abstract: A novel and selective method based on inhibition reactions coupled with a prior separation step consisting of analytical pervaporation has been designed and used in order to develop a method for the determination of diclorvos. The method is based on the inhibitory effect of this organophosphorous pesticide (low boiling point 35°C) on the acetylcholinesterase catalysis after selective pervaporation of the analyte, The derivatization reaction is a two-step reaction involving choline oxidase (ChOD) and horseradish peroxidase (POD) with fluorimetric detection at lambda(ex) = 310 nm and lambda(em) = 415 nm of the dimer formed, The method applied to liquid samples has a linear determination range of 0.05-0.5 mmol L-1 (n = 8, r2 = 0.9959) with excellent precision (RSD<3.2%) and a sampling frequency of 3 h-1. When applied to solid samples the method has a linear determination range of 0.001-0.04 g kg-1 (n = 5, r2 = 0.9909, RSD<4.2%) and a sampling frequency of 2 h-1. The approach has been applied to the determination of diclorvos in natural water and spiked soil samples with recoveries between 89.9 and 109.7%.
Pesticides, organophosphorus Diclorvos Fluorescence Pervaporation Indirect

"Amperometric Determination Of Se(IV) With On Line Preconcentration By Flow Injection Anlysis"
Bol. Soc. Chilena Quim. 2000 Volume 45, Issue 1 Pages 99-107
M.A. Machuca, I. De Gregori and H. Pinochet

Abstract: The experimental conditions for the indirect amperometric detection of Se(IV) by flow injection analysis have been optimized. The method is based on the Se(IV) reduction to Se(0) in acid medium in presence of an excess of iodide, being generated yotrion species which is electroactive and amperometrically detected at vitreous carbon electrode. The signal depends on the quantity of Se(IV) in the samples. Under optimized conditions, analytical conditions of the method were determined. The detection and quantification limits were 4.8 µg L-1 and 15.9 µg L-1, respectively. Because of the method proposed for its application to the determination of Se(IV) in natural water samples, it became necessary to increase the detection sensitivity and an on-line concentration stage was coupled. This stage is carried out on an anionic resin exchange (Dowex 1-X8). The detection and the quantification limits were in this case 0.06 µg L-1 and 0.2 µg L-1, respectively. The online pre-concentration stage increases the sensibility of the amperometric detection which allows the Se(IV) determination at µg L-1 levels.
Selenium(IV) Amperometry Electrode Preconcentration Optimization Speciation Volatile generation Dowex Resin Indirect

"Spectrophotometric Determination Of Phosphate And Silicate By Sequential Injection Using Molybdenum Blue Chemistry"
Anal. Chim. Acta 2000 Volume 417, Issue 2 Pages 191-200
Cristiane X. Galhardo and Jorge C. Masini

Abstract: This paper presents a spectrophotometric sequential injection (SI) determination of phosphate and silicate in environmental samples and cell cultivation medium using the molybdenum blue reaction. The interference of silicate in the determination of phosphate was eliminated by using a reagent composed of 5 mmol L-1 ammonium molybdate in 0.2 mol L-1 nitric acid, containing 0.25% (w/v) oxalic acid to avoid the formation of molybdosilicic acid. The interference of phosphate in the determination of silicate was avoided adding a 10% (w/v) oxalic acid solution to the reaction zone where the molybdophosphoric and molybdosilicic acids were previously formed, in order to destroy the molybdophosphoric acid. To perform this task in the single Line SI system, obtaining a total sample and reagent zones penetration, it was used as a combination of sandwiching the sample zone between reagent zones and flow reversal through an auxiliary reaction coil. The method has a phosphate sampling frequency of 75 hr-1, with a linear dynamic range between 0.2 and 7 mg L-1 and a detection limit of 0.1 mg L-1 PO43 = P. For silicate, the sampling frequency is 40 h-1 with a linear dynamic range between 5 and 50 mg L-1 and a Limit of detection of 1 mg L-1 SiO32 = Si.
Phosphate Silicate Spectrophotometry Sequential injection Interferences Flow reversal

"Speciation Of Antimony(III) And Antimony(V) Using Hydride Generation Inductively Coupled Plasma Atomic Emission Spectrometry Combined With The Rate Of Pre-reduction Of Antimony"
Anal. Chim. Acta 1999 Volume 386, Issue 3 Pages 297-304
Yong-Lai Feng, Hisatake Narasaki, Hong-Yuan Chen and Li-Ching Tian

Abstract: Antimony(III) and antimony(V) were speciated by hydride generation inductively coupled plasma atomic emission spectrometry (HG-ICP-AES) based on the pre-reduction kinetics of antimony(V) to antimony(III) with L-cysteine. A linear relationship between the reduced amount of antimony(V) with 3 mg mL-1 of L-cysteine and the reaction time was achieved within 10 min. The reduced amount of antimony(V) were determined after 2 and 8 min, respectively, by using HG-ICP-AES in this method. Mutual interferences of antimony(III) and antimony(V) were investigated. Interferences from transition metals were removed by a Chelex 100 resin column. The method was successfully applied to speciate antimony(III) and antimony(V) in spiked water samples. The detection limits of the method for antimony(III) and antimony(V) were 1.2 and 4.5 ng mL-1 respectively.
Arsenic(3+) Arsenic(5+) Spectrophotometry Speciation Volatile generation Chelex

"Flow Injection Speciation Of Aluminum"
Water Res. 2000 Volume 34, Issue 2 Pages 359-365
Krystyna Pyrzynska, Seref Gu&ccedil;er and Ewa Bulska

Abstract: This review discusses recent trends in chemical speciation of aluminum in natural waters. Several difficulties which arise from the complexity of aluminum species present in natural samples as well as its participation in dynamic equilibrium are highlights. Taking this into account various approaches for speciation of Al described in the literature are critically evaluated. The strategy of fractionation procedures based on the rate of reaction, sorption efficiency, chromatographic behavior of the aluminum compounds or size of the molecules are described in the paper. Besides conventional procedures involving various measuring and separation techniques, a special emphasis is focused on mechanised flow injection methodologies. This was found to be very important in order to ensure precise control of the reaction time. which is essential in aluminum species equilibrium system. The analytical performance of several separation procedures based on flow injection approaches as well as the detection methods are discussed and compared.
Aluminum, labile Aluminum, reactive Aluminum, bound HPLC Spectrophotometry Review Method comparison

"Determination Of Lead By Hydride Generation Inductively Coupled Plasma Mass Spectrometry"
Anal. Chim. Acta 2000 Volume 419, Issue 1 Pages 65-72
Jinxiang Li, Fang Lu, Tomonari Umemura and Kin-ichi Tsunoda

Abstract: A method for the determination of lead by hydride generation inductively coupled plasma mass spectrometry was explored using oxalic acid-ammonium cerium(IV) nitrate-sodium tetrahydroborate as the reaction matrix and a homemade hydride generator. The sensitivity achieved was ~7.5 times higher than that obtained using an ultrasonic nebulizer. The detection limit (3s) and the signal precision (RSD, n=13) were 0.007 µg L-1 and 0.21% for 1 µg L-1 Pb, respectively, Fe(III) or Ni(II) up to 10 mg L-1 did not affect the hydride generation of 1 µg L-1 Pb. Additionally, the present system equipped with an injector valve and a 500 µl sample loop was also operated in the flow injection mode. Because of the short memory effect (typically 25-30 s), six replicate injections of a solution containing 4 µg L-1 Pb were performed within 5 min. The RSD values (n=13) were 0.33 and 1.41% for peak height and area measurements, respectively. The method was applied to the determination of lead in three environmental reference materials involving natural water, plant tissue and pond sediment. Good agreement was obtained between the certified values and the experimental results with the precisions (RSD, n=5) less than 1.0% for both continuous and flow injection modes.
Lead Mass spectrometry Interferences Volatile generation Reference material Method comparison

"An Improved Technique For The Determination Of Oxidised Nitrogen In Natural Waters With A Sequential Injection Analysis (SIA) System"
Water SA 2001 Volume 27, Issue 3 Pages 355-360
EB Naidoo and JF van Staden

Abstract: An SIA systems proposed for the determination of oxidized nitrogen (nitrate + nitrite as N) in natural waters. A cadmium reductor, made of cadmium granules, closely packed in a glass column reduces the nitrate to nitrite. The reduced nitrate and the nitrite present in the water samples is diazotised in the SIA system with sulphanilamide and coupled with N - (1-napthyl) ethylene diammoniumdichloride to form a highly colored azo dye which is detected at 540 nm with a UV/Vis spectrophotometer. The proposed system is fully computerised and is able to monitor total oxidized nitrogen as nitrite at a frequency of 36 samples per hour with a standard deviation of < 1.2%, The calibration curve is linear up to 5 mg/l with a detection limit of 0.01 mg/l.
Nitrate Nitrite Spectrophotometry Column Solid phase reagent Automation

"Flow Injection On-line Sorption Preconcentration And Separation Coupled With Atomic (mass) Spectrometry For Trace Element (speciation) Analysis"
Acta Chim. Sin. 2001 Volume 59, Issue 7 Pages 987-993
YAN Xiu-Ping

Abstract: Flow injection (FI) on - line sorption separation and pre-concentration coupled with atomic (mass) spectrometry using knotted reactors (KRs) for trace element (speciation) analysis is discussed. Compared with FI on - line C-18 column pre-concentration systems, the KR sorption system permits use of higher sample loading rates to achieve higher concentration efficiencies due to low hydrodynamic impedance in the KR. Moreover, the KR allows the analysis to be conducted at low cost, owing to the long lifetime of the KR and its ease of construction with no need for packing materials, offering a good alternative to conventional C-18 column pre-concentration systems.
Lead Copper Mass spectrometry Preconcentration Knotted reactor C18 Speciation

"Flow Injection Methods Of Analysis For Waters. I. Inorganic Species"
Crit. Rev. Anal. Chem. 2001 Volume 31, Issue 3 Pages 191-222
Andrei. F. Danet, Mihaela Cheregi, Jose Martinez Calatayud, Jose Vicente Garcia Mateo and Hassan Y. Aboul Enein

Abstract: A comprehensive, critical, and an updated review of the applications of flow-injection analysis (FIA) techniques for the analysis of inorganic cations and anions in several types of water samples except marine waters is presented. The pre-concentration of metals in water samples and automaton of FIA systems for monitoring water quality are also discussed. The review is documented with 280 references.
Automation Preconcentration Review

"A New Device For Improving Sensitivity And Stabilization In Flow Injection Analysis"
Anal. Chim. Acta 1978 Volume 97, Issue 2 Pages 427-431
H. Bergamin F, B. F. Reis and E. A. G. Zagatto

Abstract: In flow injection anal., an aqueous sample is injected into a continuous moving carrier stream of reagent. If the sample injection is done by forcing the liquid into the carrier stream, the regularity of the flow is disturbed momentarily. There is a temporary difference in mixing ratios at those points in the manifold where 2 streams meet. This can cause a change in the blank values. To minimize these changes, while increasing sensitivity, a confluence manifold was used for the spectrophotometric and/or turbidimetric determination of NO2-, SO42-, and Cl- in natural waters. An injection pulse dampener is described and is recommended when flow injection confluence systems are employed for anal. of very dilute samples.
Chloride Chlorine Chlorate ion Perchlorate Nitrite Sulfate Spectrophotometry Turbidimetry Apparatus Pulse dampener

"The Determination Of Sulfate By Flow Injection Analysis With Exploitation Of PH Gradients And EDTA"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 319-323
S. Baban, D. Beetlestone, D. Betteridge and P. Sweet

Abstract: A modified method for the turbidimetric determination of sulfate as BaSO4 is proposed. The carrier stream is an alkaline Ba-EDTA solution; the sample zone is sufficiently acidic to allow precipitation of BaSO4. The excess of EDTA in the carrier stream ensures that residual ppt. is redissolved and the system kept clean.
Sulfate Turbidimetry Precipitation pH gradient EDTA

"Improved Flow Injection Determination Of Nitrite In Waters By Using Intermittent Flows"
Anal. Chim. Acta 1980 Volume 120, Issue 1 Pages 399-403
E. A. G. Zagatto, A. O. Jacintho, J. Mortatti and Bergamin F&deg; H

Abstract: An injector-commutator with a 0:1:2 section is employed to achieve intermittent flows without intermittent pumping. The resulting flow injection system is very simple, manually operated, and requires only one peristaltic pump. When applied to the spectrophotometric determination of nitrite in waters, the device leads to an enhancement of the sensitivity and sampling rate without affecting other analytical characteristics. The merging zones approach is employed to decrease consumption of reagents.
Nitrite Spectrophotometry Intermittent pumping Merging zones Proportional injector

"Merging Zones In Flow Injection Analysis. 6. Determination Of Calcium In Natural Waters, Soil And Plant Materials With Glyoxal-bis(2-hydroxanil)"
Anal. Chim. Acta 1981 Volume 130, Issue 2 Pages 361-368
A. O. Jacintho, E. A. G. Zagatto, B. F. Reis, L. C. R. Pessenda and F. J. Krug

Abstract: A flow injection procedure is proposed for the spectrophotometric determination of calcium in natural waters, soil extracts and plant digests, employing glyoxal bis(2-hydroxyanil) as the color-forming reagent. The necessary dissociation of this reagent, which is rather slow, proceeds outside the analytical path, and the merging-zones approach is used for reagent addition. Composition of reagents, dissociation time of the colorforming reagent, ethanol content in the carrier streams and interferences are described. In the analysis of plant and soil materials, zone sampling is required for initial sample dilution. The proposed systems are very stable and permit a sampling rate of 180 determinations per hour. Relative standard deviations are less than 1%. The results compare well with those obtained by inductively-coupled argon-plasma atomic emission spectrometry.
Calcium Spectrophotometry Apparatus Injector Zone sampling Merging zones

"Flow Injection Potentiometric Determination Of Residual Chlorine In Water"
Anal. Chim. Acta 1982 Volume 136, Issue 1 Pages 85-92
Marek Trojanowicz, Wojciech Matuszewski and Adam Hulanicki

Abstract: Residual chlorine is measured in water by using a potentiometric system composed of an iodide-selective electrode and a platinum electrode sensing the iodine-iodide ratio. When the sample is added to acidified iodide solution, the cell response is in a logarithmic relation to the iodine concentration which in turn depends on the concentration of residual chlorine. In the flow injection system evolved, 0.1-5.0 mg L-1 residual chlorine can be determined at a rate of 40-60 samples per hour. The results of potentiometric determinations of residual chlorine in tap water compared to spectrophotometric results suggest that the presence of various organic substances is responsible for discrepancies between these measurements.
Chlorine Electrode Electrode Potentiometry

"Automated Simultaneous Determination Of Nitrate And Nitrite By Pre-valve Reduction Of Nitrate In A Flow Injection System"
Anal. Chim. Acta 1982 Volume 138, Issue 1 Pages 403-408
Jacobus F. Van Staden

Abstract: Nitrate is reduced to nitrite by using the pre-valve in-valve reduction technique prior to the sampling system. One loop of a two-position sampling valve is replaced by a copperised cadmium column. Nitrite from the samples as well as nitrite formed in the reduction procedure is sampled by a second valve and introduced into the flow system. The two sampling valves are synchronised in such a way that two peaks are obtained, one corresponding to the nitrate plus nitrite and the other to the nitrite only. The method is suitable for the simultaneous determination of nitrate and nitrite at a sampling rate of up to 72 determinations per hour with coefficients of variation better than 1.96% for nitrate and 0.83% for nitrite.
Nitrite Nitrate Spectrophotometry Sample valve manipulation Simultaneous analysis

"Continuous Monitoring Of Total And Inorganic Mercury In Wastewater And Other Waters"
Anal. Chim. Acta 1982 Volume 140, Issue 1 Pages 179-185
Masashi Goto, Takahiro Shibakawa, Tomomitu Arita and Daido Ishii

Abstract: An automated continuous monitoring system for the determination of total as well as inorganic mercury by cold-vapor atomic absorption spectrometry is described. The method uses continuous flow digestion, reduction and extraction in small bore tubes at slow flow rates, and is suitable for use in the analysis of wastewater and natural waters. A detection limit of 0.1 ppb is obtained when a specially designed, complete gas-liquid separator is used with a condenser circulated with ice-chilled water for removing water vapor, and an 8-l flow cell for detection. The response times for the determination of inorganic and total mercury are about 3 and 5 min, respectively. The amount of reagents required is about one-tenth of that in conventional Auto-Analyzer methods.
Mercury Mercury(II) Spectrophotometry Computer

"Determination Of Molybdenum At µg/L Levels By Catalytic Spectrophotometric Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 143-150
Fang Zhao-Lun and Xu Shu-Kun

Abstract: A flow injection analytical method based on the catalytic action of molybdenum on the oxidation of iodide by hydrogen peroxide in acidic medium is proposed. The triiodide formed is measured spectrophotometrically at 350 nm. Molybdenum is determined in natural water samples without pre-concentration at a sampling rate of 90 h-1 with 200 µL sample injections. The detection limit is 0.7 µ L-1 and the calibration curve is linear over the range 1-1000 µ l-1. The relative standard deviation is 0.83% for 50 µ L-1 molybdenum and 1.9% for 13 µ L-1 molybdenum.
Molybdenum Spectrophotometry Catalysis Merging zones

"Spectrophotometric Determination Of Calcium With A Flow Injection System"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 135-141
G. Nakagawa, H. Wada and C. Wei

Abstract: The indirect spectrophotometric determination of 0.8-7.2 ppm calcium in the presence of magnesium, phosphate and sulphate by flow injection analysis (f.i.a.) is described. The method is based on the exchange reaction between the calcium and the zinc complex of ethylene glycol-bis(2-aminoethylether)tetraacetic acid (EGTA) in the presence of 4-(2-pyridylazo)resorcinol (PAR): Ca + Zn(EGTA) + 2 PAR ⇔ Zn(PAR)2 + Ca(EGTA). A home-made and a commercial flow injection system with a sampling rate of 80 h-1, are compared. Results for water samples are in good agreement with those obtained by atomic absorption spectrometry.
Calcium Spectrophotometry

"Turbidimetric Determination Of Sulfate In Plant Digests And Natural Waters By Flow Injection Analysis With Alternating Streams"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 179-187
F. J. Krug, E. A. G. Zagatto, B. F. Reis, O. Bahia F&deg; and O. JacinthoS. S. J&oslash;rgensen

Abstract: An improved flow injection system with alternating streams of reagents is described for the turbidimetric determination of sulphate. Samples are injected into an inert carrier stream which is mixed with barium chloride to form a barium sulphate suspension. The range of the method can be extended to low concentrations by continuously adding sulphate to the sample carrier stream. System performance is improved by automatic alternate pumping of the reagent stream and an alkaline EDTA solution at high flow rate. All operations are controlled by an electronically-operated proportional injector-commutator. Even after routine analysis of 3000 samples of natural waters and plant digests, baseline drift was not observed. The proposed method is suitable for 120 samples per hour with a relative standard deviation less than 1% for sulphate concentrations in the range 1-30 ppm (waters) or 5-200 ppm (plant digests). The results compare well with those obtained by standard manual procedures.
Sulfate Sample preparation Turbidimetry Intermittent pumping Injector

"Performance And Characteristics Of The Fluoride-selective Electrode In A Flow Injection System"
Anal. Chim. Acta 1983 Volume 145, Issue 1 Pages 207-212
P. Van Den Winkel and G. De Backer, M. Vandeputte, N. Mertens, L. Dryon and D. L. Massart

Abstract: A simple, inexpensive home-made timer for coupling cam-controlled samplers to injectors for flow injection analysis is presented. Experimental conditions and a flow diagram are described for the determination of fluoride by means of a fluoride-selective electrode in the concentration range 0.3-10 ppm, with a sample rate up to 120 hr-1.
Fluoride Electrode Apparatus

"Transient Oxidation Of Brucine In Solution As A Tool For The Determination Of Chromium(VI) And Brucine"
Anal. Chim. Acta 1983 Volume 146, Issue 1 Pages 181-190
Takeshi Yamane and Horacio A. Mottola

Abstract: The oxidation of the alkaloid brucine by chromium(VI) in sulfuric acid medium in the presence and absence of oxalic acid is described. Photometric monitoring of a red intermediate (λmax = 525 nm) permits determinations of both chromium (VI) and brucine at low concentrations (Cr(VI), 0-7.5 µg mL-1; brucine, 0-197 µg mL-1) in an unsegmented continuous-flow system by direct injection of the sample into the detection area. Detection limits are 0.1 µg mL-1 for chromium and 4 µg mL-1 for brucine. Other alkaloids structurally related to brucine (e.g., strychnine, yohimbine and corynanthine) do not give intermediates with the high molar absorptivity exhibited by brucine. Determination of chromium in water samples and standards is described.
Chromium(VI) Brucine Spectrophotometry

"Zone Trapping In Flow Injection Analysis. Spectrophotometric Determination Of Low Levels Of Ammonium Ion In Natural Waters"
Anal. Chim. Acta 1983 Volume 151, Issue 1 Pages 39-48
F. J. Krug, B. F. Reis, M. F. Gin&eacute; and E. A. G. ZagattoJ. R. Ferreira, A. O. Jacintho

Abstract: The advantages of zone-trapping flow injection analysis over stopped-flow and intermittent-flow methods are discussed. In this method, the central portion of a processed sample is removed from the analytical path, set aside for a specified time under certain conditions, and later re-introduced into the same carrier stream. The technique was studied for a model system without chemical reaction, and then applied to the determination of NH4+ in natural waters via a modified Berthelot reaction. The main portion of the reacting sample zone is retained in a water bath at 38°C so that ~80% complete reaction is achieved without affecting the sampling rate. About 90 to 100 measurements can be made per hour; the coefficient of variation is 0.5%. Beer's law is obeyed up to 1 mg l-1, and the detection limit is 5 µg l-1. Interfering metal ions are masked by EDTA.
Ammonium Spectrophotometry Interferences Heated reaction Intermittent pumping Stopped-flow Zone trapping

"Spectrophotometric Determination Of Nitrite In Natural Waters By Flow Injection Analysis"
Anal. Chim. Acta 1983 Volume 155, Issue 1 Pages 263-268
Susumu Nakashima and Masakazu Yagi, Michio Zenki and Akinori Takahashi, Kyoji T&ocirc;ei

Abstract: The sample is injected into a stream of 0.04% 4'-aminoacetophenone solution (pH 1.3), which is then mixed with 0.11% m-phenylenediamine solution (pH 2.4). The mixture is passed through a 1-m reaction coil, and the absorbance is measured at 456 nm. Calibration graphs are rectilinear for 30 µg L-1 of N (as NO2-), and the coefficient of variation at levels of 10, 20 and 30 µg L-1 are 1.3, 1.1 and 0.39%, respectively. The limit of detection is 0.2 µg L-1 of N; at the level of 30 µg L-1 there is no interference from 50 mg L-1 of Ca(II), Mg(II), Na+, K+, NH4+, HCO3-, SO42-, Cl-, SiO32-, NO3- or H2PO4-. The method has been applied to various natural waters. The sampling rate is 30 h-1.
Nitrite Spectrophotometry Interferences

"Potentiometric Stripping Analysis For Manganese(II) In Natural Waters"
Anal. Chim. Acta 1984 Volume 161, Issue 1 Pages 293-302
Hel&eacute;n Eskilsson and David R. Turner

Abstract: Potentiometric stripping analysis (p.s.a.) methods for the measurement of manganese(II) in natural waters are described; batch and flow approaches are discussed. The more versatile flow p.s.a. technique is suitable for concentrations in the range 2 nM-30 µM. Application of these techniques is illustrated by measurements in a variety of natural waters. Interferences arising from manganese-copper interactions in the mercury electrode can be suppressed by the addition of zinc or gallium depending on the concentration of the interfering copper. The relative merits of the batch and flow p.s.a. techniques are discussed.
Manganese(II) Potentiometric stripping analysis

"Fluorimetric Determination Of Trace Hydrogen Peroxide In Water With A Flow Injection System"
Anal. Chim. Acta 1985 Volume 170, Issue 2 Pages 347-352
Hoon Hwang and Purnendu K. Dasgupta

Abstract: Reagent solution containing 6% of 4-hydroxyphenylacetic acid and 0.312% of Na2EDTA in 0.1 M NH3 (pH 9.5), to which peroxidase (type II; 450 iu dl-1) was added shortly before use, was mixed with a carrier water stream containing H2O2, and the reaction mixture was directed, via a knotted delay line, to a fluorescence detector operated at 412 nm (excitation at 329 nm). The calibration graphs were rectilinear for 0.01 to 100 µM-H2O2, and the coefficient of variation (n = 7) were 7.1, 2.7 and 0.3% for 1, 4 and 8 µg l-1, respectively. Use of NH3 in the reagent solution increased the reaction rate at high pH values, which maximized the fluorescence intensity, allowing a single-step procedure to be used.
Hydrogen peroxide Fluorescence Knotted reactor

"Determination Of Nickel And Cobalt In Natural Waters And Biological Material By Reductive Chronopotentiometric Stripping Analysis In A Flow System Without Sample Deoxygenation"
Anal. Chim. Acta 1985 Volume 175, Issue 1 Pages 79-88
H. Eskilsson and C. Haraldsson, D. Jagner

Abstract: Samples (100 ml) of natural waters, or portions (0.5 to 5 ml) of acid digests of seawater sediments or bovine liver, were mixed with 3 M NH3 - HCl buffer (pH 9.2) and 0.1 M dimethylglyoxime(I) solution in ethanol; Co(III) species formed during acid digestion were reduced with NaBH4. Electroanalysis was performed in a thin-layer flow cell with a vitreous-carbon working electrode. The microprocessor-controlled operational sequence included(I) plating of a mercury film on to the carbon electrode;(II) potentiostatic adsorption (at -0.5 V vs. the SCE) of the Ni(II) - and Co(II) - I complexes on to the mercury film; (iii) constant-current reduction of the metal ions in a 5 M CaCl2 medium and simultaneous recording of the working-electrode potential vs. time; (iv) chemical removal of the mercury film; and (v) cleaning of the vitreous-carbon surface. To determine Co in presence of a large excess of Ni, an adsorption potential of -0.75 V vs. the SCE was used. Detection limits (after 70 s of adsorption) were 8.6 ng L-1 for Ni(II) and 10.5 ng L-1 for Co(II).
Nickel Cobalt Potentiometric stripping analysis Electrode Sample preparation Interferences

"Polarographic Detection By Reverse-pulse Amperometry In Cation-exchange Chromatography [of Trace Metals In Water] Without Interference From Dissolved Oxygen"
Anal. Chim. Acta 1985 Volume 175, Issue 1 Pages 23-35
Taisung Hsi and Dennis C. Johnson

Abstract: Samples of ground waters were acidified to pH 1.6 and treated with 10% Na acetate and 5% hydroxylammoniun chloride, to reduce Fe(III) to Fe(II). Power-plant water samples were pre-concentrated with use of a Dowex 50W-X8 cation-exchange column. Filtered aliquots (100 µL) were then injected on to a column (5 cm x 4 mm) packed with Durrum DC-4A sulfonated cation-exchange resin, with 0.25 M Na H tartrate - 0.06 M Mg(II) at pH 3.8 as mobile phase (0.62 mL min-1). Polarographic flow injection detection of Cu(II), Zn(II), Ni(II), Pb(II), Cd(II) and Fe(II) was carried out with use of a static dropping-mercury electrode at +0.20 V vs. the SCE. Rectilinear calibration graphs were obtained for all cations. Detection limits in ground-water samples were 64 µg L-1 (Cu(II)), 13 µg L-1 (Zn(II)), 120 µg l-1(Ni(II)), 83 µg L-1 (Pb(II)), 56 µg L-1 (Cd(II)) and 100 µg L-1 (Fe(II)); pre-concentration improved these limits ~100-fold. Removal of dissolved O was not needed because the anodic signals for oxidation of the reduction products were measured at a potential at which O was not electroactive.
Cadmium(2+) Copper(II) Iron(2+) Lead(2+) Nickel(II) Zinc(II) Amperometry HPIC Electrode Polarography Interferences Dowex Preconcentration Resin

"Comparison Of Four Chromogenic Reagents For The Flow Injection Determination Of Aluminum In Water"
Anal. Chim. Acta 1985 Volume 178, Issue 2 Pages 223-230
Oddvar R&oslash;yset

Abstract: Detection limits for Al in water by flow injection with use of(I) aluminon,(II) catechol violet, (iii) Eriochrome cyanine R and (iv) Eriochrome cyanine R - hexadecyltrimethylammonium bromide as chromogenic reagents were 50, 5, 5 and 1 µg l-1, respectively. Interference from <5 mg L-1 of Fe was suppressed by hydroxylammonium chloride and 1,10-phenanthroline in methods(II) and (iv) and masked by ascorbic acid in methods(I) and (iii). All methods could tolerate <0.2 mg L-1 of F-. The aluminon method could tolerate 500 mg L-1 of phosphate but phosphate interfered at concentration. of >5 mg L-1 in the three other methods. All methods were sensitive to changes in sample acidity; the acidity should be 0.08 to 0.12 M HCl. Methods (iii) and (iv) showed no special advantages for the routine determination of Al in water and therefore catechol violet remained the chosen reagent.
Aluminum Spectrophotometry Interferences Tecator Chromogenic reagent

"Coated Tubular Solid-state Chloride-selective Electrode In Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 407-417
J. F. Van Staden

Abstract: The construction of the electrode is described and illustrated. Response times are 3 to 4 s and the range is 5 to 5000 mg L-1 for 30 µL samples. Mean recoveries of 67 and 114 mg L-1 are 97.8 and 98.9%, respectively, with coefficient of variation in the analysis of 16 water samples being <1.7% (n = 15). The results agree well with those obtained spectrophotometrically.
Chloride Electrode Electrode Apparatus Method comparison

"Determination Of Some Organophosphorus Insecticides By Flow Injection With A Molecular Emission Cavity Detector"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 497-502
J. L. Burguera and M. Burguera

Abstract: The insecticides are extracted from waters into hexane - CH2Cl2 (17:3) at pH <7 followed by measurement of the HPO emission at 528 nm vs. time in the system previously described (Ibid., 1985, 170, 331). Dicrotophos and dimethoate are measured in the range of 5 to 100 ng of P and malathion and parathion from 10 to 120 ng with detection limits between 0.8 and 2.5 ng. Recoveries are between 73.4 and 98.1% for 50 ng of P with coefficient of variation between 2.5 and 3.4% for 20 ng (n = 8).
Insecticides Dicrotophos Dimethoate Malathion Parathion Spectrophotometry Sample preparation Extraction

"Flow Injection Spectrophotometric Determination Of Aluminum In Water With Pyrocatechol Violet"
Anal. Chim. Acta 1986 Volume 185, Issue 1 Pages 75-81
Oddvar Royset

Abstract: The sample was injected into a stream of 0.1 M HCl (0.8 mL min-1) and mixed in a 50-cm coil with a stream of Fe-masking solution containing 0.5 M hydroxylammonium chloride and 10 mM 1,10-phenanthroline (0.32 mL min-1). The mixed stream was merged with streams of 5 mM catechol violet (0.23 mL min-1) and 3.0 M hexamine buffer adjusted to pH 6.1 to 6.2 with 0.2 M HCl (1.0 mL min-1) in a 6-m coil and the absorbance of the product was measured at 581 nm. Calibration graphs were rectilinear for up to 3 or 10 mg L-1 of Al with 200- and 10 µL injection loops, respectively; the detection limit was 3 µg L-1 of Al. In determination of 0.1 mg L-1 of Al the coefficient of variation was <2%. Interference of 40 common inorganic ions and 20 organic compounds, including fulvic acid, was studied. The method could be applied to natural water samples at a rate of 100 h-1 after digestion with S2O82- to remove organic compounds.
Aluminum Spectrophotometry Sample preparation Interferences Tecator

"The Efficiency Of Cellex-P For The Preconcentration Of Lead And Other Trace Metals From Waters"
Anal. Chim. Acta 1986 Volume 185, Issue 1 Pages 271-277
Krystyna Brajter and Krystyna Sonawska

Abstract: The cheating ion-exchanger Cellex-P, a cellulose phosphate ester, is shown to be effective for the pre-concentration of Cu, Ni, Mn, Cd, Zn and Pb from water. The pH of the sample is not critical within the approximate range 5-8. The collected ions can be eluted efficiently in 10^-25 mL of 1 M nitric acid from 2-16.5-cm columns of resin. Common salts present in natural waters do not interfere. Cellex-P is used for the pre-concentration and determination of the metal ions in potable water by graphite-furnace atomic absorption spectrometry.
Lead Metals, trace Cellex Preconcentration Resin

"Flow Injection Method For The Determination Of Trace Amounts Of Chloride By Using Differences In Electric Conductivity"
Anal. Chim. Acta 1987 Volume 196, Issue 1 Pages 163-169
G. Lach and K. B&auml;chmann

Abstract: Chloride in water was determined by a method involving ion exchange on a column of Dowex 50W-X8 resin (200 to 400 mesh; Ag+ form) and then on a column of resin in the H+ form. Detection was effected with a conductivity cell; the signal for the solution passing through only H+-form resin corresponded to all the anions present, whereas the other signal excluded Cl-. Response was rectilinear from ~0.5 to 10 µg g-1 of Cl- (with 3 µg g-1 of NO3- and 5 µg g-1 of SO42-) and the limit of detection was ~50 ng g-1 of Cl- but depended strongly on the concentration. of other anions.
Chloride Conductometry Ion exchange Interferences Resin

"Spectrophotometric Field Monitor For Water Quality Parameters. The Determination Of Phosphate"
Anal. Chim. Acta 1987 Volume 197, Issue 1 Pages 43-50
Paul J. Worsfold and J. Richard Clinch, Harry Casey

Abstract: Aliquots (30 µL) of a mixture of 8% ascorbic acid solution in aqueous 10% (w/v) glycerol and 1% (NH4)6Mo7O24 solution in 0.4 M HNO3 were injected into a continuous sample stream (1.1 mL min-1) of water flowing in PTFE tubing (0.5 mm i.d.) and, after passing through a reaction coil, the absorbance was measured at 660 nm. The detector block through which the tubing passed incorporated a pair each of light-emitting diodes and silicon photodiode monitors. A double-beam configuration was achieved by passing the untreated sample through one half of the block before addition of the reagent. Rectilinear response was observed from 12 µg L-1 (detection limit) to 2000 µg L-1 of PO43- with coefficient of variation of <0.9%. The reagents were stable for 30 days.
Phosphate Spectrophotometry Light emitting diode Portable Photodiode

"Multidetection Flow Injection Techniques For Manipulation Of Sensitivity Amplification And Dilution Methods"
Anal. Chim. Acta 1987 Volume 199, Issue 1 Pages 15-27
A. R&iacute;os, F. L&aacute;zaro, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: Different multi-detection flow injection methods available for use with a single diode-array spectrophotometric detector were compared for the determination of formaldehyde in water by reaction with pararosaniline - SO32-. The sample was directly inserted into the system without prior dilution or concentration. and the detector data was treated by amplification or dilution methods as indicated by conventional calibration graphs. Three manipulation methods were compared in terms of accuracy and precision. The linear systems, monitoring at single and several wavelengths, and the cyclic systems had the same lower determination limit but detection at several wavelengths showed the widest determination range, cyclic systems the narrowest. All three techniques allowed extensive manipulation of the analysis signal in unsegmented flow systems.
Formaldehyde Spectrophotometry Multidetection Tecator Method comparison

"Continuous-flow Determination Of Manganese In Natural Waters Containing Iron"
Anal. Chim. Acta 1987 Volume 199, Issue 1 Pages 221-226
D. J. Hydes

Abstract: Removal of interference by Fe in the formaldoxime method for Mn determination has been re-evaluated. Addition of EDTA at controlled pH after formation of the Mn - formaldoxime complex could remove interference from up to 100 µM-Fe. In the proposed procedure, the formaldoxime reagent is added at pH 9.9 to form both Mn and Fe complexes, and EDTA is added to pH 7.7 to break down the Fe complex at 37°C during 25 min before the absorbance is measured. The system could be operated at Mn concentration. up to 100 µM.
Manganese Spectrophotometry Complexation Heated reaction Interferences

"Fundamental And Practical Considerations In The Design Of Online Column Preconcentration For Flow Injection Atomic Spectrometric Systems"
Anal. Chim. Acta 1987 Volume 200, Issue 1 Pages 35-49
Zhaolun Fang, Shukun Xu and Suchun Zhang

Abstract: The terms concentration. efficiency (expressed as the enrichment factor per min), retention efficiency, recovery data and elution efficiency are recommended as criteria for the critical evaluation of an online column pre-concentration. system. Efficiency is improved with time-based sampling and double-column systems without intermediate column washing. Columns (4.5 cm x 3 mm) with sample loading rates of 9.5 mL min-1 are proposed for achieving high efficiency and accuracy with AAS detection. More careful optimization of column dimensions is needed for detection by ICP-AES. A procedure for the online pre-concentration. of Co in water, involving columns of CPG-8Q exchanger (Pierce Chemicals) and a mobile phase of 25 mM ammonium acetate (pH 8), is presented. An enrichment factor of 48 was achieved at a sampling rate of 60 h-1. The coefficient of variation was 1.7% at the 40 µg L-1 level (n = 11) and the detection limit was 0.2 µg l-1.
Cobalt Spectrophotometry Controlled pore glass Optimization Preconcentration Review

"Improved Monosegmented Continuous-flow System For Sample Introduction In Flame Atomic Spectrometry"
Anal. Chim. Acta 1988 Volume 206, Issue 1-2 Pages 253-262
J. S. Brodbelt and R. G. Cooks

Abstract: An improved monosegmented system with only one air plug placed in the tailed portion of the sample, which is intercalated into an unsegmented carrier stream, is proposed for AAS. Air removal is not required, allowing a simpler system to be designed; flame instability is not a problem with the larger samples. The system is compared with the original approach in which the sample was introduced between two air bubbles. The effects of sample volume (25 to 1000 µL) and air-plug length (5 to 200 cm) on the recorded peak and measurement reproducibility are discussed. The single-line system proposed for determining Zn in plant digests is very stable, and the precise results agreed with those obtained by conventional AAS. The determination of Ca in natural waters demonstrates the feasibility of monosegmentation when a reagent solution (La) must be added. The accuracy, precision, sample consumption and system stability attained are good.
Calcium Zinc Spectrophotometry Injection technique Merging zones Method comparison

"Selective Flow Injection Determination Of Residual Chlorine At Low Levels By Amperometric Detection With Two Polarized Platinum Electrodes"
Anal. Chim. Acta 1988 Volume 207, Issue 1 Pages 59-65
Wojciech Matuszewski and Marek Trojanowicz

Abstract: Residual free Cl in swimming-pool water was determined by flow injection amperometry with two polarized platinum electrodes. Sample (200 µL) was injected into distilled water (2.4 mL min-1) and merged with streams of 0.2 M KI containing 0.02% of EDTA and of 0.1 M acetate buffer (pH 4.0), both at 1.0 mL min-1. The released iodine was measured amperometrically. Interference by Fe(III), Cu(II), NO2- and O was eliminated. The detection limit was 2 µg L-1 of Cl at a sampling rate of 120 h-1. The calibration graph was rectilinear up to 0.8 mg L-1 of Cl. Free Cl and Cu(II) could be determined simultaneously (method described) with detection limits of 20 and 60 µg l-1, respectively.
Chlorine, residual Copper(II) Amperometry Electrode Interferences Indirect Simultaneous analysis

"Automated Spectrophotometric Field Monitor For Water Quality Parameters. Determination Of Ammonia"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 401-407
J. Richard Clinch and Paul J. Worsfold, Frank W. Sweeting

Abstract: A manual flow injection manifold (illustrated) was incorporated into an automated field monitor as described previously (Anal. Abstr., 1988, 50, 6H74). Sample (0.7 mL min-1) and NaOH (0.7 mL min-1) were mixed online in a 50-cm reaction coil before introduction into the water carrier stream (0.7 mL min-1). The carrier stream then passed together with bromothymol blue solution into a gas diffusion cell and the acceptor stream flowed to a solid-state spectrophotometric detector for determination of total NH3 at 635 nm. The calibration graph was rectilinear obtained for up to 5000 µg L-1 of NH3 and the limit of detection was 17 µg l-1. The coefficient of variation (n = 6) were 0.7 to 2.1%. Results are presented for a three-day field trial.
Ammonia Spectrophotometry Calibration Light emitting diode Optimization Gas diffusion Portable

"Simultaneous Determination Of Phenolic Compounds In Water By Normal And Derivative Flow Injection/cyclic Voltammetry"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 375-384
Francisco Can&ntilde;ete, Angel R&iacute;os, M. D. Luque De Castro and Miguel Valc&aacute;rcel

Abstract: Binary and ternary mixtures of phenol, guaiacol and 2,4-dichlorophenol were analyzed by using the apparatus described previously (Ibid., 1988, 211, 287). Various supporting electrolytes were tested as carrier and dilution solution and KCl (1 g l-1) was chosen for subsequent analyzes. Optimum results were achieved with a flow rate of 0.9 mL min-1, an injected volume of 150 µL and a connecting tube length of 25 cm. Normal and derivative cyclic voltammetry was carried out by using a carbon-paste working electrode, a Ag - AgCl reference electrode and a vitreous-carbon auxiliary electrode. In the derivative mode the determination limit was 20 ng mL-1 and the coefficient of variation was 3.5%. Determination of analytes whose halfwave potentials overlapped was carried out by using simultaneous equations.
Phenol Guaiacol 2,4-Dichlorophenol Electrode Voltammetry Multicomponent Simultaneous analysis

"Potentiometric Flow Injection Determination Of Trace Chlorine Based On Its Redox Reaction With An Iron(III)/iron(II) Buffer"
Anal. Chim. Acta 1988 Volume 214, Issue 1-2 Pages 349-357
Nobuhiko Ishibashi and Toshihiko Imato, Hiroki Ohura and Sumio Yamasaki

Abstract: Sample solution (140 µL) is injected into the water carrier stream (0.71 mL min-1) which then merges with the potential buffer solution (0.71 mL min-1) consisting of 0.01 M Fe(III) - 0.01 M Fe(II) containing 0.3 M KCl and 0.5 M H2SO4. The sample passes through a 90-cm reaction coil, and the change in potential of the flow-through electrode is recorded. The detector comprises a gold-plated oxidation - reduction potential electrode and a Ag - AgCl reference electrode. Calibration graphs are rectilinear for 0.1 to 10 µM-Cl and the detection limit is 50 nM. The coefficient of variation at the 2.5 and 8 or 10 µM levels are 2.5 and 1.1%, respectively. Tolerance limits for co-existing ions are tabulated. Results for two water samples agreed with those obtained by the o-tolidine method.
Chlorine Electrode Electrode Potentiometry Dilution Interferences Method comparison Redox

"Determination Of Boron In Water By Flow Injection Inductively Coupled Plasma Emission Spectrometry"
Anal. Chim. Acta 1989 Volume 218, Issue 1 Pages 69-76
Phillip L. Kempster and Henk R. Van Vliet, Jacobus F. Van Staden

Abstract: An 11 mL mini-cloud chamber, containing a tangentially attached aerosol exit tube that induced spiral motion in the aersol within the chamber, was incorporated into a flow injection ICP-AES system (illustrated) for the cited analysis. The carrier stream (H2O) was pumped through each 300 µL sample loop, or in turn to the ICP nebulizer, the opposite sample loop being filled via the sample via negative pressure. The carrier outlet port of the sampling valve was connected to the nebulizer by polyethylene tubing, and B was determined at 249.68 nm. The calibration graph was rectilinear from 0.5 to 25 mg L-1 of B, and the coefficient of variation for 2.5 to 25 mg L-1 were 5.4% (n = 10). 'Memory effects' were ~5-fold smaller with the mini-cloud chamber than with a 110 mL cloud chamber. Aluminum, Ca, Cr, Fe, Na and P did not interfere. Sample throughput was 320 h-1 at a carrier flow rate of 3.5 mL min-1. The method was also applied in the determination of Ca, Mg, Mn and Sr in water.
Boron Calcium Magnesium Manganese Strontium Spectrophotometry Nebulizer Interferences

"Integrated Retention - Spectrophotometric Detection In Flow Injection Analysis. Determination Of Iron In Water And Wine"
Anal. Chim. Acta 1989 Volume 219, Issue 2 Pages 231-238
F. Lazaro, M. D. Luque de castro and M. Valc&aacute;rcel

Abstract: A sample (2 ml) containing 10 to 200 ng mL-1 of Fe(III) at pH 2 is inserted into the carrier stream, comprising 0.2 M NaF - 0.5 M NaOH - 0.02 M Na acetate - 2 mM Na2EDTA, at 2.0 mL min-1. After mixing in a coil, the stream is mixed with 0.4 M NH4SCN - 0.5 M HCl reagent solution at 2.0 mL min-1, and the Fe(III) - SCN- complex formed is retained on Dowex 1-X2-200 anion exchanger located in the flow cell. When the sample plug reaches the resin, the pH change causes an increased absorbance at 480 nm. Subsequently, the absorbance increases because of retention of the complex. The method is selective, with a determination limit of 10 ng mL-1 and a rectilinear range of 10 to 400 ng mL-1. Peak height, absorbance increment and tangent curve measurements each have advantages. Preconcentration of the analyte is rapid and the blank signal from colored samples is avoided. The method was applied in the determination of Fe in water and wine, with an average recovery of 100.3 and 98.8%, respectively.
Iron Spectrophotometry Preconcentration Dowex Solid phase detection Resin

"Determination Of Molybdenum(VI) In Natural Water And Rock By Ion-exchange Absorptiometry Combined With Flow Analysis"
Anal. Chim. Acta 1989 Volume 225, Issue 1 Pages 313-321
Kazuhisa Yoshimura and Shiro Matsuoka, Hirohiko Waki

Abstract: Ion-exchange absorptiometry combined with flow analysis has been applied to the determination of trace amounts of molybdenum(VI) in natural water and rock. By using a pretreatment column packed with Sephadex G-25 gel, molybdenum(VI) in a sample solution can be sorbed selectively on the gel at pH 3.5. The molybdenum(VI) in the column was desorbed with EDTA as the molybdenum(VI)-EDTA complex, and the solution was introduced into a Tiron solution stream. The yellow complex formed between molybdenum(VI) and Tiron in the flow system was then concentrated on a QAE-Sephadex A-25 anion exchanger packed in a flow-through silica micro-cell. The attenuation of incident light by the molybdenum(VI)-Tiron complex on the anion exchanger in the cell was continuously recorded with a spectrophotometer at 410 nm. The complex on the anion exchanger was easily desorbed with sodium nitrate, so the flow-through cell could be used repeatedly. The minimum amount that could be detected corresponded to 15 ng of molybdenum(VI). Molybdenum(VI) in three or four sample solutions could be determined within 1 h.
Molybdenum(VI) Ion exchange Spectrophotometry

"Flow Injection Ultraviolet Spectrophotometric Determination Of Sulfate In Natural Waters"
Anal. Chim. Acta 1990 Volume 228, Issue 1 Pages 287-292
Anatol Kojo and Jacek Michaowski, Marek Trojanowicz

Abstract: Sample-injection and reagent-injection manifolds are presented for the formation of FeSO4+ in a stream of dilute HClO4 in the presence of Al(III) and Hg(II) to mask F- and Cl-, respectively. The absorbance is measured at 355 nm; the response is rectilinear for 25 to 600 and 10 to 150 mg L-1 of SO42-, respectively, and the detection limit of the former method is 19 mg l-1. Results agreed well with those obtained gravimetrically. Organic compounds that interfere by UV absorbance can sometimes be removed on a charcoal column, but the possibility exists of loss of SO42-; a subtractive procedure with sample injections in the presence and absence of Fe(III) can alternatively be used. The sampling rate is 10 to 30 h-1.
Sulfate Spectrophotometry Detection limit Interferences Charcoal

"Flow Injection Technique For The Determination Of Low-levels Of Phosphorus In Natural Waters"
Anal. Chim. Acta 1990 Volume 234, Issue 2 Pages 409-416
Paul R. Freeman, Ian D. McKelvie and Barry T. Hart, Terence J. Cardwell

Abstract: A flow injection instrument for determining low concentration. of P in waters is described and illustrated. The main feature is the use of an inexpensive detector consisting of a flow cell and a photometer that incorporates a super-bright red-light emitting diode as the source and a photodiode as the detector. The procedure is a modification of the tin(II) chloride - molybdate method (cf. Tecator Application Note ASN 60-01183, Tecator AB, 1983) optimized by a modified simplex optimization method. Silicate interference (5 mg mL-1) was removed by addition of aqueous 0.1% tartaric acid. The calibration graph was rectilinear up to 100 µg L-1 of P and the detection limit was 0.6 µg l-1. The coefficient of variation were 2.9% and 0.5% for 2.0 and 50 µgl-1 of P, respectively. An inline pre-concentration anion-exchange column was used to obtain a lower detection limit of 0.1 µg l-1.
Phosphorus Spectrophotometry Detector Flowcell Calibration Detection limit Preconcentration Column Light emitting diode Simplex Interferences Photodiode Optimization

"Automated Method For The Determination Of Boron In Water By Flow Injection Analysis With Inline Preconcentration And Spectrophotometric Detection"
Anal. Chim. Acta 1990 Volume 234, Issue 1 Pages 199-206
I. Sekerka and J. F. Lechner

Abstract: The system (schematically presented) involved pre-concentration. of B from a sample by ion-exchange on a column of Amberlite IRA-743, elution with a stream of azomethine-H in 2 M ammonium phosphate buffer (pH 6.6) containing EDTA, and detection of the B complex at 420 nm. Full operating details are given. Online pre-concentration. was carried out for 3 or 6 min for 10 or 10 µg L-1 of B, respectively. Recoveries were 96 to 101%. The coefficient of variation were 10% for 10 µg L-1 and 5% for 10 to 200 µg l-1. The detection limit was 1 µg l-1, with a sampling rate of 10 h-1. The method was applied to natural- and tap-water. Results show good agreement with those of ICP-AES. There was no interference, even for colored samples.
Boron Ion exchange Spectrophotometry Preconcentration Column Amberlite Buffer pH Detection limit Method comparison Interferences

"Spectrophotometric Determination Of Silicate With Rhodamine B By Flow Injection Analysis"
Anal. Chim. Acta 1990 Volume 239, Issue 1 Pages 151-155
F. M&aacute;s, J. M. Estela and V. Cerd&aacute;

Abstract: A method is proposed based on the formation of an ion pair between molybdosilicic acid and rhodamine B (C. I. Basic Violet 10). Sample solution was reacted with 24 mM molybdate solution in 0.2 M HNO3 and 10 mM rhodamine B solution in 1 M HNO3 containing 0.1% poly(vinyl alcohol) and the absorbance was measured at 590 nm. The calibration graph was rectilinear from 0.2 to 2.0 mg L-1 of silicate. Tolerance levels for foreign ions are given. The sampling rate was 40 h-1. The method was applied in the determination of silicate in waters.
Silicate Spectrophotometry Calibration Interferences Ion pair formation

"Spectrofluorimetric Determination Of Diquat By Manual And Flow Injection Methods"
Anal. Chim. Acta 1991 Volume 244, Issue 1 Pages 99-104
T. P&eacute;rez-Ruiz, C. Mart&iacute;nez-Lozano and V. Tom&aacute;s

Abstract: In the manual method, sample solution, containing 0.03 to 9 µg of diquat (I), was mixed with 2 mL of 0.5 M borax buffer (pH 8), 1 mL of 0.5% sodium dithionite and water to 10 mL and, after 5 min, the resulting stable radical of I was detected fluorimetrically at 497 nm (excitation at 428 nm). The method was also adapted for use in a flow injection procedure (diagram of apparatus and details given. The calibration graph was rectilinear from 3 to 900 and 18 to 4000 µg L-1 of I by the manual and flow injection methods, respectively; the detection limit by the manual method was 0.4 µg L-1 and coefficient of variation were 2%. The method was applied in the determination of I in commercial herbicide formulations, water, potatoes, flowers and soil (sample prep. described) and in serum and urine directly with use of a standard additions method.
Diquat Fluorescence Buffer Standard additions calibration

"Flow Injection Determination Of Cyanide By Detecting An Intermediate Of The Pyridine - Barbituric Acid Chromogenic Reaction"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 247-252
Huichang Ma* and Jingfu Liu

Abstract: A kinetic study of the reaction between CN- and pyridine - barbituric acid (I) reagent is described; the intermediate product reaches its max. absorbance (at 494 nm) within 35 to 40 s and, at CN- concentration. 0.1 µg mL-1, exhibits absorbance higher than that of the final product (at 580 nm). An optimized procedure is described in which the sample solution is merged with a mixture of 0.5 M NaH2PO4 - NaOH buffer solution of pH 5.9 and aqueous 0.5% chloramine T, and a solution containing 4.8% of I, 24% (v/v) of pyridine and 4.8% (v/v) of HCl is injected into the resulting stream (which contains CNCl). The calibration graph is rectilinear for up to 4 µg mL-1 of CN- and the detection limit is 20 ng mL-1. The sampling rate is 60 h-1. Interference is caused by Co, Hg(II), Ni, Cu(II), SCN-, I- and formaldehyde. The method was used to determine free CN- in natural and waste water samples without pre-treatment. An unstable intermediate product with peak absorbance at 494 nm was found in the reaction of cyanide with pyridine-barbituric acid reagent. The intermediate was applied to the determination of cyanide by reagent-injection flow injection analysis The calibration graph was linear over the range of 0-4 µg mL-1 cyanide and the detection limit was 20 ng mL-1 cyanide; the relative standard deviation at 1.0 µg mL-1 was 0.6% (n = 16) and the sampling rate was 60 h-1. Interference studies showed that the main interferents are Co2+, Ni2+, SCN-, I- and formaldehyde. The proposed method was applied successfully to determine free cyanide in natural and wastewater samples.
Cyanide, free Spectrophotometry Chromogenic reagent Kinetic Interferences

"Determination Of Chemical Oxygen Demand In Aqueous Environmental Samples By Segmented Flow Injection Analysis"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 301-305
Li-Ching Tian* and Sao-Ming Wu

Abstract: A method is described for the determination of chemical oxygen demand (C.O.D) in aqueous environmental samples by segmented flow injection analysis. KMnO4 solution used as both an oxidant and a spectrophotometric reagent and D-glucose as a standard. When the reaction temperature is 95°C, the residence time is about 8 min and a sample throughput of 80/h can be achieved. The detection limit and relative standard deviation are 2 mg/litre and 0.7%, respectively, and the recovery is 85-95%. Chloride ion up to levels of 1500 mg/litre does not interfere with the results. C.O.D compared with those obtained using the Japanese Industrial Standard method and agreed within an error range of ±10%.
Chemical oxygen demand Spectrophotometry Interferences Method comparison Standard method Heated reaction

"Flow Injection Determination Of Low Levels Of Ammonium Ions In Natural Waters Employing Preconcentration With A Cation-exchange Resin"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 339-343
Marina Menezes Santos Filha, Boaventura Freire dos Reis and Henrique Bergamin Fo.*, Nivaldo Baccan

Abstract: Methods used to determine the effects of sampling time and of flow rates of sample and eluent are described, results from which led to the system described and illustrated. The water sample (freed from dissolved organic matter by C18 resin) is passed through a column (9 mm x 4 mm) of Bio-Rad AG 50W-X8 resin (100 to 200 mesh; H+ form), and the adsorbed NH4+ is eluted with 0.5 M NaOH. The eluate is mixed with Nessler reagent (a solution of 14 g of KI in 50 mL of water is treated with saturated Hg2Cl2 solution until a faint reddish color persists, then 50 mL of 10 M NaOH is added and the solution is diluted to 500 ml; this solution is diluted 1:3 with 1 M NaOH before use) before passage through a 1-m reaction coil to a spectrophotometric detector at 410 nm. The flow system includes a step for regeneration of the resin with HCl. The detection limit is 3 µg L-1 and sample throughput is 40 h-1 for samples containing 50 to 500 µg L-1 of NH4+. Reagent consumption is only 50 µL per determination, and results on nine water samples agreed with those by the indophenol blue method. NH4+ in natural waters at the 50 µg/L level were determined using Nessler reagent after pre-concentration. in a cation-exchange column coupled to a flow injection analysis (FIA) system. The loading cycle, the elution cycle, and the regeneration cycle were programmed for the resin used. The zone sampling approach using a computer-controlled commutator was employed in the FIA system design. Flow rates, resin loading, elution time, loop dimensions and resampling times for the zone sampling, column and coil dimensions, sensitivity, and reproducibility were studied. The detection limit was improved 10-fold over an earlier method that did not use a concentration. step. A throughput of 45 sample analyzes/h was achieved for samples with concentrations. ranging from 50 to 500 µg/L. The results show agreement of better than 99% with those obtained by the manual procedure.
Ammonium Ion exchange Spectrophotometry Method comparison Preconcentration Biorad Optimization Reagent consumption Resin Zone sampling Computer

"Simultaneous Determination Of Nitrite And Nitrate In Water Using Flow Injection Biamperometry"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 391-398
Marek Trojanowicz*, Wojciech Matuszewski and Bogdan Szostek, Jacek Michaowski

Abstract: The sample is injected into a carrier stream of aqueous 0.2% NH4Cl, which is split into two streams; one passes through a 30-cm tube and is then merged with the second stream, which flows through a column (6 cm x 2 mm) of Cd powder (0.1 to 1.5 mm) as reducing agent and a delay coil. The combined stream is mixed with 0.1 M KI - 0.125 M H2SO4 before reaching a detector equipped with two Pt electrodes polarized at 100 mV, where NO2- is detected by means of the I2 - I- redox system (Hulanicki et al., Ibid., 1987, 194, 119). The first peak obtained corresponds to NO2- and the second to NO3- plus NO2-. Under optimized conditions (described), the coefficient of variation for 60 µM-NO2- was 1.4 to 2.2% and that for 60 µM-NO2- and 0.4 mM NO3- was 0.5 to 0.8%. The max. sampling rate was 15 h-1. Copper (3 mg l-1) could be masked with EDTA, >1 mg L-1 of residual Cl had to be removed initially on a charcoal column, Fe(III) could be masked by adding oxalate to the sample before injection, and Cr(VI), which interfered in the determination of NO2-, could be removed by anion exchange at pH 7.8. In the analysis of natural water, results were well correlated with those of ion-selective potentiometry. Detection with 2 polarized Pt wire electrodes is based on the oxidation of I- by NO2-. The current is proportional to the amt. of I formed. The injected sample is split in a flow injection manifold into 2 segments. One of them is transported through a reductor minicolumn containing copperized Cd, where reduction of NO3- to NO2- occurs. The effects of interfering species such as Cu(II), Fe(III), Cr(VI) and residual Cl were examined and procedures for their elimination are proposed. With a sampling rate of 15/h, detection limits of 40 and 70 µg/L were obtained for NO2- and NO3-, respectively.
Nitrate Nitrite Electrode Potentiometry Optimization Reduction column Interferences Method comparison

"Kinetic - Spectrofluorimetric Determination Of Nitrite And Nitrate At The Nanograms-per-millilitre Level By Manual And Flow Injection Methods"
Anal. Chim. Acta 1992 Volume 265, Issue 1 Pages 103-110
Tomas P&eacute;rez-Ruiz*, Carmen Martinez-Lozano and Virginia Tom&aacute;s

Abstract: To a mixture of 0.1 mM phenosafranine, 2 M H2SO4 and 0.02 M KBrO3 was added sample or NO2- standard solution After dilution with water, a portion of the reaction mixture was placed in a cell at 30°C and the fluorescence intensity (excitation 525 nm, emission 576 nm) was measured against time from 30 s after the addition of NO2-. The method was rectilinear in the range 0.9 to 13.8 ng mL-1 of NO2-, with a coefficient of variation of 1.5%. The method was adapted for flow injection analysis in the stopped-flow mode, using 140 µL samples and a 30 cm x 0.5 mm reactor. The calibration graph was rectilinear in the range 46 to 460 ng mL-1 and the detection limit was 27 ng mL-1 of NO2-. Inclusion of a copperized cadmium reductor column allowed the determination of NO3-; the calibration graph was rectilinear in the range 62 to 620 ng mL-1 and the coefficient of variation was 1.3% for 248 ng mL-1 of NO3- (n = 10). Addition of a selection valve permitted the simultaneous determination of NO2- and NO3-. Both the manual and flow injection methods were applied to the analysis of natural and waste waters and meat products. The catalytic effect of nitrite on the oxidation of phenosafranine by bromate in acidic medium was studied by using the decrease in fluorescence intensity of phenosafranine. This kinetic- spectrofluorimetric method for nitrite is linear over the range 0.9-13.8 ng mL-1 with a relative standard deviation of about 1.5%. The method can be successfully adapted to flow injection analysis in the stopped-flow mode. Manual and flow injection methods were satisfactorily applied to the determination of nitrite in water and meat products. The inclusion of a copperized cadmium column in the flow system allowed the determination of nitrate and the sequential determination of nitrate and nitrite in mixtures.
Nitrate Nitrite Fluorescence Kinetic Catalysis Stopped-flow Reduction column

"Flow Injection Spectrophotometric Determination Of Propoxur With P-aminophenol"
Anal. Chim. Acta 1992 Volume 266, Issue 1 Pages 119-126
Karim D. Khalaf, J. Sancen&oacute;n and M. de la Guardia

Abstract: The sample solution was injected into a stream (2.2 mL min-1) of water, which was merged with 0.33 M NaOH (2.2 mL min-1) and mixed in a 2-m coil. The resulting stream, containing the hydrolysis product of propoxur (2-isopropoxyphenol, as the Na salt), was mixed (in a 7-m coil) with a stream containing the quinonimine produced by oxidation via mixing of 9 mM 4-aminophenol and 0.02 M KIO4 (each flowing at 2.2 mL min-1) in a 1-m coil. The optimum reaction temperature was 25°C, and the absorbance of the indo dye produced was measured at 600 nm. The calibration graph was rectilinear for up to 16 µg mL-1 of propoxur, and the detection limit was 0.1 µg mL-1. The coefficient of variation (n = 5) was 0.1% for 38 µM. Recoveries ranged from 94.0 to 98.3%. The method was applied to natural and tap-water. The spectrophotometric determination of propoxur [2-(1-methylethoxy)phenyl Me carbamate] was carried out with p-aminophenol (PAP) in a flow system. The method involves the online hydrolysis with NaOH of propoxur to 2-isopropoxyphenol and the oxidation of PAP to its reactive quinoneimine with KIO4 and the reaction between the phenolate and the quinoneimine. A 4-channel flow manifold was employed to carry out all the different steps of the reaction considered, monitoring the indo dye formed at 600 nm. The developed procedure provides a typical calibration line of A = -0.0007 + 1.8 x 103C (A = absorbance; C = concentration. in M) with a regression coefficient of 0.9998 and a limit of detection, for a probability level of 95% (for K = 3) of 0.1 µg mL-1. In the anal. of synthetic samples containing propoxur and 2-isopropoxyphenol, the total concentration. of propoxur was determined with a recovery from 94% to 98.3%. The method provides results comparable to those obtained by the batch anal. of natural water samples spiked with propoxur.
Propoxur Spectrophotometry Optimization

"Amperometric Techniques In Flow Injection Analysis: Determination Of Magnesium In Sera And Natural Waters"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 41-48
Alison J. Downard, Joanne B. Hart, H. Kipton J. Powell* and Shuanghua Xu

Abstract: For water analysis, the flow injection analysis system (described) was based on the complexation of Mg by 0.15 mM Eriochrome Black T at pH 11.5 in 15% 1,2-diaminoethane - 0.3 M KCl during flow-through a reaction coil (100 cm x 0.51 mm); water was used as the carrier (0.6 mL min-1) with amperometric detection in a wall-jet microflow cell with a glassy carbon electrode (cf., Downard et al., ibid., 1992, 256, 117) and 0.45 mM EGTA and 0.04 M triethanolamine as masking agents. Rectilinear calibrations from 0.027 to 1.8 mg kg-1 of Mg were achieved with a detection limit of 5.5 µg kg-1 and coefficient of variation of 0.7% for water. Similarly conditions for serum were described (details given). Results were compared with those obtained by AAS. Magnesium was determined in a flow injection system by formation of the magnesium-Eriochrome Black T (EBT) complex at pH 11.5 (5% 1,2-diaminoethane in 0.1 M KCl) and amperometric measurement of the excess of EBT at +0.175 V on a glassy carbon electrode. From modeling calculations, pH and concentrations of EBT (3.75 x 10^-5M) and masking agent EGTA (1.12 x 10^-4M) were chosen so as to minimize interference from calcium. Electrode fouling from EBT oxidation products was countered by use of 0.2% surfactant (Hostapur SA 93) in the carrier stream. Iron(III) was masked with triethanolamine. For anal. of natural waters the linear working range was 0.027-1.8 mg kg-1 Mg and the relative standard deviation was 0.7% at 1.6 mg kg-1 Mg (n=11); the detection limit was 5.5 µg kg-1. Anal. of human blood serum samples was effected by two methods: direct injection of serum after a 20-fold dilution (Hostapur SA 93 countered the association of EBT with serum albumin) and after dialysis (2.5 min) to sep. Mg from acidified serum in the flow system. The linear working range for direct injection was as above and the relative standard deviation was 0.4% (n=9) at 1.0 mg kg-1 Mg. For each method the results were compared with those from flame atomic absorption spectrometry.
Magnesium Amperometry Electrode Method comparison Interferences Linear dynamic range Dialysis

"Coupled Flow Injection Analysis - Flame-atomic Absorption Spectrometry For The Quantitative Determination Of Aluminum In Beverages And Waters Incorporating Online Cation-exchange"
Anal. Chim. Acta 1992 Volume 269, Issue 1 Pages 1-7
Henryk J. Salacinski, Philip G. Riby, Stephen J. Haswell*

Abstract: Tea leaf samples (0.5 g) were digested at 85°C for 45 min in a mixture of HNO3 (4 ml) and HClO4 (1 ml) and diluted to 10 mL with 5% HNO3. Samples of tea and coffee infusions and water were acidified with 5% HNO3. These samples (250 µL) were injected via a loop into a SCX preparative column (500 mg) with water as the carrier, followed by elution with 4 M HCl (250 µL) directly into the nebulizer of a flame AAS for the determination of Al. The AAS and nebulizer were optimized for max. absorbance prior to the determination and the peristaltic pump of the flow system set to give an equivalent delivery. Rectilinear calibrations were obtained from 0.07 to 6.45 µg mL-1 of Al from various timed depositions with a coefficient of variation of 1.1% and a detection limit of 75 ng mL-1. A method for determining the aluminum levels in local water, tea leaf digest, tea and coffee infusions by means of online cation exchange flow injection - flame atomic absorption spectrometry (FIA-FAAS) is described. Quant. results can be carried out down to 75 ng mL-1 of Al using sample volumes in the range 6.0-24.0 mL. The method using a conventional FAAS system was found to be rapid, simple and relatively inexpensive offering good selectivity and typical relative standard deviation of 1-2% (n=10) with a relative error of about 2%.
Aluminum Ion exchange Sample preparation Sample preparation Spectrophotometry Nebulizer Column

"Determination Of Chloride Ion Concentration In Natural And Waste Waters By Flow Injection Analysis With A Silver Chloranilate Reaction Column"
Anal. Chim. Acta 1992 Volume 270, Issue 1 Pages 217-221
Fumio Sagara*, Tetsuya Tsuji, Isao Yoshida, Daido Ishii and Keihei Ueno

Abstract: A carrier solution comprising ethanol - water - 0.1 M Na acetate buffer of pH 5.57, (5:4:1) was pumped into the flow system at 2.0 mL min-1. A 100 µL portion of sample water - ethanol - buffer (4:5:1) was injected and the mixture was passed through a cation-exchange column (5 cm x 4.61 mm) of Muromac 50W-X 4 (100 to 200 mesh; NH4+ form). The eluate was treated in a reaction column (same size) packed with Ag chloranilate powder connected to a spectrophotometric detector set at 530 nm. The calibration graph was rectilinear from 2 to 20 µg mL-1 of Cl-. Interferences from anions were negligible. When applied to the analysis of natural and waste waters, the Cl- could be determined in 2 min. The results agreed well with results obtained by a standard manual method. Cl- in natural water and wastewater was determined by flow injection analysis using a column packed with Ag chloranilate powder. EtOH-water-0.1 M Na acetate buffer (pH 5.57) (5+4+1, v/v/v) was used as the carrier at a flow rate of 2 mL/min. The chloranilate ion concentration, which corresponds to the Cl- concentration, in the carrier from the reaction column was monitored by a spectrophotometric detector at 530 nm. Interferences from multi charged cations were eliminated with the combined use of a cation-exchange column inserted in the upper stream of the reaction column. Interferences from anions were negligible. Cl- in natural water and wastewaters (1-20 µg/mL) could be determined rapidly (1 sample/2 min) with high reproducibility. The results agreed well with those obtained by the standard manual method.
Chloride Spectrophotometry Muromac Method comparison Interferences Solid phase reagent Indirect

"Determination Of Arsenic And Selenium In Environmental Samples By Flow Injection Hydride-generation Atomic Absorption Spectrometry"
Anal. Chim. Acta 1992 Volume 270, Issue 1 Pages 231-238
Chris C. Y. Chan* and Ram S. Sadana

Abstract: Environmental samples such as soil, vegetation, water, sediments and industrial wastes were digested (except for water) by heating at 200°C with HNO3 - H2SO4 - HClO4 (6:3:1). The cooled digest or water was treated with concentrated HCl to reduce Se6+ to Se4+; for As analysis the solution was treated with 10% KI - 1% ascorbic acid (10:1) to reduce As5+ to As3+. The analytes were converted to the hydrides with 1% NaBH4 in an automated hydride-generation system. A stream of Ar (3 mL min-1) carried the evolved hydride via a gas - liquid separator and an impinger to a heated quartz tube atomizer for analysis by AAS. The effects of the experimental variables are discussed. Interference by Cu and Ni on the determination of Se was masked with 1,10-phenanthroline. The detection limits for both As and Se were 0.3 ng mL-1. The coefficient of variation was 2.6% for As in a sediment (n = 10) and 2% in water (n = 5); similar precision was obtained for Se. The results for the standard reference materials agreed closely with their certified values. Flow injection analysis is applied to sample introduction in conjunction with automated hydride generation and AAS for the determination of As and Se in environmental samples such as soil, vegetation, waters, sediments, and industrial wastes. A large sample loop was used to provide high sensitivities with an absorbance of 0.4 for 10 ng mL-1 for both As and Se. The samples, except waters, are digested with a mixture of nitric, sulfuric, and perchloric acids. Se6+ in the digested solutions is pre-reduced to Se4+ by exothermic reaction in 6-8 M HCl solution, and As5+ to As3+ by reacting with KI. The analyte is then converted to hydride by NaBH4 in an automated hydride generation system. The evolved hydride is carried through to a heated quartz tube by a stream of argon, and the atomic absorption of the analyte is measured. 1,10-Phenanthroline is used as masking agent to control interferences from Cu and Ni on Se. The detection limits for both As and Se are 0.3 ng mL-1, equivalent to 75 ng g-1 in solid sample. Precision is 2.6% RSD Results for standard reference materials agree closely with the certified values.
Arsenic Selenium Spectrophotometry Reference material Interferences Volatile generation Volatile generation

"Determination Of Nitrate In Natural Waters With The Photo-induced Conversion Of Nitrate To Nitrite"
Anal. Chim. Acta 1993 Volume 276, Issue 1 Pages 25-32
Kazuhiko Takeda and Kitao Fujiwara*

Abstract: A flow injection system with a UV irradiation coil cell, in which NO3- was reduced to NO2-, and a spectrophotometric detector is described (diagram given). The carrier solution was phosphate buffer or water and the reagent solution contained 1.9 mM N-1-naphthylethylenediamine, 29 mM sulfanilamide and 0.6 M HCl. It was propelled by plunger pump to a reaction coil. The absorbance was monitored at 540 nm by a UV spectrophotometer. Peak height of the absorbance was taken as the signal intensity, which depended strongly on the carrier solution pH. The calibration graph was rectilinear from 0.05 to 100 µM-nitrate in natural waters and the coefficient of variation at 10 µM was 3%. Up to 10 samples h-1 could be analyzed.
Nitrate Spectrophotometry Photochemistry Redox

"Automatic Continuous-flow Determination Of Paraquat At The Sub-nanogram Per Millilitre Level"
Anal. Chim. Acta 1993 Volume 281, Issue 1 Pages 103-109
Manuel Agudo, Angel R&iacute;os and Miguel Valc&aacute;rcel*

Abstract: A water sample (I 0.05 M in NaNO3) pumped at 4 ml/min was mixed with 1% dithionite reagent of pH 12.5 pumped at 2.5 ml/min in a 30 cm-long coil and the mixture was passed to a flow cell containing Dowex 50W-X8-200 (ammonium form). The blue complex bound to the resin was monitored at 605 nm, then the sample stream was changed to an elution solution of ammonium chloride using a switching valve. The calibration graphs depended on the sample volume used; 1 mL gave a linear graph up to 0.2 µg/ml of paraquat with an RSD of 4.6% at a sampling frequency of 10/h, whereas 250 mL gave a linear graph from 0.4-5.5 ng/ml with an RSD of 7.9% and a sampling frequency of 0.9/h. At a volume of 250 mL the detection limit was 0.11 ng/ml. Interference studies showed that other pesticides were tolerated at a ratio of 100:1 except for diquat where this value was 10:1. The method was applied to the determination of paraquat in natural and tap waters and in studies of the adsorption of the herbicide by different soils.
Paraquat Dowex Resin Interferences

"Automated Determination Of Mercury At Ultratrace Level In Waters By Gold-amalgam Preconcentration And Cold Vapor Atomic-fluorescence Spectrometry"
Anal. Chim. Acta 1993 Volume 282, Issue 1 Pages 109-115
Chris C. Y. Chan and Ram S. Sadana

Abstract: Sample (25 ml) was heated with 1.2 mL of H2SO4, 0.5 mL of HNO3, 0.3 mL of 5% K2S2O8 solution and 0.3 mL of saturated K2Cr2O7 solution at 85-90°C for 2 h. The continuous-flow Hg-generation apparatus consisted of an autosampler, a peristaltic pump that propelled both the sample solution and the reducing reagent (4% SnCl2 solution in 10% HCl) at 3.9 ml/min, a gas-liquid separator that permitted the Hg vapor to be transferred to Ar carrier gas (20 ml/min), two moisture absorbers connected in series, and a six-port flow injection module that collected and transferred an portion of the gaseous Hg to a Au-wire absorber, which comprised a quartz tube (4 in. x 0.25 in. i.d.) wrapped with a Chromel wire heater and containing 0.5-1 g of Au wire (0.1-0.2 mm diameter). The Hg was desorbed by heating to ~500°C and carried to the spectrophotometer in an Ar stream (22 ml/min) for measurement at 253.7 nm. The calibration graph was linear up to 1 ng/ml and the detection limit was 2 pg/ml. The RSD (n = 10) for natural water containing 0.06 ng/ml of Hg was 3%. The procedure was applied to 11 water samples, and the results were confirmed by cold vapor AAS.
Mercury Fluorescence Preconcentration Amalgamation Method comparison Ultratrace

"Dual Flow Injection Analysis System For Determining Bromide And Reactive Phosphorus In Natural Waters"
Anal. Chim. Acta 1993 Volume 282, Issue 2 Pages 379-388
Paul R. Freeman, Barry T. Hart and Ian D. McKelvie

Abstract: A computer-controlled injection system (description given) and a manifold constructed from PTFE tubing were used in the simultaneous determination of P and bromide by methods based on previously published methods (cf. Ibid., 1990, 234, 409; and Anagnostopoulou and Koupparis, Anal. Chem., 1986, 58, 322). The bromide was determined first by injecting a sample (60 µL) into a stream of water (0.75 ml/min) which was mixed (0.31 ml/min) with 2.4 mM HCl in a 30 cm coil before removal of dissolved organic matter in a PVC column (2 cm x 2.8 mm i.d.) containing Sep-Pak C18. Streams (0.31 ml/min) of 0.01 or 0.02 g/l of phenol red, e.g., in 50 mM acetate buffer, and chloramine T, were mixed in a 60 cm coil before mixing with the column eluate in a 43 cm coil and detection at 583 nm. To determine P, a sample (600 µL) was injected into a stream of water (1.2 ml/min) and mixed with acid molybdate and SnCl2 streams (0.54 ml/min) in 30 and 120 cm coils, respectively, before detection at 650 nm. Calibration graphs were linear up to 2 mg/l of bromide and 50 µg/l of P and the detection limits were 4 and 0.6 µg/l, respectively. The corresponding RSD ranged from 0.3-5.3 (n = 10) and 0.5-2.9% (n = 3).
Bromide Phosphorus Spectrophotometry Computer Buffer

"Integrated Reduction Method For The Determination Of Urea As Ammonia In Fresh Water Samples"
Anal. Chim. Acta 1993 Volume 284, Issue 2 Pages 249-255
Andre Schmitt, Louise Buttle and Roger Uglow, Kathleen Williams and Stephen Haswell*

Abstract: A flow injection system for the online microwave preparation of water samples with colorimetric determination of urea as ammonia is described. Samples (10 ml) were mixed with 1 mL of reducing agent (20 mL of 96% H2SO4 containing 13.4 g of K2SO4 and 0.2 g of HgSO4, diluted to 100 mL with H2O) and portions (0.8 ml) were injected into a stream (4 ml/min) of water and carried to a 30 m reaction coil mounted in a microwave oven operated at 485 W, where urea was reduced to ammonium ions. After passage through a 7 m cooling coil, the samples were mixed with a stream (1 ml/min) of 1.5 M NaOH in a 12 cm mixing coil and the ammonia produced passed through a gas diffusion cell with a PTFE membrane, causing a pH change in an indicator stream (1 ml/min) of bromothymol blue (0.3 g/l) for detection at 635 nm. The calibration graph was linear from 5-45 µM-urea and the RSD (n = 10) for 40 µM-urea was 3.53%; the detection limit was 2.4 µM. The recoveries were 101% and 95% for 40 and 20 µM-urea, respectively. The sample throughput time was 14 min.
Urea Ammonia Spectrophotometry Redox Gas diffusion Teflon membrane Microwave Heated reaction

"New Spray Chamber For Use In Flow Injection Plasma Emission Spectrometry"
Anal. Chim. Acta 1994 Volume 286, Issue 2 Pages 155-167
Min Wu, Yoland Madrid, Jake A. Auxier and Gary M. Hieftje*

Abstract: A 200 W microwave plasma torch using Ar carrier and plasma support gases with a 2.45 GHz microwave generator, was used with a novel low-volume 4 cm vertical rotary spray chamber and a glass-concentric nebulizer in the cited technique (details given). The spray chamber was optimized for both continuous-flow (2 ml/min) nebulization, and discrete sample injection (200 µL). With an aqueous flow carrier, detection limits of 5-50 ng/ml were obtained for ten cations, with RSD typically 2.5% at sub ppm concentrations. Using methanol and ethanol as sample solvents, flowing at up to 2.5 ml/min, sensitivity decreases of approximately 40-50% were obtained compared to H2O.
Cations Spectrophotometry

"Micellar Enhanced Fluorimetric Determination Of Carbendazim In Natural Waters"
Anal. Chim. Acta 1994 Volume 287, Issue 1-2 Pages 49-57
J. Sancen&oacute;n and M. de la Guardia

Abstract: Sample (500 µL) containing 0.52-2.62 µM-carbendazim was injected into a carrier stream of water (4.4 ml/min) and merged with a buffer stream (4.2 ml/min) followed by a stream of a micellar solution (11.2 ml/min). The fluorescence of resulting stream was measured in a quartz flow cell. Two systems were studied; the first was based on the use of 0.5% SDS micelles in 0.1 M HCl with detection at 368 nm (excitation at 283 nm) and the second was based on the use of 0.1% hexadecyltrimethylammonium bromide in 0.1 M NaOH with detection at 327 nm (excitation at 306 nm). Linear calibration graphs were obtained over the range given above. The detection limits for carbendazim were 0.11 µM (system 1) and 0.013 µM (system 2) and the RSD (n = 5) for 2 µM-carbendazim were 2.25% (system 1) and 0.5% (system 2). Recoveries of 0.6-2.76 µM-carbendazim from spiked natural waters were >94%. The recoveries of 1 µM-carbendazim from polluted waters containing 0.8 µM-carbendazim were 102.9% (system 1) and 99.3% (system 2). The sample throughput was 160 injections/h.
Carbendazim Fluorescence Micelle

"Determination Of Chromium In Different Oxidation States By Selective Online Preconcentration On Cellulose Sorbents And Flow Injection Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1994 Volume 288, Issue 3 Pages 247-257
Abdulmagid M. Naghmush, Krystyna Pyrzyska and Marek Trojanowicz*

Abstract: Functionalized cellulose sorbents, a chelating resin and conventional ion-exchange resins were evaluated for pre-concentrating Cr(III) and Cr(VI). Cellulose with phosphonic acid exchange groups (Cellex P) and cellulose derivatives with quaternary amine groups (Cellex T) were superior in pre-concentrating Cr(III) and Cr(VI), respectively. A linear dual-column flow injection manifold was used to separate the Cr species using a Cellex T and a Cellex P column connected in series, with the Cellex T column placed first in the manifold. Sample of pH 2.5 was aspirated and the solution inlet was switched to the HCl carrier solution of pH 2.5. Cr(III) was eluted from Cellex P by injection of 1 M HCl via an injection valve placed between the Cellex T and P columns. The eluate was analyzed by AAS. Cr(VI) was eluted from Cellex T with 1 M NaOH injected via an injection valve placed in front of the Cellex T column. The eluate by-passed the Cellex P column and was analyzed by AAS. Calibration graphs were linear from 1-10 µg/l and the detection limits were 0.78 and 1.4 µg/l of Cr(III) and Cr(VI), respectively. The corresponding RSD (n = 10) for 10 µg/l were 2.6 and 4.5%. The method was used to analyze water.
Chromium(III) Chromium(VI) Spectrophotometry Preconcentration Cellex

"Determination Of Total Phosphorus In Waters And Waste Waters By Online Microwave-induced Digestion And Flow Injection Analysis"
Anal. Chim. Acta 1994 Volume 291, Issue 3 Pages 233-242
Richard L. Benson*, Ian D. McKelvie and Barry T. Hart, Ian C. Hamilton

Abstract: Digestion was performed using a flow-through reactor in a modified domestic microwave oven and the orthophosphate formed was detected as phosphomolybdenum blue after online filtration. Different digestion mixtures were evaluated and a 10 g/l acidified solution of potassium peroxydisulfate was selected. Phosphorus standards or unfiltered effluent samples were continuously mixed online with the digestion reagent and the solution was passed through the microwave reactor. A 30 µL portion of the solution was injected into a water carrier stream via a PTFE rotary valve, and sequentially merged with a further water carrier stream, the colorimetric reagent and the reducing reagent. The transmittance was monitored by a solid-state photometer incorporating red a light-emitting diodes (635 nm). The technique was rapid (7 samples/h, 4 replicates). The calibration graph was linear upto 18 mg/l of P with a detection limit of 0.09 mg/l.
Phosphorus Sample preparation Microwave Online digestion Filter Light emitting diode

"Investigation Of Chromium(III) And Chromium(VI) Speciation In Water By Ion Chromatography With Chemiluminescence Detection"
Anal. Chim. Acta 1994 Volume 293, Issue 3 Pages 237-243
H. G. Beere and P. Jones*

Abstract: A 100 µL volume of sample was injected into an effluent stream of 0.28 M KCl/1 mM EDTA of pH 2.5 (1 ml/min) and passed through a 25 cm AS4A anion exchange column. The column eluate was merged with a stream of 15 mM sulfur dioxide (0.06 ml/min) to reduce Cr(VI) to Cr(III) and then with a stream of 0.34 mM luminol/0.1 M orthoboric acid/0.01 M H2O2 of pH 11.5 (1 ml/min). The chemiluminescence was monitored using a 30 µL detection cell with a photomultiplier as detector. The calibration graphs for Cr(III) and Cr(VI) were linear up to 500 µg/l and the detection limits were 0.05 µg/l and 0.1 µg/l, respectively. The method was applied to the analysis of a certified reference material, IAEA/W4, simulated fresh water containing 9.9 µg/l of Cr(III) and spiked with 10 µg/l of Cr(VI). Due to the instability of both Cr(III) and Cr(VI), it was necessary to adjust portions of the test sample to pH 3 and 5 for the determination of Cr(III) and Cr(VI), respectively. The RSD (n = 6) for Cr(III) and Cr(VI) were 4.3 and 2.7%, respectively.
Chromium(III) Chromium(VI) HPIC Chemiluminescence Reference material Speciation

"Analysis Of Total Dissolved Nitrogen In Natural Waters By Online Photooxidation And Flow Injection"
Anal. Chim. Acta 1994 Volume 293, Issue 1-2 Pages 155-162
I. D. McKelvie*, M. Mitri, B. T. Hart, I. C. Hamilton and A. D. Stuart

Abstract: The method is based on the conversion of inorganic and organic nitrogen species to nitrate by photooxidation by UV radiation in an alkaline peroxodisulfate median. After reduction, excess peroxodisulfate reagent was removed with sodium metabisulfite and the solution was injected into a flow injection manifold to determine nitrate by reduction to nitrite, diazotization, coupling and detection at 540 nm. A sample stream (0.3 ml/min) and a 10 g/l potassium peroxodisulfate/8.5 g/l sodium tetraborate stream (0.3 ml/min) were merged and passed through the UV photoreactor coil (3 m x 0.3 mm i.d.). The stream was passed through a Accurel debubbler and merged with a 10 g/l sodium metabisulfite stream (0.3 ml/min). The solution was injected into the 2.8 M NH4Cl pH 8-8.5 carrier stream (0.5 ml/min) of the FIA system. After passing through the Cd reduction column (12 cm x 2 mm i.d.), the stream was merged successively with streams of 1% sulfanilamide and 0.1% N-1-naphthylethylenediamine dihydrochloride (both at 0.5 ml/min). The absorbance was measured at 540 nm. The calibration graph was linear from 0.03-3 mg/l of N; the RSD (n = 8) for 1 mg/l of N was 0.47%. The method was applied to natural and waste water samples.
Nitrogen, total Spectrophotometry Debubbler Reduction column

"Flow-spectrophotometric Method For Determination Of Hydrogen Peroxide Using A Cation Exchanger For Preconcentration"
Anal. Chim. Acta 1994 Volume 295, Issue 1-2 Pages 159-163
A. M. Almuaibed* and A. Townshend

Abstract: H2O2 solution was pumped for 4 min at 1.5 ml/min, merging with 1 mM Ti(SO4)2 in 20 mM H2SO4, also pumped at 1.5 ml/min. The yellow complex was adsorbed on a column (2.5 mm x 0.25 mm i.d.) of Dowex 50W (100-200 mesh, H+ form) and eluted with 1.2 M H2SO4 for measurement at 410 nm. The resin column was washed with 20 mM H2SO4 before the next sample. Calibration graphs were linear for 4-60 µM-H2O2 with a detection limit of 1 µM. At 10 µM-H2O2, the RSD (n = 5) was 2%. The sample throughput was 10/h. For higher concentrations of H2O2, samples were injected directly into a carrier (1 ml/min) of 2 mM Ti(SO4)2 in 0.1 M H2SO4, with measurement as before. The calibration graphs were linear for 40-400 µM-H2O2 with a detection limit of 20 µM and a throughput of 65/h. Methods of increasing the sensitivity further are discussed.
Hydrogen peroxide Spectrophotometry Preconcentration

"Online Preconcentration And Determination Of Trace Platinum By Flow Injection Atomic Absorption Spectrometry"
Anal. Chim. Acta 1994 Volume 296, Issue 2 Pages 205-211
A. Cantarero, M. M. G&oacute;mez, C. C&aacute;mara and M. A. Palacios*

Abstract: The analytical performance of a platinum pre-concentration method using a 0.01 M HNO3 carrier solution and an alumina microcolumn is discussed. Online pre-concentration is followed by flame atomic absorption spectrometry (FAAS) and off-line pre-concentration by graphite furnace atomic absorption spectrometry (GFAAS). The pre-concentration factors were 600 for FAAS (256 µL elution volume), both with a 15 mL sampling volume. The detection limits in these conditions were 0.02 mg/litre, and relative standard deviation (RSD) of 9% (0.1 mg/litre solution, n = 5) for FAAS and 0.33 µg/litre, and a RSD of 7% (5 µg/litre solution, n = 5) for GFAAS. The proposed method is suitable for platinum determination in natural water samples.
Platinum Spectrophotometry Preconcentration Alumina

"Turbidimetric Determination Of Sulfate In Waters Employing Flow Injection And Lead Sulfate Formation"
Anal. Chim. Acta 1995 Volume 300, Issue 1-3 Pages 149-153
Ricardo Erthal Santelli*, Paulo Roberto Salgado Lopes, Regina C&eacute;lia Leme Santelli and Angela De Luca Rebello Wagener

Abstract: A 1.3 mL water sample was injected into a carrier stream of 1 mM HNO3 in ethanol/H2O (1:1) at a flow rate of 0.92 ml/min and the mixture was merged with a reagent solution (0.17 ml/min) comprising 1.9% lead nitrate and 1% poly(vinyl alcohol) in ethanol/H2O (1:1). An auxiliary stream (0.03 ml/min) containing 100 µg/ml of sulfate was merged with the sample plug before it entered a 100 cm x 0.5 mm i.d. precipitation coil at 61°C. After reaction, the absorbance was measured at 410 nm. Interference from chloride was eliminated by maintaining the coil at >55°C. The calibration graph was linear in the range 2-20 µg/ml of sulfate, the detection limit was 0.3 µg/ml and the RSD for 2 µg/ml of sulfate was 3% (n = 11). The analytical throughput was 35 samples/h. The method was applied to the determination of sulfate in fresh and saline waters.
Sulfate Turbidimetry Interferences Heated reaction Precipitation

"Characterization Of Inhibitors Of Acetylcholinesterase By An Automated Amperometric Flow Injection System"
Anal. Chim. Acta 1995 Volume 300, Issue 1-3 Pages 117-125
Alexander G&uuml;nther* and Ursula Bilitewski

Abstract: Acetylcholinesterase was immobilized on amino-terminated magnetic particles and a suspension was pumped into a magnetic reactor of a flow injection manifold. The system was used for enzyme inhibition tests, with a carrier stream of 0.01 M phosphate buffer of pH 8 flowing at 1 ml/min and acetylthiocholine chloride as enzyme substrate. Inhibition constants were obtained for the insecticides carbofuran, paraoxon-ethyl and -methyl and malaoxon and the enzyme activity was determined amperometrically by the oxidation of thiocholine at screen-printed Pt electrodes at a potential of 600 mV. The experimental detection limits were 3-7 µg/l, which agreed with those calculated from the inhibition constants. The results were comparable with those obtained photometrically by the reaction of thiocholine with Ellman's reagent (5,5'-dithiobis-2-nitrobenzoic acid) in the same FIA system. The method was applied to the analysis of insecticides in natural and drinking waters.
Insecticides Carbofuran Malaoxon Paraoxon Amperometry Electrode Immobilized enzyme Magnetic particles

"Determination Of Trace Metals In Natural Waters By Flame Atomic Absorption Spectrometry Following On-line Ion-exchange Preconcentration"
Anal. Chim. Acta 1995 Volume 303, Issue 2-3 Pages 341-345
M. C. Yebra-Biurrun, A. Bermejo-Barrera, M. P. Bermejo-Barrera* and M. C. Barciela-Alonso

Abstract: An on-line column pre-concentration technique for flow-injection flame atomic absorption spectrometry has been developed for the determination of trace metals in natural waters. A minicolumn (20 mm x 2 mm i.d.) filled with a poly(aminophosphonic acid) chelating resin (PAPhA, 20-30 mesh) was used for the pre-concentration procedure. For 2 mL samples, detection limits of 0.5, 5.0, 1.5, 1.6, 3.5, 0.6, 3.2, 3.1 and 0.4 g 1-1 for Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, respectively, were achieved. The precision (coefficient of variation) obtained was in the range between 1.1 (Cd and Cu) and 3.3% (Co). Accuracy was also investigated and results agreed with the certified values of the reference material. The sampling rate was 48 h-1. The method was applied to the determination of trace metals in natural waters samples from Galicia (Spain).
Cadmium Cobalt Chromium Copper Iron Manganese Nickel Lead Zinc Ion exchange Spectrophotometry Preconcentration Column Resin Reference material

"Determination Of Trace Aluminum In Natural Waters By Flow Injection Analysis With Fluorescent Detection Of The Lumogallion Complex"
Anal. Chim. Acta 1995 Volume 303, Issue 2-3 Pages 211-221
Susan H. Sutheimer and Stephen E. Cabaniss*

Abstract: Samples (20-100 µL) were injected into a carrier stream (1 ml/min) of 100 mM acetate buffer of pH 5.2 reacted at 55-57°C in a mixing coil with 1.8 mM lumogallion (100 µL/min). After passing through a second mixing coil at room temperature, fluorimetric detection at 595 nm (excitation at 500 nm) was achieved. Calibration graphs were linear over the range 36 nM- to 3.6 µM-Al with a detection limit of 3.7 nM-Al. At 1.1 µM-Al an RSD (n = 6) of 0.8% was obtained. The kinetics of formation the Al-lumogallion chelate is discussed. Comparative results were obtained with the treatment of 10 mL of sample with Al(III) in 2% HNO3 and using 10 µL of 1 g/l magnesium nitrate in 2% as a matrix modifier and GFAAS.
Aluminum Fluorescence Complexation Heated reaction Method comparison Optimization Kinetic

"In-flow Speciation Of Copper, Zinc, Lead And Cadmium In Fresh Waters By Square-wave Anodic-stripping Voltammetry. 2. Optimization Of Measurement Step"
Anal. Chim. Acta 1995 Volume 305, Issue 1-3 Pages 183-191
W. Martinotti, G. Queirazza, A. Guarinoni and G. Mori*

Abstract: Square-wave anodic-stripping voltammetry measurements were performed in a wall-jet type flow cell with a glassy carbon working electrode (5 mm diameter), a Ag/AgCl/3 M KCl reference electrode and a Pt counter electrode. The five other units of the system (potentiostat, thermometer, current measurement block, ultrasound generator and pump/valve driver) were controlled by a micro-processor. A measurement cycle consisted of three rinse steps, a Hg-film renewal step and two identical measurement steps. Each measurement step had six separate phases, (i) heavy metal deposition at -1100 mV, (ii) first rest period with pump off, (iii) stripping current measurement with square wave potential ramp from -1100 to +100 mV at 2000 mV/s with square wave period of 5 ms, step height of 10 mV and square wave amplitude of 25 mV, (iv) cleaning of the Hg film by oxidizing the heavy metals at a constant potential and with the pump on, (v) rest period with pump off and (vi) background current measurement as in (iii). The flow rate through the detector cell was 0.9 ml/min and measurements were made with a supporting electrolyte of 0.2 M HNO3. A fresh Hg film was deposited on the working electrode before each measurement cycle by electrolysing a mercury nitrate solution. Calibration graphs were linear for up to 100 µg/l of Zn, 5 µg/l of Cd and 15 µg/l of Pb and Cd in water. The complete measurement cycle took ~e;30 min.
Cadmium Copper Lead Zinc Voltammetry Electrode Electrode Speciation Computer Optimization

"The Simultaneous Speciation Of Aluminum And Iron In A Flow Injection System"
Anal. Chim. Acta 1995 Volume 306, Issue 1 Pages 5-20
Nicholas Clarke* and Lars-G&ouml;ran Danielsson

Abstract: The flow injection system for the speciation of Al and Fe used oxime as the reagent for Al and Fe(III) and 1,10-orthophenanthroline/iodide as the reagent for Fe(II). The reaction products were extracted into chloroform and determined by spectrophotometry. A 0.24 mL volume of sample (buffered to pH 5) was injected into a water carrier stream (1.6 ml/min) and merged with a reagent stream (1.2 ml/min) containing 6.5 mM oxime, 7 mM 1,10-orthophenanthroline and 0.3 M KI in 0.15 M sodium acetate at pH 5. The flow passed through a reaction coil (length 0.5 m, residence time 1.9-2.1 s). The flow was then merged with a chloroform stream (0.6 ml/min) and passed through the extraction coil (length 3 m, residence time 9.5-10.6 s). The phases were separated and the chloroform phase was passed to the diode array detector. The absorbance was measured at 12 or 13 wavelengths between 350 and 650 nm at a rate of 5 spectra/s. The results were analyzed by partial least squares to separate the contribution from Al, Fe(II) and Fe(III). Linear calibration graphs were obtained for up to 2 mg/l of each analyte and the detection limits were 0.06 mg/l. The RSD (n = 31) for 0.15 mg/l of each analyte were 5-12%. The sampling frequency was 85 injections/h. The method was applied to the analysis of natural waters.
Aluminum Iron(2+) Iron(III) Spectrophotometry Sample preparation Extraction Kinetic Multivariate calibration Organic phase detection Speciation Partial least squares

"A Mechanized System For The Determination Of Low Levels Of Quickly Reacting Aluminium In Natural Waters"
Anal. Chim. Acta 1995 Volume 306, Issue 2-3 Pages 173-181
Lars-G&ouml;ran Danielsson and Anders Spar&eacute;n*

Abstract: A continuous flow system has been connected to a graphite furnace atomic absorption spectrometer. The system is used to determine low levels of 'quickly reacting Al' (Alqr) in natural waters. In the flow system, aluminium reacts with oxine for 2.3 s and the formed complex is then extracted into toluene. Iron interference is minimized with a masking buffer present in the reagent. Via a simple interface, the toluene extract is introduced into the graphite tube. Good repeatabilities (RSD ~2%, n = 10) were obtained, both for standard solutions and for natural waters. The detection limit is < 0.5 g l-1, and the sample throughput using 3 injections/sample, is ~10 samples h-1. The system has been used for determining Alqr in tap water, and is well suited for aluminium fractionation in near-neutral waters.
Aluminum, reactive Spectrophotometry Speciation Solvent extraction Organic phase detection Complexation Masking agent Buffer

"Photo-induced Reduction Of Nitrate To Nitrite And Its Application To The Sensitive Determination Of Nitrate In Natural Waters"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 406-412
Shoji Motomizu* and Masahiro Sanada

Abstract: An FIA method was described for the determination of nitrate in water based on the photo-induced reduction of nitrate to nitrite. Water (280 µL) was injected into a carrier stream (0.6 ml/min) containing 0.1 M KH2PO4 and 1 mM EDTA of pH 7. The flow passed to the photo-reactor which consisted of a PTFE tube (3 m x 0.8 mm i.d.) wound directly around a low-pressure Hg lamp (4 W). The flow from the photo-reactor was merged with the chromogenic reagent stream (0.6 ml/min) which contained 30 mM sulfanilamide and 2 mM N-(1-naphthyl)ethylendiamine in 0.6 M HCl. After passing through the reaction coil (2 m x 0.5 mm i.d.) the absorbance was measured at 540 nm. The calibration graph for nitrate was linear up to 0.1 mM, the detection limit was 0.03 µM and the RSD (n = 7) for the determination of 4 µM-nitrate was 0.8%.
Nitrate Spectrophotometry Indirect Photochemistry Chromogenic reagent

"Application Of Photoacoustic Spectrometry To Flow Injection Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 20-27
I. Carrer, P. Cusmai, E. Zanzotter, W. Martinotti,* and F. Realini

Abstract: The cited method was used to determine nitrite, nitrate, Fe, NH3 and phosphate ions in water. Excitation was performed with a Q-switched Nd:YAG laser equipped with a 2nd harmonic generator for the determination of nitrite, nitrate and Fe at 532 nm. The same laser was used to pump the dye laser for the detection of NH3 at 632 nm and phosphate at 810 nm. The generated acoustic wave was detected by an acoustic transducer. The FIA manifold allowed the sample solution to be injected into a water carrier stream which was merged sequentially with two reagent streams (R1 and R2) before passing to the detector cell. For the determination of nitrite, R1 and R2 were NH3 buffer and α-naphthylethylenediamine dihydrochloride. The same reagents were used for the determination of nitrate by incorporating a copperized Cd reduction column to reduce nitrate to nitrite. R1 and R2 were hydroxylamine hydrochloride and 1,10-phenanthroline, respectively, for the determination of Fe and ammonium molybdate and antimony potassium tartrate, respectively, for the determination of orthophosphate. The Berthelot reaction was used for the detection of NH3. The detection limits (tabulated) were comparable with those obtained by FIA with spectrophotometric detection for Fe, NH3 and phosphate. For nitrite and nitrate poorer detection limits were obtained.
Ammonia Iron Nitrate Nitrite Phosphate Spectrometry Sensor Laser Reduction column Method comparison

"Online Pervaporation Separation Process For The Potentiometric Determination Of Fluoride In 'dirty' Samples"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 246-252
I. Papaefstathiou, M. T. Tena and M. D. Luque de Castro*

Abstract: The FIA method was based on the reaction of fluoride with hexamethyldisilazane (HMDSA) in acidic medium to form trimethylfluorisilane (TMFS). TMFS was evaporated, diffused through a hydrophobic membrane and adsorbed into a NaOH acceptor stream. Fluoride was detected using a fluoride ISE. Streams of the sample solution and 1.5% HMDSA in 2 M H2SO4 were merged to give a combined flow of 0.5 ml/min and passed through a reactor coil (300 cm length) at 90°C. A portion of the solution was injected into a 1 M H2SO4 carrier stream (1.3 ml/min) and transferred to the pervaporation cell which was maintained at 80°C. The volatile TMFS was collected in a 0.05 M NaOH acceptor stream (1.3 ml/min). The acceptor stream was merged with a stream (1.3 ml/min) containing 0.2 M acetic acid and 1 M KCl before passing to the ISE detector. The system was operated in the continuous- and stopped-flow modes. The linear dynamic ranges were 40-100 ng/l (RSD = 2.6%) in the continuous-flow mode and 5-20 mg/l (RSD = 3.58%) in the stopped-flow mode. The sampling frequencies were 8 samples/h for the continuous-flow mode and 6 samples/h for the stopped-flow mode. The method was used to determine fluoride in water, fertilizers and ceramic industry waste water. The recovery of 10 and 50 mg/l fluoride from tap and well water was >89% and the RSD (n = 3) was 3.45%.
Fluoride Potentiometry Electrode Pervaporation Stopped-flow Hydrophobic membrane

"Development Of An Optical Flow-through Biosensor For The Determination Of Sulfite In Environmental Samples"
Anal. Chim. Acta 1995 Volume 311, Issue 3 Pages 281-287
M. D. Luque de Castro* and J. M. Fern&aacute;ndez-Romero

Abstract: The method was based on the enzymatic oxidation of sulfite in the presence of sulfite oxidase (SOD) to yield sulfate and H2O2. The H2O2 reacted with 4-aminophenazone (4-AAF) and 3-methyl-N-ethyl-N'-(β-hydroxyethyl)aniline (MEHA) in the presence of peroxidase (HPOX) to yield an alkyl aniline cationic derivative (4-AMHA) which was detected spectrophotometrically following retention on an ion exchanger. Water sample (2 ml) was injected into a stream (0.6 ml/min) of 10 mM Tris hydrochloride buffer of pH 8.4 and passed through a column containing SOD immobilized onto controlled pore glass beads. The eluate was merged with a stream (0.6 ml/min) containing 10 µM-4-AAF and 200 µM-MEHA in 50 mM citrate buffer of pH 5 and passed through a column containing an upper layer of HPOX immobilized on to controlled pore glass beads and a lower layer of Sephadex carboxymethyl cation ion-exchange resin. The absorption of the retained 4-AMHA was monitored at 565 nm and the retained 4-AMHA was then eluted with 15 mM NaCl. The calibration graph for sulfite was linear for 10^-1000 ng/ml, the detection limit was 3 ng/ml and the RSD (n = 11) were 0.7-2.6%. The recoveries of 30-100 ng/ml sulfite from spiked water were >94%. The sampling frequency was 16/h.
Sulfite Spectrophotometry Sensor Immobilized enzyme Controlled pore glass Sephadex

"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 Spectrophotometry Preconcentration C18 Solid phase extraction

"Self-configuration Of Sequential Injection Analytical Systems"
Anal. Chim. Acta 1995 Volume 316, Issue 1 Pages 27-37
A. Rius, M. P. Callao and F. X. Rius*

Abstract: An expert system for the self-configuration of sequential injection analysis (SIA) systems was presented. The expert system derived all the necessary parameters for the flow system and also controlled the measurement processes including optimization, calibration and quality assurance. The expert system was applied to the SIA system for the spectrophotometric determination of Ca and Mg in water using arsenazo III as the chromogenic reagent. Detection was carried out using a diode-array spectrometer with absorption measurements every 2 nm from 450-650 nm and multivariate calibration. Ca and Mg were simultaneously determined in the range 0-280 and 0-140 mg/l, respectively, and the sample throughput was 20 samples/h.
Calcium Magnesium Spectrophotometry Sequential injection Computer Optimization Expert system Simultaneous analysis Chromogenic reagent Multivariate calibration

"Analysis Of Ammonia And Methylamines In Natural-waters By Flow Injection Gas Diffusion Coupled To Ion Chromatography"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 291-304
Stuart W. Gibb, R. Fauzi C. Mantoura and Peter S. Liss

Abstract: Flow injection gas diffusion-ion chromatography (FIGD-IC), is a new hyphenated technique for the simultaneous analysis of nanomolar levels of ammonia (NH3) and methylamines (MAs) in < 50 mi of marine, estuarine and freshwaters. Alkaline EDTA is added online to flowing sample to achieve a sufficiently high pH (> 12.0) needed to deprotonate > 95% of the amines to their uncharged volatile forms. In addition the reagent chelates Mg2+ and Ca2+ to prevent their precipitation as Ca(OH)(2) and Mg(OH)(2). The amines diffuse selectively across a gas-permeable microporous PTFE Goretex(R) membrane into a recirculating flow of acidic 'acceptor' in which they are reprotonated and pre-concentrated. The acceptor solution is then injected onto an ion chromatograph (IC) where NH4+ and MA cations are separated within 15 min and detected by chemically suppressed conductimetry using cyclopropylamine as an internal standard for quantification. The response of the coupled FIGD-IC system was sensitive (ca. 3-5 nM for MAs, 20-40 nM for NH3), linear (r2 = 0.99, 0-2000 nM in seawater) and precise (RSD = 1-6% at 1 µM) for all analytes. The applicability of FIGD-IC is demonstrated through laboratory analysis of NH3 and MAs in a range of natural water samples, on-board a research vessel, and through inter-comparisons with fluorimetric assay of NH3. (40 References)
Amines, methyl Ammonia HPIC Conductometry Gas diffusion Goretex Internal standard Preconcentration Simultaneous analysis

"Use Of Immobilized 3-phytase And Flow Injection For The Determination Of Phosphorus Species In Natural Waters"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 277-289
I. D. McKelvie*, B. T. Hart, T. J. Cardwell and R. W. Cattrall

Abstract: A proportion of dissolved organic phosphorus (DOP) compounds found in natural waters may be utilized by algae and bacteria through hydrolysis by extracellular phosphomonoesterases such as alkaline phosphatase. The fraction of DOP remaining unhydrolyzed may consist of organic phosphorus species such as myo-inositol hexakisphosphate (phytic acid), and comprise part of the pool of biologically unavailable or even refractory DOP. Of this bio-unavailable DOP fraction, a major portion is amenable to hydrolysis by 3-phytase, a phosphohydrolytic enzyme which is not found widely in aquatic systems. This paper describes the development and application of a flow injection system which utilises immobilized 3-phytase for the determination of phytase hydrolyzable phosphorus (PHP) present in natural waters. The product of enzymatic hydrolysis is orthophosphate, and a conventional phosphomolybdenum blue detection method was used. The use of a suitable flow injection manifold and a multiple linear regression calibration procedure for quasi-simultaneous determination of phytase-hydrolysable and dissolved reactive phosphorus (DRP) coexisting in natural waters is outlined. The proposed technique is rapid (ca. 40 injections h-1), sensitive and reproducible, and the immobilized phytase exhibited good operational and storage stability over a period of several months.
Phosphorus Immobilized enzyme

"Hollow Fiber Cartridges For Removal Of Particulate Matter From Natural Waters Prior To Matrix Isolation And Trace Metal Enrichment Using An 8-quinolinol Chelating Ion Exchanger In A Flow System"
Anal. Chim. Acta 1995 Volume 316, Issue 3 Pages 305-311
Nii-Kotey Djane, Fredrik Malcus, Eduardo Martins, Gerald Sawula and Gillis Johansson*

Abstract: Natural water samples are normally filtered through a 0.45 µm membrane filter before analysis. Such filters clog rapidly, however, when the content of humic acids is high. An alternative approach for natural water filtration is reported in this paper. Sample solutions are pumped into tubing containing a coaxial hollow fiber and a needle valve restrictor at the outlet. One end of the hollow fiber is plugged and the other is connected to a chelating ion exchange column for uptake of trace metal ions. The differential pressure between the inside and the outside of the fiber forces a filtered liquid through the fiber and into the ion exchanger. It was found that flow rates of about 2.0 mL min-1 could be obtained with a pressure difference of around 1 bar. The concentrations of copper, cadmium and cobalt ions were the same in the filtrate as in the inlet solution, indicating that the membrane is uncharged. In one configuration more than 4 I of a sample containing 20 µg mL-1 humic acids could be passed through the fiber before clogging caused unacceptable reduction of the flow rate. A hollow fiber cartridge, therefore, seems to be very useful for enrichment of ions from samples with a high solids content. The trace metals were enriched about 15 times using the described procedure.
Ion exchange Chelation 8-Hydroxyquinoline Hollow fiber membrane Filtration Matrix removal Preconcentration

"Application Of Ion-exchanger Phase Visible-light Absorption To Flow-analysis Determination Of Vanadium In Natural-water And Rock"
Anal. Chim. Acta 1995 Volume 317, Issue 1-3 Pages 207-213
Shiro Matsuoka*, Kazuhisa Yoshimura and Akira Tateda

Abstract: Ion-exchanger phase visible light absorptiometry combined with flow analysis has been developed and applied for the determination of vanadium in natural water and rock. The vanadium(IV) and vanadium(V) in the sample solution reacted with xylenol orange (XO) which was immobilized on the AG 1-X2 anion-exchanger packed in flow-through cell, and the increase in light absorption caused by the formation of the vanadium-XO complex in the resin was directly measured with a spectrophotometer at 532 nm. The interference by most of the co-existing ions can be effectively eliminated using trans-1,2-cyclohexanediamine-N,N,N',N'-tetraacetic acid (CyDTA) and ammonium tartrate. The detection limit was 80 ng L-1 with 5.0 cm(3) of sample solution. Vanadium contents in three sample solutions could be determined within 1 hour. (24 references)
Vanadium(IV) Vanadium(V) Ion exchange Spectrophotometry Immobilized reagent Interferences Solid phase detection

"Model Compounds For The Determination Of Organic And Total Phosphorus Dissolved In Natural Waters"
Anal. Chim. Acta 1996 Volume 318, Issue 3 Pages 385-390
Roger K&eacute;rouel and Alain Aminot*

Abstract: Methods for the determination of organic and total P in natural waters based on the hydrolysis and oxidation of all complexed forms of P to phosphate by acidic and alkaline persulfate oxidation, continuous-flow UV irradiation and high temperature combustion (HTC) were studied. Ten compounds were used to test the efficiency of these hydrolysis/oxidation reactions. The results indicated that in such methods, recoveries should be tested using model compounds with HTC as the reference method. One labile compound (phosphoenolpyruvate, glycerophosphate or riboflavin-5-phosphate) and one refractory compound (aminoethylphosphonic acid, phytic acid or phosphorylcholine) should be used to determine an upper and lower recovery, respectively. The recoveries depended on the matrix; quantitative recoveries were obtained with fresh water but not with seawater. For the determination of P in seawater the alkaline persulfate oxidation method is recommended.
Phosphorus

"Determination Of Total Phenols In Waters And Waste Waters Using Flow Injection With Electrochemical Detection; An Alternative To The Standard Colorimetric Procedure"
Anal. Chim. Acta 1996 Volume 323, Issue 1-3 Pages 39-46
M. J. Christophersen and T. J. Cardwell*

Abstract: The flow injection manifold for the determination of total phenols was equipped with an up-stream coulometric carbon electrode at +0.35 V (reference electrode not given) for the oxidative removal of interference followed by an amperometric carbon electrode at +0.78 V for the oxidative detection of phenols. Phosphate buffer of pH 6.8 was used as carrier (0.5 ml/min) and the injection volume was 10 µL. The method was calibrated with 2,5-dichlorophenol, and a linear calibration graph was obtained for 0.1-20 mg/l. RSD were 0.5-4% within the calibration range. The method was tested with several synthetic aqueous samples and found to give more accurate results for samples containing p-substituted phenols and nitrophenols than the 4-aminoantipyrine spectrophotometric method. The proposed method was applied to the analysis of industrial waste water samples.
Phenols, total Amperometry Electrode Interferences

"Determination Of Total Phosphorus In Waters And Waste Waters By Online UV/thermal Induced Digestion And Flow Injection Analysis"
Anal. Chim. Acta 1996 Volume 326, Issue 1-3 Pages 29-39
Richard L. Benson*, Ian D. McKelvie, Barry T. Hart, Yen B. Truong and Ian C. Hamilton

Abstract: The online FIA method utilized a two-stage UV photo-oxidation/thermal digestion procedure and oxidizing/hydrolyzing reactions to convert phosphorus compounds to orthophosphate for detection by the phosphomolybdenum blue reaction. A sample stream (0.69 ml/min) was merged with 6 g/l ammonium peroxydisulfate in 2.1 M perchloric acid (0.69 ml/min) and passed through a UV digestor (8 W) and a thermal digestor at 90°C. A 60 µL portion of the digestate was injected into a water carrier stream (1.24 ml/min) and sequentially merged with a water diluent (0.58 ml/min), 10 g/l ammonium molybdate in 35 ml/l H2SO4 (0.86 ml/min) and 0.2 g/l tin(II) chloride/2 g/l hydrazinium sulfate in 28 ml/l H2SO4 (0.58 ml/min). The transmittance of the mixture was monitored with a solid-state photometer equipped with a red light-emitting diode (635 nm) and an optical path of 0.8 mm. The method was validated with a series of organic and condensed phosphorus species at concentrations of 10 mg/l; recoveries of >85% were obtained. The calibration graph was linear for 0.5-18 mg P/l and the detection limit was 0.15 mg/l. The sample throughput was 8 samples/h. The method was applied to waste water and the results were confirmed by a conventional batch digestion method.
Phosphorus Spectrophotometry Sample preparation Light emitting diode UV reactor Photochemistry

"Determination Of Copper In Natural Waters By Batch And Oscillating Flow Injection Stripping Potentiometry"
Anal. Chim. Acta 1996 Volume 330, Issue 1 Pages 79-87
Christopher W. K. Chow, Spas D. Kolev, David E. Davey*, and Dennis E. Mulcahy

Abstract: Batch potentiometric stripping analysis (PSA) and oscillating flow injection stripping potentiometry (OFISP) were compared for determining Cu in water rich in chloride ions and organic matter. PSA was performed at a glassy carbon electrode coated with a Hg film deposited from 30 mg/l mercury nitrate in 0.1 M HCl at -900 mV vs. Ag/AgCl (3 M KCl). The deposition of Cu was carried out at the same potential for 1 min from 50 mL water acidified to 0.1 M HCl or 0.1 M HNO3 and containing 10 mg/l mercury nitrate. The remaining experimental details were given by Chow et al. (Anal. Chim. Acta, 1995, 307, 15). OFISP was performed using the same PSA apparatus incorporated into a FIA system. A carrier stream of 0.1 M HNO3 or 0.1 M HCl was used with a 100 µL injection loop. The experimental details were given by Kolev et al. (Ibid., 1995, 309, 293. For both PSA and OFISP external and standard addition calibration procedures were employed. The two analytical technique gave the same results when HCl media were used. The flow injection OFISP method was recommended for analyzing natural waters because it showed a low sensitivity to matrix effects. The analysis of natural waters by adsorption stripping voltammetry was unsatisfactory due to the adsorption of the organic matter onto the working electrode.
Copper Potentiometric stripping analysis Potentiometry

"Determination Of Sulfate In Natural Waters And Industrial Effluents By Sequential Injection Analysis"
Anal. Chim. Acta 1996 Volume 331, Issue 3 Pages 271-280
J. F. van Staden* and R. E. Taljaard

Abstract: A sequential injection analysis method with turbidimetric detection is described for the determination of sulfate. A flow rate of 5 ml/min was used to draw the following liquids into a holding column (2.8 m x 1.02 mm i.d.): 40% EDTA in NH4Cl/NH3 buffer for 5 s; water for 15 s; 1% BaCl2 in potassium hydrogen phthalate/HCl buffer of pH 2.5 containing 0.1% thymol and 0.06% gelatine for 3 s; sample for 9 s. The direction of the pump was reversed and the liquid zones were propelled through two reaction coils (1.3 m x1.02 mm i.d. and 1 m x 0.64 mm i.d.) to the detector were the turbidity was measured at 540 nm. A linear calibration graph was obtained for 10^-200 mg/l sulfate and the RSD (n = 10) were 1.1-2.81% over the same concentration range. The sampling frequency was 26/h. The method was applied to natural waters and industrial effluents and the results were confirmed by ion chromatography and a standard procedure using an AutoAnalyser.
Sulfate Turbidimetry Sequential injection

"Highly Sensitive Spectrophotometric Determination Of Nitrite Ion Using 5,10,15,20-tetrakis(4-aminophenyl)porphine For Application To Natural Waters"
Anal. Chim. Acta 1996 Volume 333, Issue 1-2 Pages 175-180
T. Kawakami and S. Igarashi*

Abstract: To 1 mL 0.05 mM 5,10,15,20-tetrakis(4-aminophenyl)porphine aqueous solution was added 1 mL 1 M HCl to give a final pH of 1 and a portion of standard nitrite (I) solution, and the mixture was diluted to 10 mL. After 30 min at 30°C, the change in absorbance due to diazotization was measured at 434 nm. The calibration graph was linear up to 0.4 µM-I (up to 18 ng/ml) with a detection limit of 4 nM (0.18 ng/ml). The RSD (n = 10) was 1% for 0.2 µM-I. Many foreign ions were tolerated in large amounts. The method was applied to the determination of nitrite in rain, spring and tap water. Interference by Fe(III) was masked by adding 1 mL 1 mM EDTA to the initial mixture. The results agreed with those obtained by ion chromatography and a FIA method.
Nitrite Spectrophotometry Interferences

"Determination Of Chlorine Dioxide Using 4-aminoantipyrine And Phenol By Flow Injection Analysis"
Anal. Chim. Acta 1997 Volume 341, Issue 2-3 Pages 257-262
Takaho Watanabe*, Toshikazu Ishii, Yoshihiro Yoshimura and Hiroyuki Nakazawa

Abstract: A flow injection spectrophotometric method was developed for determining ClO2 in the presence of metal ions and various chlorinated species that can occur under normal water treatment conditions. ClO2 was separated from the water sample using a purge-trap system with a 15 min purge time, N2 purge gas at 600 ml/min and a sample temperature of 25°C. The trapping solution was analyzed by injecting a measured volume into a Tris hydrochloride buffer carrier stream (0.5 ml/min) which was merged with a reagent stream (2 ml/min) containing 0.8 mM 4-aminoantipyrine and 2 mM phenol in Tris hydrochloride buffer of pH 9. The mixture was passed through a heated coil (0.3 m x 0.5 mm i.d.) at 30°C and the absorbance was measured at 503 nm. The calibration graph was linear for 0.005-1.5 ppm ClO2, the detection limit was 5 ppb and the RSD for 0.05 ppm ClO2 was 2.4%.
Chlorine dioxide Spectrophotometry Heated reaction

"Flow Injection Determination Of Aluminum(III) Ions And Al13O4(OH)24 (H2O)127+ Species Using A 1.3 S Reaction With 8-quinolinol-derivatized Fractogel"
Anal. Chim. Acta 1997 Volume 343, Issue 1-2 Pages 19-32
Stuart L. Simpson, Kipton J. Powell*, and Nils H. S. Nilsson

Abstract: A flow injection spectrophotometric method is described to determine (i) 'free Al', viz. Al3+ plus Al(OH)2+ and very labile Al complexes, (ii) Al in moderate labile complexes and (iii) Al-hydroxo polymers, viz. Al13(OH)327+. A sample volume of 650 µL was inserted into a carrier stream (1 ml/min) of 0.05 M sodium acetate/0.05 M NaCl of pH 5 and propelled through a column reactor (22 µL) containing 8-quinolinol immobilized onto Fractogel. Free Al and Al-hydroxo polymers were retained by the column while moderate labile Al complexes passed through. The column effluent was merged with a reagent stream formed online by merging 2 M acetate buffer of pH 5.3 (0.21 ml/min) and 2 mM chrome azurol S (0.04 ml/min). The flow then passed through a reactor coil (300 cm x 0.5 mm i.d.) to the detection cell (70 µL) where the absorbance was measured at 545 nm. Free Al was eluted from the column reactor with 250 µL 0.02 M NaOH and the Al-hydroxo polymers were eluted with 60 µL 0.2 M NaOH using a 2 min stopped-flow procedure. The linear range of the method was 0.3-16 µM-Al3+, the detection limit was 70 nM and the RSD for 0.5 µM was 7%. The method was applied to aqueous soil extracts and humic waters and the results for free Al were compared to those obtained by the 7 s chrome azurol S method.
Aluminum(III) Aluminum, free Spectrophotometry Sample preparation Speciation 8-Hydroxyquinoline Immobilized reagent Method comparison Stopped-flow Column

"Prototype Of A Newly Developed Immunochemical Detection System For The Determination Of Pesticide Residues In Water"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 187-198
Petra M. Kr&auml;mer*, Bert A. Baumann and Peter G. Stoks

Abstract: Methods based on flow injection immunoaffinity analysis (FIIAA) are described for determining atrazine and diuron in water. The analyzes were performed on a prototype instrument consisting of an affinity column packed with protein A immobilized on polymethacrylate and a flow-through fluorimeter. The sequential experimental procedure was carried out by subjecting the affinity column to the following treatments; (i) incubating with anti-pesticide antibodies, (ii) rinsing, (iii) incubating with pesticide solution, (iv) rinsing, (v) incubating with peroxidase tracer for 3 min, (vi) rinsing and (vii) incubating with 3-hydroxyphenyl propionic acid/H2O2 substrate solution. The product of the enzyme reaction was detected at 415 nm (excitation at 320 nm). Between each determination the protein A affinity column was regenerated with 100 mM sodium citrate buffer. The linear range of the assays was 0.02-0.5 µg/l for both atrazine and diuron and the concentration producing 50% inhibition of the maximum response for atrazine was 0.1 µg/l. Diuron and isoproturon had no effect on the atrazine determination but simazine caused a decline in the atrazine signal. Recoveries for 0.02-0.5 µg/l atrazine were satisfactory.
Atrazine Diuron LC Immunoassay Fluorescence Interferences Buffer Column

"Flow Injection Enzyme Immunoassay Of Atrazine Herbicide In Water"
Anal. Chim. Acta 1997 Volume 347, Issue 1-2 Pages 111-120
Bjarni Bjarnason, Nikolas Bousios, Sergei Eremin and Gillis Johansson*

Abstract: The FIA manifold was equipped with an immunocolumn (13 x 1 mm i.d.) packed with an anti-atrazine antibody immobilized onto an epoxy activated Poros support (20 µm particle diameter) and a spectrophotometric detector. The antibody was raised in rabbits using an atrazine derivative conjugated to keyhole limpet haemocyanin (KLH). The enzyme tracer was prepared by coupling horseradish peroxidase with an atrazine derivative. The assays were performed by injecting 100 µL of an analyte/enzyme tracer mixture into the eluting buffer stream (50 µl/min) of 100 mM acetate buffer at pH 5 containing 0.5% Tween-20, 0.05% Kathon CG and 0.5 mM EDTA. After 5 min, 200 µL of the substrate solution was injected and the absorbance at 405 nm was monitored. The substrate solution contained 0.36 mM 2,2'-azino-di-(3-ethylbenzthiazoline-6-sulfonic acid) and 5 mM H2O2 in the eluting buffer. The column was regenerated between each measurement by injecting 200 µL 100 mM phosphoric acid/methanol (1:1). The detection limit for atrazine was 0.5 ng/ml. The antibody exhibited some cross-reactivity with other triazines with similar structures (e.g., simazine, propazine and terbutylazine) but low cross-reactivity towards 2,4-D.
Atrazine Immunoassay Spectrophotometry Column Enzyme Selectivity Immobilized antibody Interferences

"Online Automated Analytical Signal Diagnosis In Sequential Injection Analysis Systems Using Artificial Neural Networks"
Anal. Chim. Acta 1997 Volume 348, Issue 1-3 Pages 113-127
I. Ruis&aacute;nchez*, J. Lozano, M. S. Larrechi, F. X. Rius and J. Zupan

Abstract: This paper describes an automated anal. system able to diagnose multivariate spectrophotometric responses, with the aim of detecting faulty responses and assigning causes to the symptoms detected. Not only does this system detect faulty spectra, but it is also capable of modifying, by a 'feed-back response', the entire anal. system, and, when it is necessary, to report the conditions of the sequential injection analysis system to give an online diagnosis signal. Artificial neural networks (ANNs), in particular counter-propagation neural networks, were applied to detect faults and diagnose signals obtained in a sequential injection analysis system. This strategy was used to analyze natural water samples and, in particular, to simultaneously determine Ca and Mg by spectrophotometric detection of the complex which both cations form with the reagent Arsenazo III.
Calcium Magnesium Spectrophotometry Neural network Complexation Sequential injection Neural network

"A Novel Gas Diffusion/flow Injection System Coupled With A Bulk Acoustic-wave Impedance Sensor For Total Inorganic Carbonate And Its Application To Determination Of Total Inorganic And Total Organic-carbon In Waters"
Anal. Chim. Acta 1997 Volume 349, Issue 1-3 Pages 143-151
Xiao-li Su, Li-hua Nie and Shou-zhuo Yao*

Abstract: A novel flow injection analysis (FIA) system has been developed for the rapid and selective determination of total inorganic carbonate (TIC). The method is based on the diffusion of CO2 across a PTFE gas-permeable membrane from a stream of 0.5 mol L-1 H2SO4 (0.50 mL min-1) and water (0.50 mL min-1) merging into a stream of 10 mM tris(hydroxymethylamino)-methane containing 0.5 mM KCl (1.00 min min-1). The CO2 trapped in the acceptor solution is determined online by a bulk acoustic wave impedance sensor and the signal is proportional to the concentration of TIC present in the original samples. The proposed system was applied to the direct determination of TIC in natural and waste waters and the indirect determination of the total organic carbon content based on wet chemical oxidation of the samples, it exhibited a linear frequency response up to 20 mM bicarbonate with a detection limit of 10 µM, and the precision was better than 1% (RSD) at a throughput of 45 samples per hour. The effects of composition of acceptor stream, cell constant of the conductivity sensor, sample volume, flow rates and potential interferents on the FIA signals were discussed in detail. 32 References
Carbon, organic, total Carbon, inorganic, total Sensor Gas diffusion Teflon membrane Interferences Optimization

"Evaluation Of Spectrophotometric Methods For Determination Of Orthophosphates By Sequential Injection Analysis"
Anal. Chim. Acta 1997 Volume 350, Issue 1-2 Pages 21-29
A. Mu&ntilde;oz, F. Mas Torres, J. M. Estela and V. Cerda*

Abstract: Three methods for the determination of orthophosphate have been studied by using the same sequential injection analysis manifold, namely the vanadomolybdate, the malachite green and the molybdenum blue methods. The calibration graphs were linear up to 18.0, 0.4 and 4.0 mg P l-1, respectively. Relative standard deviations and detection limits were 2.1%, 18% and 1.7% and 0.15, 0.01 and 0.01 mg P L-1 respectively. The three methods were applied to the determination of phosphate in several water samples, both from natural and waste origin at a frequency of about 30 determinations per hour.
Phosphate Spectrophotometry Sequential injection Method comparison

"Determination Of Manganese In Natural Water And Effluent Streams Using A Solid-phase Lead(IV) Dioxide Reactor In A Flow Injection System"
Anal. Chim. Acta 1997 Volume 350, Issue 1-2 Pages 15-20
J. F. van Staden*, and L. G. Kluever

Abstract: The determination of manganese(II) in natural water and effluent streams, using a solid-phase reactor incorporated into a flow-injection system, was investigated. Mn2+-ions in samples injected into a carrier stream, were oxidized by solid lead(IV) dioxide suspended on silica gel beads to form MnO4--ions which were detected spectrophotometrically at 526 nm. The linear range of the system is between 1 to 5 mg L-1 with a detection limit of 0.56 mg l-1. The proposed system is suitable for the determination of manganese(II) in natural water and effluent streams with a relative standard deviation of better than 1.8%.
Manganese Solid phase reagent Reactor

"Speciation Of Copper, Lead, Cadmium, And Mercury In Waters Of The Oporto Coast In Portugal, Using Preconcentration In A Chelamine Resin Column"
Anal. Chim. Acta 1997 Volume 353, Issue 2-3 Pages 189-198
M. Teresa S. D. Vasconcelos* and M. Fernanda C. Leal

Abstract: Sea water was collected monthly between January and March 1996 from the shore of the Oporto coast at three different representative sampling points and speciation of Cu, Pb, Cd and Hg were carried out. For the purpose, total particulate (retained on a 0.45 µm pore-size filter), particulate sorbed to inorganic matter, total dissolved, and dissolved and operationally labile metal was discriminated. The filters were digested by microwaves. The filtered water was pre-concentrated on a microcolumn of Chelamine, eluted with 5 mL of 2 mol L-1 HNO3 and analyzed by flame atomic absorption spectrometry (FAAS) or mercury cold vapor (CVAAS) for Hg. Spike recovery percentages did not differ significantly (P>0.05) from 100% for any metal studied. The organic matter (OM) destruction was performed by UV photolysis. For quality control of the results, determination of Cu, Pb and Cd total dissolved concentration by differential pulse anodic stripping voltammetry was also performed; for Hg only the pre-concentration in the column was changed to partial evaporation of the sea water, followed by CVAAS. No statistically significant difference was observed between the results provided by the comparative methods. Online pre-concentration with Chelamine showed to be expeditious and effective for extraction of the heavy metals in coastal waters. The distribution of each metal in the different fractions, including ascertainment of significant correlation between pairs of metal fractions and the respective partition coefficients, is discussed.
Copper Lead Cadmium Mercury Preconcentration Speciation Resin

"Preconcentration And Separation Of Inorganic Selenium Species On Activated Alumina"
Anal. Chim. Acta 1998 Volume 363, Issue 2-3 Pages 141-146
Krystyna Pyrzy&#324;ska, Przemys&#322;aw Drzewicz and Marek Trojanowicz

Abstract: A simple and convenient method has been developed for the speciation of inorganic selenium in aqueous solutions using alumina microcolumn. Both Se(IV) and Se(VI) are retained on the microcolumn in a widely pH range of solution. The successive gradient elution of pre-concentrated species with ammonia solution allows to differentiate between them. Se(VI) and Se(IV) were eluted with 1 mL of 1 mol L-1 NH3 and 6 mL of 4 mol L-1 NH3, respectively, and determined by graphite furnace atomic absorption spectrometry. The detection limit for Se(VI) is 0.80 µg mL-1 and for Se(TV) 49 ng L-1. The method has been applied to the speciation of inorganic selenium in natural water samples.
Selenium(IV) Selenium(VI) Spectrophotometry Column Preconcentration Alumina pH Speciation

"Automatic Multicommutation Flow System For Wide Range Spectrophotometric Calcium Determination"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 45-53
F&aacute;bio R. P. Rocha, Patr&iacute;cia B. Martelli, Rejane M. Frizzarin and Boaventura F. Reis*

Abstract: An automatic flow system based on multicommutation concept is proposed to widen the linear concentration range for spectrophotometric calcium determination The flow network was build up with three way solenoid valves to permit implementation of different sample processing conditions to achieve limited, medium and large dispersion degree without modification of the manifold configuration. Dilutions were carried out by changing both sampled volume and the analysis path length or applying zone sampling approach. The software was developed to control all steps of sample processing and to allow changing the manifold configuration to obtain suitable sample dilution This condition was attained with up to 3 trials. A linear response from 0.250 to 1000 mg L-1, and a detection limit of 7 µg L-1 (99.7% confidence level) were achieved. The relative standard deviation was 0.83% (n = 10) or better. The sampling rate was ~60 h-1 and 0.27 µg of the chromogenic reagent (3,3'-bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolphthalein) was consumed per determination The procedure was applied to calcium determination in waters, plant materials, milk, antacid tablets, fertilizers and calcareous rocks. The results were in agreement with certified values or with those obtained with flame atomic absorption spectrophotometry at a 95% confidence level.
Calcium Spectrophotometry Automation Commutation Method comparison Reference material Valve Dilution

"Sampling Strategies In Sequential Injection Analysis. Exploiting The Monosegmented-flow Approach"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 257-262
Jonas A. Vieiraa, Ivo M. Raimundo, Jr.a, Boaventura F. Reisb,*, Elias A. G. Zagattob and Jos&eacute; L. F. C. Limac

Abstract: An evaluation of different sampling techniques employing sequential injection analysis (SIA) is described. The reaction between Fe(II) and 1,10-phenanthroline, which needs a pH adjustment with acetate buffer and a prior reduction with hydroxylamine solution, was employed. As a general rule, sensitivity, compared to that of the usual SIA technique, can be enhanced with binary sampling, sandwich sampling and monosegmented flow, in that order. Under the employed conditions, signals 13, 31 and 58% higher than those provided by conventional SIA can be obtained with the binary, sandwich and monosegmented sampling, respectively. The monosegmented-flow approach was applied in determining Fe in natural waters and results do not differ significantly from those obtained by ICP/AES at the 95% confidence level. The precision was 1.1%, expressed as relative standard deviation obtained by the measurement of nine replicates of 1.0 mg L-1 Fe(III) reference solution.
Iron(2+) Spectrophotometry Sequential injection Method comparison Buffer Sensitivity Sandwich technique

"Flow Injection Biamperometric Determination Of Nitrate (by Photoreduction) And Nitrite With The NO2-/I- Reaction"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 241-249
I. Gil Torr&oacute;a, J. V. Garc&iacute;a Mateob and J. Mart&iacute;nez Calatayuda,*

Abstract: An unsegmented continuous-flow method for the determination of nitrite and nitrate is proposed. Nitrate is photoreduced by UV irradn. with a low-pressure 8 w Hg lamp. The nitrite in the sample and that resulting from the photoredn. of nitrate were used to oxidize iodide ion. Tri-iodide thus formed is detected biamperometrically in excess iodide by using a flow-cell furnished with two Pt electrodes polarized at 100 mV. The limits of detection, throughput and reproducibility (n = 26) thus achieved for nitrite and nitrate are 25 and 50 µg L-1, 27 and 25 h-1, and 1.2 and 1.6%, respectively. The proposed method was used to determine nitrate and nitrite in natural waters, waste waters, soils, meat products and fertilizers. (29 References)
Nitrate Nitrite Biamperometry Electrode Catalysis Reduction column Indirect Photochemistry UV reactor

"Simultaneous Determination Of Cobalt(II) And Nickel(II) In Water And Soil Samples With Sequential Injection Analysis"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 177-186
R. E. Taljaard and J. F. van Staden*

Abstract: The discontinuous nature of the sequential injection technique make it ideally suitable for kinetic determinations One of the advantages of kinetic analysis over equilibrium methods is the possibility of carrying out simultaneous determinations based on the different rates of their reactions with a common reagent. The different rates of the pseudo-first order dissociation of the citrate complexes of cobalt(II) and nickel(II) at pH 8.00 are used as a basis for the kinetic determination of these ions at trace levels in water and soil extracts The reactions are followed by measuring the absorbance of complexes of the metal ions with 4-(2-pyridylazo)resorcinol (PAR) which are formed in a subsequent rapid reaction. EDTA is added to mask the major interferences. The proposed system is fully computerized and is able to monitor Co(II) and Ni(II) in samples at a frequency of 11 samples per h with a relative standard deviation better than 1.2%. The detection limits are 0.14 and 0.20 mg/l for Ni(II) and Co(II), respectively.
Cobalt(II) Nickel(II) Sample preparation Spectrophotometry Sequential injection Simultaneous analysis pH EDTA Complexation Computer Kinetic

"Flow Injection Analysis With Potentiometric Detection For The Speciation Of Fluoride And Calcium"
Anal. Chim. Acta 1998 Volume 366, Issue 1-3 Pages 23-33
Marek Trojanowicza,*, Peter W. Alexanderb and D. Brynn Hibbertc

Abstract: Three flow injection systems with potentiometric detection were developed for speciation of fluoride using a fluoride ion-selective electrode with a single flow-through detector. Among systems with (i) splitting of the sample zone and confluence point, (ii) flow reversal and (iii) resampling, the latter was most suitable. Its application was demonstrated for a study of the effectiveness of releasing fluoride from complexes with Al(III). Several ligands were examined as decomplexing agents such as EDTA, cyclohexane-1,2-diamine-N,N,N',N'-tetraacetic acid (DCTA), citrate and 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt (Tiron). In flow injection measurements, only Tiron was found suitable for decomposition of Al(III)-fluoride complexes. In stopped-flow measurements, using citrate or DCTA about a 10 min delay was required to release fluoride from Al(III) complexes. A flow injection system with resampling was also utilized for speciation of calcium ion-selective electrode in ligand solutions and in natural waters.
Calcium Fluoride Potentiometry Electrode Speciation Stopped-flow Interferences Flow reversal Sample splitting Manifold comparison Resampling Tiron Complexation

"Online Separation And Preconcentration Of Cadmium, Lead And Nickel In A Fullerene (C60) Minicolumn Coupled To Flow Injection Tungsten Coil Atomic Absorption Spectrometry"
Anal. Chim. Acta 1998 Volume 368, Issue 3 Pages 255-263
Marcia M. Silvaa, Marco A. Z. Arrudab, Francisco J. Kruga,*, Pedro V. Oliveirac, Zilvanir F. Queiroza, Mercedes Gallegod and Miguel Valc&aacute;rceld

Abstract: A flow system was coupled to a W coil electrothermal atomizer (150 W) for online separation and pre-concentration of Cd, lead and Ni based on the formation of DDC complexes and sorption into a minicolumn packed with fullerene C60. Three way solenoid valves used for sample and reagents management as well as the W coil power supply were controlled by a computer running a program written in Visual Basic, which was employed in synchronism with the original software of the atomic absorption spectrometer. The fullerene column (5 mm length, 2 mm internal diameter) was inserted into the tip of the autosampler arm, and elution was performed by sampling 35 µL of MeOH from the autosampler cup. With 3.0 mL of sample (loading time of 60 s) enrichment factors ranging from 100 to 150 were achieved. The detection limits for Cd, lead and Ni were 2.2, 23 and 75 ng L-1, respectively. No interference effects were observed on Cd, lead and Ni pre-concentration in the presence of up to 106 fold concentrations of Na, K, Ca or Mg. Application of t-test to the results obtained by the proposed method and the certified values of Cd, lead and Ni in five water reference materials did not reveal significant differences at the 5% probability level.
Cadmium Lead Nickel Spectrophotometry Preconcentration Fullerene Column Interferences Reference material Complexation

"Time-division Multiplex Technique For Producing Concentration Profiles In Flow Analysis"
Anal. Chim. Acta 1998 Volume 368, Issue 1-2 Pages 105-111
Xue D. Wanga, Terence J. Cardwella, Robert W. Cattralla,*, Robert P. Dysonb and Graeme E. Jenkinsc

Abstract: A technique is described that uses computer-controlled solenoid valves for creating concentration. profiles for various flow-based methods of anal. These profiles can be quickly selected through software and, similarly, parameters such as the volume of the sample, carrier, and reagents can be set and altered when required, with minimal changes to the hardware. The technique has been demonstrated for flow titration and flow injection but is equally applicable to other methods. In all these methods, only a single channel pump is required to draw the mixed solutions through the detector, and individual solutions are introduced into the flowing stream by selection through solenoid-operated valves. Results are presented for the determination in water samples of calcium using potentiometric titration and orthophosphate by flow injection using the molybdenum blue method. The technique uses only small volumes of solutions and is fully automated and so is ideal for use in portable instrumentation.
Calcium Phosphate Potentiometry Spectrophotometry Peak shape Gradient technique Titrations Apparatus Computer Valve

"Catalytic Simultaneous Spectrophotometric Determination Of Nitrite And Nitrate With A Flow Injection System"
Anal. Chim. Acta 1998 Volume 370, Issue 1 Pages 59-63
Zhang Zhi-Qi*, Gao Lou-Jun, Zhan Han-Ying and Liu Qian-Guang

Abstract: A catalytic spectrophotometric flow injection method is proposed for the simultaneous determination of nitrite and nitrate based on the catalytic effect of nitrite on oxidation of naphthol green B (NGB) by K bromate in H3PO4 medium and nitrate being reduced to nitrite by a Cd-coated Zn reductor column. The redox reaction was monitored spectrophotometrically by measuring the decrease in the absorbance of NGB at the max. absorption wavelength of 722 nm. A technique of double zone injection of the sample isolated by a reductor column is adopted with a single valve. The flow system produces two signals, one corresponds to the concentration. of nitrite and the other corresponds to the sum of both the ions. The detection limit is 0.5 µg L-1 for nitrite and 2.5 µg L-1 for nitrate. Up to 30 samples can be analyzed per h with a relative precision of ~2%. The procedure was successfully applied for the determination of nitrite and nitrate in natural waters.
Nitrate Nitrite Spectrophotometry Catalysis Kinetic Reduction column Redox Indirect

"Rapid Determination Of Chemical Oxygen Demand By A Semi-automated Method Based On Microwave Sample Digestion, Chromium(VI) Organic Solvent Extraction And Flame Atomic Absorption Spectrometry"
Anal. Chim. Acta 1998 Volume 372, Issue 3 Pages 399-409
Angel Cuesta, Jos&eacute; L. Todol&iacute;*, Juan Mora and Antonio Canals

Abstract: In the present work, a new flow injection analysis (FIA) manifold for the rapid determination of COD is presented and evaluated. The FIA manifold combines sample digestion by means of an oxidant solution (i.e., potassium dichromate and mercury sulfate) and an acid solution (sulfuric acid and silver sulfate) in a domestic microwave oven with the liquid-liquid extraction of Cr(VI) with tri-Bu phosphate (TBP). Finally, the remaining (non-reduced) Cr(VI) is determined in the organic phase by atomic absorption spectrometry. The digestion of the organic matter is carried out in the stopped-flow mode. Potassium hydrogenphthalate has been used for optimization of the method and as a standard to check its performance. The optimized conditions (oxidation) are: digestion time, 7 min; acid concentration, 67% (v/v). The optimized conditions for the extraction of the remaining Cr(VI) are: acid concentration, ≥30% (v/v); TBP, 1 mL. The proposed method has been successfully applied, with the exception of pyridine, to several organic compounds and waters. A semi-micro method has been used for comparison. The application range extends from 40 to 12,000 mg O2/L, whereas the lowest limits of detection and quantification are 13.5 and 45 mg O2/L, respectively. Following this method, the interference of Cl- can be compensated for at least up to 10,000 mg L-1 Cl-. Up to nine samples per h can be analyzed.
Chemical oxygen demand Sample preparation Spectrophotometry Microwave Online digestion Solvent extraction Stopped-flow Optimization Interferences

"Procedures For The Storage And Digestion Of Natural Waters For The Determination Of Filterable Reactive Phosphorus, Total Filterable Phosphorus And Total Phosphorus"
Anal. Chim. Acta 1998 Volume 375, Issue 1-2 Pages 5-47
W. Maher* and L. Woo

Abstract: A review, with 150 references, is given. An overview of the forms of P species likely to be encountered in natural waters and the implications for the measurement of filterable and total P is given. Procedures reported in the literature for the storage and digestion of water samples for filterable reactive P (FRP), total filterable P (TFP) and total P (TP) measurements are summarized and the advantages and limitations of methods discussed. Water samples for FRP and TFP measurements need to be filtered immediately on collection as exchange on and off particles may occur in the sample container. Slow freezing of filtered or turbid water samples in acid washed low density polyethylene bottles appears to be satisfactory for the long term storage (years) of a variety of water sample types. Storage of water samples at room temperature or refrigeration (1-5°C) with a preservative is suitable only for short term storage (days-months). If water samples contain <20 µg P/L, adsorption to containers may be significant. Batch digestion of samples with alkaline or acid peroxodisulfate using autoclave or microwave heating offers the advantages of ease, simplicity and precision. Good recoveries of P from a range of P compounds containing P-O-P, C-O-P and C-P bonds expected in natural waters have been reported. If turbid samples are to be analyzed, caution must be exercised to ensure that the C or suspended solids concentration. does not exceed the capacity of the digestion procedure to oxidize the C present and release occluded P from particulate materials. Better recoveries of P from turbid water samples are achieved using microwave heating with closed vessels, probably because of the higher temps. and pressures generated. The use of online heating (microwave, thermal induced) coupled with flow injection analysis and using peroxodisulfate or an oxidizing acid mixture should also allow the automation of TFP and TP measurements. Reliable procedures for the removal of unwanted particulate material prior to or after the digestion step need to be developed.
Phosphorus Sample preparation Review

"Simultaneous Flow Injection Determination Of Iron(II) And Total Iron By Micelle Enhanced Luminol Chemiluminescence"
Anal. Chim. Acta 1998 Volume 376, Issue 2 Pages 247-254
Kumiko Saitoh, Takashi Hasebe, Norio Teshima, Makoto Kurihara and Takuji Kawashima*

Abstract: A flow injection method is proposed for the determination of Fe(II) and for the simultaneous determination of Fe(II) and total Fe based on the catalytic effect of Fe(II) on the oxidation of luminol with H2O2 in an alkaline medium. The activating effect for the catalysis of Fe(II) was extremely exhibited in the presence of citric acid, while citric acid acted as a masking agent for Fe(III). Also, the sensitivity of the method was enhanced by adding tetradecyltrimethylammonium bromide (TTAB) as a cationic surfactant together with citric acid. The Fe(III) in sample solution can be determined by passing through the Ag reductor column introduced in the FIA system to reduce Fe(III) to Fe(II), which allows total Fe determination Calibration graphs for Fe(II) and total Fe were linear over the range 5 x 10^-9-1 x 10^-6 mol L-1 at a rate of 18 samples h-1 (36 peaks h-1). The relative standard deviations (n = 10) for 4 x 10^-8 mol L-1 Fe(II) and 1 x 10^-7 mol L-1 total Fe were 3.0% and 1.5%, respectively. The proposed method was successfully applied to the determination of Fe in human hair (NIES, number 5) and natural waters.
Iron(2+) Iron Chemiluminescence Indirect Speciation Catalysis Micelle Surfactant Sensitivity Reference material

"Flow Injection Analysis. 1. A New Concept In Fast Continuous-flow Analysis"
Anal. Chim. Acta 1975 Volume 78, Issue 1 Pages 145-157
J. Ruzicka and E. H. Hansen

Abstract: The concept of a new continuous-flow analyzer system is described. Based on instant discrete sampling by injection into a carrier stream, the system allows continuous-flow anal. to be performed in a fast, much simplified way. As the continuous flowing stream is characterized by a turbulent rather than a laminar flow, the discrete instant sampling creates geometrically well-defined segments of sample solution within the flowing stream. Because of the absence of lag phase, an unprecedented sampling rate for continuous-flow anal. of well over 200 samples per hr can be achieved; and even manual injection of the samples allows a very high degree of accuracy and precision to be obtained (≤ ±1%). Uses of the system in various anal. procedures are described and discussed. A potentiometric sensor (the air-gap electrode used in a flow-through unit) and a spectrophotometric arrangement with a flow-through cell were used as detector units.
Ammonia Ammonium Phosphate Phosphates Electrode Electrode Spectrophotometry Theory

"Automated Flow Injection Pseudotitration Of Strong And Weak Acids, Ascorbic Acid And Calcium, And Catalytic Pseudotitrations Of Aminopolycarboxylic Acids"
Talanta 1985 Volume 32, Issue 5 Pages 411-417
M. A. Koupparis* and P. AnagnostopoulouH. V. Malmstadt

Abstract: An automated spectrophotometric system applicable to acid - base, redox, complexometric and catalytic titrations is described. Peak widths (in time units) from 10 to 100 s can be measured with coefficient of variation of <0.3%. Strong and weak acids, both 0.5 to 20 mM, were titrated with NaOH in presence of bromothymol blue, ascorbic acid (0.1 to 10 mM) with 2,6-dichlorophenolindophenol and Ca (0.5 to 50 mM) with EDTA - Mg(II) complex and calmagite as indicator. Aminopolycarboxylic acids, EDTA and similar compounds (5 µM to 10 mM) were measured by monitoring at 470 nm the product of the manganese-catalyzed periodate diethylaniline reaction. The proposed method was applied to the determination of total hardness in water and to the determination of ascorbic acid in various pharmaceuticals.
Acids Ascorbic acid Calcium Hardness Spectrophotometry Computer Titrations Peak width

"Flow Injection Analysis With Iron-induced Perbromate - Iodide Reaction: Spectrophotometric Determination Of Iron"
Talanta 1986 Volume 33, Issue 6 Pages 547-549
T. D. Yerian, T. P. Hadjiioannou and G. D. Christian

Abstract: The formation of I3- from the Fe(II) or Fe(III) catalyzed BrO4- - I- reaction was monitored at 353 nm; this method for total-Fe determination was adapted to a flow injection system. Calibration graphs were rectilinear from 10 to 100 ng mL-1 with r2=0.9998 and the rectilinear range could be extended up to 10 µg mL-1 by appropriate adjustment of conditions. The coefficient of variation for samples containing 100 and 10 ng mL-1 of Fe(II) were 0.6 and 3.0%, respectively, and the detection limit was 0.4 ng mL-1. The average sampling rate was 30 h-1. The system was sufficiently sensitive for the determination of Fe in natural waters.
Iron Spectrophotometry

"Fluorimetric Differential-kinetic Determination Of Silicate And Phosphate In Waters By Flow Injection Analysis"
Talanta 1986 Volume 33, Issue 11 Pages 889-893
P. Linares, M. D. Luque De Castro and M. Valcarcel

Abstract: The determination is based on the reaction of the sample with 0.02 M (NH4)6Mo7O24 - 0.48 M HNO3 - 0.24 M HClO4 with formation of silicate and phosphate heteropoly-acids at different rates, and subsequent oxidation of 0.03 M thiamine; the thiochrome produced is detected by fluorimetry at 440 nm (excitation at 375 nm) . Flow rates for sample, molybdate and thiamine solution are 3.0, 2.2 and 1.1 mL min-1, respectively. The flow injection configurations permit measurements at two different residence times for each sample. The anions are determined in the range 30 to 600 ng mL-1 in ratios from 1:10 to 10:1, with coefficient of variation <2%. Good results were obtained with samples of natural and potable water. The sampling rate is 60 h-1.
Phosphate Silicate Fluorescence Kinetic Simultaneous analysis

"Spectrophotometric Determination Of Bromide And Iodide In A Flow System After Oxidation By Peroxodisulfate"
Talanta 1987 Volume 34, Issue 7 Pages 615-618
Annika Carlsson, Ulla Lundstr&ouml;m and &Aring;ke Olin*

Abstract: An earlier method (cf. Lundstrom, Ibid., 1982, 29, 291) for the determination of Br- was modified to include flow injection spectrophotometric measurement and a smaller ion-exchange column for pre-concentration. Sample solution containing BrO3- and IO3- obtained by oxidation of Br- and I- is mixed with a carrier solution containing 0.2 M NaCl, 1 M NaClO4, 0.05 M Na2SO4, 0.09 M NaH2PO4 and 0.01 M Na2HPO4 before detection at 355 nm. Calibration graphs are rectilinear for 1 to 15 µM and the limit of detection is 0.7 µM for both IO3- and IO3- plus BrO3-. The injection frequency is 60 h-1. Results were compared with those obtained by the original method and agreed to within ±1.5%. The method was applied to water samples.
Bromide Iodide Spectrophotometry Method comparison Preconcentration

"7,7,8,8-Tetracyanoquinodimethane Chemiluminescence Sensitized By Rhodamine B On Surfactant Bilayer Membrane Assemblies For Determination Of Sulfide By A Flow Injection Method"
Talanta 1989 Volume 36, Issue 4 Pages 505-508
Qian Xue-Xin, Guo Yue-Ying, Masaaki Yamada*, Eigo Kobayashi and Shigetaka Suzuki

Abstract: Optimum conditions have been established for the cited analysis. The two reagent streams (7.5 mL min-1) comprising 0.1 mM 7,7,8,8-tetracyanoquinodimethane - 0.5 mM rhodamine B - 40% acetonitrile and 1 mM dioctadecyldimethylammonium chloride - 1 mM NaOH, respectively, were separately heated in 1-m PTFE coils at 57°C. The streams were then mixed before injection of sample solution (30 µL) and measurement of the chemiluminescence signal by using a photomultiplier tube. The calibration graph was rectilinear from 0.05 to 5 µM-S2- ,and the detection limit was 0.01 µM. The coefficient of variation (n = 19) was 3.0% for 0.3 µM-S2-. The effects of various common ions were studied. Bivalent Mn and Fe and species forming a ppt. with S2- interfere. The method was applied to determine S2- in hot-spring water, and results agreed with those obtained by iodimetry.
Sulfide Chemiluminescence Injection technique Calibration Detection limit Interferences

"Preconcentration And Separation Of Inorganic Selenium On Dowex 1X8 Prior To Hydride-generation Atomic Absorption Spectrometry"
Talanta 1994 Volume 41, Issue 1 Pages 67-74
Ulf &Ouml;rnemark* and &Aring;ke Olin

Abstract: Portions of 6 M and 1 M HCl were added sequentially to deaerated water samples (100 ml) of pH 9, containing 200 ng/l of Se(IV) and 27-216 ng/l of Se(VI), until a stable pink color (methyl red indicator) was observed. Ammonium chloride/ammonia buffer of pH 9, (0.4 ml) was added and the solution passed (2 ml/min) through 1 g (dry wt.) of conditioned Dowex 1X8 resin in chloride form (100-200 mesh; prep. described). Se(IV) was eluted with 10 mL of 0.025 M HCl and Se(VI) with 7.5 mL of 5 M HCl, flow rates 1 ml/min, prior to determination by hydride-generation (HG) AAS (Ibid., 1986, 33, 249). Recoveries of Se(IV) and Se(VI) were 98-102%. Total Se was determined as Se(VI), following the oxidation of Se(IV) to Se(VI) with KMnO4 (described) before pre-concentration and elution. Values of Se(IV) and total dissolved Se (tabulated) in drinking water and fresh water, obtained by the above enrichment procedure coupled with flow injection HG AAS, were in good agreement with those obtained by a HG AAS procedure which incorporated pre-concentration of Se as SeH4 in a liquid N2 trap.
Selenium Spectrophotometry Preconcentration

"Gas Diffusion With Preconcentration For The Determination Of Fluoride In Water Samples By Flow Injection"
Talanta 1994 Volume 41, Issue 1 Pages 115-123
T. J. Cardwell*, R. W. Cattrall and M. Mitri

Abstract: Fluoride-containing solution (0.8 ml/min) and 1.25% hexamethyldisilazane in 1 M H2SO4 (0.8 ml/min) were mixed in a 330 cm coil held at 88-90°C and the trimethylsilane generated was absorbed in a stationary 0.1 M NaOH acceptor stream after diffusion through a gas-permeable fluoropolymer membrane in a gas diffusion module (illustrated). The pre-concentrated sample was flushed with additional 0.1 M NaOH (1.5 ml/min), then mixed with a pre-mixed solution of 2.3 mM alizarin red S (0.6 ml/min) and 1.1 mM zirconyl chloride in 0.2 M H2SO4/0.55 M HCl (0.6 ml/min). The yellow alizarin sulfonate ion, arising from the reaction of zirconium/alizarin sulfonate with fluoride, was measured at 520 nm. The calibration graph was linear for 0.1-4 mg/l of fluoride although the method is suitable for analysis of 0.1-10 mg/l of fluoride with a RSD of ~3% for fluoride concentration 3 mg/l. The detection limit was 0.055 mg/l and the quantification limit was 0.18 mg/l. Phosphate ions did not interfere with toleration levels of Al and Fe at 200 and 500 times the fluoride concentration, respectively.
Fluoride Spectrophotometry Interferences Preconcentration Gas diffusion

"Exploiting The Hydrodynamic Aspects Of Continuous-flow Systems"
Talanta 1991 Volume 38, Issue 12 Pages 1359-1368
Angel R&iacute;os and Miguel Valc&aacute;rcel,

Abstract: An overview of the analytical potential of the hydrodynamic aspects of unsegmented flow systems is presented. Different approaches involving flow manipulation are described: stopped-flow methodologies, intermittent pumping, selecting-diverting carrier (reagent) streams, open-closed flow systems, flow reversal and flow gradient.
Sample preparation Detector Extraction Kinetic Merging zones Multidetection Reverse Speciation Stopped-flow

"Fluorimetric Determination Of Uranium(VI) In Waters By Flow Injection Analysis After Preconcentration On A Silica Gel Micro-column"
Talanta 1992 Volume 39, Issue 7 Pages 795-799
Josef Havel, Milan Vrchlabsk&yacute; and Zdenk Kohn

Abstract: Uranyl cations were selectively adsorbed or pre-concentrated on a PTFE or fused-silica column (4 cm x 2 mm) of activated silica gel (Merck Kieselgel or Kavalier Silpearl; 0.05 to 0.2 mm diameter) from a medium (1.5 mL min-1) containing 0.03 M EDTA, 0.05 M NaF and 0.06 M tartrate (pH 9.3). The column was washed with water or NaClO4 before elution of uranyl with aqueous 1.33 M H3PO4 - 1.33 M H2SO4 and fluorimetry at 495 nm (excitation at 325 nm). The estimated detection limit was 0.1 to 0.2 µg of U. For 18 tested cations tolerable concentration. (interference 2% of signal) ranged from 20-fold for Zr(IV) to 2300-fold for La. The method was verified with synthetic aqueous solution and applied to waste and natural waters, for which the reproducibility ranged from 2.7 to 5.0%. A method for the selective determination of trace U(VI) uses flow injection analysis (FIA) with fluorimetric detection. U(VI) is selectively separated and(or) pre-concentrated from a volume of 20 mL on an activated silica gel microcolumn (2 x 40 mm) from a medium of 0.03 M EDTA, 0.06 M tartrate, and(or) 0.05 M NaF at pH 9.3. After washing of the column, the U is eluted with a mixture of 1.33 M H2SO4 and H3PO4 and determined with a relative standard deviation not exceeding 6% for concentrations. in the range 10^-250 µg/L. The detection limit was estimated to be 0.1-0.2 mg U. The method was verified using water samples with a high content of interfering elements and applied to the analysis of wastewater and natural waters.
Uranium(VI) Fluorescence Interferences Preconcentration Silica gel

"Simultaneous Determination Of Chloride, Bromide, Iodide And Fluoride With Flow Injection - Ion-selective Electrode Systems"
Talanta 1992 Volume 39, Issue 10 Pages 1259-1267
Fadhil M. Najib* and Shireen Othman,

Abstract: Electrodes for Cl-, Br- and I- were constructed (preparation described) from Ag2 - AgCl or AgBr (1:1) and Ag2S - AgI (1:3); for F- a commercial electrode was used. By combining the electrodes and suppressor columns of AgCl and amalgamated Pb, the ions were simultaneously determined in a carrier stream (0.5 mL min-1) of e.g. 0.1 M HClO4 at pH 4.0. The calibration graphs were rectilinear down to 100, 5, 1 and 5 µM for Cl-, Br-, I- and F-, respectively. The reproducibility was 1% for the determination of the halides in eight water samples, the results agreed well with those obtained by three reference methods. Flow-through ion-selective electrodes were constructed from compressed pellets (8-10 mm thick, 13 mm diameter, 10 tons/cm2 pressure) of Ag2S/AgX (X = Cl-, Br- or I-) drilled longitudinally (1.5 mm diameter hole) to be suitable for use in flow injection analysis. A column of AgCl (5.5 cm long, 2-3 mm internal diameter) was included in the Cl- electrode manifold to remove interferences from 10^-4 M Br- and 3 x 10^-5 M I- and S2-. A column of amalgamated lead (2-3 cm long, 2-3 mm internal diameter) was used in the Br--electrode manifold to remove interference from 2 x 10^-5 M I-, 3 x 10^-5 M S2- and 7 x 10^-4 M Cl-. These columns and the addition of ascorbic acid were not required when I- was determined with the iodide electrode. The carrier stream was 0.1 M sodium perchlorate (pH 4) at a flow-rate of 0.5 mL/min. The sample pH could be 4-7. Simultaneous determination of Cl- and I-, Cl-, I- and Br-, and Cl-, I-, Br- and F- ions was possible with combinations of the corresponding electrodes and columns in series and/or parallel in specially designed manifolds. Calibration plots were linear, with almost theoretical slopes, down to 10^-6 M I-, 5 x 10^-6 M Br-, 10^-4 M Cl- and 5 x 10^-6 M F-, with precision better than 1%. Sampling rates for single-ion determinations were 72, 102, 90 and 80 per h for the one-, two-, three- and four-electrode systems respectively. Determinations of these ions in water samples by the recommended procedure and by established batch methods showed no significant difference at the 95% confidence limits in a paired comparison t-test.
Chloride Bromide Iodide Fluoride Electrode Electrode Electrode Electrode Method comparison pH Interferences

"Spectrophotometric Flow Injection Determination Of Formetanate And M-aminophenol In Water After Reaction With P-aminophenol"
Talanta 1993 Volume 40, Issue 8 Pages 1173-1181
Karim D. Khalaf, Jose Sancenon and Miguel de la Guardia

Abstract: For the direct determination of 3-aminophenol [I; the metabolite of formetanate (II)], the sample was injected into a stream of water, which was mixed with a stream of aqueous 0.02 M NaOH before merging with a pre-mixed stream of aqueous 4 mM KIO4 (oxidant) and 0.26 mM 4-aminophenol. The mixture passed through an 8-m reaction coil before the absorbance of the resulting compound was measured at 576 nm. To determine the sum of I and II, NaOH was added to a final concentration. of 0.05 M and the sample was maintained at 90°C for 1 h to hydrolyse II, before analysis. To determine I and II in the same sample, I was determined directly and the mixture was subjected to hydrolysis and re-analyzed. The calibration graph for I was rectilinear from 0.5 (detection limit) to 73 µM, with a RSD of 1.8%. The calibration graph for II was rectilinear from 0.19 (detection limit) to 77 µM with a RSD of 0.5%. The method was used in a stopped-flow mode, to increase sensitivity four-fold. The method was applied to natural water samples spiked with I and II with recoveries of >100%.
Formetanate 3-Aminophenol Spectrophotometry Stopped-flow

"Study And Analytical Application Of Rare Earth Inhibition Of Laccase"
Talanta 1994 Volume 41, Issue 5 Pages 735-738
Cai Ruxiu, Huang Houping, Wang Guangfei, Lin Zhixin and Zeng Yun'e

Abstract: Laccase is a multi copper-containing oxidase. The effects of metal ions on the laccase-catalyzed redox reaction of 5,6-dibromo-2,3-dicyanohydroquinone to 5,6-dibromo-2,3-dicyanosemiquinone were studied. Rare-earth ions (Y, Sc, La, Lu) strongly inhibited the reaction. The degree of inhibition of La(III) on laccase activity was proportional to the concentration of La. A stopped-flow enzyme-catalyzed analytical kinetic method for determination of rare earths was proposed. The degree of inhibition of La(III) on the laccase-catalyzed reaction was linear from 0.033-0.2 ppm of La. The detection limit was 0.033 ppm and the RSD was 5.3% (n = 11). The method was used to determine rare-earth elements in water.
Metals, rare earth Biochemical analysis Stopped-flow Enzyme Kinetic Catalysis

"Flow Injection Spectrophotometric Determination Of Nitrite"
Talanta 1994 Volume 41, Issue 8 Pages 1275-1279
Anupama Chaurasia and Krishna K. Verma*

Abstract: 4-nitroaniline which produces a strong yellow solution when dissolved in diluted hydrochloric acid, reacted almost instantaneously in acidic medium giving a colorless product identified as 4-nitrophenyl diazo cation. The decrease in color intensity suggested a new simple one-step reaction procedure for the determination of reversed flow injection of 5 µg - 5 mg/litre nitrite, without any interference from Cu or Pb which affected other spectrophotometric procedures. The method was used for the determination of nitrite in natural waters when % RSD was 1.8-3.5%.
Nitrite Spectrophotometry Indirect Reverse Interferences

"Chemiluminescence Determination Of Nitrate With Photochemical Activation In A Flow Injection System"
Talanta 1995 Volume 42, Issue 3 Pages 437-440
Liu Renmin, Liu Daojie, Sun Ailing and Liu Guihua

Abstract: A flow-through photochemical reactor was used for the determination of nitrate in a FIA system, based on photochemical activation and chemiluminescence reactions (diagrams given). The carrier solution (1.5 ml/min) was H2SO4 of pH 5 and the reagent solution was 50 µM-luminol with 0.1 M NaOH (0.5 ml/min). An iminodiacetyl ligand exchange resin was used in the FIA system to remove the interference of Fe3+, Cu2+, Co2+ and Ni2+. The chemiluminescence signal was recorded with a XWT-S platform recorder. The sampling frequency was 60/h. The calibration graph was linear from 70 nM-0.1 mM. The RSD were 0.76-0.97%. The method was applied to the determination of nitrate in natural waters. Recoveries were 96-103%.
Nitrate Chemiluminescence Photochemistry Resin Interferences

"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 Spectrophotometry Sample preparation Solid phase extraction 8-Hydroxyquinoline Amberlite Cellex Chelex Preconcentration Speciation

"Flow Injection Photometric Determination Of Nanogram Levels Of Iron Based On The Catalysis Of Oxidative Coupling Of N-phenyl-p-phenylenediamine With M-phenylenediamine In A Micellar Medium"
Talanta 1995 Volume 42, Issue 8 Pages 1051-1056
Shigenori Nakanoa,*, Keisuke Tsujiia and Takuji Kawashimab,

Abstract: A sensitive photometric flow injection method for the determination of Fe(II) and Fe(III) is described (diagram also presented). The method is based on the catalytic action on the oxidative coupling of N-phenyl-p-phenylenediamine (I) with m-phenylenediamine (II) in the presence of water. A carrier solution of 0.1 M HCl (R1) was pumped into the analytical line at 0.8 ml/min. At the same flow rate, the reagent solutions in reservoirs R2 (0.4 M H2O2) R3 (2 mM I containing 0.2% Tween 80) and R4 (0.4 mM II, 0.5 M ammonium acetate and 0.12 mM triethylenetetramine) were pumped to the carrier stream at confluence points downstream. A 180 µL portion of the sample solution was introduced into the carrier flow line by a loop-valve injector and then merged in the reagent solutions. The color-forming reaction proceeded in a reaction coil (length 5 m) at 55°C and the absorbance was monitored at 620 nm. The calibration graphs for Fe(II) and Fe(III) were linear up to 30 ng/ml and the detection limit was 0.2 ng/ml. RSD were 1.4-2.6% and the sampling rate was 30/h. The method was applied in the determination of Fe in natural waters.
Iron(2+) Iron(III) Spectrophotometry Catalysis Micelle Speciation

"On The Spectrophotometric Flow Injection Determination Of Chromium(VI) In Natural Waters After Online Preconcentration On Activated Alumina"
Talanta 1995 Volume 42, Issue 11 Pages 1609-1617
Mauricio C. Pannain and Ricardo E. Santelli*

Abstract: A minicolumn made of silicone rubber (2.5 cm x 1.6 mm i.d.) was packed with 50 µL activated alumina (Brockman grade 1, particle size range 63-100 µm; Merck, Germany). Sample solution containing Cr(VI) was injected into the column at 5.1 ml/min. The column with adsorbed Cr(VI) was inserted into the eluting stream (0.1 M NH4OH; 2.73 ml/min) and the displaced Cr(VI) was then mixed with 0.7 M HNO3 (0.92 ml/min). The sample was then merged with the reagent stream (0.05% 1,5-diphenylcarbazide; 0.76 ml/min), the color was developed in a reaction coil and the absorbance was measured at 540 nm. Calibration graphs were linear from 10^-50, 2-10 and 1-5 µg/l for 5, 25 and 50 mL sample volumes, respectively. Corresponding detection limits were 3, 0.3 and 0.2 µg/l, respectively. The effects of interferents are tabulated. RSD were 0.6-4.7%. The method was used to determine of Cr(VI) in potable water. The feasibility of chromium(VI) pre-concentration on to activated alumina in a continuous-flow system with spectrophotometric detection was investigated. Chemical and flow variables, and the influence of concomitant species were studied both with and without pre-concentration systems. The best results were obtained by using a 2.5 cm long, 1.6 mm i.d. alumina minicolumn, and selecting 1 x 10^-4 M nitric acid as the pre-concentrating medium and 0.1 M ammonium hydroxide as the eluent. The eluted chromium(VI) was mixed with diphenylcarbazide in acidic medium and the absorbance of the colored complex was measured at 540 nm. Linear calibrations for 5, 25 and 50 mi sample volumes were established over the concentration ranges 10^-50 µg L-1, 2-10 µg L-1 and 1-5 µg L-1 with sensitivity enhancements of 44, 196 and 392 and detection limits (3s) of 3.0 µg L-1, 0.3 µg L-1 and 0.2 µg L-1, respectively. The method is relatively fast and cheap. Natural waters were analyzed with use of the developed procedure. (40 references)
Chromium(VI) Ion exchange Spectrophotometry Preconcentration Speciation Low cost Activated alumina Interferences

"Flow Injection Fluorimetric Determination Of Nabam And Metham"
Talanta 1996 Volume 43, Issue 2 Pages 193-198
Tom&aacute;s P&eacute;rez-Ruiza,*, Carmen Mart&iacute;nez-Lozanoa, Virginia Tom&aacute;sa and Rocio Casaj&uacute;sa

Abstract: Cereal grain was dried in the sun for 1 h and in the shade for 24 h. The grain was ground, mixed with 0.1 M NaOH, sonicated for 10 min and centrifuged for 5 min at 2000 rpm. The filtered supernatant or diluted natural water was injected into a carrier stream (0.3 ml/min) of pre-mixed streams of 0.3 M HCl and 0.2 mM TlCl3 in 0.5 M HCl. The resulting stream passed through a reaction coil [100 cm for nebam or 150 cm for metham (metam) x 0.5 mm i.d.] and the fluorescence intensity was measured at 419 nm (excitation at 227 nm). Calibration graphs were linear for 1-10 µM-nabam and metam with RSD (n = 10) at 3 and 7 µM of 1.4 and 0.8%, respectively, for nabam and 1.2 and 0.5%, respectively, for metam. The effects of foreign substances on the analysis are tabulated and discussed. Recoveries of nabam from water were 96.6-104% and 95.75-104% from cereals with corresponding recoveries for metam of 96.6-105% and 95-101.6%.
Methylcarbamodithioic acid Nabam Fluorescence Interferences

"Field Portable Flow Injection Analysers For Monitoring Of Air And Water Pollution"
Talanta 1996 Volume 43, Issue 6 Pages 915-925
Peter W. Alexandera,*, Lucy T. Di Benedettoa, Telis Dimitrakopoulosa, D. Brynn Hibbertb, J. Catherine Ngilab, Margaret Sequeirab and Damien Shielsb

Abstract: An overview of portable monitors for the analysis of aqueous and gas samples including chemical ion sensors, multi-sensor arrays, test kits, disposable test strips, submersible probes and gas analyzer.s is presented. The use of a portable flow injection potentiometric analyzer. and the monitoring of car exhaust gases, air pollution in houses and ethanol in alcoholic drinks are described. (29 references).
Potentiometry Portable Review Gas phase detection

"Simultaneous Spectrophotometric Determination Of Nitrite And Nitrate By Flow Injection Analysis"
Talanta 1996 Volume 43, Issue 7 Pages 1009-1018
M. J. Ahmeda, C. D. Stalikasa, S. M. Tzouwara-Karayannia and M. I. Karayannisa,*

Abstract: Meat products, flour, soil, beer and cheese were prepared and digested by the AOAC method ['Official Methods of Analysis of the Association of Official Analytical Chemists', Helrich (Ed.), Association of Official Analytical Chemists, Arlington, VA, USA, 1990]. The digests were filtered and the filtrate or filtered water was diluted with 0.4 M NH4Cl. The prepared samples or standards were injected into a carrier stream (0.4 ml/min) of 0.4 M NH4Cl, the stream was split into two and one stream passed through a glass reaction column (2 cm x 3 mm i.d.) packed with copper particles and a reduction column (10 cm x 3 mm i.d.) packed with copperized cadmium granules. The reduced stream merged with a reagent stream (1 ml/min) of 7.24 mM 3-nitroaniline/3.86 mM N-(1-naphthyl)- ethylenediamine dihydrochloride (1:5), the resulting stream passed through a reaction coil (50 cm) and the absorbance was measured at 535 nm. The second part of the stream by-passed the reduction columns, merged with the reagent stream and the absorbance was measured. Calibration graphs were linear for 0.01-2.2 µg/ml of nitrite and 0.1-3.5 µg/ml of nitrate with detection limits of 1 ng/ml and 10 ng/ml, respectively. The RSD (n = 5) were 0.1-2% over the calibration range for nitrate and nitrite. The permissible levels of interfering ions are tabulated.
Nitrate Nitrite Sample preparation Spectrophotometry Interferences Column Reduction column

"Flow Injection Gas Diffusion Amperometric Determination Of Trace Amounts Of Ammonium Ions With A Cupric Hexacyanoferrate"
Talanta 1996 Volume 43, Issue 7 Pages 1049-1054
Renmin Liu, Bianting Sun, Daojie Liu and Ailing Sun

Abstract: Sample was injected into a carrier stream (4 ml/min) of water which then merged with a reagent stream (1 ml/min) of 0.2 M NaOH containing 0.1 M sodium citrate. The resulting stream and a stream (1.4 ml/min) of 0.1 M H2SO4 passed to a gas diffusion cell, the ammonium ions passed into the H2PO4 and were determined by amperometry using a previously described electrode (Ruzicka and Hansen, 'Flow injection Analysis', John Wiley and Sons, New York, 1981, p. 207). The flow-through three-electrode cell contained a copper hexacyanoferrate film electrode coated with Nafion Film as the working electrode, a Ag/AgCl reference electrode and a Pt auxiliary electrode. An applied voltage of 0.4 V was used. The calibration graph was linear for 2-40 µM-ammonium ions. The method was applied to the determination of ammonium ions in lake and rain water with recoveries of 94.4-104.4% and RSD of 1.1-2.3% (n not given).
Ammonium Amperometry Gas diffusion

"High-sensitivity Flow-based Analysis System Using A Semiconductor Laser And Thin Long Flow-through Cell For The Determination Of Total Phosphorus In Water"
Talanta 1996 Volume 43, Issue 9 Pages 1471-1479
Takashi Korenagaa,* and Fusheng Suna

Abstract: A flow-through cell with an optical pathlength of 10 cm machined from a 2.5 cm diameter PTFE rod (details given) was used in conjunction with a GaAlAs semiconductor laser source (emission wavelength 793 nm) and a Hamamatsu model S1087-01 photodiode detector. A light-emitting diode (Toshiba model TLS143) and a second photodiode were used to generate a reference signal. In the flow injection determination of P in water, a 300 µL portion of sample was injected into a stream of 0.3% K2S2O8 solution (600 µL/min) and the resulting mixture was passed through a reaction coil (10 m x 1 mm i.d.) at 140°C and then mixed with color reagent prepared by mixing 7.2% ascorbic acid solution with with 0.048% antimony potassium tartrate hemihydrate/1.2% ammonium molybdate tetrahydrate solution in 8% H2SO4 in the ratio 1:5. The mixture was passed through a second reaction coil (10 m x 1 mm i.d.) at 140°C and then into the detector cell. The calibration graph was linear for 1-50 µg/l of P, and for 20 µg/l of P the RSD was 1% (n = 10). The limit of detection was 0.6 µg/l and recoveries of various P compounds were 94-107%. The method was applied to eight samples of waste water, 18 samples of treated water and five samples of natural water; the results agreed with those obtained by an official method.
Phosphorus Spectrophotometry Light emitting diode Photodiode

"Preconcentration And Atomic Absorption Determination Of Iron By Sequential Injection Analysis"
Talanta 1997 Volume 44, Issue 4 Pages 553-562
E. Rub&iacute;a, M. S. Jim&eacute;nezb, F. Bauz&aacute; de Mirab&oacute;c, R. Fortezac and V. Cerd&agrave;c,*

Abstract: Water sample (250 ml) was boiled with 25 mL HNO3, adjusted to pH 3-3.5 with NH3 and diluted to 100 mL with water. Analysis was by sequential injection AAS with pre-concentration of Fe(III) on a microcolumn (5.5 cm x 2.5 mm i.d.) packed with Chelex 100 resin (50-100 mesh) prior to detection at 248.3 nm using an air-acetylene flame. The instrumental set-up is shown and operating parameters are tabulated. The sample was eluted from the pre-concentration column with 2 M HNO3. The optimal flow rate was 6.5 ml/min. The calibration graph was linear for 0.05-1.2 mg/l Fe(III) and the detection limit was 0.012 mg/l. The RSD (n = 10) at 1 mg/l with 9 mL injections was 4%. Using 27 mL injections the detection limit was 0.006 mg/l and the RSD was 4.8%. The retention efficiencies of the column were 93.1% and 7.4% at 0.4 and 1 mg/l Fe(III), respectively, for 9 mL injections and 8.4% at 0.2 mg/l Fe(III) for a 27 mL injection.
Iron Spectrophotometry Chelex Optimization Sequential injection Preconcentration

"Flow Injection Determination Of Lead And Cadmium Traces With Graphite Furnace Atomic Absorption Spectrometry"
Talanta 1997 Volume 44, Issue 5 Pages 867-875
M. Colognesi, O. Abollino, M. Aceto, C. Sarzanini and E. Mentasti*

Abstract: Natural or potable water sample, 10 mM Tiron solution (1,2-dihydroxy-3,5-benzenedisulfonic acid) and ammonium borate buffer of pH 9 were loaded at 1 ml/min into a pre-concentration manifold (diagram given) and pumped through a column (1.5 cm x 3.9 mm i.d.) of macroporous anion-exchange resin (AGMP-1; BioRad, 100-200 mesh, chloride form). The bound Pb and Cd were eluted with 0.1 M HCl and the eluate was collected in to a sampling cup for GFAAS using a matrix modifier of NH4H2PO4/magnesium nitrate. The program details are tabulated. Pb and Cd were determined at 283.3 nm and 228.8 nm, respectively. Recoveries were 92.7±0.4% for Pd and 28±1% for Cd. Using a batch method, Cd recoveries were higher. Detection limits were 9 and 7 ng/l for Pb and Cd, respectively, for a pre-concentration ratio of 5O. No calibration data are given. Interferences and the effect of Tiron purity were investigated.
Cadmium Lead Spectrophotometry Column Preconcentration Complexation Interferences Tiron Column Resin Biorad

"Catalytic Flow Injection Determination Of Copper At Nanogram Levels By Using Color Formation Of N-phenyl-p-phenylenediamine With M-phenylenediamine In The Presence Of Pyridine And Ammonia As Activators"
Talanta 1997 Volume 44, Issue 5 Pages 765-770
Shigenori Nakanoa,*, Keiko Nakasoa, Kazunori Noguchia and Takuji Kawashimab

Abstract: Sample (215 µL) was injected into a carrier stream of 0.1 M HCl, into which streams (1 ml/min) of 0.5 M H2O2, 1 mM N-phenyl-p-phenylenediamine hydrochloride/0.5% Tween 80 and 3 mM phenylenediamine dihydrochloride/0.5 M NH3/0.2 M pyridine/ 2 mM citric acid were pumped. The flow passed through a reaction coil (8 m x 0.5 mm i.d.) at 55°C and the absorbance of the dye formed was measured at 620 nm. The calibration graph was linear from 0.1-2 ng/ml Cu(II) and the detection limit was 0.05 ng/ml. RSD (n = 10) at 1 and 2 ng/ml Cu(II) were 2.4% and 1.6%, respectively. Sample throughput was 30/h. Tolerance limits for interfering ions are tabulated. The method was applied to natural waters.
Copper Spectrophotometry Catalysis Interferences Heated reaction Surfactant

"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 Spectrophotometry Sample preparation Preconcentration Amalgamation Preconcentration Solid phase extraction Method comparison Amberlite Resin

"Sequential Injection Wetting Film Extraction Applied To The Spectrophotometric Determination Of Chromium(VI) And Chromium(III) In Water"
Talanta 1997 Volume 44, Issue 9 Pages 1563-1571
Yongyi Luo, Shigenori Nakano, David A. Holman, Jaromir Ruzicka and Gary D. Christian*

Abstract: The spectrophotometric determination of Cr(VI) and Cr(III) via sequential injection was used to demonstrate the sensitivity enhancement provided by a newly developed wetting film extraction system. The reaction product of Cr(VI) with 1,5-diphenylcarbazide was ion-paired with perchlorate and extd. into an organic wetting film consisting of octanol and 4-methyl-2-pentanone on the inner wall of a Teflon tube. The wetting film, with the extd. analyte, was then eluted with 100 µL acetonitrile and the analyte determined spectrophotometrically at 546 nm. Important optimized parameters were the selection of wetting film and elution solvents, the flow rate, the length and diameter of the extraction coil and the conditions for the formation of the ion paired chelate. Cr(III) was previously oxidized to Cr(VI) and calculated as the difference between total Cr and Cr(VI). An enrichment factor of 25 and a detection limit of 2.0 µg L-1 Cr(VI) were achieved with a sampling frequency of 17 h-1. The calibration curve was linear up to 100 µg L-1 Cr(VI) (r = 0.999). The relative standard deviations were 2.8 and 2.0% at the 25 and 100 µg L-1 levels.
Chromium(III) Chromium(VI) Spectrophotometry Extraction Sequential injection Optimization Organic phase detection Chelation

"Rapid Automated In-situ Monitoring Of Total Dissolved Iron And Total Dissolved Manganese In Underground Water By Reverse-flow Injection With Chemiluminescence Detection During The Process Of Water Treatment"
Talanta 1997 Volume 44, Issue 11 Pages 2041-2049
Yanxiu Zhou and Guoyi Zhu*

Abstract: Measurement of iron and manganese is very important in evaluating the quality of natural waters. We have constructed an automated Fe(II), total dissolved iron(TDI), Mn(II), and total dissolved manganese(TDM) analysis system for the quality control of underground drinking water by reverse flow injection analysis and chemiluminescence detection(rFIA-CL). The method is based on the measurement of the metal-catalyzed light emission from luminol oxidation by potassium periodate. The typical signal is a narrow peak, in which the height is proportional to light emitted and hence to the concentration of metal ions. The detection limits were 3 x 10^-6 µg mL-1 for Fe(II) and the linear range extents up to 1.0 x 10^-4 and 5 x 10^-6 µg mL-1 for Mn(II) cover a linear range to 1.0 x 10^-4 µg mL-1. This method was used for automated in-situ monitoring of total dissolved iron and total dissolved manganese in underground water during water treatment.
Iron Manganese Chemiluminescence Reverse

"Rapid Determination Of Dissolved Organic Phosphorus In Soil Leachates And Runoff Waters By Flow Injection Analysis With Online Photooxidation"
Talanta 1997 Volume 45, Issue 1 Pages 47-55
D. M. W. Peata, I. D. McKelvieb, G. P. Matthewsa, P. M. Haygarthc and P. J. Worsfolda,*

Abstract: A rapid method suitable for the determination of dissolved organic phosphorus (DOP) in soil leachates and runoff waters is presented. The flow injection (FI) manifold contains an inline PTFE reaction coil wrapped around a low power UV lamp and is based on the spectrophotometric determination of dissolved reactive phosphorus (DRP) and mineralised DOP at 690 nm after reduction of phosphomolybdate to molybdenum blue with tin(II) chloride. The linear range was 0-1.5 mg L-1 PO4-P, with a detection limit (3s) of 7 µg L-1 and a sample throughput of 40 h-1 Tolerance to potential matrix interferences in soil pore waters, particularly Al(III), Si(IV), Fe(II) and Fe(III), was achieved using a combination of online sample pretreatment by a strong acid ion exchange column, low photoreactor pH and acid induced control of the kinetics of the molybdenum blue reaction. The results obtained with this manifold were in good agreement with those obtained by a batch spectrophotometric reference method.
Phosphorus Ion exchange Spectrophotometry Photochemistry Interferences Kinetic Method comparison UV reactor

"Online Cryogenic Trapping With Microwave Heating For The Determination And Speciation Of Arsenic By Flow Injection/hydride Generation/atomic Absorption Spectrometry"
Talanta 1998 Volume 45, Issue 3 Pages 531-542
J. L. Burguera*, M. Burguera, C. Rivas and P. Carrero

Abstract: An online flow injection-hydride generation/at. absorption spectrometry method was developed for the pre-concentration and selective determination of inorganic As (As(III) and As(V)) and its methylated species. The separation of the As species was performed by an automated pH-selective arsines generation technique, using Na tetrahydroborate(III) as reductant. Each arsine was cryogenically trapped in a PTFE coil, knotted and sealed inside another wider diameter tube, through which liquid N was suctioned by negative pressure. Then, based on their different b.ps., the arsine species were selectively liberated using a heating cycle of microwave radiation, followed by atomic absorption detection. A sample solution aliquot mixed with 1% citric acid was used for the determination of As(III) alone, while a 2nd sample aliquot mixed with 2 mol/L nitric acid was used for the quant. determination of total inorganic As, monomethylarsonic acid and dimethylarsinic acid. Based on 10 mL sample, the detection limits are 20-60 ng As/L, which are sufficiently low to detect the arsines-forming species in natural waters. These values are negative affected by the reagents purity and background noise due to flame flickering, but the sensitivity can substantially be improved by increasing sample size or running several consecutive reactions.
Arsenic(3+) Arsenic(5+) Dimethylarsenic Monomethylarsine Spectrophotometry Cold trap Speciation Microwave

"Determination Of Arsenic(III) And Arsenic(V) By Electrothermal Atomic Absorption Spectrometry After-complexation And Sorption On A C-18 Bonded Silica Column"
Talanta 1998 Volume 45, Issue 6 Pages 1167-1175
Dirce Pozebon, Valderi L. Dressler, Jos&eacute; A. Gomes Neto and Adilson J. Curtius*

Abstract: A flow injection procedure for the separation and pre-concentration of inorganic arsenic based on the complexation with ammonium diethyl dithiophosphate (DDTP) and sorption on a C-18 bonded silica gel minicolumn is proposed. During the sample injection by a time-based fashion, the As3+-DDTP complex is stripped from the solution and retained in the column. Arsenic(V) and other ions that do not form complexes are discarded. After reduction to the trivalent slate by using potassium iodide plus ascorbic acid, total arsenic is determined by electrothermal atomic absorption spectrometry (ETAAS). Arsenic(V) concentration can be calculated by difference. After processing 6 mL sample volume, the As3+-DDTP complexes were eluted directly into the autosampler cup (120 µl). Ethanol was used for column rinsing. Influence of pH, reagent concentration, pre-concentration and elution time and column size were investigated. When 30 µl of eluate plus 10 µl of 0.1% (w/v) Pd(NO3)(2) were dispensed into the graphite tube, analytical curve in the 0.3-3 µg As L-1 range was obtained (r = 0.9991). The accuracy was checked for arsenic determination in a certified water, spiked tap water and synthetic mixtures of arsenite and arsenate. Good recoveries (97-108%) of spiked samples were found. Results are precise (RSD 7.5 and 6%, for 0.5 and 2.5 µg 1-1, n = 10) and in agreement with the certified value of reference material at 95% confidence level.
Arsenic(3+) Arsenic(5+) Arsenate ion Arsenite Spectrophotometry Diethyldithiophosphate C18 Silica gel Complexation Speciation Optimization Preconcentration Reference material

"Flow Injection Catalytic Spectrophotometric Determination Of Nitrite Using The Redox Reaction Between Naphthol Green B And Potassium Bromate"
Talanta 1998 Volume 47, Issue 2 Pages 497-501
Zhang Zhi-Qi*, Gao Lou-Jun and Zhan Han-Ying

Abstract: A flow injection catalytic spectrophotometric method is proposed for the determination of nitrite based on its catalytic effect on the redox reaction between naphthol green B and K bromate in phosphoric acid media. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of naphthol green B at the max. absorption wavelength of 722 nm. The detection limit is 0.5 ng/mL in a sample volume of 90 mm3. Up to 50 samples/h can be analyzed with a relative precision of ~2%. The method is free from most interferences, especially from large amounts of nitrate. The procedure was applied to the determination of trace nitrite in natural waters.
Nitrite Spectrophotometry Redox Catalysis Indirect Interferences

"A Metallic Cobalt Electrode For The Indirect Potentiometric Determination Of Calcium And Magnesium In Natural Waters Using Flow Injection Analysis"
Talanta 1998 Volume 47, Issue 3 Pages 779-786
ZuLiang Chen* and Mark A. Adams

Abstract: A flow injection analysis of Ca2+ and Mg2+ using indirect potentiometric detection in natural waters is proposed, where Ca2+ or Mg2+ are injected into a buffer carrier containing phosphate, resulting in the formation of Ca3(PO4)2 or Mg3(PO4)2. The consequent reduction in free phosphate in the carrier solution is detected using a metallic cobalt wire electrode. Indirect electrode response was used and the experimental conditions affecting electrode response were optimized. Responses were linear at concentrations 5 x 10^-4 - 5 x 10^-3 M with a detection limit of 1 x 10^-5 M in 20 mM phosphate buffer at pH 8.0. The relative standard derivation at 1 mM of Ca2+ and Mg2+ were 3.9 and 3.7% (n = 10), respectively. EGTA and 8-hydroxyquinoline were used as the masking agents for Ca2+ and Mg2+, respectively. Concentrations of Ca2+ and Mg2+ in natural waters were determined by this method.
Calcium Magnesium Potentiometry Electrode Indirect Optimization 8-Hydroxyquinoline Interferences

"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 Sample preparation Fluorescence Solid phase extraction Speciation Volatile generation Reference material C18 Resin Column

"Rapid Determination Of Sulfate In Natural Waters And Plant Digests By Continuous-flow Injection Turbidimetry"
Analyst 1977 Volume 102, Issue 1216 Pages 503-508
F. J. Krug, H. Bergamin Filho, E. A. G. Zagatto and S. Storgaard J&oslash;rgensen

Abstract: SO42- in plants was determined by digesting 1 g samples in concentrated HNO3-concentrated HClO4, injecting 0.4 mL diluted digest into a carrier stream of a 1:1 mixture of 0.01 M HCl and 5% BaCl2.2H2O - 0.05% poly(vinyl alcohol), and measuring the turbidity at 480 nm in a standard spectrophotometer fitted with a flow-through cuvette. Natural water samples were injected without pretreatment. The calibration graphs were linear at 40-140 ppm SO42-. Analyses may be carried out at ≤180 samples/h with standard deviation 0.85%. The results agreed with those obtained by a standard turbidimetric method. The turbidimetric determination of sulphate as barium sulphate has been adapted to the continuous flow injection procedure of Rika and co-workers. The effects of reagent composition, reagent flow-rates and length of mixing coils have been investigated. Optimum conditions were established for the determination of sulphate in natural waters and in plant digests. The results agree satisfactorily with those obtained by a standard turbidimetric method and analyzes can be carried out at a rate of up to 180 samples per hour.
Sulfate Sample preparation Spectrophotometry Turbidimetry Method comparison Optimization

"Determination Of Ammonia In Low Concentrations With Nesslers Reagent By Flow Injection Analysis"
Analyst 1979 Volume 104, Issue 1234 Pages 47-54
F. J. Krug, J. Ruzicka and E. H. Hansen

Abstract: NH3 (0.5-6.0 ppm) was determined turbidimetrically at 410 nm with good precision and accuracy in 30 µL samples of natural water and soil extracts at a rate of 100 samples/h by using Nessler's reagent and continuous-flow injection. Variables such as optimum reagent concentrations, alkalinity, flow rates, mixing coil lengths, temperature, and the presence of protective colloids in the flow injection system were studied.
Ammonia Sample preparation Turbidimetry Optimization

"Semiautomatic Determination Of Manganese In Natural Waters And Plant Digests By Flow Injection Analysis"
Analyst 1979 Volume 104, Issue 1237 Pages 371-375
M. F. Gin&eacute;, E. A. G. Zagatto and H. Bergamin Filho

Abstract: Mn was determined in water and plant digests by the formaldoxime method by a semi-automatic process. The sample was injected onto a stream of carrier (water for water samples, and a suitable acid solution for plant digests prepared by HNO3 + HClO4 treatment). This was mixed, in an automatic analyzer, with 5% ascorbic acid and this stream was then mixed with a premixed stream of reagent, neutralizing solution (aqueous NaOH), and masking agent (KCN, which suppressed interference from Fe up to 20 ppm). With an injected volume of 0.35 mL, about 135 samples per h could be analyzed, with a standard deviation of better than 1% over the range 0.2-2 ppm of Mn.
Manganese Sample preparation Interferences

"Determination Of Iron In Natural Waters And Plant Material With 1,10-phenanthroline By Flow Injection Analysis"
Analyst 1982 Volume 107, Issue 1275 Pages 659-663
J. Mortatti, F. J. Krug, L. C. R. Pessenda, E. A. G. Zagatto and S. Storgaard J&oslash;rgensen

Abstract: A flow injection analysis procedure for the determination of total iron in natural waters and plant digests by the 1,10-phenanthroline method is described. Effects of mixing-coil lengths, sample volume, flow-rates, reagent concentrations and interfering species were investigated. The proposed procedure allows the determination of iron concentrations in the range 0.1-30 ppm at a rate of up to 180 samples per hour with a relative standard deviation of lower than 1%. The results agree with those obtained by atomic absorption spectrometry, and an iron concentration identical with the certified value was found by analysis of an NBS standard reference material.
Iron Spectrophotometry Apparatus Injector

"Rapid Sequential Determination Of Chromium(III) - Chromium(VI) By Flow Injection Analysis - Inductively Coupled Plasma Atomic-emission Spectrometry"
Analyst 1985 Volume 110, Issue 4 Pages 331-333
Alan G. Cox, Ian G. Cook and Cameron W. McLeod

Abstract: Standard aqueous solution of Cr(III) - Cr(VI) (0.2 to 2 ml, containing 10 to 1000 µg l-1) were injected via a carrier stream of 0.01 M HNO3 (flow-rate 1 mL min-1) on to a micro-column (2.5 cm x 1.5 mm) of activated alumina. The Cr(VI) was adsorbed selectively and Cr(III) in the eluate was determined by ICP-AES at 267.72 nm. The Cr(VI) was then eluted from the column by injection of 0.2 mL of 1 M NH3 into the carrier stream and determined similarly at 267.72 nm. Calibration was rectilinear for both species for up to 1000 µg l-1. The coefficient of variation at the 10 µg L-1 level for a 2 mL sample injection were 2.2% for Cr(III) and 1.1% for Cr(VI), and the corresponding detection limits were 1.4 and 0.20 µg l-1, respectively. Determinations of the Cr species at µg L-1 levels in NBS and British Geological Survey reference waters are demonstrated.
Chromium(III) Chromium(VI) Spectrophotometry Reference material Activated alumina Speciation

"Automated Flow Injection Spectrophotometric Determination Of Zinc Using Zincon: Applications To Analysis Of Waters, Alloys, And Insulin Formulations"
Analyst 1986 Volume 111, Issue 11 Pages 1311-1315
Michael A. Koupparis and Paraskevi I. Anagnostopoulou

Abstract: Water samples were filtered (0.45 µm membrane filter) followed by adjustment of the filtrate to pH 9 with 0.5 M borate buffer. Copper alloy samples were dissolved in concentrated HNO3 (10 ml), and the solution was diluted, neutralized with 5 M NaOH to phenolphthalein, and diluted with 0.05 M borate buffer. Insulin formulations were deproteinized with 1 M HCl (1 ml) and 0.61 M trichloroacetic acid (8 ml). After centrifugation, the supernatant solution (2 ml) was neutralized with 1 M NaOH (2 ml) and diluted to 10 mL with 0.05 M borate buffer. Aliquots (300 µL) of test solution containing <10 µg mL-1 of Zn were injected into a stream of mixed reagent (0.01 M KCN - 0.1 M ascorbic acid in borate buffer solution) at pH 9. After passing through a 150-cm mixing coil, the stream was mixed with a second reagent stream (10% cyclohexanone - aqueous 0.016% zincon in borate buffer solution) at pH 9. After reaction, the absorbance was measured at 620 nm with a detection limit of 0.05 µg mL-1 of Zn. Results were in agreement with reference values for the alloys by AAS.
Zinc Clinical analysis Spectrophotometry Method comparison Reference material

"Spectrophotometric Determination Of Iron In Boiler And Well Waters By Flow Injection Analysis Using 2-nitroso-5-(N-propyl-N-sulfopropylamino)phenol"
Analyst 1987 Volume 112, Issue 8 Pages 1127-1130
Noriko Ohno and Tadao Sakai

Abstract: A flow injection system is described in which Fe is determined spectrophotometrically at 753 nm with the cited reagent in phosphate buffer medium (pH 8.0) and in the presence of Na ascorbate to reduce Fe(III). The analytical range is 4 to 100 µg l-1, the detection limit is 1 µg L-1 and the sampling rate is 25 h-1. Nickel, Co, Cu, Zn and Cd at the 500 µg L-1 level do not interfere. The average recovery error is ±1%. The results obtained agree well with those obtained by using 2,4,6-tri-2-pyridyl-1,3,5-triazine. A flow injection system is described in which Fe is determined spectrophotometrically at 753 nm with the cited reagent in phosphate buffer medium (pH 8.0) and in the presence of Na ascorbate to reduce Fe(III). The analytical range is 4 to 100 µg l-1, the detection limit is 1 µg L-1 and the sampling rate is 25 h-1. Nickel, Co, Cu, Zn and Cd at the 500 µg L-1 level do not interfere. The average recovery error is ±1%. The results obtained agree well with those obtained by using 2,4,6-tri-2-pyridyl-1,3,5-triazine.
Iron Spectrophotometry Interferences Method comparison

"Continuous-flow Determination Of Low Concentrations Of Ammonium Ions Using A Gas Dialysis Concentrator And A Gas Electrode Detector System"
Analyst 1988 Volume 113, Issue 1 Pages 113-115
Hirokazu Hara, Atsushi Motoike and Satoshi Okazaki

Abstract: A gas-dialysis unit based on a micro-porous PTFE membrane (cf. Fraticelli and Meyerhoff, Anal. Chem., 1981, 53, 992) is described. The recipient buffer system is 0.01 M K H phthalate in which the diffused NH3 is converted into NH4+, which is detected by an NH3-selective electrode (Orion 95-12) after addition of NaOH. The concentration. factor is ~10 between 11°C and 29°C. The response is rectilinear for three decades up to 1000 µg L-1 with a limit of detection of 3 µg L-1 of N. The method is applied to purified and natural waters.
Ammonium Electrode Dialysis Heated reaction Preconcentration Teflon membrane

"Transient Responses Of Glass Electrodes In Dilute Solutions And Freshwaters"
Analyst 1988 Volume 113, Issue 10 Pages 1537-1540
illiam Davison and Terence R. Harbinson

Abstract: Glass electrodes respond slowly in dilute, nearly neutral solutions (l= 0.1-1 mmol dm-3, pH 6-9) of either natural lake water or simple inorganic salts, taking ~10 min to equilibrate irrespective of whether the solution is flowing or static. Although buffer capacity and ionic strength influence the response, they are not critical factors. The transient effect is associated with low concentrations of cations. There was no great difference in response for the different cations tested, but the sluggishness appeared to increase in the order K+ Ca2+ < Na+ Mg2+ < NH4+. The time dependence of the response is consistent with it being due to a diffusional exchange process. Glass electrodes are inappropriate pH sensors for the determination of the pH of dilute neutral solutions by flow injection analysis.
pH Electrode Theory

"Re-examination Of The Determination Of Environmental Nitrate By Reduction With Hydrazine"
Analyst 1988 Volume 113, Issue 7 Pages 1117-1120
Alexander J. Kempers and Arno G. Luft

Abstract: The determination of nitrate as nitrite remains the method of choice owing to the accuracy with which low concentrations of nitrite can be detected. A manual procedure for the reduction of nitrate to nitrite using hydrazine sulphate (HS) was described as impractical owing to the capricious nature of the reaction. The homogeneous catalyzed reduction proposed in this work compares well with the usual heterogeneous catalyzed cadmium reduction column technique without, however, being subject to interfering substances, and offers the possibility of increasing the number of simultaneous nitrate reductions using sample volumes down to a few microlitres. The relative standard deviation of the method is 0.7% with a detection limit of 0.2 µmol l-1 of nitrate. It is demonstrated that uncontrolled fluctuations in the concentration of oxygen, present during the reduction, were the main cause of the earlier erratic results. The Mg2+ ion, also responsible for complete suppression of the reduction, was inactivated by pyrophosphate.
Nitrate Spectrophotometry

"Rapid Determination Of Nitrite In Water By Flow Injection With Chemiluminescence Detection"
Analyst 1989 Volume 114, Issue 6 Pages 747-748
Alexander R. Thornton, Josef Pfab and Robert C. Massey

Abstract: Nitric oxide (produced by chemical reduction of NO2-), in equilibrium with HNO2, is separated from the flowing stream (0.1 M H3PO4) by entrainment in Ar carrier gas and detected with high specificity in the gas stream by its chemiluminescent reaction with O3. The calibration graph was rectilinear up to 10 µM-NO2- and the detection limit was 0.14 ng. The coefficient of variation was 7.8%. Interference from N-nitrosamines was negligible.
Nitrite Chemiluminescence Interferences

"Spectrophotometric Determination Of Total Cyanide, Iron - Cyanide Complexes, Free Cyanide And Thiocyanate In Water By A Continuous-flow System"
Analyst 1989 Volume 114, Issue 8 Pages 959-963
ohannes C. L. Meeussen, Erwin J. M. Temminghoff, Meindert G. Keizer and Ivo Novozamsky

Abstract: The spectrophotometric method used is based on that of Nagashima (Anal. Abstr., 1979, 36, 1B81), except that 1,3-dimethylbarbituric acid is used instead of barbituric acid, and 0.1 M phthalate instead of 1 M phosphate buffer. Total cyanide plus SCN- is determined spectrophotometrically after UV irradiation and distillation with citric acid at pH 3.8; free CN- plus SCN- is determined without irradiation and distillation; and SCN- is determined after masking of CN- with formaldehyde. Iron - CN- complexes are determined as the difference between the first two measurements. The detection limit is 0.6 µg L-1 of CN-, and recovery of Fe - CN- complexes is quantitative. Interference from NO3- is minimized.
Cyanide, total Thiocyanate ion Iron(2+) hexacyanide Cyanide, free Spectrophotometry Buffer Interferences UV reactor Photochemistry

"Spectrophotometric Determination Of Dissolved Organic Phosphorus In Natural Waters Using Inline Photo-oxidation And Flow Injection"
Analyst 1989 Volume 114, Issue 11 Pages 1459-1463
Ian D. McKelvie, Barry T. Hart, Terence J. Cardwell and Robert W. Cattrall

Abstract: The method involves mixing of the sample (100 or 600 µL) in a water carrier stream (1.3 mL min-1) with a solution (1.3 mL min-1) of K2S2O8 (4%) and NaBH4 (3.4%) and irradiation in a UV source. The mixture is debubbled and mixed with a solution (0.5 mL min-1) of 8.1 mM ammonium molybdate in 0.63 M H2SO4, and passed through a coil (30 cm x 0.5 mm), and this mixture is then mixed with a solution (0.36 mL min-1) of 0.89 mM SnCl2 and 15 mM hydrazine sulfate in 0.5 M H2SO4 and passed through a coil (60 cm x 0.5 mm), and a debubbler. Finally, detection is at 690 nm. The calibration graph is rectilinear for 6 mg L-1 of such P, and the detection limit is 10 µg l-1. Recoveries were 97.6 to 100.2%. About 50 and 72 samples h-1 could be analyzed for 0.1 and 0.1 to 4 mg l-1, respectively.
Phosphorus Spectrophotometry Debubbler Photochemistry UV reactor

"Flow Injection System For Online Potentiometric Monitoring Of Ammonia In Freshwater Streams"
Analyst 1989 Volume 114, Issue 11 Pages 1443-1447
Salvador Alegret, Juli&aacute;n Alonso, Jordi Bartrol&iacute; and Esteve Mart&iacute;nez-F&agrave;bregas

Abstract: The system involves mixing a sample stream with 1 M NaOH, passage of the mixture through a dialysis chamber to transfer NH3 via a gas diffusion chamber into 10 mM Tris (pH 7.5), and detection of NH4+ by an ion-selective electrode. The electrode construction involves in situ formation and direct casting of the sensing nonactin - PVC membrane on to an epoxy resin loaded with graphite. The calibration graph was rectilinear from 0.02 to 10 mM, and the limit of detection was ~1 µM. Over 30 samples could be analyzed in 1 h. The system involves mixing a sample stream with 1 M NaOH, passage of the mixture through a dialysis chamber to transfer NH3 via a gas diffusion chamber into 10 mM Tris (pH 7.5), and detection of NH4+ by an ion-selective electrode. The electrode construction involves in situ formation and direct casting of the sensing nonactin - PVC membrane on to an epoxy resin loaded with graphite. The calibration graph was rectilinear from 0.02 to 10 mM, and the limit of detection was ~1 µM. Over 30 samples could be analyzed in 1 h.
Ammonia Potentiometry Electrode Electrode Injection technique Membrane Calibration Resin Dialysis Gas diffusion

"Flow Injection Procedure For The Determination Of Tertiary Amines In Water And Seawater Using Chemiluminescence Detection"
Analyst 1989 Volume 114, Issue 12 Pages 1659-1661
J. Steven Lancaster, Paul J. Worsfold and A. Lynes

Abstract: Sample was injected into a stream of borate buffer (pH 11.0), which merged first with 1 mM rhodamine B and then with 1.64 mM NaOCl (all at 1 mL min-1); detection of chemiluminescence was by a photomultiplier tube. The calibration graph for triethylamine was rectilinear for 0.2 mM in water and 0.1 mM in seawater. Coefficients of variation were generally 2% (n = 5). The method can also be used to determine trimethyl- and tripropyl-amine. Quenching of the chemiluminescence occurs in the presence of a 10-fold excess of diethylamine or ethylamine.
Trimethylamine Triethylamine Tripropylamine Amines, alkyl Chemiluminescence Buffer Quenching Indirect

"Studies On The Application Of Photochemical Reactions In A Flow Injection System. 1. Determination Of Trace Amounts Of Nitrite, Based On Its Inhibitory Effect On The Photochemical Reaction Between Iodine And Ethylenediaminetetra-acetic Acid"
Analyst 1991 Volume 116, Issue 5 Pages 497-499
Ren-Min Liu and Dao-Jie Liu

Abstract: Natural water samples, 0.01 M ethanolic iodine solution, 0.01 M NaH2EDTA solution and pH buffer solution (0.1 M sodium acetate - 0.1 M acetic acid adjusted with 0.1 M NaOH) were pumped into photochemical reactors (diagram given) and the reactants were injected into another channel of buffer solution Residual iodine was determined in the flow-through amperometric detector at 100 mV vs. SCE. Calibration graphs were rectilinear from 0.1 to 4 µM-nitrite. Coefficient of variation for tap, rain, well and lake water were 0.91, 0.84, 0.93 and 0.87%, respectively. Recoveries were 91%. Tolerance limits of foreign ions are tabulated.
Nitrite Amperometry Buffer pH Photochemistry Reactor

"Determination Of Iron By Flow Injection Based On The Catalytic Effect Of The Iron(III) - Ethylenediaminetetra-acetic Acid Complex On The Oxidation Of Hydroxylamine By Dissolved Oxygen"
Analyst 1991 Volume 116, Issue 9 Pages 913-917
Andreu Cladera, Enrique G&oacute;mez, Jose Manuel Estela and Victor Cerd&aacute;

Abstract: The flow injection (FI) method involves use of a Hewlett-Packard 8452A diode-array spectrophotometer with a flow cell with a pathlength of 10 mm and a void volume of 18 µL. The system was controlled by a PC which allowed the automatic injection of samples, and continuous acquisition and processing of spectra. The absorbance response was rectilinear from 3.5 to 150 ng mL-1 of Fe. The detection limit was 2 ng mL-1. Interference from Co, Cr and Cu was reduced so that 10- to 40-fold concentration could be tolerated. The method was satisfactorily applied to water and white wine at a sampling rate of 60 samples per h.
Iron Spectrophotometry Automation Computer Catalysis Interferences

"Combined Generator/separator For Continuous Hydride Generation: Application To Online Pre-reduction Of Arsenic(V) And Determination Of Arsenic In Water By Atomic Emission Spectrometry"
Analyst 1992 Volume 117, Issue 3 Pages 407-411
an D. Brindle, Hosen Alarabi, Samir Karshman, Xiau-chun Le, Shaoguang Zheng and Hengwu Chen

Abstract: A continuous hydride generator is described which incorporates a combined generator/separator. The low acid concentrations necessary in the tetrahydroborate(III)-L-cysteine mediated determination of most hydride-forming elements require that the gas is purged from solution As the hydride transfer reaction is so rapid, this allows both the hydride-forming reaction and the stripping reaction to take place in the same vessel. The system has been further modified to allow online pre-reduction. of As(V) to As(III) by L-cysteine. Detection limits for As, Ge, and Se are 4, 0.3 and 9 ng/mL, respectively, at a sample flow rate of 15 mL/min. Application of the system to the determination of As in water is described. Concentrations of As in several Ontario waters were 7-600 ng/mL. Interferences from Ni and Pd, two of the most strongly interfering elements in the continuous hydride generation process, are diminished to a greater extent with the system described here than with the conventional high acid continuous system.
Arsenic(5+) Germanium Selenium Spectrophotometry Volatile generation Interferences Optimization Volatile generation

"Selective Spectrophotometric Determination Of Trace Amounts Of Chromium(VI) Using A Flow Injection System With A Microcolumn Of Zirconium(IV) Oxide Modified Silica Gel"
Analyst 1992 Volume 117, Issue 6 Pages 1029-1032
Carlos R. M. Peixoto, Yoshitaka Gushikem and Nivaldo Baccan

Abstract: A microcolumn (2 cm x 3 mm) packed with ZrO2 coated on a silica gel surface was activated with 0.1 M HNO3 (1.7 mL min-1) for 20 s. A Cr(VI) solution (pH 3 ) was passed through the column for 1 to 6 min (3.4 mL min-1), the column was washed with 1 mM HCl (2 mL min-1) for 10 s and Cr(VI) was eluted in a reversed flow (2 mL min-1) with 0.1 M tris(hydroxymethyl)methylamine. A 0.05% solution of 1,5-diphenylcarbazide previously mixed with 0.8 M HNO3 was reacted with Cr(VI) in the flow solution The absorbance of the complex was measured at 540 nm. Coefficients of variation were 2.4% (n = 10). Interference was observed for SO32- and PO43-, resulting in an incomplete separation of Cr(VI). The method was applied to natural water. Zirconium(IV) oxide coated on a silica gel surface is effective for extracting Cr(VI) from aqueous solutions at a pH of ~3. A microcolumn packed with this material was inserted into a flow injection system for the separation and pre-concentration. of Cr(VI). By this process, a concentration. level of 2 ppb was detected with a relative standard deviation of 2.4%. Because of the high selectivity of the immobilized substrate, it was possible to determine Cr(VI) in the presence of larger amounts of other ions. The analysis was also carried out on natural water spiked with Cr(VI), and compared with a standard method.
Chromium(VI) Spectrophotometry Column Silica gel Solid phase reagent Method comparison Interferences

"Determination Of Total And Free Cyanide In Water After Distillation"
Analyst 1992 Volume 117, Issue 6 Pages 1009-1012
Johannes C. L. Meeussen, Meindert G. Keizer and Wendy D. Lukassen

Abstract: Separation of total CN- from SCN- was achieved by illumination with (i) standard UV radiation and replacement of the quartz coil with a Pyrex coil, (ii) an 8-W fluorescent lamp in the continuous-flow system and (iii) a fluorescent lamp 1 to 170 h before analysis, with no illumination during analysis. Samples were kept at pH 12. Separation of free CN- from hexacyanoferrate and SCN- was performed by distillation of samples at pH 4 in a citrate buffer solution in the presence of Cu2+. Decomposition of hexacyanoferrate and evaporation of SCN- as HSCN was prevented. The method was applied to the determination of total CN- and free CN- in soil extracts by extraction of two contaminated soils with 0.25 M NaOH for 3 h on a boiling-H2O bath (details given). Both methods combine the advantages of sample distillation with a high specificity for total and free CN-.
Cyanide, total Cyanide, free Sample preparation UV reactor Photochemistry

"Potentiometric Detection In Flow Injection Without Use Of A Conventional Reference Electrode"
Analyst 1992 Volume 117, Issue 8 Pages 1335-1337
Ren-Min Liu, Dao-Jie Liu and Ai-Ling Sun

Abstract: A flow injection system is described which has two ion-selective electrodes arranged in parallel to serve as the detector. Two types of ion can be determined by using a double sample loop and an asynchronous sample injection technique. The carrier stream channels of the electrodes alternate between the sampling and sample injection modes. The potential of the electrode of the channel in the sampling state is kept constant and this then serves as the reference electrode. The method was used for the determination of F- and NO3--N in natural waters, Na and K in natural waters, and K and NO3--N in soil extracts. The calibration graphs were rectilinear in the ranges 0.02 to 2000, 0.8 to 6000, 0.5 to 2000 and 0.3 to 3500 ppm for F-, NO3--N, Na and K, respectively. The sampling rates were 180 h-1 for F- and NO3--N and 120 h-1 for Na and K. An ion-selective electrode flow injection system has been developed with two ion-selective electrodes arranged in parallel in a flow injection system. The system does not contain a conventional reference electrode, and no liquid junction is present. The sample is injected into the two carrier streams alternately and gives a potential response at the electrode. The proposed method is simple and convenient and was applied successfully to the determination of fluoride and nitrate in natural waters, the determination of sodium and potassium in natural waters and the determination of potassium and nitrate in soil extracts.
Nitrate Potassium Sodium Fluoride Potentiometry Electrode Electrode Electrode Electrode Sample preparation

"Flow Cell With Double Slope Factor For Potentiometric Determination Of Fluoride At Low Concentrations"
Analyst 1993 Volume 118, Issue 7 Pages 859-861
Juri A. Borzitsky, Alexei Dvinin, Oleg M. Petrukhin and Yuri I. Urusov

Abstract: A simple and reliable double-cell device with three identical ion-selective membranes for fluoride determinations in a continuous-flow system with an increased slope factor is presented. The composition of the membranes was 1 mol-% EuF2/5 mol-% SrF2/94 mol-% LaF3. Membranes (5 mm diameter) were positioned inside the PTFE tubes (i.d. 5 mm) and the tubes were press-fitted into Plexiglass blocks. The internal reference solution of the cell was 5 mM NaF and 0.1 M-NaCl and the Ag/AgCl wires served as the inner reference electrodes. The RSD for the analysis of environmental water samples was from 0.01-0.03. The slope factor was 113-44 mV/decade. The sampling rate was 120/h.
Fluoride Potentiometry Flowcell

"Determination Of Ultratrace Amounts Of Selenium(IV) By Flow Injection Hydride-generation Atomic Absorption Spectrometry With Online Preconcentration By Coprecipitation With Lanthanum Hydroxide"
Analyst 1994 Volume 119, Issue 2 Pages 333-337
Guanhong Tao and Elo H. Hansen

Abstract: Water was filtered, acidified with concentrated HCl (10 ml/l) and boiled for 5 min. After cooling, NaOH was added to pH 3 and 0.5% lanthanum nitrate was added to a concentration of 20 mg/l. The resulting solution was mixed in a flow manifold (4 ml/min) with 0.2 M ammoniacal buffer solution of pH 9.1 (1.5 ml/min) and the precipitate formed was collected on the inner walls of a knotted reactor. After 100 s, the flow manifold configuration was changed so that the analyte was eluted from the reactor walls with 1 M HCl (9 ml/min). The eluate was merged with 0.3% NaBH4 in 0.05 M NaOH (1.5 ml/min) and the resulting stream was passed through a reaction coil (20 cm) and a gas-liquid separator, where H2Se was generated. The hydride, together with evolved H2 was swept into the atomizer and absorption was measured at 196.1 nm. The elution sequence lasted 10 s. Calibration graphs were linear from 0.01-0.5 µg/l of Se, with a detection limit of 0.001 µg/l. RSD for the determination of 0.5 and 0.1 µg/l of Se were 0.7% and 3.0%, respectively. Effects of co-existing ions were studied. The method was applied to natural and potable waters.
Selenium Spectrophotometry Preconcentration Volatile generation Coprecipitation Knotted reactor Phase separator Interferences Ultratrace Volatile generation

"Determination And Application Of Ion-selective Electrode Model Parameters Using Flow Injection And Simplex Optimization"
Analyst 1994 Volume 119, Issue 5 Pages 749-758
F. J. S&aacute;ez de Viteri and Dermot Diamond

Abstract: A modified form of the Nikolskii-Eisenman equation is proposed in which the power dependence of the interfering ion activity is removed. Selectivity was determined for PVC membrane electrodes in terms of constants rather than coefficients. These constants and other electrode parameters were measured by use of an flow injection ion-selective array approach. Each electrode in the array was characterized by means of a fractional factorial calibration design and simplex optimization of the electrode parameters. The approach was used for the simultaneous determination of NH4+, Ca2+, K+ and Na+ in solution with widely varying background ion composition.
Ammonium Calcium(2+) Potassium Sodium Electrode Electrode Electrode Interferences Optimization Simplex

"Flow-through Photometric Sensor For Determination Of Sulfonamides"
Analyst 1994 Volume 119, Issue 7 Pages 1625-1628
M. T. Tena, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: The cited sensor was based on the integration of spectrophotometric detection and retention of the product of the Bratton-Marshall reaction and was used for determining sulfanilamide, sulfamethazine, sulfaquinoxaline and sulfathiazole. The flow injection manifold features two low-pressure peristaltic pumps, low-pressure injection valves and a Unicam Model 8625 UV spectrophotometer. The solid support packed in the flow cell was C18-bonded silica from Sep-Pak cartridges. The method did not require a de-bubbler to remove N2 from the flowing system. Linear ranges for the above analytes were 10^-1200 ng/ml with RSD of 2.6%. The method was used to determine the analytes in milk and water.
Sulfonamides Sensor Spectrophotometry C18 Solid phase detection

"Determination Of Trace Amounts Of Urea By Using Flow Injection With Chemiluminescence Detection"
Analyst 1994 Volume 119, Issue 8 Pages 1829-1833
Xincheng Hu, Norimichi Takenaka, Masaru Kitano, Hiroshi Bandow, Yasuaki Maeda and Masaharu Hattori

Abstract: Sample was injected into a carrier stream (10 ml/min) of water and passed through a cation-exchange column before merging with a reagent stream (10 ml/min) consisting of 0.04 M sodium hypobromite and 0.2 M NaOH. The two solutions were fed into a double concentric tube mixer before passing to the reaction cell. The chemiluminescence emitted was measured at 510 nm. Diagrams of the flow injection manifold and the chemiluminescence cell and mixer used are given. The calibration graph was linear from 0.5-50 µM-urea with a detection limit of 90 nM. The RSD (n = 6) for 0.5 µM-urea was 1.9%%. The method was used to determine urea in urine and natural water. The results obtained agreed with those obtained by a spectrophotometric method.
Urea Chemiluminescence Spectrophotometry

"Flow Injection Potentiometric And Voltammetric-stripping Analysis Using A Dialysis Membrane Covered Mercury Film Electrode"
Analyst 1994 Volume 119, Issue 8 Pages 1813-1818
Joseph H. Aldstadt, Dewey F. King and Howard D. Dewald

Abstract: The cited electrode was prepared by fixing a cellulose triacetate dialysis membrane to the end of a vitreous C electrode. The Hg film was deposited on the electrode from an acidified mercury(II) nitrate solution (details given). The electrode was incorporated in a wall-jet flow cell (diagram given) and used for the determination of Pb in various samples. Water and urine were acidified with 0.5 M HNO3. Blood (10 µL) was diluted (1:29) with 5% HCl or Metexchange M reagent. A 190 µL portion of the resulting solution was injected into a carrier stream (1.1 ml/min) of 10 mM KNO3/10 mM HNO3 and transported to the wall-jet cell. Pb was determined by Osteryoung square-wave anodic-stripping voltammetry (OSWASV) or by potentiometric-stripping analysis (PSA; details given). The flow was stopped during the deposition and stripping cycles. OSWASV was applied to water: the calibration graph was linear up to 1000 ppb of Pb; RSD (n = 8) were 1.7-6%. PSA was applied to all the samples: for water and urine, RSD (n = 8) were 3-5.4%. For blood, the calibration graph was linear up to 60 ppb of Pb; the detection limit was 2.7 ppb; RSD (n = 8) were 5.3-10.6%.
Lead Voltammetry Potentiometric stripping analysis Electrode Electrode Dialysis

"Continuous Liquid-liquid Extraction With Online Monitoring For The Determination Of Anionic Surfactants In Waters"
Analyst 1994 Volume 119, Issue 9 Pages 2097-2100
Manuel Agudo, Angel R&iacute;os and Miguel Valc&aacute;rcel

Abstract: Sample stream (4.4 ml/min) was merged with a reagent stream (7 ml/min; prepared by dissolving 0.1 g methylene blue and 28.3 g NaH2PO4.2H2O in 7 mL concentrated H2SO4 and 250 mL methanol and diluting to 1 l with H2O). The resulting stream was passed through a mixing coil (100 cm x 0.5 mm i.d.) and then through a plug (200 µL) of CHCl3/CCl4 (3:1) situated in the cuvette of a spectrophotometer. The absorbance of the ion-pair complex formed was measured at 650 nm as a function of time. A diagram of the system used is given. Quantification of anionic surfactants was performed by measuring either the slope of the absorbance vs. time graph or the final absorbance. The calibration graph was linear from 20-400 ng/ml of anionic surfactant in both instances for a 50 mL sample volume. The detection limits were 17 and 8 ng/ml for the slope and final absorbance methods, respectively. Corresponding throughputs were 9 and 7 samples/h. The RSD (n = 11) was 6.7%.
Surfactants, anionic Spectrophotometry Sample preparation Solvent extraction

"Flow Injection Spectrophotometric Determination Of Silicate Based On The Formation Of The Ion Associate Between Molybdosilicate And Malachite Green"
Analyst 1995 Volume 120, Issue 10 Pages 2601-2604
J. Saurina and S. Hern&aacute;ndez-Cassou

Abstract: Water sample (100 µL) was injected into an aqueous carrier stream (flow rate not given) and merged with a stream (flow rate not given) of 0.08 M molybdate of pH 0.9. The mixture was passed through a reaction coil (30 cm x 0.7 mm i.d.) before merging with a stream (flow rate not given) of 60 µM- Malachite Green in 0.08 M H2SO4. Formation of the ion associate took place in a second reaction coil (160 cm x 0.7 mm i.d.) and the absorbance was measured at 645 nm. Both reaction coils were maintained at 50°C. A diagram of the manifold used is given. The calibration graph was linear up to 1.5 µg/ml of silicate (I) and the detection limit was 14 ng/ml. the RSD (n not given) was 2% and the throughput was 70 samples/h. The method was applied to the analysis of I in natural waters. Results were in good agreement with those obtained by the standard spectrophotometric method. A flow injection method is proposed for the determination of silicate; The method is based on the formation of an ion associate between molybdosilicate and Malachite Green. A three-channel manifold was used in the:development of. the reaction. The sample injected into a water carrier reacts with a molybdate solution and finally the ion associate is formed from merging molybdosilicate and Malachite Green solutions. The influence of chemical, physical and flow variables on the absorbance was studied spectrophotometrically at 645 nm. Experimental conditions to avoid the adsorption of:the ion-associate complex on the surfaces of the flow system were also investigated. The precision of the method is better than 2.0% and the detection limit is 14 ng of SiO2 per millilitre. The sample throughput is 70 samples h-1. The method proposed has been applied to the determination of silicate in natural waters. Results are in a good agreement (within 2%) with those obtained by the standard spectrophotometric method. (17 references)
Silicate Spectrophotometry Complexation Optimization Method comparison

"Multivariate Statistical Process Control Applied To Sulfate Determination By Sequential Injection Analysis"
Analyst 1997 Volume 122, Issue 8 Pages 737-741
A. Rius, M. P. Callao and F. X. Rius

Abstract: A carrier solution of 0.1 M HClO4 was aspirated (2 ml/min) into a holding coil (200 cm x 0.8 mm i.d.) for 55 s followed by the sample (2 ml/min) for 2 s and a reagent solution (2 ml/min) of 0.02 M iron(III) nitrate in 0.34 M HClO4 for 5 s. The mixture was then propelled (2 ml/min) through a reaction coil (70 cm x 0.8 mm i.d.) for 20 s and the absorbance spectrum was recorded from 300-400 nm 20 s after the flow had stopped. A partial least squares multivariate calibration model was developed and used to predict the sulfate concentration in the sample (range covered: 0-500 mg/l sulfate). The throughput was 20 samples/h. Multivariate statistical process control techniques were used to check the stability of the system before developing the model and the validity of the model when it was used to predict the concentrations of unknown samples. The method was applied to natural waters.
Sulfate Spectrophotometry Chemometrics Sequential injection Stopped-flow Modeling Multivariate calibration Partial least squares Process control

"Determination Of Phenoxy Acid Herbicides From Aqueous Samples By Improved Cleanup On Polymeric Pre-columns At High Ph"
Analyst 1997 Volume 122, Issue 9 Pages 889-893
Ren&eacute; B. Geerdink, Sylvia van Tol-Wildenburg, Wilfried M. A. Niessen and Udo A. Th. Brinkman

Abstract: An improved procedure for the determination of phenoxy acid herbicides in environmental water samples is reported. The procedure consists in solid-phase extraction (SPE) of 60 mL water samples on a polymeric pre-column at pH 2.8, a clean-up step at high pH and subsequent desorption and ion-pair LC separation at pH 8.8, The main improvements are in the basic clean-up step and in the LC eluent composition, The release of compounds which are electrostatically bound to the pre-column is favoured by a washing step with 0.1 mol L-1 sodium hydroxide solution, As regards LC, gradient elution is applied using solvents with low buffer and ion-pairing concentrations. The detection limits for the phenoxy acids (UV detection at 232 nm) are 5-20 ng L-1 for tap water samples, At the 0.1 µg L-1 spiking level, the RSD is 6% (n = 7) and the recoveries are better than 83% for all analytes. The long-term reproducibility typically has RSD values of 5% (n = 7), The method was successfully tested on water samples from various origins, and the results obtained with the present online SPE-LC-UV procedure mere found to compare well with those obtained with procedures involving SPE combined off-line with GC-MS or flow injection MS-MS. 12 References
Herbicides, phenoxy acid Mass spectrometry Method comparison

"Flow Injection Photometric Determination Of Zinc And Copper With Zincon Based On The Variation Of The Stability Of The Complexes With PH"
Analyst 1997 Volume 122, Issue 10 Pages 1045-1048
Pablo Richter, M. In&eacute;s Toral, A. Eugenia Tapia and Emely Fuenzalida

Abstract: A flow injection photometric method for the sequential determination of zinc and copper in mixtures was developed based on the variation of the stability of the chromogenic complexes between the analytes and the reagent zincon with pH. At pH 5.0 only the Cu-zincon complex exists, whereas at pH 9.0 the copper and zinc chelates co-exist. A three-channel manifold was implemented containing two alternating buffer streams (pH 5 and 9) which permit the colored reaction products to be formed sequentially at both pH values, and consequently the mixtures can be resolved. A continuous pre-concentration unit (Chelex-100) was used in order to increase the sensitivity of the method, thus allowing the analysis of water samples in which the analytes are present at the ng mL-1 level. On the other hand, pre-concentration was not required when the analytes were determined in brass. Under the optimum conditions and using a pre-concentration time of 2 min, the detection limits (3s) were found to be 0.35 and 0.80 ng mL-1 for zinc and copper, respectively. The repeatability of the method, expressed as the RSD, was in all instances less than 3.1%. Considering the sequential determination of both species, a sampling rate of 70 h-1 was obtained if pre-concentration of the samples was not required.
Zinc Copper Spectrophotometry Complexation pH Stability constants Buffer Chelex Preconcentration Optimization

"Multi-insertion Of Small Controlled Volumes Of Solutions In A Flow Assembly For Determination Of Nitrate And Nitrite With Proflavin Sulfate"
Analyst 1998 Volume 123, Issue 3 Pages 429-434
J. Mart&iacute;nez Calatayud, J. V. Garc&iacute;a Mateo and V. David

Abstract: A simple, maintenance-free, noncontaminating and completely automated flow system was developed for non-simultaneous determinations of nitrite and nitrate, in which spectrophotometric measurements at 328 nm were performed on the nitrite reaction with proflavin sulfate [bis(3,6-diaminoacridinium)sulfate]. The sample solutions were automatically inserted into phosphate buffer (pH 6.8) containing 10 mM EDTA by using a programmable solenoid valve; then they flowed through a 6.4 m x 0.5 mm id PTFE coil, wrapped around an 8 W low pressure Hg lamp, and finally they merged with a HCl solution of proflavin. With the lamp off the nitrite in the sample was selectively measured with a sensitivity of 0.75 x 104 absorbance (linearity range up to 0.6 absorbance; detection limit of 1.9 x 10^-7 M). With the lamp on, to determine the sum of nitrite + nitrate there was a decrease in sensitivity of 41% vs. that of the selective variant for nitrite determination The sample throughput was 15 h-1 and the relative standard deviation at a 6.4 x 10^-5 M level of nitrate was 0.4% (n = 15). Many interferences were studied and simple methods of correcting for them were applied to analyze samples such as waters, soils, fertilizers and meat. (26 References)
Nitrate Nitrite Spectrophotometry Automation Injection technique UV reactor Photochemistry Buffer Interferences EDTA Differential detection

"Optimization Of A Bipotentiometric Flow Injection Analysis System For Simultaneous Determination Of Calcium And Chloride Ions In Natural Waters"
Analyst 1998 Volume 123, Issue 4 Pages 653-659
Luis M. B. C. &Aacute;lvares-Ribeiro and Ad&eacute;lio A. S. C. Machado

Abstract: Experimental optimization using the modified simplex method of a bipotentiometric flow injection analysis (FIA) system, constituted by two different ion selective electrodes (ISE) placed in series, for the simultaneous determination of Ca2+ and Cl- in water is reported. The response function used was a weighted linear combination of three variables, chosen to achieve maximization of the Ca2+ electrode sensitivity, minimization of the interference of the Ca2+ signal on the Cl- response, and maximization of the sampling rate. The optimized system can determine Ca2+ from 5 x 10^-5 to 5 x 10^-3 mol/L with a sensitivity of ~27 mV/decade and Cl- from 2 x 10^-4 to 2 x 10^-2 mol/L (the max. value tested), with a sensitivity of ~55 mV/decade. Repeatability was 1.9 and 0.6%, respectively, at 2 x 10^-4 and 2.2 x 10^-3 mol/L (8 and 90 mg/L), for Ca2+ determinations, and 1.8 and 1.2%, respectively, at 3.4 x 10^-4 and 8.3 x 10^-4 mol/L (12 and 29 mg/L), for Cl- determinations A sampling rate of 40/h was obtained. The affect of ionic strength on the results is discussed. The relative accuracy of the bipotentiometric FIA system was demonstrated by determining the content of both ions in natural water in parallel with ASTM certified methods.
Calcium Chloride Bipotentiometry Electrode Electrode Simplex Optimization Standard method Method comparison Interferences

"Lead Hydride Generation For Isotope Analysis By Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1988 Volume 3, Issue 6 Pages 821-827
Xiaoru Wang, Miklos Viczian, Alexandra Lasztity and Ramon M. Barnes

Abstract: The hydride generator, which included a Thompson U-shaped glass phase separator or a porous PTFE tube separator, was coupled to a Sciex Elan 250 ICP-MS instrument. Generation and transfer of hydrides were optimized by flow injection ICP-MS; the best signal-to-noise ratio (SNR) was obtained with 0.6% HCl, 5% of NaBH4 in 0.1% NaOH solution and 1% of H2O2 (used for oxidation of Pb before hydride generation), and the optimum Ar flow rate was 1.46 l min-1. For standard solution containing 10 µg L-1 of Pb, calibration graphs were obtained by the isotope-dilution technique for 204Pb, 206Pb, 207Pb and 208Pb; the detection limits for each isotope were between 0.04 and 0.06 µg l-1. The technique was applied in the determination of Pb in NBS SRM 1643 (trace elements in water); recovery was quantitative and the coefficient of variation was 1.2% (n = 3). Ion abundances were also determined in certified galena and Pb samples (prep. described). The PTFE phase separator gave greater SNR and less interference. Interference from Fe(III) and Cu(II) was serious, but could be overcome by addition of sulfosalicylic acid and NaCN to the NaBH4 solution. The hydride-generation technique had significantly greater sensitivity for Pb than that involving nebulization.
Lead-206 Lead-204 Lead-207 Lead-208 Spectrophotometry Mass spectrometry Interferences Phase separator Reference material Teflon membrane Volatile generation Volatile generation

"Chelating Resins For Online Flow Injection Preconcentration With Inductively Coupled Plasma Atomic-emission Spectrometry"
J. Anal. At. Spectrom. 1989 Volume 4, Issue 6 Pages 509-518
Xiarou Wang and Ramon M. Barnes

Abstract: A poly(dithiocarbamate) (PDTC) and a methylcarboxylated poly(ethylenimine) - poly(methylenepolyphenylene) isocyanate (CPPI) chelating resin were evaluated for the online pre-concentration. of 22 elements, with subsequent elution and detection by ICP-AES. The effect of pH on recovery of elements and of parameters, such as column length and diameter, which affect the dispersion of the analyte zone were studied. The PDTC resin works effectively at pH 8 to 10, whereas the CPPI resin chelated successfully at pH 5 to 6. Some elements could be pre-concentrated on one resin only. The PDTC resin was applied in the determination of Cu and Zn in natural and drinking water. Recovery of Cu was 98% at 20 and 50 ng mL-1, and the coefficient of variation (n = 11) was ~3% for 100 ng mL-1 of Cu.
Copper Zinc Spectrophotometry Column pH Chelation Resin Preconcentration Multielement

"Flow Injection Online Separation And Preconcentration For Electrothermal Atomic Absorption Spectrometry. 1. Determination Of Ultra-trace Amounts Of Cadmium, Copper, Lead And Nickel In Water Samples"
J. Anal. At. Spectrom. 1991 Volume 6, Issue 4 Pages 295-300
Michael Sperling, Xuefeng Yin and Bernhard Welz

Abstract: A micro-scale flow injection pre-concentration. system combined online with electrothermal AAS results in a powerful integrated system. Improved detection limits and low contamination are achieved by the system. The applicability of this technique in the determination of Cd, Cu, Pb and Ni in water is demonstrated. Detection limits for Cd, Pb, Cu and Ni were 0.8, 6.5, 17 and 36 ng l-1. The selectivity of the dithiocarbamate-C18 reversed-phase system allows interference-free determination of ultra-trace amounts of elements in natural waters to be undertaken. High flexibility and only a slight reduction in precision is provided by time-based loading and subsampling.
Cadmium Copper Lead Nickel Spectrophotometry Sample preparation C18 Extraction Interferences Preconcentration Silica Ultratrace

"Flow Injection Flame Atomic Absorption-spectrometric Determination Of Copper With Preconcentration On Ligand-loaded Amberlite XAD-2"
J. Anal. At. Spectrom. 1992 Volume 7, Issue 2 Pages 323-328
Abdulmagid M. Naghmush, Marek Trojanowicz and Ewa Olbrych-Sleszynska

Abstract: A sample solution containing copper was merged with a stream (2.2 mL min-1) of 1% Na2B4O7 solution (pH 8.0) directed on to a column (7 cm x 3 mm) of Amberlite XAD-2 (20 to 60 mesh) modified with catechol violet (I), 4-(2-pyridylazo)resorcinol or Eriochrome blue black R (C.I. Mordant Black 17). Copper was eluted from the column with 2 M HNO3 and the eluate was analyzed by flame AAS. The method was applied to the determination of Cu in natural water by flame AAS with pre-concentration. on a I-loaded Amberlite XAD-2 column. Calibration graphs were rectilinear for up to 2 ppb of Cu. Chelating sorbents obtained by loading a nonpolar sorbent, Amberlite XAD-2, with pyrocatechol violet (PV), 4-(2-pyridylazo)resorcinol (PAR) or Eriochrome Blue Black R were used for a time-based pre-concentration of Cu(II). The effect of pre-concentration and elution flow-rate on the detection limit and the effectiveness of Cu(II) sorption were examined Pyrocatechol violet loaded XAD-2 was employed for the determination of Cu(II) by flow injection flame atomic absorption spectrometry in natural waters at the ppb level using a pre-concentration. time of 20 min. Superior dynamic properties of PV loaded sorbent in comparison with an hydroxyquinoline chelating resin is demonstrated. The effect of the presence of alkali, alkaline earth and some transition metal ions on Cu(II) sorption was examined. Significant interference was observed for concentrations. of Ca above 50 ppm. Interference from Fe(III) can be reduced by the addition of fluoride to the pre-concentrated sample.
Copper(II) Spectrophotometry Amberlite Preconcentration Column Interferences Method comparison

"Determination Of Arsenic In Environmental And Biological Samples By Flow Injection Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 1 Pages 31-35
Meng-Fen Huang, Shiuh-Jen Jiang and Chorng-Jev Hwang

Abstract: A simple and very inexpensive in situ nebulizer-hydride generator was used with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of arsenic in environmental and biological samples. The application of hydride generation (HG)-ICP-MS alleviated the spectral interferences and sensitivity problems of arsenic determinations encountered when conventional pneumatic nebulization is used for sample introduction. The sample was introduced by flow injection to minimize deposition of solids on the sampling orifice. The arsenic in the sample was reduced to As(III) with L-cysteine before being injected into the HG system. A detection limit of 0.003 ng ml-1 was obtained for arsenic. The method has been successfully applied to the determination of arsenic in National Research Council of Canada reference materials, CASS-2 (Nearshore Seawater Reference Material for Trace Metals), NASS-3 (Open Ocean Reference Material for Trace Metals) and SLRS-2 (Riverine Water Reference Material for Trace Metals), and in National Institute of Standards and Technology, Standard Reference Material 2670, Toxic Metals in Freeze-Dried Urine. Precision was less than 5% and analysis results were within 6% of the certified values for all determinations.
Arsenic Mass spectrometry Volatile generation Volatile generation

"Trace Enrichment And Determination Of Gold By Flow Injection Inductively Coupled Plasma Spectrometry. 2. Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 2 Pages 89-91
M. M. G&oacute;mez G&oacute;mez and C. W. Mcleod

Abstract: Water was treated with HCl or NaCl to contain 4000 and 1000 mg/l of chloride respectively, and the solutions adjusted to a pH of 6-8 with HNO3 or NH3. Standard solutions of colloidal Au and containing 10 mg/l of humic acid were similarly prepared. Portions (8-40 ml) of the solutions were passed off-line at 4 ml/min for 2-10 min through a PTFE column (7 cm x 1.5 mm i.d.) and containing ~25 mg of sulfydryl cotton fiber. The pre-concentrated Au was eluted with three injections of 250 µL of 10 mM KCN at 1 ml/min, and analyzed using a 1300 W ICP with quadrupole MS detection (details given). Calibration graphs were linear upto 20 ng/l Au, with a detection limit of 0.19 ng/l. At 5 ng/l Au an RSD (n = 5) of 3.6% was obtained. An Au enrichment factor of 32-160 was estimated. The method was applied to mineral and natural water.
Gold Mass spectrometry Column Interferences Preconcentration Sulfhydryl cotton

"Automated Technique For Mercury Determination At Sub-nanogram Per Litre Levels In Natural Waters"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 3 Pages 287-291
Daniel Cossa, Jane Sanjuan, Jacques Cloud, Peter B Stockwell and Warren T Corns

Abstract: sensitive and automatic technique for dissolved mercury determination has been developed in order to produce rapid and accurate dissolved mercury determinations in natural waters at ambient levels. This is needed for building realistic mass balance budgets and providing more accurate data in monitoring programmes for this metal. The detection limit obtained with a 45 mL sample was 0.1 ng l-1. The precision of the method over the range 0.5-50 ng l-1 was found to be approximately 5%. Eight samples per hour can be analyzed without carryover effects. The instrumentation is very robust but strict control measures are required to ensure a mercury-free environment around the instrumentation.
Mercury Fluorescence Automation

"Optimization Of Flow Injection Hydride Generation Inductively Coupled Plasma Mass Spectrometry For The Determination Of Selenium In Water And Serum Samples"
J. Anal. At. Spectrom. 1995 Volume 10, Issue 10 Pages 871-874
M. Angeles Quijano, Ana Maria Guti&eacute;rrez, M. Concepcion P&eacute;rez Conde and Carmen C&aacute;mara

Abstract: Water was acidified with concentrated HCl (3 mL per 5 mL sample), boiled to 100°C for 10 min and after cooling diluted to 10 mL with water. Serum (1 ml) was diluted to 50 mL with water and treated similarly to the water samples (loc. cit.); Si was used as anti-foaming agent. The effects of NaBH4 concentration, HCl concentration, flow rates, sample volume, forward power and carrier gas flow rates were studied and optimized. Optimum conditions were: 0.5% (m/v) NaBH4; 0.6 M HCl; HCl and NaBH4 flow rates of 3.5 and 1.7 ml/min, respectively; sample volume = 100 µL with 30 cm coil lengths, an r.f. power of 1350 W; and an Ar flow-rate = 1.01 ml/min. The interference from 31 elements was investigated; serious interference was caused by some transition elements. The calibration graph was linear up to 30 µg/l and the detection limit was 35 ng/l of Se which is 100 times better than that possible with traditional pneumatic nebulization. RSD (n not stated) were 5%. Recoveries were 92-104%.
Selenium Mass spectrometry Volatile generation Optimization Speciation Interferences Volatile generation

"Evaluation Of Controlled-pore Glass-immobilized Iminodiacetate As A Reagent For Automated Online Matrix Separation For Inductively Coupled Plasma Mass Spectrometry"
J. Anal. At. Spectrom. 1996 Volume 11, Issue 10 Pages 907-912
Simon M. Nelms, Gillian M. Greenway and Dagmar Koller

Abstract: A 0.04 g portion of PROSEP Chelating-1 iminodiacetate reagent (Bioprocessing, Consett, Co. Durham, UK) was packed as dry powder into a glass column (2.5 cm x 3 mm) that was incorporated in a flow injection manifold (diagram presented). A 3 mL sample was injected into a stream of H2O; transition-metal, U and Pb cations were retained on the column and subsequently eluted in an elution volume of 0.3 mL with 0.5 M HNO3. Calibration graphs prepared on the basis of water and seawater as matrices agreed, and both sets showed good linearity. RSD (n = 5) at 5 ng/ml were 5%, and recoveries were 62-113% for all the metals except Mn (35%).
Metals, heavy Mass spectrometry Controlled pore glass Iminodiacetate

"Determination Of Cadmium By Flow Injection Isotope-dilution Inductively Coupled Plasma Mass Spectrometry With Vapor-generation Sample Introduction"
J. Anal. At. Spectrom. 1997 Volume 12, Issue 5 Pages 579-584
TARN-JIUN HWANG and SHIUH-JEN JIANG

Abstract: The sample (0.1 ml) is injected into a carrier stream of 2% thiourea/0.0002% Co solution in 0.1 M HCl (4.8 ml/min), which then merges with a stream of 4% NaBH4 solution in 0.1 M NaOH (2.4 ml/min) for passage to a gas-liquid separator that consists essentially of a vessel (diagram presented), containing 120 glass beads (5 mm diameter), from which the Cd-containing vapor is carried to the ICP by a stream of Ar. Interference from MoO+ and ZrO+ is thereby alleviated. Sample-preparation procedures are described for sediments, urine and water, in which 111Cd is added as the tracer; the result is calculated by use of the equation proposed previously (Ibid., 1996, 11, 353). The detection limit is 26 pg/ml of Cd. Recoveries of 5 ng/ml of Cd added to standard refence waters were quantitative, and the results for standard reference freeze-dried urine and marine sediments agreed well with the certified values.
Cadmium Mass spectrometry Mass spectrometry Detection limit Interferences Isotope ratio Reference material Glass beads Volatile generation Volatile generation

"Determination Of Cadmium In Aqueous Media By Flow Injection Cold Vapor Atomic Absorption Spectrometry. Application To Natural Water Samples"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 4 Pages 295-300
Mar&iacute;a Liva Garrido, Riansares Mu&ntilde;oz-olivas and Carmen C&aacute;mara

Abstract: A simple, sensitive, and rapid flow injection system for Cd cold vapor generation coupled to atomic absorption spectrometry (FI-CV-AAS) was developed. A vesicular medium of didodecyldimethylammonium bromide (DDAM) was investigated in order to understand the possible mechanisms occurring in Cd cold vapor generation and the influence of this surfactant as a catalyst. Similar experiments in an aqueous medium were carried out with optimization of the physical and chemical parameters. Identical analysis characteristics such as linearity and precision, and similar detection limits (0.15 and 0.05 µg/L for DDAB and aqueous media, respectively), were found for both reaction media; hence, the use of surfactants was not necessary for Cd cold vapor generation. Validation of the method was carried out by determining the Cd content in several certified waters. The method was applied to the anal. of some natural waters by the standard additions calibration method.
Cadmium Spectrophotometry Surfactant Reference material Standard additions calibration Optimization

"Automated Online Separation-preconcentration System For Inductively Coupled Plasma Atomic Emission Spectrometry And Its Application To Mercury Determination"
J. Anal. At. Spectrom. 1998 Volume 13, Issue 4 Pages 243-248
Pedro Ca&ntilde;ada Rudner, Amparo Garcia de Torres, Jose M. Cano Pav&oacute;n and Enrique Rodriguez Castellon

Abstract: An automated separation-pre-concentration system coupled to an inductively coupled plasma atomic emission spectrometer is described. The pre-concentration step is performed on a chelating resin microcolumn [silica gel functionalized with 1,5-bis(di-2-pyridyl) methylene thiocarbohydrazide] placed in the injection valve of a simple flow manifold. The system was applied to the determination of mercury in sea-water and biological samples. The optimum experimental conditions were evaluated for the continuous pre-concentration of mercury, the direct generation of mercury vapor and the final determination of this element by ICP-AES. The proposed method has a linear calibration range from 2 to at least 1000 ng mL-1 of mercury, with a detection limit of 1 ng mL-1 (S/N = 3) and a throughput of 40 samples h-1, for a 6 mL sample volume The accuracy of the method was examined by the anal. of certified reference materials and by determining the analyte content in spiked environmental waters. The results show sufficiently high recoveries.
Mercury Spectrophotometry Reference material Preconcentration Optimization Resin Chelation Silica gel

"Novel Approach To Reaction-rate Based Determinations By Use Of Transient Redox Effects"
Anal. Chem. 1975 Volume 47, Issue 2 Pages 357-359
V. V. S. Eswara Dutt and Horacio A. Mottola

Abstract: A novel approach to fast, continuous kinetic-based determinations of a variety of chemical species using a flowthrough cell system and transient oxidation-reduction signals is present here. All necessary reagents contained in a single reservoir are continuously circulated, at constant flow, through the cell into which an aliquot of the sample containing the species to be determined is quickly injected.
Cerium(4+) Chlorpromazine, hydrochloride Chromium(VI) Hydroquinone Isoniazid Manganese Vanadium(V) Spectrophotometry Kinetic Redox

"Field Technique For Monitoring P-cresol In Streams"
Anal. Chem. 1982 Volume 54, Issue 14 Pages 2631-2632
R. A. Coleman, R. D. Edstrom, M. A. Unger, and R. J. Huggett

Abstract: A flow-through instrument design is described which allows reliable determinations of p-cresol [106-44-5] in water to be made by use of the bathochromic shift upon alkalization. Concentration. measurements in the low mg/L range and anal. times of 30-60 s are readily achieved. Data obtained from a continuous 96-h dose on freshwater streams showed excellent agreement (correlation coefficient = 0.9599) with gas chromatography determinations
4-Cresol

"Performance Studies Under Flow Conditions Of Silica Immobilized 8-quinolinol And Its Application As A Preconcentration Tool In Flow Injection/atomic Absorption Determinations"
Anal. Chem. 1985 Volume 57, Issue 3 Pages 729-733
Monte A. Marshall and Horacio A. Mottola

Abstract: The technique described was applied to the determination of Cu(II) in, e.g., standard water samples. The sample was injected into a carrier stream (H2O), flowing at 4 mL min-1, then 0.1 M ammonium acetate - HCl buffer (pH 5) was pumped (0.5 mL min-1) and mixed in a delay mixing coil with the sample - carrier stream. The mixture was passed via a valve through a column of silica-immobilized quinolin-8-ol for a 4-min pre-concentration step, then 1 mL of 1 M HCl - 1 M HNO3 was injected via this valve to elute ions retained on the column, and the eluate was passed into the flame (air - acetylene) of an AAS system. Results obtained for ng mL-1 levels of Cu were in good agreement with the reported values.
Copper(II) Spectrophotometry Immobilized enzyme Preconcentration 8-Hydroxyquinoline Silica

"Selective Chlorine Dioxide Determination Using Gas Diffusion Flow Injection Analysis With Chemiluminescent Detection"
Anal. Chem. 1986 Volume 58, Issue 7 Pages 1524-1527
David A. Hollowell, James R. Gord, Gilbert Gordon, and Gilbert E. Pacey

Abstract: The automated system includes a gas diffusion membrane which allows transfer of ClO2 but otherwise separates the sampling stream from the detector stream and also removes ionic interferents. The detector stream was merged with the reagent stream containing luminol and H2O2 at pH 9 just before entry into the flow-through detector cell for chemiluminescence measurement. The detection limit of ClO2 was ~5 ppb and the selectivity for ClO2 over Cl was >1500. Interference from Fe and Mn compounds and from other oxychlorine compounds was eliminated by this technique, which was devised for determination of ClO2 in waters.
Chlorine dioxide Chemiluminescence Gas diffusion Interferences Tecator

"Flow Injection Spectrophotometric Determination Of Aluminum In Natural Water Using Eriochrome Cyanine R And Cationic Surfactants"
Anal. Chem. 1987 Volume 59, Issue 6 Pages 899-903
Oddvar Roeyset

Abstract: The analysis was performed with buffered carrier stream, 0.5 M hydroxylammonium chloride - 10 mM 1,10-phenanthroline as Fe-masking reagent, and 5 mM Eriochrome cyanine R - 25 mM hexadecyltrimethylammonium bromide (pH ~2) as spectrophotometric reagent stream. A 3.0 M ethylenediamine buffer (pH 7.6) stream was also added. Detection was at 590 nm. Calibration graphs were rectilinear up to 0.8 or 4 mg L-1 for injection loops of 200 or 10 µL, respectively, with a detection limit of 1 µg L-1 of Al. The coefficient of variation was 0.7%. A sampling rate of 120 h-1 was achieved. At the optimum pH, interference from PO43- and F- was greatly reduced; 20 mg L-1 of dissolved organic C was tolerated, and only Fe, Be, La and Ce strongly interfered (of 40 elements tested).
Aluminum Spectrophotometry Interferences Tecator

"Selective Chlorine Determination By Gas Diffusion Flow Injection Analysis With Chemiluminescent Detection"
Anal. Chem. 1988 Volume 60, Issue 1 Pages 2-4
J. R. Gord, G. Gordon, and G. E. Pacey

Abstract: To determine dissolved free Cl (i.e., Cl2, ClO- and HClO) in water, the sample (0.35 ml) was injected into a donor stream (2.25 mL min-1) of 1 M HCl, from which Cl2 transferred through a 0.45 µm PTFE membrane into an acceptor stream (pH 11.75; 0.8 mL min-1) of 75 mM KOH, which was then mixed with 5 mM H2O2 - 1 mM lophine in ethanolic KOH (0.8 mL min-1) as chemiluminescence reagent to react with the ClO- formed. Rectilinear response was obtained for 175 ppb to 900 ppm of Cl, with a limit of detection of 75 ppb, and a coefficient of variation of 1.3%. Sample throughput was 120 h-1. A modified system was used for samples also containing ClO2.
Chlorine, free Chlorine dioxide Chemiluminescence Gas diffusion Teflon membrane

"Liquid-liquid Extraction In Continuous-flow Systems Without Phase Separation"
Anal. Chem. 1988 Volume 60, Issue 21 Pages 2354-2357
Francisco Canete, Angel Rios, M. Dolores Luque de Castro, and Miguel Valcarel

Abstract: The method involves the reversal of the direction of flow for a pre-selected number of cycles, and the continuous monitoring at the detector of a plug of organic phase (extractant) inserted into the aqueous phase (carrier stream) by a conventional injection valve. The method is demonstrated by determination of anionic surfactants by using the conventional methylene blue reaction and CHCl3 as the organic phase. The calibration graph was rectilinear for 0.1 to 4 µg mL-1, with a coefficient of variation of 3.0% and a sampling rate of 50 h-1. The range of application could be expanded to 0.08 to 10 µg mL-1 by using suitable pre-concentration. methods. The method was applied in the determination of anionic surfactants in water.
Surfactants, anionic Spectrophotometry Sample preparation Extraction Flow reversal Organic phase detection

"Automated Titrations Using A Discontinuous Programmed-flow Analyser"
Anal. Chem. 1989 Volume 61, Issue 18 Pages 2109-2116
Dennis P. Arnold, Russell M. Peachey, John D. Petty, and Denis R. Sweatman

Abstract: The technique of automated discontinuous programmed flow analysis is described and the operating principles and design of a working prototype instrument, employing syringe pumps driven by interchangeable cams, is discussed. Different cam profiles allow a number of direct reading or reagent addition methods, as well as both single- and dual-flow titrations. Results are presented for argentometric titrations of Cl-1 in water with anodized Ag micro-electrodes contained in two alternative mixer - sensor assemblies as detectors. Precision is generally better than 1% in the range 60 to 160 mg L-1 for analysis times of 30 s. Cycle times can range form 6 to 90 s with negligible sample carryover. Accuracy for waste water is ± 2 to 3%.
Chloride Electrode Automation Instrumentation Titrations Mixing chamber

"Determination Of Gold At Femtomolar Levels In Natural Waters By Flow Injection Inductively Coupled Plasma Quadrupole Mass Spectrometry"
Anal. Chem. 1990 Volume 62, Issue 14 Pages 1477-1481
Kelly Kenison Falkner and John M. Edmond

Abstract: A method for the determination of Au In seawater at femtomolar moi/L) levels Is presented. The technique involves pre-concentration by anlon exchange of Au as a cyanide complex, [Au(CN),-1, using lgSAu radiotracer (f,,, = 183 days) to monitor recoverles. Samples are then Introduced by flow injection into an Inductively coupled plasma quadrupole mass spectrometer for analysis. The method has a detection limit of 4 0 fM for 4 L of seawater pre-concentrated to 1 mL and a relative precision of 15 % at the 100 fM level. With slight modifications, It can also be applied to the analysis of hydrothermal flulds and freshwaters
Gold Mass spectrometry

"Nitroprusside And Methylene Blue Methods For Silicone Membrane-differentiated Flow Injection Determination Of Sulfide In Water And Waste Water"
Anal. Chem. 1992 Volume 64, Issue 1 Pages 36-43
Vlastimil Kuban, Purnendu K. Dasgupta, and John N. Marx

Abstract: A membrane gas permeation module using a silicone rubber tube (0.6 mm x 12 cm; Patto Products) was incorporated into a flow injection system (described). Hydrogen sulfide evolved from the acidified sample of water or waste water was pre-concentrated by permeation in a stationary alkali acceptor solution, before being subjected to either the nitroprusside or the methylene blue method to determine the sulfide present. The methylene blue method is ~30x more sensitive, and allows determinations at sub µg L-1 levels. The detection limit for the nitroprusside method was 2 µg L-1 for 12 mL samples pre-concentrated in the membrane system. The membrane is highly resistant to fouling and analysis of untreated waste water samples containing suspended solids, oil and grease is possible. Since the nitroprusside method uses less aggressive reagents than the methylene blue method, its use is recommended unless ultratrace determinations are essential. H2S evolved from an acidified sample is pre-concentrated by permeation in a stationary alkaline acceptor solution enclosed in a silicone rubber sample loop. Depending on the sample volume pre-concentrated, the applicable analysis range spans low µg/L to tens of mg/L for both methods. The methylene blue method is more sensitive by a factor of ~30 and actually permits practical determinations in the sub µg/L levels. The limit of detection (LOD) for the nitroprusside method is 20 µg/L for a 20 µL sample by conventional flow injection determination (no membrane, throughput 30 samples/h) and <2 µg/L for a 12 mL sample pre-concentrated in the membrane system (throughput 5 samples/h). The membrane is highly resistant to fouling and permits anal. of untreated wastewater samples bearing suspended solids, oil, grease, etc., without any pretreatment. No significant interference is observed with either chemical Although the nitroprusside chemical is less sensitive, it does not involve the use of concentrated aggressive reagents and is recommended unless ultratrace determinations are essential. Viable reaction mechanisms are proposed for both of these chemistries.
Sulfide Spectrophotometry Silicone membrane Interferences Ultratrace

"Determination Of Chromium(III) And Chromium(VI) In Water Using Flow Injection Online Preconcentration With Selective Absorption On Activated Alumina And Flame Atomic Absorption Spectrometric Detection"
Anal. Chem. 1992 Volume 64, Issue 24 Pages 3101-3108
Michael Sperling, Shukun Xu, and Bernhard Welz

Abstract: A conically shaped micro-column (Perkin-Elmer, 50 µL) was packed with acid-activated aluminum oxide 90 (Merck, 56 to 170 µm fraction). Sequential sorption was carried out using Clark - Lubs buffer of pH 7 for Cr(III) and pH 2 for Cr(VI). The species were then eluted directly from the column to the nebulizer - burner system (with the impact bead and flow spoiler removed) using 1 M HNO3 and 0.5 M ammonia for Cr(III) and Cr(VI), respectively. Retention efficiency was >80% for Cr(III) and >90% for Cr(VI) giving a sensitivity enhancement of 25 for a 3 mL sample, and corresponding detection limits were 1.0 and 0.8 µg l-1; the calibration graph for both species was rectilinear from 10 to 200 µg l-1. Recovery from natural water samples (kept at pH 4) was 90 to 106%. The effects of diverse ions are reported and no serious interference occurred from levels normally found in natural waters. A comparison of published methods for the selective determination of Cr(III) and/or Cr(VI) by online separation techniques is also presented.
Chromium(III) Chromium(VI) Spectrophotometry Activated alumina Column Speciation Interferences Optimization Preconcentration

"Usefulness Of The Stopped-flow Mixing Technique For Micelle-stabilized Room-temperature Liquid Phosphorimetry"
Anal. Chem. 1994 Volume 66, Issue 6 Pages 919-923
S. Panadero, A. Gomez-Hens, and D. Perez-Bendito

Abstract: A solution containing 0.8 mL of 0.25 M TlNO3, 0.5 mL of ammonium acetate buffer and 0.6 mL of 0.5 M Na2SO3 in a 10 mL aqueous volume was placed in one syringe of the stopped-flow module. The other contained 3 mL of 0.25 M SDS, 0.5 mL of buffer, 0.6 mL of 0.5 M Na2SO3 and a standard carbaryl solution A 0.15 mL portion of each solution was mixed per run and the variation in phosphorescence intensity was measured at 488 nm (excitation at 284 nm). The slope of the phosphorescence-time graph was proportional to the analyte concentration. An equilibrium technique is also described in which the amplitude of the kinetic curve was measured. The data were obtained within 2-3 s with a greater precision than that of solid-surface room-temp. phosphorimetry. For 0.5 µg/ml of carbaryl, the RSD (n = 11) was 2.9%. Calibration graphs were linear from 0.03-2 and 0.05-3 µg/ml of carbaryl for the kinetic and equilibrium methods, respectively, and the corresponding detection limits were 0.01 and 0.014 µg/ml. The kinetic method was more selective in the presence of other pesticides. The technique was applied to the determination of carbaryl in irrigation water.
Carbaryl Phosphorescence Stopped-flow Micelle

"1,1'-oxalyldi-imidazole As Chemiluminescence Reagent In The Determination Of Low Hydrogen Peroxide Concentrations Of Flow Injection Analysis"
Anal. Chem. 1994 Volume 66, Issue 10 Pages 1766-1770
Malin Stigbrand, Einar Ponten, and Knut Irgum

Abstract: Sample solution (50 µL) were injected into a reagent stream (1 ml/min) of 5 mM 1,1'-oxalyldi-imidazole in acetonitrile. After mixing, the solution passed through a flow cell (2.2 cm x 2.4 mm i.d.) packed with polymethacrylate beads on which the fluorophore 3-aminofluoranthrene had been immobilized. The flow cell was mounted as close as possible to the window of a side-view photomultiplier tube, with a piece of specular Al foil above the cell as a reflector. Calibration graphs were linear for 1.5-6 µM-H2O2, with a detection limit of 10 nM. This detection limit and the non-zero intercept arise from traces of background H2O2 present in water, which are difficult to remove. The signal from 6 µM-H2O2 repeatedly injected decreased 7% after 1 h. The new reagent was 10 times more sensitive than trichlorophenyl oxalate, which also required a separate imidazole catalyst reagent stream.
Hydrogen peroxide Chemiluminescence

"Solenoid Pumps For Flow Injection Analysis"
Anal. Chem. 1996 Volume 68, Issue 15 Pages 2717-2719
Debra A. Weeks and and Kenneth S. Johnson

Abstract: The peristaltic pump of a typical FIA system was replaced by three solenoid-driven diaphragm pumps with integral Viton check valves. These pumps had the ability to incorporate microprocessor control of the reagent and sample streams independently. The system was tested by the determination of nitrite in water and seawater. Reduced detector oscillations were achieved with a 140 µL flow cell, a 1 m reaction coil and a 100 µL injection loop. Detection limits were M-nitrite, the RSD was 1% for 10 µM-nitrite and 60 injections/h were possible with flow rates of 0.5 ml/min for reagents and sample. These values match the performance of the conventional FIA system.
Nitrite

"Continuous-flow System For Online Water Monitoring Using Back-side Contact ISFET Based Sensors"
Anal. Chem. 1996 Volume 68, Issue 21 Pages 3801-3807
Cec&iacute;lia Jim&eacute;nez, Isabel Marqu&eacute;s, and Jordi Bartrol&iacute;

Abstract: The active chemical agents in the CHEMFETs were immobilized in a PVC membrane deposited on to the SiN4 gate area. Electrical connections were made from the back of the sensor chips to separate them from the chemical environment. The flow system had a modular configuration with a separate dual-channel manifold for each analyte. The dual-channel manifolds allowed the water sample stream at a flow rate of 1.5 ml/min to be merged with a different ionic strength adjuster (ISA) at a flow rate of 0.55 ml/min for each determination. A Ag/AgCl reference electrode was used. The pH ISFET gave a response of ~57 mV/pH from pH 2-12 and took ~3 min to reach a steady-state value. The CHEMFETs exhibited responses of -44.8 mV/decade for 10^-4 to 0.1-M-NH4+, -27.1 mV/decade for 0.1-10 mM Ca2+ and 55.7-58.5 mV/decade for 10^-4 to 0.1 M NO3- depending on the composition of the ISA. The analyzes were carried out simultaneously and therefore the sampling rate was 20/h. The system was calibrated every 3-5 h. Long term stabilities of 3 and 5 weeks were achieved for the sensors and the reference electrode, respectively.
Ammonium Field effect transistor Electrode Sensor Ionic strength

"A Flow Injection Method For Analysis Of Residual Chlorine By The DPD Procedure"
Fresenius J. Anal. Chem. 1983 Volume 315, Issue 1 Pages 47-50
D. J. Leggett, N. H. Chen and D. S. Mahadevappa

Abstract: A flow injection method for automating the DPD reaction with free Cl in water samples has been described. The carrier stream consists of a 11 (v/v) mixture of N,N-diethyl-p-phenylene diamine (DPD) indicator and phosphate buffer. A sampling rate of 252 per hour has been obtained and the detection limit is 0.3 ppm. Substitution of DPD with N,N-p-dimethylaniline sulphate also appears to be satisfactory for Cl analysis. The effects of reagent concentrations, flow parameters and additions of anions, cations and organic haloamines on the peak height have been investigated. The ammonium-Cl reaction has been studied and potentialities of the flow technique for the analyzes of chloramines have been explored.
Chlorine Spectrophotometry

"Methods For The Determination Of Inorganic Anions. 1. Spectrophotometric Trace Determination Of Chloride In Air, Water And Technical Products In The Iron(II) - Mercury - TPTZ System. Manual, CF And Flow Injection Analysis Methods"
Fresenius J. Anal. Chem. 1983 Volume 315, Issue 3 Pages 197-200
Bernd R&ouml;ssner und Georg Schwedt

Abstract: The application of the Fe(II)/Hg-tripyridyl-s-triazine system for the photometric trace analysis of chloride in the range of 10 g/l to 10 mg/l is shown. The improvement of the method for optimum results leads in the continuous-flow-technique to a detection limit of 5 g/l. A manual procedure for the range of 1-10 mg/l is also described. As examples for application, determinations of chloride in natural waters, p. a. salts, in a bitumen sample and in air are described.
Chloride Spectrophotometry Method comparison

"Comparison Of Continuous-flow And Flow Injection Analytical Techniques For The Photometric Determination Of Traces Of Aluminum In Water And Soil Samples"
Fresenius J. Anal. Chem. 1984 Volume 317, Issue 3-4 Pages 422-426
D. Z&ouml;ltzer und G. Schwedt

Abstract: For the continuous-flow determination of Al, air is added to the stream of test solution from a multi-channel pumping system, then ascorbic acid is added to the sample - air mixture, and, after passage of the resulting mixture through a mixing coil, Chrome Azurol S (C. I. Mordant Blue 29) in aqueous 50% ethanol and acetate buffer are added. After passage through a second mixing coil, the mixture enters a debubbler, and Al is determined in the air-free solution at 546 nm. For flow injection analysis, the sample is injected into a stream of carrier (H2O), ascorbic acid is added, and after passage through a mixing coil, Chrome Azurol S solution in acetate buffer is added. After passage through a second mixing coil, the flowing solution is examined spectrophotometrically at 546 nm. The latter method gives the more symmetrical signals, and its sampling rate and reproducibility are better. The detection limit is ~10 ng mL-1 of Al. The tubing used in either method must be of PTFE (as glass adsorbs Al). In the analysis of soil solution and water, the standard-addition technique must be used.
Aluminum Spectrophotometry Method comparison Standard additions calibration Debubbler

"Determination Of Nitrate In Natural Waters By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1984 Volume 319, Issue 5 Pages 506-509
Susumu Nakashima, Masakazu Yagi, Michio Zenki, Akinori Takahashi and Kyoji T&ocirc;ei

Abstract: The sample is injected into a carrier solution containing 0.8 g L-1 of Na4EDTA and 3 g L-1 of NH4Cl (pH ~8.1), and the stream passes through copperized cadmium to reduce NO3- to NO2-. The reagent (containing 552 mg L-1 of m-phenylenediamine dihydrochloride and 200 mg L-1 of 4'-aminoacetophenone; pH 2) is added, the solution are mixed at 45°C, and the absorbance of the product is measured at 456 nm. The detection limit is 1.5 ppb with injection of 650 µL of water, and, at 0.1 to 0.3 ppm of nitrate-N, the coefficient of variation is <1%. Nitrite present in the sample is determined separately and corrected for. Of the foreign ions examined, 50 ppm of Ca(II), Mg(II), Na+, K+, NH4+, HCO3-, SO42-, Cl-, SiO32- or H2PO4- did not interfere in the determination of 0.2 ppm of nitrate-N. Results for NO3- in 10 natural water samples are reported.
Nitrate Spectrophotometry Heated reaction Interferences Reactor

"Simultaneous End Sequential Determination Of Chromium(VI) And Chromium(III) By Unsegmented Flow Methods"
Fresenius J. Anal. Chem. 1985 Volume 322, Issue 5 Pages 499-502
Juan Ruz, Angel R&iacute;os, M. D. Luque de Castro and Miguel Valc&aacute;rcel

Abstract: Sexavalent Cr and Cr(III) were determined at the µg mL-1 level by reversed flow injection analysis by using three configurations to permit simultaneous (either the completely continuous monitoring of Cr(VI) or the converging zone method) or sequential determination. Absorbance of the Cr(VI) - 1,5-diphenylcarbazide complex was measured at 540 nm with a single detector before and after Ce(IV) oxidation of Cr(III), the level of the latter being obtained by difference. Sampling frequencies of 30 to 100 h-1 were achieved. Major interferents were found to be S2-, I-, Fe(II) and NO2-. The methods could be applied to the monitoring of Cr in natural and waste waters.
Chromium(III) Chromium(VI) Spectrophotometry Interferences Process control Tecator Reverse

"Preconcentration Techniques For Inorganic Trace Analysis"
Fresenius J. Anal. Chem. 1986 Volume 324, Issue 7 Pages 672-677
Atsushi Mizuike

Abstract: A review is presented, with emphasis on control of contamination and losses of trace elements in pre-concentration from large volumes of liquids (including natural water) and micro-scale pre-concentration of trace elements from high-purity solid micro-samples. Two types of continuous-flow co-precipitation - flotation apparatus and two types of decomposition - electrolysis micro-vessel are described, with detailed diagrams and examples of applications. (19 references).
Trace elements Precipitation Preconcentration Review

"Determination Of Sulfate By A Modified Flow Injection Analysis Method And Comparison With The Method DIN 38405. 5"
Fresenius J. Anal. Chem. 1988 Volume 329, Issue 6 Pages 707-710
Bernd Koch

Abstract: In the modification described of method ASTN 15/84 (Tecator), the color of the blue complex formed between Ba(II) and methylthymol blue in alkaline and alcoholic solution is decreased by SO42- precipitation as BaSO4; the absorbance change is monitored at 620 nm. A flow diagram is given. Results obtained in the analysis of 12 water samples were similar to those obtained by the established DIN method. The sample throughput of the method (100 to 150 samples per working day) is ten times that of the DIN method.
Sulfate Ion exchange Spectrophotometry Complexation Indirect Method comparison Tecator

"Determination Of Phenol In Water By Flow Injection Analysis"
Fresenius J. Anal. Chem. 1988 Volume 329, Issue 6 Pages 728-731
J&uuml;rgen M&ouml;ller and Michel Martin

Abstract: Two manifolds are described for the automated determination of phenol with use of 4-aminoantipyrine(I). Samples (200 µL) are injected into the carrier (H2O; 2 mL min-1) and merged with 2.5% I in borate - bicarbonate buffer (0.6 mL min-1) and then with oxidant solution (5% K2S2O8 at pH 11; 0.6 mL min-1). In the first manifold, phenol is determined directly at 515 nm. Calibration is rectilinear in the ranges 1 to 15 and 0.05 to 1.0 ppm. The coefficient of variation (n = 10) is 1 to 1.5%. In the second manifold, the aqueous phase is segmented with CHCl3 and the color is extracted. After phase separation via a membrane, the absorbance of the organic phase is measured at 467 nm. Detection limit is reduced to 5 ppb of phenol and sample throughput is 50 h-1. Samples (25 ml) are cleaned up before analysis by steam distillation in 2.5 min after addition of NaCl (15 g) and 0.1 M H2SO4 (1 ml). For complete recovery of phenol (0.2 mg), 70 mL of distillate is collected.
Phenol Spectrophotometry Sample preparation Extraction Optimization Organic phase detection Stopped-flow Tecator

"New Flow Injection Analysis Methods For The Determination Of Ions. 2. Sulfate, Sulfite And Nitrate, Nitrite"
Fresenius J. Anal. Chem. 1988 Volume 330, Issue 6 Pages 494-497
N. Almhofer und F. Frenzel

Abstract: The apparatus described previously (see Part I, later in this section) is used, with measuring electrodes of Pb - PbSO4 for SO42-, Pb for SO32-, Sn for NO3-, and Sb for NO2-. Measurement is potentiometric for SO42-, otherwise amperometric. The measurement ranges are 50 µM to 10 mM for SO42- and NO3-, 10 µM to 10 mM for SO32-, and 0.1 to 10 mM for NO2-. Results for various waters are given, showing a typical coefficient of variation of 1.5% for SO42- and SO32- and 2.5% for NO3- and NO2-. Selectivity coefficient are quoted and instructions are given for electrode preparation. The measurement and calibration procedures are as described previously, except that the carrier stream consists of 100 mL of 0.1 mM Na2SO4 plus 200 mL of ion buffer (10 mM NaClO4 - 10 mM HClO4) diluted to 1 l, and cations (especially Ca) must be exchanged for Na beforehand. Results for analysis of waters are presented.
Sulfate Sulfite Nitrate Nitrite Amperometry Electrode Potentiometry Apparatus

"New Flow Injection Analysis Methods For The Determination Of Ions. 1. Halides"
Fresenius J. Anal. Chem. 1988 Volume 330, Issue 6 Pages 489-493
F. Frenzel, N. Almhofer, G. Citroni und W. Hager

Abstract: The flow injection system consists of an HPLC pump, a sample injection point and a measuring cell coupled to a potentiostat and a pH meter interfaced with a computer for amperometric recording. The cell is a Plexiglas cylinder with bores for inflow and outflow and Ag - AgCl measuring and reference electrodes; the measuring chamber volume is ~50 mm3. The carrier stream (2 mL min-1) is 1 mM NaClO4 - 1 mM HClO4. A single measurement takes ~2 min including pause. Results for determination of 3 to 450 mg L-1 of Cl- in synthetic and real water samples agree well with potentiometric measurements and the average coefficient of variation is 1.5%. Selectivity coefficient are quoted for the Cl- - I-, Cl- - Br-, Cl- - CN- and Cl- - S2- ion pairs and instructions are given for rectilinear and non-rectilinear calibration in the presence of ion matrix effects, by the method of standard addition and dilution (or precipitation with AgNO3).
Halides Chloride Amperometry Potentiometry Electrode Interferences Standard additions calibration

"Determination Of Calcium In Water By Flow Injection Analysis Inductively Coupled Plasma Emission Spectrometry"
Fresenius J. Anal. Chem. 1988 Volume 332, Issue 2 Pages 153-156
Phillip L. Kempster, Jacobus F. van Staden and Henk R. van Vliet

Abstract: Water samples or standards (300 µL) were injected into a flow injection system (described with diagram) incorporating a centrifugal spray chamber (11 ml) that introduced the carrier stream (3.5 mL min-1) of aqueous 10% HNO3 from the sample injection valve into the plasma torch, which was operated at 1.25 kW with Ar as carrier gas. The calibration graph was rectilinear from 4 to 200 mg l-1. The coefficient of variation was 3.1% for 10 to 200 mg L-1 of Ca (n = 3). Recoveries of 24.9 and 27 mg L-1 of Ca were 93 and 102%, respectively. Results agreed with those by AAS. The sampling rate was ~320 injections h-1 and Ar consumption was less than that of conventional ICP spectrometry.
Calcium Spectrophotometry Method comparison

"Use Of Flow Injection Analysis Based On Iodometry For Automation Of Dissolved Oxygen (Winkler Method) And Chemical Oxygen Demand (dichromate Method) Determinations"
Fresenius J. Anal. Chem. 1988 Volume 332, Issue 7 Pages 750-755
M. Novic, B. Pihlar and M. Dular

Abstract: In the modified Winkler method, water (300 ml) was mixed with 1 mL of each of the precipitation solution and 1 mL of concentrated H2SO4 and, after 30 min, an aliquot was injected into a stream of water (0.56 mL min-1) and mixed with 0.4 M KI (0.56 mL min-1). After passing through a PTFE reaction tube (50 cm x 0.5 mm), the I3- in solution was determined amperometrically in a wall-jet cell at a vitreous-carbon electrode at -200 mV vs. Ag - AgCl. Dissolved O was determined by the standard-additions method with use of KIO3 as standard. Calibration graphs were rectilinear for up to 30 mg L-1 of dissolved O and the detection limit was 5 µg l-1. Results agreed with those obtained with a WTW OXI 91 oxymeter. The apparatus could also be modified for use in the determination of COD by oxidation of organic compounds with K2Cr2O7 in H2SO4 and reaction of the excess of K2Cr2O7 with KI producing I3- which was determined amperometrically as above.
Chemical oxygen demand Oxygen Amperometry Electrode Electrode Standard additions calibration

"Continuous Micro-flow Monitoring Method For Total Mercury At Sub-ppb Level In Waste Water And Other Waters Using Cold Vapor Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1988 Volume 332, Issue 7 Pages 745-749
Masashi Goto, Edison Munaf and Daido Ishii

Abstract: The sample stream (200 µL min-1) was mixed with a stream of aqueous 2% K2S2O8 containing 65 ppm of Cu(II) (100 µL min-1) before passing through a PTFE tube (27 cm x 0.5 mm) in which organic Hg was oxidized to Hg(II). The stream was then mixed with 3.4 M NaOH containing 2% of SnCl2, passed through a PTFE tube (4 cm x 0.5 mm), mixed with Ar (9.0 mL min-1) and passed through a PTFE reduction and extraction tube (60 cm x 1.3 mm). The resulting stream containing gaseous Hg was passed through a gas - liquid separator cf. Anal. Chim. Acta, 1982, 140, 179) from which the gaseous phase was passed, via a condenser for water vapor removal, to a 1.13 mL flow cell for the AAS determination of Hg at 253.7 nm. Calibration graphs were rectilinear from 0.5 to 5.0 µg L-1 of Hg as HgCl2 or methylmercury chloride; the detection limit was 0.1 µg l-1. In the determination of 3.0 µg L-1 of Hg, the coefficient of variation was 1.1% (n = 4). The response time was ~5 min. There was no interference from up to 10% of NaCl in solution or from COD (up to 600 mg l-1). The method was used to monitor laboratory waste water continuously for 6 h.
Mercury Spectrophotometry Interferences Phase separator

"Flow Injection System For The Determination Of Nickel By Means Of MIP OES After Conversion To Nickel Tetracarbonyl"
Fresenius J. Anal. Chem. 1989 Volume 332, Issue 8 Pages 862-865
W. Drews, G. Weber and G. T&ouml;lg

Abstract: The sample solution (100 µL) was mixed with streams of 40 mM HCl (4 mL min-1), 0.1 M NaOH containing 0.6% of NaBH4 for reduction of the sample to Ni0 (4 mL min-1), Ar (2 l h-1) and CO (150 mL h-1). After formation of Ni(CO)4 in a 13-turn glass reaction coil (coil diameter 2 cm; capillary i.d. 2 mm), the combined stream was passed through a gas - liquid separator (Broekaert and Leis, Ibid., 1980, 300, 22) with additional Ar (37 l h-1). The separated gas phase and O (800 mL h-1) were fed into a microwave-induced plasma for detection of Ni at 341.5 nm (input and reflected power 130 and 4 W, respectively; frequency 2.45 GHz). Calibration graphs were rectilinear from the detection limit (1 µg L-1 of Ni) to 100 µg l-1. In the determination of 10 µg L-1 the coefficient of variation was 2.2% (n = 10). The analysis rate was 120 h-1. There was no interference from a 4000-fold excess of Fe. The method was applied to water and urine samples. A flow injection - HPLC procedure for speciation of Ni in urine is also described.
Nickel Spectrophotometry Interferences Phase separator Glass Volatile generation Speciation

"Investigations On The Equivalence Of Analytical Procedures - Determination Of Chloride By Flow Injection Analysis And DIN Method In Water Analysis"
Fresenius J. Anal. Chem. 1989 Volume 334, Issue 1 Pages 9-12
G. Schulze, O. Elsholz, R. Hielscher, A. Rauth, S. Recknagel und A. Thiele

Abstract: Water was de-gassed and analyzed by one of the following methods. (i) A portion is injected into a stream of water, then mixed with a 15% methanolic solution of 2 mM Hg(SCN)2, 80 mM Fe(NO3)3 and 50 mM HNO3 and the absorbance is measured at 463 nm. (ii) A portion is injected into a stream of water, then mixed with 0.7 M Na acetate followed by 0.1 M Na acetate containing 1 mg mL-1 of Cl-. Detection is by means of tubular silver flow-through electrodes. (iii) A portion is injected into a stream of 2 M HNO3, this is mixed with a solution of 100 mg L-1 of AgNO3, the ppt. is filtered off and the filtrate is analyzed by AAS at 328.1 nm. The results obtained were reproducible and accurate and compared well with those obtained by the German standard (DIN) method. The methods developed were faster and more economic in the use of reagents than the standard method. For methods (i), (ii) and (iii), 120, 180 and 40 samples h-1, respectively, could be analyzed.
Chloride Spectrophotometry Spectrophotometry Electrode Precipitation Filter Standard method

"Direct Determination Of Calcium, Magnesium, Sodium And Potassium In Water By Flow Injection Flame Atomic Spectroscopy, Using A Dilution Chamber"
Fresenius J. Anal. Chem. 1989 Volume 335, Issue 8 Pages 975-979
M. de la Guardia, V. Carbonell, A. Morales and A. Salvador

Abstract: The cited elements were determined in water using a dilution chamber to extend the calibration range and allow a single concentration. standard to be used for the calibration of each analyte. A double channel injector and the merging zone technique were used to add La solution to the samples (1:1) and reduce reagent consumption. Samples were analyzed by flow injection flame AAS, peak heights were measured at 422.67, 285.21, 589.00 and 766.49 nm for Ca, Mg, Na and K, respectively. Results agreed well with those obtained by a batch AAS procedure and gave better precision. Sensitivities were 0.0408, 0.046, 0.0122 and 0.20 ppm and detection limits were 2.5, 1.5, 7.0 and 0.5 ppm for Ca, Mg, Na and K, respectively. The sample throughput was ~180 samples h-1. The cited elements were determined in water using a dilution chamber to extend the calibration range and allow a single concentration. standard to be used for the calibration of each analyte. A double channel injector and the merging zone technique were used to add La solution to the samples (1:1) and reduce reagent consumption. Samples were analyzed by flow injection flame AAS, peak heights were measured at 422.67, 285.21, 589.00 and 766.49 nm for Ca, Mg, Na and K, respectively. Results agreed well with those obtained by a batch AAS procedure and gave better precision. Sensitivities were 0.0408, 0.046, 0.0122 and 0.20 ppm and detection limits were 2.5, 1.5, 7.0 and 0.5 ppm for Ca, Mg, Na and K, respectively. The sample throughput was ~180 samples h-1.
Calcium Magnesium Sodium Potassium Spectrophotometry Calibration Injector Merging zones Peak analysis Sensitivity Detection limit Dilution Reagent consumption

"New Screening Procedure For The Estimation Of Oxidizable Organic Compounds In Water Samples"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 10 Pages 822-826
B. Ruchti, C. Schramm, S. Kubitschko and B. Neidhart

Abstract: A solid phase reactor (prepared by the in situ precipitation of PbO2 on silica gel) was used in a flow injection system for the online oxidation of organic compounds in water samples. The Pb2+ ions released were determined either photometrically at 512 nm [after complex formation with 4-(2-pyridylazo)resorcinol] or directly by flame AAS. For almost all organic compounds tested the oxidation yields were found to be lower than those obtained with the standard COD procedure, but calibration was possible in all cases. It is suggested that this system can be used for the screening of polluted waters and as a post-column chemical-reaction detector.
Organic compounds Spectrophotometry Spectrophotometry Solid phase reagent Oxidation column Complexation Post-column derivatization

"Sensitive Fluorescence Labelling For Analysis Of Organotin Compounds With Morin"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 10 Pages 839-845
M. Pfeffer, B. Gelbe, P. Hampe, B. Steinberg, E. Walenciak-Reddel, B. Woicke and B. Wykhoff

Abstract: An HPLC method has been developed for the determination of the toxicity of organotin compounds in peanut oil, water or diet mixtures as test compounds. According to the formulation, the tin compounds were diluted or extracted with propan-2-ol or methanol and portions were applied to reversed-phase columns (Spherisorb and Hypersil) with mobile phases of mixtures of acetonitrile, water, acetic acid and LiCl. Post-column derivatization was carried out with morin and the organotin complexes were determined fluorimetrically. No peak interferences were observed and the coefficient of variation were generally 5%. Results were in good agreement with those by AAS.
Tin, organic HPLC Fluorescence Post-column derivatization Interferences Method comparison

"Indirect Determination Of Bromide By Diffusion Flow Injection Analysis With Amperometric Detection"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 1-2 Pages 98-102
Snezana D. Nikolic, Teodora D. Jankovc, Emil B. Milosavljevic, James L. Hendrix and John H. Nelson

Abstract: Samples containing Br- are injected into the flow injection analysis manifold (diagram given), where the Br- is converted online into Br by KMnO4, which diffuses from the donor stream through a hydrophobic membrane [see Nikolic et al., Analyst (London), 1991, 116, 49] into the acceptor solution The Br is carried to a flow-through amperometric cell (see Rocklin and Johnson, Anal. Chem., 1983, 55, 4) where it is reduced by a Pt electrode (vs. Ag - AgCl). The cathodic current is proportional to the sample Br- concentration. Calibration graphs are rectilinear up to 10 mM Br-. Use of a mixture of KMnO4 and NaCl reduces the detection limit to 1 µM (16 ng) Br-. The method was applied to the determination of Br- in Cl- and other reagents, as well as in natural waters. A rapid, indirect diffusion flow injection analysis (FIA) method with amperometric detection has been developed for the selective and sensitive determination of Br-. The method is based on permanganate oxidation of Br- to bromine. Bromine diffuses through a PTFE membrane and is quantified amperometrically at a platinum working electrode. Calibration graphs were linear up to the max. concentration. of Br- investigated (10.0 mmol/L). The precision of the technique was better than a relative standard deviation of 0.7% at 10.0 µmol/L, with a throughput of 30 samples per h. The effects of temp., acidity, working potential, composition of the reagent solution and interferents on the FIA signals were studied. The catalytic effect of Cl- on the permanganate oxidation of the analyte was utilized to lower the detection limit to 1 µmol/L (16 ng Br-). Similar detection limits were achieved by combining the effects of higher acidity (4.0 mol/L H2SO4) and elevated temps. (40°C). The method was successfully applied to the determination of Br- in chloride and other reagents, as well as in natural waters.
Bromide Amperometry Electrode Teflon membrane Indirect Interferences Hydrophobic membrane

"Determination Of Arsenic(III) And Total Inorganic Arsenic By Online Pre-treatment In Hydride Generation Atomic Absorption Spectrometry"
Fresenius J. Anal. Chem. 1992 Volume 343, Issue 4 Pages 352-356
Wolfgang Driehaus and Martin Jekel

Abstract: A continuous-flow hydride generation AAS system (suitable for monitoring water supplies) is described. In order to determine As(III) and As(V) with the same sensitivity the sample is continuously mixed with concentrated HCl and a KI - ascorbic acid solution in a 1.5-m reaction coil heated to 75°C. The calibration graph extends from 1 to 100 µg L-1 with a rectilinear range up to 20 µg L-1 and a detection limit of 0.6 µg l-1. The chosen reaction medium for the selective determination of As(III) was 0.5 M acetic acid which gave a working range from 1 to 50 µg L-1 with a rectilinear range up to 20 µg l-1. With this determination Cu, Fe and Ni can interfere at a concentration. of 1 mg l-1, but the interferences can be suppressed by the addition of thiourea (60 mM) and EDTA (20 mM) to the acetic acid matrix.
Arsenic(3+) Arsenic, total Sample preparation Spectrophotometry Volatile generation Interferences Heated reaction Volatile generation

"Simultaneous Determination Of Zinc And Mercury With 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine By Differential Rate Kinetics And Flow Injection Analysis"
Fresenius J. Anal. Chem. 1994 Volume 348, Issue 10 Pages 644-647
Xue-jun Peng, Qun-kai Mao and Jie-ke Cheng

Abstract: The kinetics of the cited reactions were investigated over the pH range 1.42-6.22 by measuring the absorbances at 422.4 nm for Zn and 425.7 nm for Hg. Only Zn reacted at pH 4.2, whereas both analytes reacted at pH 6.22. The method was applied to a FIA system consisting of 187 µM-5,10,15,20-tetrakis-(3-chloro-4-sulfophenyl)porphine in acetate buffer of pH 4.2 as the reagent stream (1.8 ml/min). After introduction of the sample, the flow was stopped for 60 s and Zn was determined by measuring the absorbance at 422.4 nm. The mixture was merged with the carrier stream (1.8 ml/min) consisting of acetate buffer of pH 6.22 and the flow was stopped again for a further min. The absorbance at 425.7 nm was measured and the combined Zn and Hg content was calculated. From the difference of the two measurements, the Hg content was determined. Calibration graphs were linear up to 3 µg/ml for Zn and 12 µg/ml for Hg. Recoveries were >90% of the ions investigated; Cu(II) and Mn(II) interfered.
Mercury Zinc Spectrophotometry Interferences Kinetic

"Low Molecular Weight Analytes In Water By Spectral Interferometry Using A Competitive Immunoassay"
Fresenius J. Anal. Chem. 1994 Volume 348, Issue 8-9 Pages 602-605
G. Lang, A. Brecht and G. Gauglitz

Abstract: Dinitrophenol (I), covalently bound with human serum albumin, was coated onto the surface of a high RI glass fiber and the fiber sensor (10 µL volume) mounted within a flow cell. The fiber surface was additionally blocked to non-specific adsorption using ovalbumin. Solution (100 µg/ml) of monoclonal anti-I in PBS of pH 7.4, were incubated with 5-5000 ng/ml solution of I for 5 min and then pumped through the sensor cell via a flow injection system. The evanescent internal reflectance spectra of I were recorded over 350-780 nm. Calibration graphs of initial response slopes of I with concentration are discussed. A detection limit of 50 ng/ml of I was obtained.
2-Nitrophenol Immunoassay Electrode Interferences

"Polymer Based RIFS Sensing: An Approach To The Indirect Measurement Of Organic Pollutants In Water"
Fresenius J. Anal. Chem. 1994 Volume 348, Issue 8-9 Pages 598-601
G. Kraus, A. Brecht, V. Vasic and G. Gauglitz

Abstract: Thin polymer films (250 nm-4 µm) of polymethyltrifluoropropylsiloxane (I), polydimethylsiloxane (II) and styrenebutylmethacrylate were fabricated by spin coating high RI glass fibers with 10% solution of the polymers (details given) for use in RIFS (reflectometric interference spectrometry). The sensors (3 m x 25 µL volume) were mounted within a flow cell and water containing toluene (III), 1,2-dichloroethane (IV), trichloroethene (V) and tetrachloroethene (VI) pumped through via a flow injection system at 0.5-0.75 ml/min. The evanescent internal reflectance spectra were recorded over the range 350-780 nm. Calibration graphs of II-coated sensors were linear for 77.2 ng/ml-1.2 mg/ml of IV with a detection limit of 12 ng/ml. The sensitivity of I-coated sensors to III-VI were 14, 3.2, 2.4 and 4 nl/ng, respectively. Sensor response times were typically less than 3 s.
Organic compounds Spectrophotometry Sensor Interferences Indirect

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

"Spectrophotometric Determination Of Cationic And Anionic Surfactants With Anionic Dyes In The Presence Of Non-ionic Surfactants. 2. Development Of Batch And Flow Injection Methods"
Microchim. Acta 1992 Volume 106, Issue 1-2 Pages 67-74
Shoji Motomizu, Mitsuko Oshima and Yasuhiro Hosoi

Abstract: Organic onium ions could be determined by a flow injection, spectrophotometric method based on changes in the absorption spectra of the azo dye, propyl orange, in the presence of Triton X-100. Anionic surfactants were similarly determined using propyl orange and either tetradecyldimethylbenzylammonium or n-octadecyltrimethylammonium ion in the presence of Triton X-100 by measuring the absorbance at 485 nm. Organic onium ions could be determined between 0 and 30 µM by the batch method and 0 and 20 µM by the flow injection method. Determination ranges for anionic surfactants were 0 to 20 µM by the batch method and 0 to 50 µM by the flow injection method with a detection limit of 0.3 µM. The method was used to determine anionic surfactants in water samples with no interferences and fairly good recoveries. On the basis of the changes in absorption spectra of azo dyes on the addition of an organic onium ion, spectrophotometric methods for the determination of organic onium salts and anionic surfactants were developed, and applied to flow injection method. Propyl orange anion (I) was used for the determination of organic onium ions. Pairs of I and tetradecyldimethylbenzammonium ion or I and n- octadecyltrimethylammonium ion were used for the determination of anionic surfactants. The determination range of organic onium ions were (0-3) x 10^-5 M by a batch method and were (0-2) x 10^-5 M by a flow injection method. The determination ranges of anionic surfactants were (0-2) x 10^-5 M by the batch method, and were (0-5) x 10^-5 M by the flowinjection method, and the detection limit corresponding to S/N = 3 was 3 x 10^-7 M by the flow injection method. By the proposed flow injection method, anionic surfactants in water samples were determined.
Surfactants, anionic Surfactants, cationic Spectrophotometry Triton X Interferences Surfactant

"Spectrophotometric Determination Of Mercury With 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine By Flow Injection Analysis"
Microchim. Acta 1994 Volume 113, Issue 1-2 Pages 81-89
Xue-Jun Peng, Qun-Kai Mao and Jie-Ke Cheng

Abstract: Sample solution and reagent solution, containing 0.945 mM 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine and 0.01% of 8-hydroxyquinoline in 1 M acetate buffer of pH 6.22 were simultaneously introduced into separate water carrier streams (both 1.8 ml/min) via 100 µL sample loops. The streams were merged and passed into a reaction coil held at 85°C and the flow was stopped. After 60 s the flow was resumed and the absorbance of the reaction mixture was measured at 425.7 nm in a flow-through cell. The calibration graph was linear for 0-12 µg/ml of Hg(II) and the detection limit was 0.025 µg/ml of Hg(II). For 5 µg/ml of Hg(II) the RSD was 0.82% (n = 12). Tolerable amounts are listed for 20 foreign ions and of these the most serious interferences were from Zn(II), Cu(II), and Mn(II) which could be masked with glycine or ethylenediamine. The method was applied to water samples.
Mercury Spectrophotometry Interferences 8-Hydroxyquinoline

"Online Monitoring Of Phosphate In Natural Water And Effluent Streams Using Sequential Injection Analysis"
Microchim. Acta 1998 Volume 128, Issue 3-4 Pages 223-228
Jacobus Frederick van Staden and Rosa Elizabeth Taljaard

Abstract: Automation of the molybdenum blue method by sequential injection (SIA) for the online monitoring of phosphate in natural waters is presented. Although sequential injection analysis runs at 1/5 the speed of conventional FIA, it presents many advantages such as simplicity of the manifold, robustness, and computer compatibility. A reduction in reagent and sample consumption is also observed Flow detector fouling does not occur in SIA manifolds as the detector is in contact with water between anal. The proposed SIA analyzer is able to monitor phosphate in the range 0-70 mg/L with a standard deviation of 0.9%. The detection limit is 0.5 mg/L PO43-.
Phosphate Spectrophotometry Sequential injection Automation

"Determination Of Organic Carbon In Natural Water With Inductively Coupled Plasma Atomic-emission Spectrometry After Evaporation Of Inorganic Carbon"
Microchem. J. 1991 Volume 43, Issue 2 Pages 87-93
O. Emteryd, B. Andersson and H. Wallmark

Abstract: A continuous-flow system interfaced with an ICP-AES instrument was evaluated for use in the cited determination. The system (described with diagram) enabled the separation of inorganic from organic C and determination of the latter at 193.091 nm (cf. Van Hall et al., Anal. Chem., 1963, 35, 315). Instrumental and flow injection parameters are tabulated. Between 15 and 500 mg L-1 of organic carbon could be determined in water with a detection limit of 5 mg L-1 in the presence of 500 mg L-1 of carbonate carbon.
Carbon Spectrophotometry

"Determination Of Cadmium, Cobalt, Copper, Manganese, Nickel, Lead And Zinc By Inductively Coupled Plasma Mass Spectroscopy Or Flame Atomic Absorption Spectrometry After Online Preconcentration And Solvent Extraction By Flow Injection System"
Microchem. J. 1996 Volume 54, Issue 4 Pages 402-411
A. Bortoli a, M. Gerottoa, M. Marchioria, F. Maricontib, M. Palontaa and A. Troncona

Abstract: A flow injection manifold and sequence of operations for online separation and pre-concentration of Cd, Co, Cu, Mn, Ni, Pb and Zn are diagramatically presented. Bonded silica with octadecyl functional group C18, packed in a microcolumn of 100 µL capacity, was used to collect diethyldithiocarbamate complexes of the heavy metals in aqueous solution. The metals were complexed with a chelating agent, adsorbed on the C18 column and eluted with methanol directly in the flow injection system. The metals were then determined by GF AAS or ICP-MS (details given). Calibration graphs and detection limits are presented.
Metals Cadmium Cobalt Copper Lead Manganese Nickel Zinc Spectrophotometry Mass spectrometry Sample preparation Spectrophotometry Preconcentration Solvent extraction C18 Chelation

"Optimization Of Flow Injection Online Microcolumn Preconcentration Of Ultratrace Elements In Environmental Samples Prior To Their Spectrochemical Determination"
Microchem. J. 1996 Volume 54, Issue 4 Pages 391-401
Zs. Horv&aacute;th, A. L&aacute;sztity, K. Zih-Per&eacute;nyi and &Aacute;. L&eacute;vai

Abstract: Multi-element pre-concentration of elements in water was performed by online flow injection on an iminodiacetic acid/ethyl cellulose (IDAEC) microcolumn. The eluent was 2 M HNO3 (2.5 ml/min). The pre-concentration of the elements was modelled in the presence of complexing agents such as citrate and oxalate at high Ca, Mg and sulfate concentrations. Elements were determined by ICP-MS or AAS. The effect of the species present in the solution was studied after construction of the species distribution curves using critical, estimated and measured stability constants. The stability constants of the IDAEC chelates were determined potentiometrically, and the constants were estimated using computer programs.
Trace elements Mass spectrometry Preconcentration Optimization Ultratrace

"Flow Injection Analysis Of Mercury By Cold Vapor Atomic Fluorescence Spectrophotometry"
Anal. Lett. 1983 Volume 16, Issue 15 Pages 1187-1195
Hideyoshi Morita; Tetsuya Kimoto; Shigeru Shimomura

Abstract: The sample solution (64 µL) is injected into a stream of 0.1 M HCl and mixed with 3% of SnCl2 in 3% H2SO4. Bivalent Hg is reduced to elemental Hg, which is then introduced into a specially designed gas - liquid separation vessel. Vaporized Hg is swept into a flow-type fluorescence cell by a continuous stream of Ar, after removal of water by passage through a condenser. Mercury is excited with an electrodeless discharge lamp and fluorescence is measured at 184.9 and 253.7 nm with a solar-blind photomultiplier. The calibration graph is rectilinear for 0 to 20 ppb of Hg, and the limit of detection is 8 pg; the coefficient of variation is <1% for 1 to 20 ppb. About 35 aqueous samples can be processed in 1 h.
Mercury Fluorescence Phase separator

"Continuous-flow Determination Of Carbon Dioxide In Water By Membrane Separation-chemiluminescent Detection"
Anal. Lett. 1988 Volume 21, Issue 10 Pages 1881-1886
Aoki, T.;Ito, K.;Munemori, M.

Abstract: The continuous-flow system used is illustrated schematically. Sample solution (2.18 mL min-1) was mixed with 3 M H2SO4 (0.2 mL min-1) before passing to the separation unit, which consisted of an outer PTFE tube (50 cm x 2 mm) and an inner microporous PTFE tube (50 cm x 1 mm). A solution (0.4 mL min-1) of 1 mM luminol - 0.02 mM Co(II) in 0.1 M borate buffer (pH 9) was mixed with 20 mM H2O2 solution (0.4 mL min-1) in a reaction coil before passing to the separation unit. The CO2 liberated from sample solution by H2SO4 was absorbed in the reagent solution, which was then fed to the chemiluminescence detector. The calibration graph was rectilinear for 0.04 to 8 µg mL-1 of CO2. The coefficient of variation (n = 5) for 4 µg mL-1 of CO2 was 2.8%. Interference from other species present in water was studied.
Carbon dioxide Chemiluminescence Merging zones Interferences Teflon membrane

"Continuous-flow Determination Of Phenol With Chemically Immobilized Polyphenol Oxidase"
Anal. Lett. 1989 Volume 22, Issue 5 Pages 1145-1158
Zachariah, K.;Mottola, H.A.

Abstract: The open tubular reactor was made from Tygon tubing (20 or 60 cm x 1.3 mm), on the inner surface of which controlled-pore glass (200 to 400 mesh) was thermally embedded. The glass surface was modified by reaction with (aminophenyl)trimethoxysilane and the adsorbed aminophenyl groups were converted into diazonium groups by reaction with HNO2. Tyrosinase (I) was then attached via the diazonium groups (cf. Gosnell et al., Anal. Chem., 1986, 58, 1585). The reactor tube was coiled and used to detect phenol in water. Phenol was converted by I to 1,2-benzoquinone; in the presence of ferrocyanide (II), the quinone formed ferricyanide which was detected by absorbance mesurement at 420 nm; 10 to 40 µg mL-1 of phenol could be determined. For amperometric detection, a carbon paste electrode containing immobilized II was used; mesurement was at -0.2 V vs. Ag - AgCl. This method could determine up to 500 ng mL-1 of phenol, with a detection limit of 18 ng mL-1 for a 30-s contact time.
Phenol Spectrophotometry Electrode Open tubular reactor Controlled pore glass Immobilized enzyme

"Indirect Spectrophotometric Determination Of Fluoride In Water With With Zirconium - SPADNS [2-(4-sulfophenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonate] By Flow Injection Analysis"
Anal. Lett. 1989 Volume 22, Issue 6 Pages 1581-1599
Haj Hussein, A.T.;Al Momani, I.F.

Abstract: The APHA standard method for F- in water, based on the bleaching effect of F- on the Zr - SPADNS complex (cf. Bellack and Schouboe, Anal. Chem., 1958, 30, 2032), has been modified for use in flow injection analysis. Both the carrier stream (H2O) and the reagent solution (0.2 mM ZrOCl2 - 0.4 mM SPADNS - 0.48 M HCl) were pumped at 0.37 mL min-1, and 0.1 mL samples were injected. The (negative) signal at 590 nm was measured. The calibration graph was rectilinear for 3.5 ppm of F-, and the detection limit was 0.02 ppm. Analysis rates were 50 h-1. At 2 ppm of F-, the coefficient of variation was 1%. Interference was caused by Fe(III), Al and relatively high concentration. of SO42- and PO43-, but these effects were not likely to be serious for most natural water samples. For five such samples (0.87 to 1.54 ppm of F-), results agreed well with those obtained by an ion-selective electrode.
Fluoride Spectrophotometry Interferences Method comparison Indirect Standard method

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

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

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

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

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

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

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

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

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

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

"Ammonium Detection Using An Ion-selective Electrode Array In Flow Injection Analysis"
Electroanalysis 1994 Volume 6, Issue 1 Pages 9-16
F. J. S&aacute;ez de Viteri, Dermot Diamond *

Abstract: Due the low selectivity of the nonactin NH4+ ISE toward some common ions, especially K+, an array of ISE selective for NH4+, Na+, K+ and Ca2+ was used as the FIA detector. Preparation of the PVC-based membranes described and the FIA system is shown schematically. A Ag/AgCl flow-through electrode, through which saturated KCl was continuously pumped was used as the reference system. After conditioning the system overnight (details given), sample (50 µL) was injected and mixed with the carrier stream (1 ml/min) comprising 0.01 M Tris hydrochloride buffer of pH 7.2-7.5/0.1 µM-cation solution containing ammonium, sodium, potassium and calcium chloride solution The resulting peaks were recorded. The whole system was interfaced to a PC (details given) and the array response was modelled using the Nikolskii-Eisenmann equation and the Projection Pursuit technique. The latter method gave the best results in the activity range 0.1-10 mM. The sensor array gave improved results for NH4+ determination in aqueous samples in the activity range 0.01-10 mM compared to the use of a single NH4+ electrode.
Ammonium Electrode Electrode Electrode Electrode

"Separation Of Metal Complexes Of Ethylenediaminetetraacetic Acid In Environmental Water Samples By Ion Chromatography With UV And Potentiometric Detection"
J. Chromatogr. A 1991 Volume 558, Issue 1 Pages 181-186
W. Buchberger, P. R. Haddad* and P. W. Alexander

Abstract: An ion chromatographic method is described for the analysis of several metal complexes of ethylenediaminetetraacetic acid (EDTA) in water samples. Separations are achieved on C18 bonded silica, typically using a mobile phase comprising 1% (w/v) cetrimide-1.2 mM phosphate buffer (pH 7)-25% (v/v) acetonitrile-15% (v/v) methanol, as well as on a polymer-based anion exchanger using 2 mM phosphate buffer (pH 7) as eluent. Direct UV detection at 250 nm is employed for EDTA complexes of Fe(III), Cu(II), Pb(II) and Ni(II), whilst UV detection at 250 nm after post-column reaction with copper ions is utilized for EDTA complexes of Zn(II), Cd(II), Co(II), Pb(II), Ni(II) and Cu(II). Detection limits are in the range 1.5-4.0 ng for direct UV detection and 30-50 ng for post-column reaction detection. Indirect potentiometric detection after post-column reaction with copper ions is utilized with metallic copper as the indicator electrode, giving detection limits in the range 1.0-1.5 g. These separations are applied to the determination of metal-EDTA complexes in river water at the ppbb level and to remobilization studies of metal ions in sediment.
HPIC Electrode Potentiometry Complexation

"Normal-phase High Performance Liquid Chromatography With UV Irradiation, Morin Complexation And Fluorescence Detection For The Determination Of Organotin Pesticides"
J. Chromatogr. A 1992 Volume 609, Issue 1-2 Pages 195-203
Joan A. St&auml;b, Marcel J. M. Rozing, Bert van Hattum and Wim P. Cofino, and Udo A. Th. Brinkman

Abstract: Surface waters were extracted with n-hexane, while soil and sediments were Soxhlet-extracted for 12 h with hexane - acetone (9:1). The extracts were analyzed on a column (15 cm x 4.6 mm) of cyanopropyl-bonded silica (3 µm) with n-hexane - THF - acetic acid (48:1:1) as mobile phase (1 mL min-1). Post-column derivatization was effected by UV irradiation followed by reaction with ethanolic 0.0025% morin (0.15 mL min-1) in a reaction coil and fluorimetric detection at 495 nm (excitation at 430 nm). The detection limits were 0.02 to 0.03 µg L-1 in water and 0.2 to 0.3 µg g-1 in solids. The mean recoveries from water were between 61 and 114% and from the solids between 44 and 135% for three such compounds.
Tin, organic HPLC Fluorescence Sample preparation Post-column derivatization Complexation

"Low-pressure Ion Chromatography"
J. Chromatogr. A 1994 Volume 671, Issue 1-2 Pages 23-28
Xinshen Zhang* and Xiaoping Jiang

Abstract: Two types of instrument, a low-pressure fast analysis ion chromatograph and a low-pressure transition metal ion chromatograph, were used with conductivity and optical detectors, respectively, in the analysis of a variety of ions. Both systems were operated at 30-40 psi using 30 mm long columns packed with spherical particles of ion exchanger. The conditions are described for the determination of alkali metals and NH4+, alkaline earth metals, inorganic anions and organic acids using conductivity detection and transition metals using post-column derivatization with a chromogenic reagent and optical detection. An improved conductivity cell is described which has an electrode at the solution entry end for high sensitivity. The detection limit for each ion was generally 10-9 g/ml. The technique was applied to the analysis of acid rain and Chinese medicines and the determination of Na+, K+ and chloride in blood and Fe2+, Zn2+ and Mn2+ in oilfield water.
Metals, alkali Metals, alkaline earth Metals, transition Ammonium Anions, inorganic Acids, organic HPIC Chromogenic reagent

"High Performance Liquid Chromatographic Method For The Analysis Of Aminocarb, Mexacarbate And Some Of Their N-methylcarbamate Metabolites By Post-column Derivatization With Fluorescence Detection"
J. Chromatogr. A 1994 Volume 672, Issue 1-2 Pages 117-124
K. M. S. Sundaram* and J. Curry

Abstract: Water and soil were extracted with CH2Cl2 and ethyl acetate, respectively, the extracts were dried with Na2SO4, flash evaporated at 30°C, the residue was dissolved in acetonitrile and partitioned twice with hexane. The polar layer was flash evaporated, dissolved in ethyl acetate, concentrated under N2 and cleaned up on alumina with elution by ethyl acetate containing 0 and 10% methanol. After evaporation to dryness, the residue was dissolved in acetonitrile for analysis by HPLC on a column (20 cm x 4.6 mm i.d.) of HP RP-8 OS (10 µm) at 30°C with a guard column (3 cm x 4.6 mm i.d.) of HP RP-8 (10 µm), a gradient mobile phase (1 ml/min) of aqueous 0-30% acetonitrile over 25 min, then to 50% (held for 10 min) over 10 min, post-column derivatization by hydrolysis with 50 mM NaOH in a 1 mL reaction coil at 95°C, reaction with o-phthalaldehyde/2-mercaptoethanol in a 0.5 mL reaction coil at 40°C and fluorimetric detection at 418 nm (excitation at 230 nm). Calibration graphs were linear for 0.1 (detection limit) to 500 ng of aminocarb, mexacarbate and four carbamate metabolites; recoveries from water (2 and 20 ng/ml) and soil (20 and 200 ppb) were 72±7.9% to 98.4±5.2% with RSD of 5-11.5%.
Aminocarb Mexacarbate Carbamates, N-methyl HPLC Fluorescence Post-column derivatization Heated reaction

"Application Of An Automated Quasi-continuous Immuno Flow Injection System To The Analysis Of Pesticide Residues In Environmental Water Samples"
Sens. Actuat. B 1993 Volume 15, Issue 1-3 Pages 119-126
Christine Wittmann and Rolf D. Schmid

Abstract: The cited FIA system (diagram of manifold presented) was used to determine trace atrazine, the results being compared with those obtained by enzyme immunoassay, GC and HPLC. The atrazine derivative 6-~[4-chloro-6-(isopropylamino)-1,3,5-triazin-2-yl]amino~hexanoic acid was conjugated to BSA and used to raise antibodies in rabbits, and was also coupled to peroxidase for use as tracer. The usable range for atrazine was 30 ng/l-1 µg/l, the mid-point of which (100 ng/l) corresponded to the maximum concentration permitted by EC guidelines for drinking water. RSD were 3-20% for the cited technique as compared with 2-10% for enzyme immunoassay. The cited technique does not require concentration or clean up steps.
Pesticides Atrazine Immunoassay Automation Method comparison

"Nitrate Sensor System For Continuous-flow Monitoring"
Sens. Actuat. B 1994 Volume 19, Issue 1-3 Pages 362-364
Otto Wassmus and Karl Cammann

Abstract: An 80 µm thick PVC-nitrate selective membrane, (cf. J. Sander, Thesis, University of Munster, 1991) was mounted on a Polyamid miniaturized body with a Ag tube internal reference covered with AgCl. The electrode was mounted within a purpose-constructed perspex flow-cell, together with a Ag/AgCl external reference electrode filled with AgCl saturated 3 M KCl. Both the working and reference electrodes were arranged perpendicular to the flow-through channel, of volume 20 µL. Calibration graphs of standard nitrate pumped through the cell at about 0.2 ml/min were linear for 0.01-10 mM nitrate with a detection limit of 3.6 µM. Higher chloride concentrations interfered with the sensor performance; interference from sulfate was negligible. The sensor system was used for environmental monitoring of ground water and water plants. Sensor lifetime was better than 6 months.
Nitrate Electrode Electrode Sensor Interferences

"Aqueous Ozone Detector Using Indium(II) Oxide Thin-film Semiconductor Gas Sensor"
Sens. Actuat. B 1995 Volume 25, Issue 1-3 Pages 548-551
Tadashi Takada, Hiromasa Tanjou, Tatsuo Saito and Kenji Harada

Abstract: Aqueous samples were introduced continuously into an extraction vessel and the sample was bubbled with air at 30 cm/min to extract ozone (the carrier air had been passed through an activated charcoal column). The carrier air plus ozone was mixed with a stream of dry air (30 cm/min) which had passed through a silica gel column and the mixed air was monitored for ozone using an In2O3 thin-film semiconductor gas sensor. The calibration graph for ozone obtained at 18°C is shown; down to 0.5 ppb aqueous ozone could be detected due to a high extraction rate. Little interference from aqueous Cl2 was found due to the selectivity of the sensor and the 10-fold higher extraction rate of ozone compared to HClO. No RSD are given. The method was affected slightly by changes in water temperature over 0-40°C and temperature correction was applied.
Ozone Sensor Gas phase detection Optimization Interferences

"Flow Injection Method For The Rapid Determination Of Chemical Oxygen Demand Based On Microwave Digestion And Chromium Speciation In Flame Atomic Absorption Spectrometry"
Spectrochim. Acta B 1996 Volume 51, Issue 14 Pages 1791-1800
A. Cuesta, J. L. Todoli* and A Canals

Abstract: In the manifold illustrated, the water sample is mixed with a K2Cr2O7/H2SO4/ HgSO4/Ag2SO4 reagent prep. described and a 10^-240 µL portion is injected into a stream of water, which carries it through a microwave oven. The residual Cr(VI) is retained on an anion-exchange resin column and subsequently eluted for determination by flame AAS. COD values of 25-5000 mg/l can be measured, and the detection limit is ~7 mg/l. Fifty determinations can be performed per h. There is no matrix effect.
Chemical oxygen demand Spectrophotometry Microwave Speciation Interferences Online digestion

"Evaluation Of Electrochemical Hydride Generation For The Determination Of Arsenic And Selenium In Seawater By Graphite-furnace Atomic Absorption With In-situ Concentration"
Spectrochim. Acta B 1996 Volume 51, Issue 11 Pages 1325-1334
W. -W. Ding and R. E. Sturgeon*

Abstract: A continuous-flow electrochemical hydride generation technique coupled with in situ concentration in a graphite furnace has been developed for determination of As and Se in seawater. Lead is used as cathode material for the production of arsine and hydrogen selenide. The efficiency of generation of arsine from As(III) is 86±6%, that from As(V) ranges from 73% to 86%. The efficiency of generation of hydrogen selenide from Se(IV) is 60±5% and from Se(VI) is 30±5%. The hydrides are trapped in an iridium-palladium coated graphite furnace prior to atomization. Absolute detection limits and concentration detection limits of 84 pg (3s(blank)) and 84 pg mL-1 for determination of As using 1 mL sample volume and 75 pg (3s(blank)) and 7.5 pg mL-1 for determination of Se using 10 mL sample volumes are obtained, respectively. The precision of replicate measurement for the analysis of reference materials at the 1.3 µg L-1 level for As(III) (0.8 ng absolute mass level) and at the 0.042 µg L-1 level for Se(IV) (0.42 ng absolute mass level) is better than 4% and 23% (relative standard deviation, RSD), respectively. The RSD values quoted above for Se include errors introduced by the sample preparation procedure.
Arsenic Selenium Spectrophotometry Reference material Electrochemical product conversion Preconcentration

"Catalytic Determination Of Nanogram Amounts Of Vanadium In Natural Water By Flow Injection Analysis"
Anal. Sci. 1989 Volume 5, Issue 1 Pages 69-72
S. NAKANO, M. TAGO and T. KAWASHIMA

Abstract: A 0.2 mL sample was injected into a carrier stream (0.8 mL min-1), which was then mixed with streams (0.8 mL min-1) of (i) 4 mM 4-aminoantipyrine, 30 mM NN-dimethylaniline and 0.1 M Tiron, (ii) 0.08 M BrO3-, and (iii) 0.15 M formate buffer in a coil (10 m x 0.5 mm) at 55°C. The absorbance was measured at 555 nm. The calibration graph was rectilinear for 0.05 to 2 ng mL-1 of VV; the detection limit was 20 pg mL-1. Coefficients of variation for 1 and 2 ng mL-1 were 0.8 and 0.5% (n = 10), respectively.
Vanadium(V) Spectrophotometry Buffer Heated reaction Tiron

"Lophine Chemiluminescence For Determination Of Chromium(VI) By Continuous-flow Method"
Anal. Sci. 1989 Volume 5, Issue 4 Pages 429-433
T. KAMIDATE, K. YAMAGUCHI, T. SEGAWA and H. WATANABE

Abstract: Quantitative recovery of Cr(VI) was achieved by passage (10 mL min-1) of the aqueous sample (25 ml) through a column (20 cm x 7 mm) of activated alumina. The column was washed with 0.01 M HNO3 to remove other metal ions, then 0.2 M KOH (10 ml) was used to elute Cr(VI). The eluate was mixed with 0.02 M HNO3 and 0.3 M H2O2 in a continuous-flow analyzer. and the resulting solution was treated with methanolic 1 mM lophine and 0.3 M KOH in a chemiluminescence detection cell. The calibration graph (log. - log. plot) was rectilinear from the detection limit of 0.02 to 30 µg mL-1 of Cr(VI). The method was used to determine Cr(VI) in water.
Chromium(VI) Chemiluminescence Column Interferences Activated alumina Detection limit Method comparison

"Flow Injection Spectrophotometric Determination Of Trace Amounts Of Iodide By Its Catalytic Effect On The 4,4'-bis(dimethylamino)diphenylmethane [4,4'-methylenebis-(NN-dimethylaniline)] - Chloramine T Reaction"
Anal. Sci. 1991 Volume 7, Issue 2 Pages 229-234
N. YONEHARA, S. KOZONO and H. SAKAMOTO

Abstract: Sample solution (300 µL) was injected into a water carrier stream (3 mL min-1) and this was mixed successively with acetate buffer solution (pH 4.5), 1.2 mM 4,4'-methylenebis-(NN-dimethylaniline) in aqueous 0.23% acetic acid, and 0.75 mM chloramine T (all 0.5 mL min-1). The reaction mixture was passed through a 4-m reaction coil at 30°C and then through a flow cell in which the absorbance was monitored at 600 nm. Calibration graphs were rectilinear for up to 2 µg L-1 of I-; the coefficient of variation at 0.4 and 4 µg L-1 were 2.8 and 0.8%, respectively (n = 10). The sampling rate was 85 h-1. Free iodine exhibits a lower catalytic effect, and IO3- has no effect at concentration. 50 µg L-1 (as iodine), but both species can be determined after reduction to I- by treatment with thioacetamide in acid solution The effects of >30 foreign ions are reported. Only ions that participate in redox processes or combine with I- interfere significantly. The method has been applied to various natural waters.
Iodide Spectrophotometry Buffer Catalysis Heated reaction Interferences

"Spectrophotometric Determination Of Nitrite Based On Its Catalytic Effect On The Oxidation Of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic Acid)"
Anal. Sci. 1991 Volume 7, Issue 5 Pages 793-797
T. OKUTANI, A. SAKURAGAWA, S. KAMIKURA, M. SHIMURA and S. AZUCHl

Abstract: Sample solution was mixed with 4 M HClO4 at 25°C, the cited reagent was added and, after 30 min the absorbance of the mixture was measured at 415 nm vs. water. By employing a calibration curve obtained under identical conditions the concentration. of nitrite could be determined. The analysis was also carred out by a flow injection method (details given). Down to 10 ppb of nitrite could be determined by both methods. Severe interference from oxidizing cations could be eliminated by the introduction of an ammonium form cation-exchange resin. By using the batchwise method the coefficient of variation (n = 10) was 1.2% for 100 ppb of nitrite. The method was applied in the determination of nitrite in natural water.
Nitrite Spectrophotometry Catalysis Interferences PPB Resin

"Primaquine Phosphate As A Promising Substitute For N-(1-naphthyl)ethylenediamine. 1. Determination Of Nitrate In Natural Waters In Egypt"
Anal. Sci. 1992 Volume 8, Issue 1 Pages 71-75
M. E-S. METWALLY and F. F. BELAL

Abstract: A sensitive, selective and rapid colorimetric method was developed for the determination of nitrate in natural water samples, based on coupling primaquine phosphate (PP) with diazotized p-nitroaniline (PNA) or with diazotized p-aminobenzophenone (PABP) in acid medium. The orange color produced with both amines was stable for more than 24 h, and had an absorption maximum at 484 nm, and 482 for PNA and PABP, respectively. The calibration graph was linear in the concentration range of 0.025-1.25 ppm of nitrate, with a minimum detection limit of 0.015 ppm. The molar adsorptivities were 8 x 104 mol-1 cm-1 and 7.11 x 104 mol-1 cm-1 for PNA and PABP, respectively. Heavy metals did not interfere and the interference from reducing anions was eliminated by precipitation as insoluble lead salts. The excess lead ions did not interfere. Because PP is less liable to self-diazotization-coupling reaction than N-(1 naphthyl)ethylenediamine, the method could be adopted for automated flow injection analysis of nitrate. The coupling agent used is safe; a promising substitute for the Bratton-Marshal reagent which was reported to be carcinogenic.
Nitrate Spectrophotometry Interferences

"Sensitive Determination Of Boric Acid By Online Complexation/anion-exchange Chromatography With H-resorcinol"
Anal. Sci. 1992 Volume 8, Issue 5 Pages 719-722
J. ZOU, S. MOTOMIZU, M. OSHIMA and H. FUKUTOMI

Abstract: A rapid and sensitive anion-exchange HPLC method for determining boric acid is based on post-column online complexation with H-resorcinol and spectrophotometric detection. The calibration curve was linear up to 2 x 10^-5 M boric acid. The method was applied to determine boric acid in water.
Boric acid HPIC Complexation Post-column derivatization

"A Flow Injection System For Spectrophotometric Catalytic Determination Of Copper In Plant Digests And Natural Waters"
Anal. Sci. 1998 Volume 14, Issue 3 Pages 565-569
Fabiana C. CAMARGO), Elias A. G. ZAGATTO) and Claudio C. OLIVEIRA

Abstract: The Cu(II)-catalyzed oxidation of 2,6-dichlorophenolindophenol (DCPI) in the reduced form by hydrogen peroxide was exploited for the development of a flow injection procedure for Cu determination in plant digests and natural waters. For selectivity enhancement, a Chelex-100 resin mini-column (50 - 100 mesh) was incorporated to the manifold. The proposed system is very stable, handles about 60 samples/h, yields precise results (RSD<2% within 5.0 and 70.0 µg/L Cu) and requires only 0.87 mg DCPI/measurement. Beer's law is followed up to about 100 µg/L Cu and the detection limit is 0.09 µg/L Cu (in the injectate). Baseline drift was not observed during extended (5 h) operation periods. Results were in agreement with certified values of standard reference materials and recoveries within 95 and 104% were found.
Copper Spectrophotometry Catalysis Chelex Reference material Column

"Flow Injection Analysis Of C-fuel Oil-contaminated Samples Based On The Fluorescence Detection Of Polycyclic Aromatic Hydrocarbons"
Anal. Sci. 1998 Volume 14, Issue 4 Pages 845-847
Akiko UTSUMI, Atsuko NAKASHIMA, Kyoko ANDO, Ryoichi KIZU and Kazuichi HAYAKAWA

Abstract: On Jan. 2, 1997, >6,000 kL of C-fuel, a fuel oil, was spilled in the Sea of Japan and drifted toward 8 Prefectural sea coasts from Shimane to Yamagata. Polycyclic arom. hydrocarbons were determined in the spilled oil, sea sand, and water using HPLC equipped with a fluorescence detector. Although the HPLC method was accurate and quant., it takes too much time for rapid anal. of many oil-polluted environmental samples. Thus, a flow injection analysis method was used as a rapid screening test of C-fuel oil pollution. Results using this method to analyze sea sand polluted with oil from this spill are also reported.
Polycyclic aromatic hydrocarbons Fluorescence

"Studies On The Determination Of Sulfide Using N,N-diethyl-p-phenylenediamine"
Anal. Proc. 1983 Volume 20, Issue 12 Pages 609-622
M. O. Babiker, J. A. W. Dalziel, B. Law, J. R. Joyce, T. S. Bal, C. P. Goddard, M. Japp, I. J. Humphreys, P. J. Hobbs, P. Jones, L. Ebdon, S. J. Lyle, N. Za'tar, M. G. Batham and C. F. Simpson

Abstract: Two techniques, i.e., continuous-flow analysis with air segmentation (Carlo Erba model 1510) and flow injection analysis (Tecator FIAstar model 5001), for automating the determination (cf. Kloster and King, J. - Am. Water Works Assoc., 1977, 69, 544) are outlined. A suitable medium for stabilization of the colloidal suspension of ZnS is described. Results obtained by the flow injection method are slightly better with respect to speed (180 samples h-1) and detection limit (10 µg L-1 of S2-), but have slightly lower precision than those obtained by the segmentation technique. The method is intended for use in analysis of natural and waste waters.
Sulfide Spectrophotometry Tecator

"A Semi-continuous Flow Method For The Trace Analysis Of Dissolved Inorganic Antimony"
Anal. Proc. 1989 Volume 26, Issue 1 Pages 32-34
A. T. Campbell and A. G. Howard

Abstract: A 5 mL sample is mixed with 0.5 mL of 1 M KI pre-reductant, and masking agents (if required), and placed in the continuous-flow system (details and diagram given). The solution is acidifed with HCl for determination of total Sb, or mixed with acetate buffer of pH 5.0 for determination of Sb(III), segmented with air, and treated with aqueous 2% NaBH4; the products are swept through a delay coil and stripped from solution in a gas - liquid separator. Stibine is condensed in a cryogenic trap at -196°C, liquid N is then removed and the trap is warmed to room temp., before atomization of stibine and AAS detection at 217.6 nm. Calibration graphs are rectilinear for up to 3 ng of Sb(III) or total Sb, with a detection limit of 24 ng L-1 of total Sb (for a 5 mL sample). Interfering ions are tabulated. The method is applied in determination of total Sb in natural water.
Antimony(3+) Antimony, total Spectrophotometry Buffer Calibration Detection limit Interferences Phase separator Cold trap

"Reduction Of Interference Effects In Flame Atomic Absorption Spectrometry Using Flow Injection Techniques"
Anal. Proc. 1989 Volume 26, Issue 2 Pages 58-61
C. E. Adeeyinwo, J. F. Tyson

Abstract: The determination of Ca in the presence of Al was achieved by precipitation of Ca oxalate in a specially designed manifold (details given). The sample was injected into a carrier stream of H20 that was mixed with the reagent stream, viz, aqueous 0.05 M NH3 containing 50 mg L-1 of ammonium oxalate monohydrate; after 5 min a stream of 5% HCl was used to dissolve the ppt. Calcium was determined by AAS at 422.7 nm in an air - acetylene flame. The detection limit was 0.25 mg L-1 of Ca, which is comparable with that of conventional nebulization. The method was applied in the analysis of cement and water.
Calcium Spectrophotometry Precipitation Filter Manifold comparison Interferences

"Spectrophotometric Flow Injection Techniques For Process Monitoring"
Anal. Proc. 1989 Volume 26, Issue 11 Pages 385-387
Richard L. Benson, Paul J. Worsfold, Frank W. Sweeting

Abstract: The robust, low-cost analyzer. described for automated water quality monitoring (described) incorporates a solid-state double-beam photometer with both sample and reference flow cells constructed from the same PTFE tubing (diameter 0.8 mm), as used in the rest of the flow manifold. Maximum sensitivity is achieved in the visible and near-IR regions; the red and green bands (635 and 565 nm, respectively) of the light-emitting diode sources are those most commonly used. A sampling unit and data transmission facilities are also included, as well as a supply of reagents for two week's unattended operation. The monitor was field-tested for the determination of NO3- by reduction (by copperized Cd) to NO2- and conventional azo-dye formation. The rectilinear range was 1.5 to 12.0 mg L-1 of nitrate-N, and the precis
Nitrate Spectrophotometry Automation Reduction column Dual detection Precision Light emitting diode Process monitoring Low cost

"Simultaneous Determination Of Hydride And Non-hydride Forming Elements By Inductively Coupled Plasma Atomic-emission Spectrometry"
Anal. Proc. 1992 Volume 29, Issue 10 Pages 438-439
Zhang Li, Susan McIntosh and Walter Slavin

Abstract: Arsenic, Se, Sb, Bi, Cd, Cr, Cu, Fe, Mn, Ni and Pb were determined in the NIST environmental standard reference materials steel, coal fly ash, urban particulated and 1643b water by ICP-AES. A Perkin-Elmer FIAS-2000 flow injection system was used for hydride generation (experimental conditions tabulated). The sample solution was split into two streams, one being pumped directly to the nebulizer, the other mixed with HCl and NaBH4 solution in the mixing tubes of the chemifold. After separation, the hydride was swept into the spray chamber through a slightly modified cross-flow nebulizer cap. The hydride was then carried into the plasma together with sample aerosol. Recoveries of 20 µg L-1 of As, Sb and Se and 50 µg L-1 of non-hydride forming elements in river- and seawater standards were >80%.
Arsenic Selenium Antimony Bismuth Cadmium Chromium Copper Iron Manganese Nickel Lead Spectrophotometry Spectrophotometry Reference material FIAS-200 Nebulizer Volatile generation Volatile generation

"Detection Of Chlorine Species In Water By Chemiluminescence With Electrochemical Analyte Modification"
Anal. Proc. 1994 Volume 31, Issue 3 Pages 91-93
Gordon P. Irons and Gillian M. Greenway

Abstract: Water (140 µL) containing hypochlorite was injected into a carrier stream (2 ml/min) of phosphate buffer of pH 8.7 and merged with a stream of 2 mM Rhodamine 6 G in 10% Tween 60 solution A modified system using 5% Tween 40 as surfactant was used to calculate a standard curve allowing the determination of free chlorine at pH 6.7 in phosphate buffer and the elimination of background effects caused by the viscosity and insolubility of cold Tween 60. The streams were merged at a T-piece within a light-tight housing before being fed into the flow cell (diagram of flow manifold given). The calibration graph was linear from 1.6-4 mg/l of free Cl2 with a detection limit of 0.5 mg/l. The bound Cl2 in water was detected by electrochemical conversion to free Cl2 at a Pb electrode followed by chemiluminescence. Principal-components analysis was used for the identification of Cl2-containing species. No interference was observed.
Chlorine Chemiluminescence Electrode Interferences Viscosity

"Stopped-flow Thin-layer-coulometric Method For The Determination Of Disinfectants In Water"
Anal. Proc. 1995 Volume 32, Issue 1 Pages 13-15
Stephen Dennison and David M. Bonnick

Abstract: A coulometric technique, using a thin layer electrochemical cell and stopped-flow sampling to minimize interference from non-faradaic contributions to the signal, has been developed and applied to the analysis of oxidants employed in water treatment. It is shown that the coulombic efficiency of the method is very close to 100%, resulting in a linear relationship between charge and analyte concentration.
Disinfectants Coulometry Stopped-flow

"Chemiluminescence Analysis With Reversed Flow Injection Analysis: Studies On ABEI-H2O2-Co(II) Chemiluminescence System And Its Application"
Acta Chim. Sin. 1991 Volume 49, Issue 9 Pages 906-911
LI GUANGHAO;YU ZHENAN

Abstract: A new method has been recommended for the determination of trace amounts Co(II) by reversed flow injection analysis. The optimum reaction conditions of ABEI-H202-Co(II) chemiluminescence system were studied by modified simplex method. The mechanism of this chemiluminescence reaction was studied in detail and a possible reaction mechanism was presented. The selectivity of this chemiluminescence reaction was increased by selecting a proper masking agent. On the basis of above research a chemiluminescence method for the determination of trace amounts Co(II) in natural water has been developed. The detection limit of this method is 1.0 x 10^-11 g mL-1. The linear range is from 5 x 10^-11 to 1 x 10^-7 g mL-1. Recovery is 98-102%. The analysis rate is 100 samples per hour.
Cobalt(II) Hydrogen peroxide Chemiluminescence Catalysis Reverse

"Use Of Segmented Micro-continuous-flow Analysis And FIA In Water Analysis"
Am. Environ. Lab. 1989 Volume 1, Issue 2 Pages 60-63
Straka, M.R.

Abstract: The complementary nature of the methodologies of macrosegmented and microsegmented continuous-flow and nonsegmented FIA is discussed. The relative advantages and disadvantages are highlighted and general guidelines for selection of one technique over another are suggested.
Method comparison Alpkem Review Apparatus

"Optimizing Mercury Determinations"
Am. Lab. 1994 Volume 26, Issue 3 Pages 18-22
Schneider, C.A.;Schulze, H.;Baasner, J.;McIntosh, S.A.;Hanna, C.P.

Abstract: An overview is given of a dedicated system, the flow injection mercury system (FIMS; Perkin-Elmer Corp. Norwalk, CT, USA), which uses an EPA-approved flow injection technique with a built-in atomic absorption spectrometer. The system is capable of a high sample throughput, requiring 30 s for each determination, with detection limits of 0.01 µg of Hg. The software used is based on Microsoft Windows and permits up to 15 quality control check samples which can be used in different sequences. In addition, the system also has an online HELP function. A list of sample types and the precision of the system are tabulated.
Mercury Spectrophotometry

"Pulsed Flow Chemistry. A New Approach To The Generation Of Concentration Profiles In Flow Analysis"
Anal. Commun. 1998 Volume 35, Issue 3 Pages 97-101
Xue D. Wang, Terence J. Cardwell, Robert W. Cattrall and Graeme E. Jenkins

Abstract: Pulsed flow chemical (PFC) is described as a new approach to automated online anal. chemical In contrast to existing flow-based anal. chemical methods, PFC is characterized by pulsed flow, turbulent mixing and low axial dispersion. The PFC system is fully computerized and all operations are under software control. Consequently, most flow analysis methods (e.g., flow injection, continuous-flow, flow titration, etc.) can be selected with a simple click of the mouse. The system is easily miniaturized and portable which makes it particularly suited to field instrumentation. The system has been tested using several flow-based techniques including online titration for the determination of calcium in waters with potentiometric detection and a calcium ion sensor.
Calcium Potentiometry Gradient technique Axial dispersion Turbulent flow Pulsed flow Titrations

"A Tungsten Oxide Coated Wire Electrode Used As A PH Sensor In Flow Injection Potentiometry"
Anal. Commun. 1998 Volume 35, Issue 12 Pages 395-398
Lucy T. Dimitrakopoulos, Telis Dimitrakopoulos, Peter W. Alexander, Dusan Logic and D. Brynn Hibbert

Abstract: A W oxide wire electrode is described for use as a pH electrode in a portable battery-powered flow injection analyzer described previously. The W oxide electrode exhibits a linear response of 44.8 ± 0.5 mV change per pH unit over a wide range, pH 2-11 in the steady-state mode. In the flow injection mode, the W oxide wire electrode exhibited a slope of 42.4 ± 0.9 mV per pH unit. The W oxide electrode was employed to determine the pH of various alcohol beverages and environmental water samples.
pH Potentiometry Electrode Apparatus Detector Remote instrument

"Comparison Of Flow Injection Methods For Nitrate Analysis In Aqueous Environmental Samples"
Anal. Methods Instrum. 1995 Volume 2, Issue 6 Pages 330-336
A.Cerd&agrave;, M.T.Oms, V.Cerd&agrave;, R.Forteza

Abstract: Reduction of nitrate to nitrite was carried out by means of a Cd-Cu column, by hydrazine, or by photochemical reduction. The chromogenic reagent was 0.5 g/l N-(1-naphthyl)ethylenediamine hydrochloride, 20 g/l sulfanilamide and 50 mL concentrated HCl. Nitrites were detected at 540 nm using a diode array detector. Liquids were pumped with Gilson peristaltic pumps and tubing was of PTFE (0.5 mm i.d.). The UV light source was a 15 W Hg lamp. With the Cd-Cu column, calibration was linear in the range 6-250 µM-nitrate and 2-250 µM-nitrite and detection limits were 0.5 µM-nitrate and 0.2 µM-nitrite. There was no interference from 200 ppm chromate, sulfate and carbonate, 100 ppm Ca(II), Fe(II), NI(II) and Cu(II) and 40 ppm Mg(II) and Zn(II). With hydrazine reduction, detection limits were 0.01 µM and 0.05 µM for nitrite and nitrate, respectively, with response linear up to 300 µM and 200 µM, respectively. With photochemical reduction, calibration graphs were linear in the range 1-300 µM-nitrate, and 1-400 µM (with UV radiation) and 1-200 µM (without UV radiation) for nitrite. The detection limit for nitrate was 0.12 µM.
Nitrate Spectrophotometry Reduction column Interferences Method comparison Photochemistry Chromogenic reagent

"Determination Of Boron In Plants, Soils And Waters By Flow Injection Analysis"
Analusis 1988 Volume 16, Issue 9-10 Pages 196-200
Lopez Garcia, I.;Sanchez Pedreno, C.;Hernandez Cordoba, M.;Garcia Lorente, A.

Abstract: The method described earlier (cf. Anal. Abstr., 1986, 48, 6D31), involving spectrophotometry of the ion-pair complex between crystal violet (C. I. Basic Violet 3) and the anionic B - 2,6-dihydroxybenzoic acid complex without extraction, has been adapted for flow injection analysis, both conventional, with measurement at 490 nm, and in reverse mode, with injection of the dye reagent into a stream of the anionic complex solution and measurement at 590 nm. The rectilinear ranges of the respective methods are 0.02 to 0.5 and 0.05 to 0.5 µg mL-1 of B. Plant samples are mixed with Ca(OH)2 and dry-ashed, the ash is extracted with 0.5 M H2SO4 and the solution is neutralized before analysis. Soil is extracted with water at 80°C. Water is adjusted to pH 2 to 3 with H2SO4 on collection. Tolerance levels for a range of foreign ions are tabulated.
Boron Sample preparation Spectrophotometry Complexation Interferences Reverse

"Fluorimetric Determination Of Nitrate And Nitrite"
Analusis 1995 Volume 23, Issue 7 Pages 312-319
ML Viriot, B Mahieuxe, MC Carre, JC Andre

Abstract: Fluorimetric determination of nitrate and nitrite in the last 20 years is reviewed. First, the necessity of nitrate and nitrite analysis is recalled. Second, the fluorimetric available methods are described, especially with normalization of the units for the reported data (mg/l and M (mol/l)); the major results are summarized in two tables (I and II) and in order to allow a comparison, the methods are listed according to their detection limit (tables III and IV), which is also related to the fluorescence emission wavelength through two graphs (figs 1 and 2). Third, in a critical discussion, the reported methods are briefly evaluated(chronological classification; tables V and VI). Fluorescence use as chromatographic detection for nitrate and nitrite is only mentioned. (49 references)