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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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Iron(III)

  • IUPAC Name: iron(3+)
  • Molecular Formula: Fe3+
  • CAS Registry Number: 20074-52-6
  • InChI: InChI=1S/Fe/q+3
  • InChI Key: VTLYFUHAOXGGBS-UHFFFAOYSA-N

@ ChemSpider@ NIST@ PubChem

Citations 100

"Simultaneous Preconcentration And Speciation Of Iron(II) And Iron(III) In Water Samples By 2-mercaptobenzimidazole-silica Gel Sorbent And Flow Injection Analysis System"
Anal. Chim. Acta 2000 Volume 424, Issue 2 Pages 233-242
H. Bagheri, A. Gholami and A. Najafi

Abstract: 2-Mercaptobenzimidazole, loaded on silica gel (MBI-SG) was used for pre-concentration and speciation of iron(II) and iron(III) in water samples. The speciation is based upon selective retention of iron(III) on MBI-SG sorbent and quantitatively passing iron(II) ions. This type of sorbent was not only capable of separating theses two ions but also could concentrate them. The adsorbed iron(III) on MBI-SG was desorbed from the column by an SCN- solution and transferred to the detection device. The effluent, then, was treated with hydrogen peroxide to oxidize iron(II) into iron(III) and subsequently was pumped through the MBI-SG column. A home-made flow injection system was coupled with a UV-VIS and an atomic absorption spectrometer, simultaneously. This method was applied to four different water samples and sub-ppb detection limit, high accuracy (>99% recovery), good precision (RSD < 5%), and good potential for automation were observed.
Sea Spectrophotometry Spectrophotometry Immobilized reagent Preconcentration Silica gel Speciation Complexation

"A Robust Multisyringe System For Process Flow Analysis Part II. A Multi-commuted Injection System Applied To The Photometric Determination Of Free Acidity And Iron(III) In Metallurgical Solutions"
Analyst 2000 Volume 125, Issue 12 Pages 2364-2371
Fernando Albert&uacute;s, Andreu Cladera and Victor Cerda

Abstract: A new software-controlled volume-based system for sample introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one or two additional commutation valves, the multi-commuted injection of precise sample volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Three configurations were implemented in order to achieve two different tasks: the single injection of a sample in a two- or three-channels manifold, and the dual injection into different streams. The two channel flow system using the single injection was applied to the determination of free acidity in diluted samples containing high levels of iron(iii), by employing the single point titration methodology. The precipitation of ferric hydroxide was prevented using the ammonium and sodium salts of oxalate and acetate as buffer titrant. Methyl Red was employed as indicator. The procedure allows determination of acid concentration in solutions with a Fe(iii)/H+ molar ratio up to 0.2. Samples with higher Fe(iii)/H+ molar ratios were spiked with a known strong acid at dilution. The three-channel configuration was applied to the determination of ferric ions, using, as reagent, a merging mixture of sulfuric acid and potassium thiocyanate. The double injection system was implemented in series in a single (three-channel) manifold in such a way that a different injection volume and a changed reagent were used for each analyte. It was applied to the separated or sequential determination of free acidity and ferric ions. In this configuration, iron(iii) was determined using 0.5-0.7% (w/v) sodium salicylate solution as reagent. The systems can operate at up to 100, 84 and 78 injections per hour, respectively. Determinations on synthetic and process samples compared well with the reference values and procedures. Recoveries of 95-102% with a maximum RSD value of 5.4% were found for acidity. The respective values obtained for iron determinations were 96-105% and 4.3%.
Industrial Spectrophotometry Multicommutation Multisyringe Computer Titrations

"Simultaneous Quantitative Analysis Of Overlapping Spectrophotometric Signals Using Wavelet Multiresolution Analysis And Partial Least Squares"
Talanta 2000 Volume 50, Issue 6 Pages 1163-1173
Shouxin Ren and Ling Gao

Abstract: The mathematical bases and program algorithms of discrete wavelet transform (DWT), multiresolution and Mallats pyramid algorithm were described. The multiresolution analysis (MRA) based on Daubechies orthogonal wavelet basis was studied as a tool for removing noise and irrelevant information from spectrophotometric spectra. After wavelet MRA pre-treatment, eight error functions were calculated for deducing the number of factors. A partial least squares based on wavelet MRA (WPLS) method was developed to perform simultaneous spectrophotometric determination of Fe(II) and Fe(III) with overlapping peaks. Data reduction was performed using wavelet MRA and principal component analysis (PCA) algorithm. Two programs, SPWMRA and SPWPLS, were designed to perform wavelet MRA and simultaneous multicomponent determination. Experimental results showed the WPLS method to be successful even where there was severe overlap of spectra.
Water Spectrophotometry Partial least squares Wavelet transform Speciation

"Preliminary Studies Of Iron Speciation (Fe2+ And Fe3+) In Peat Samples Using Polarography"
Anal. Sci. 2000 Volume 16, Issue 7 Pages 751-756
Paavo Per&auml;m&auml;ki, Mia Kumpum&auml;ki, Ilkka V&auml;lim&auml;ki, Ritva Heikknen

Abstract: Current-sampled (tast) polarography was used in the determination of the two iron oxidation states Fe2+ and Fe3+ in peat samples. The iron couple was reversible in the 0.1 mol L-1 citrate-supporting electrolyte used. The total iron concentration in the samples was determined by differential pulse polarography. Sample decomposition was done in a nitrogen atmosphere by hydrofluoric acid and sulfuric acid. The accuracy of the determinations was verified by spiking experiments and analyzing in-house standards (Geological Survey of Finland) RS 31 (Rapakivi granite), RS 71 (Diabase) and certified reference material PCC-1 (Peridotite, U.S. Geological Survey). The method, developed for this purpose, proved to be reasonably accurate.
USGS PCC-1 Polarography Reference material Interferences Optimization

"Repetitive Determinations Of Iron(III) In Closed Flow-through Systems By Series Reactions"
Anal. Chim. Acta 1977 Volume 94, Issue 2 Pages 289-296
V. V. S. Eswara Dutt, Daniel Scheeler and Horacio A. Mottola

Abstract: The determination of iron(III) with thiocyanate by means of sample injection into a chamber in a closed loop system of circulating reagent is described. Restitution of the absorbance to baseline by ligand exchange and by a redox process in the presence of iodide is discussed, together with some kinetic aspects of the decolorization reaction responsible for the return to the baseline. The iron content of the samples is deduced from the height of the generated transient signal, which is directly proportional to the iron(III) content. As many as 350 determinations/h can be processed when ligand exchange is used and 120/h when iodide is used for baseline restitution. Sample injection techniques of this type are particularly useful in industrial processes and quality control, and environmental monitoring, since they result in a decrease in operating cost and time.
Environmental Industrial Spectrophotometry Closed loop Redox Kinetic

"Determination Of Iron(II) And Iron(III) By Flow Injection And Amperometric Detection With A Glassy Carbon Electrodes"
Anal. Chim. Acta 1980 Volume 114, Issue 1 Pages 267-274
J. W. Dieker and W. E. Van Der Linden

Abstract: Flow injection analysis can be used for the determination of both Fe(II) and Fe(III) with an amperometric detector. The flow-through cell contains a glassy C electrode. Selection of the appropriate voltammetric technique choice of the indication potentials, sample size, composition of the carrier stream, etc., are discussed. The limit of determination is ~10-6M; the calibration curves are linear in the concentration. ranges 10^-3-10-5 M for Fe(III) and 5 x 10^-4-10-5 M for Fe(II). To illustrate the potentialities of the proposed method, standard rocks have been analyzed.
Geological Environmental Amperometry Electrode Speciation Optimization Reference material

"Application Of A Reducing Column For Metal Speciation By Flow Injection Analysis"
Anal. Chim. Acta 1985 Volume 167, Issue 1 Pages 225-231
Azad T. Faizulah and Alan Townsend

Abstract: A Jones reductor mini-column is used to reduce Fe(III) to Fe(II), which is determined spectrophotometrically with 1,10-phenanthroline in citrate buffer at pH 5. The calibration graph is rectilinear in the range 3 to 500 µM-Fe(III), with a detection limit of 3 M Fe(III). The method is extended by introducing a splitting device to allow one portion of the sample to pass through a reductor and a delay coil before recombination with the unreduced portion and reaction with 1,10-phenanthroline. Two consecutive peaks are produced, the first representing Fe(II), the second total Fe. The problems of achieving reproducible splitting are discussed. Interference by V(V) and Mo(VI) is noted.
Spectrophotometry Interferences Jones reductor Speciation

"Simultaneous Multiwavelength Detection In Flow Injection Analysis"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 279-287
F. L&aacute;zaro, A. R&iacute;os, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: A Hewlett-Packard 8451A diode-array detector was used in the simultaneous determination of Fe(III) or Fe(II) and Cu(II) with 1,10-phenanthroline and neocuproine reagents at 454 and 512 nm, respectively. The coefficient of variation (n = 11) at the 5 µg mL-1 level was 1.69% for Fe(III) and 1.07% for Cu(II). An example of the use of the detector, in conjunction with two computer programs (MIXFIA and DINAFIA), for amplification and dilution methods was demonstrated in the determination of NO2- by the Griess reaction. The coefficient of variation (n = 11) were 0.4% at the 25 µg mL-1 level for the dilution method, 0.13% at the 2.0 µg mL-1 level for the normal method and 0.10% at the 0.15 µg mL-1 level for the amplification procedure.
Spectrophotometry Simultaneous analysis Speciation

"Simultaneous Determination By Iterative Spectrophotometric Detection In A Closed Flow System"
Anal. Chim. Acta 1986 Volume 179, Issue 1 Pages 463-468
A. R&iacute;os, M. D. Luque de Castro and M. Valc&aacute;rcel

Abstract: A flow-injection configuration based on a closed flow system which includes a single spectrophotometric detector and allows iterative detection by passage of the reacting plug n times through the same detector is described. The information obtained can be used in the simultaneous determination of species by kinetic methods. The example given is the simultaneous determination of iron(III) and cobalt(II) via the EGTA/PAR ligand displacement reaction.
Water Spectrophotometry Kinetic Simultaneous analysis Tecator

"Flow Injection Determination Of Iron(II), Iron(III), And Total Iron With Chemiluminescence Detection"
Anal. Chim. Acta 1986 Volume 184, Issue 1 Pages 311-315
E. G. Sarantonis and Alan Townshend

Abstract: The determination of Fe(II) (1 nM to 1 µM) was carried out by the production of chemiluminescence from 5 mM luminol solution, with no added oxidants, in a flow injection chemiluminescence analyzer.. Tervalent Fe (20 nM to 2 µM) was determined after acidification with 0.01 M HCl and reduction to Fe(II) in a silver reductor mini-column in the flow system. Calibration graphs were rectilinear over the above ranges, with detection limits of 0.5 nM and 20 nM for Fe(II) and Fe(III), respectively; coefficient of variation were <3%. Cobalt, Cr, Cu and Mn interfered.
Chemiluminescence Column Interferences

"Spectrophotometric Determination Of Iron(III) In A Flow Injection System With A Mixed Solvent"
Anal. Chim. Acta 1987 Volume 192, Issue 1 Pages 129-132
T. J. Cardwell, D. Caridi and R. W. Cattrall, I. C. Hamilton

Abstract: Tervalent Fe solution was injected into a carrier stream containing 0.01 M ammonium di-isopropyl phosphorodithioate in aqueous 50% propan-2-ol adjusted to pH <3 with HNO3. The intense blackish-green ppt. formed was soluble in aqueous 50% alcohol and could be used for the spectrophotometric determination of Fe(III) at 365 nm (e = 8500). Response was rectilinear for 0.05 to 15 mg L-1 of Fe(III). The detection limit was 0.01 mg L-1 and the coefficient of variation was <2%. At a carrier flow rate of 1 mL min-1, the residence time for each injection was <10 s, so that a very high injection rate (350 to 400 h-1) was possible.
Spectrophotometry

"Use Of Acetohydroxamic Acid In The Direct Spectrophotometric Determination Of Iron(III) And Iron(II) By Flow Injection Analysis"
Anal. Chim. Acta 1987 Volume 196, Issue 1 Pages 333-336
A. T. Senior and J. D. glennon

Abstract: The sample (20 µL) containing Fe(III) and Fe(II) was injected into parallel streams (manifold illustrated) of 20 mM acetohydroxamic acid(I) and 2 mM 1,10-phenanthroline(II) in acetate buffer (pH 3.7) which were merged in turn with the water carrier stream (2 mL min-1). The absorbances of the Fe(III) - I and Fe(II) - II complexes were measured at 440 and 512 nm, respectively. The calibration graphs were rectilinear for 1.0 to 10 and 10 to 60 mg L-1 of Fe(III) and Fe(II), respectively, with a detection limit for Fe(III) of 0.2 mg l-1. The coefficient of variation (n = 6) was 2% and the results obtained for acid extracts of haematite samples agreed well with those from AAS. Interference studies showed that the method is highly selective.
Haemitite Spectrophotometry Multidetection Interferences Speciation Tecator

"Sandwich Techniques In Flow Injection Analysis. 2. Simultaneous Determination Of Iron(II) And Total Iron"
Anal. Chim. Acta 1989 Volume 219, Issue 2 Pages 345-350
J. Alonso, J. Bartrol&iacute;, M. del Valle and R. Barber

Abstract: Water samples (1500 µL) are inserted in one of the channels of the manifold described previously (Ibid., 1987, 199, 191) between zones of water and 1% ascorbic acid solution, with subsequent addition of 1,10-phenanthroline at pH 5.0. Absorbance is measured at 520 nm. The signal exhibits a plateau region corresponding to Fe(II) followed by a peak corresponding to total Fe. The system allows up to 90 injections h-1. The rectilinear working ranges are 0.1 to 9 and 0.3 to 12 mg L-1 for Fe(II) and total Fe, respectively. The coefficient of variation (n = 22) were 0.6 and 1.2% for Fe(II) and total Fe in the analysis of a solution containing 2 mg L-1 each of Fe(II) and Fe(III). Results obtained for various ground waters agreed with those obtained by a standard spectrophotometric method.
Ground Spectrophotometry Dual reaction zones Speciation Method comparison Sandwich technique Standard method

"Simultaneous Differential Rate Determination Of Iron(II) And Iron(III) By Flow Injection Analysis"
Anal. Chim. Acta 1990 Volume 230, Issue 1 Pages 113-123
Helmut M&uuml;ller and Volkmar M&uuml;ller, Elo H. Hansen

Abstract: The rate difference in the reaction between the leuco-form of malachite green (C. I. Basic Green 4) and K2S2O8 in the presence of Fe(II) and Fe(III) permitted the Fe(II) to be determined independently of the Fe(III), whereas the near-equalization of the rates that occurred in the presence of 1,10-phenanthraline permitted total Fe to be determined. Two flow injection manifolds are presented.
Spectrophotometry Simultaneous analysis Kinetic Catalysis Speciation Differential detection

"Detection By Magnetic Susceptibility For Flow Analysis Procedures"
Anal. Chim. Acta 1992 Volume 261, Issue 1-2 Pages 29-38
J. F. Tyson* and R. M. LaRue, S. Bogdanski

Abstract: A Johnson Matthey model MSB-1 magnetic susceptibility balance was applied in conjunction with a flow system with its measurement cell positioned between the poles of the balance magnets. Initial measurements were made after the injection of solution of Cr(III) or Fe(III) into water, Fe(III) into 0.5 M NaOH (to form a paramagnetic solid precipitate), and Mn(VII) into ascorbic acid solution (to form Mn(II)). Detection limits in solution were between 25 and 50 µg mL-1, and calibration graphs were rectilinear over two orders of magnitude. Subsequently, solid-phase extraction of metal ions was effected with a column of Rexyn 101(H) cation-exchange resin positioned in the measurement path. Continuous-flow extraction experiments were carried out with Cu(II), and flow injection extraction with Fe(III) and Fe(II) (from reduction with NaBH4). The resin removed cations most efficiently at low flow rates. A preliminary study was made of the effect of pH on the extraction of Cu. The potential of the measurement of magnetic susceptibility as a quant. detection mode for flow anal. procedures was studied. The performance of an Evans-type balance, which is easily adapted to the monitoring of magnetic species in flowing streams, was evaluated. A preliminary study was performed to establish the anal. capabilities of the balance for the quant. determination of cations in flowing streams. The balance was estimated to have sensitivities of 155, 276, 67 and 319 mV L mol-1 for Fe(III), Fe(OH)3, Cr(III) and Mn(II), respectively. Detection limits, based on concentration. injected, were between 25 and 50 µg mL-1. Calibration graphs were linear over two orders of magnitude. By locating a small mass of strong cation-exchange resin between the poles of the magnets, the rate of uptake and release of cations from and into the flowing stream could be followed. Experiments involving both continuous-flow and flow injection procedures with solutions of Cu(II) and Fe(III) were done. The resin was most efficient at removing cations from flowing streams at low flow-rates under both continuous-flow and flow injection conditions, although the time taken to achieve saturation decreased with increasing flow-rate. A simply study of the effect of pH showed the possibilities for the study of the cation-binding characteristics of such resins. The differential displacement of Cu(II) and H+ could be clearly observed, with the removal of the Cu(II) from the resin, by the passage of 10%(v/v) HCl through the column, proceeding at a slower rate than the uptake of Cu(II) from solution by the resin in the H+ form.
Ion exchange Magnetic susceptibility Precipitation Rexyn

"Single-phase Liquid-liquid Extraction In Mono-segmented Continuous-flow Systems"
Anal. Chim. Acta 1994 Volume 285, Issue 3 Pages 287-292
Ileana Facchin, Jos&eacute; W. Martins, Patr&iacute;cio G. P. Zamora and Celio Pasquini*

Abstract: The method depends on mixing an aqueous sample solution, an immiscible reagent solution and a common solvent for the other two phases. Reaction occurs rapidly in the single phase, which is then air-segmented and carried to a confluence with an aqueous solution, causing separation of the reagent phase for subsequent spectrophotometric measurement. The method was illustrated by the extraction of Fe(III). The sample solution was mixed with 50 mM thenoyltrifluoroacetone solution in isobutyl methyl ketone and with ethanol in a mixing chamber. The single-phase solution passed through a debubbler, then through a loop, where it was segmented between two air bubbles. A water stream carried the segment to a junction with saturated NaNO3 solution and phase separation occurred in an inverted U-tube. The complex in the organic phase was detected with light from a light-emitting diode (560 nm) passing through the liquid to a light-dependent resistor, which formed one arm of a wheatstone bridge. Calibration graphs were linear for 2-30 mg/l of Fe(III). The RSD was 1.5% (n = 10) for 10 mg/l. The results were similar to those obtained by manual extraction. Up to 80 samples/h could be processed.
Spectrophotometry Sample preparation Light emitting diode Segmented flow Method comparison Organic phase detection Debubbler Solvent extraction

"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.
Environmental Spectrophotometry Sample preparation Extraction Kinetic Multivariate calibration Organic phase detection Speciation Partial least squares

"Iron(II) And Iron(III) Determination In Seawater At The Nanomolar Level With Selective Online Preconcentration And Spectrophotometric Determination"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 425-432
S. Blain* and P. Tr&eacute;guer

Abstract: An FIA method which included online filtration, acidification, reduction, pre-concentration and spectrophotometric detection is described for the shipboard determination of Fe(II) and Fe(III) in seawater. The pre-concentration was carried out using a C18-phase column impregnated with ferrozine, a selective reagent for Fe(II). Fe(III) was determined following reduction to Fe(II) with ascorbic acid. The analysis was performed by propelling a filtered mixture of seawater/2.5 M acetate buffer of pH 4.5 (25:1) through the pre-concentration column at 2 ml/min for 2-20 min. The pre-concentration column was rinsed with 0.7 M NaCl for 2 min at 2 ml/min. The retained Fe(II)-ferrozine complex was eluted with methanol at 0.42 ml/min. The resulting stream was diluted by merging with a methanol/H2O stream (4:1; 0.32 ml/min) prior to measuring the absorbance at 280 nm. Ascorbic acid (100 µM) was added to the acetate buffer to reduce Fe(III). The calibration graphs for Fe(II) and Fe(III) were linear up to 75 and 200 mM, respectively, with a sampling period of 2 min. The detection limit was 0.1 nM-Fe(II) was with a 20 min sampling period. The accuracy of the method was verified by determining Fe(II) in a certified reference seawater containing 1.87±0.28 nM-Fe(III).
Sea Spectrophotometry Speciation Reference material Preconcentration C18

"Continuous-flow Analysis: Simultaneous Spectrophotometric Determination Of Metals"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 386-396
Yu. A. Zolotov, E. I. Morosanova*, S. V. Zhalovannaya and S. S. Dyukarev

Abstract: Continuous-flow analysis methods for the simultaneous determination of (i) aluminum and manganese, (ii) aluminum and iron(III) and (iii) calcium and magnesium were developed. The methods were based on ligand-exchange reactions or reactions at different rates. For (i) the Al and Mn complexes with xylenol orange (XO) were formed and the combined adsorption was measured at 570 nm in the first detection cell. EDTA was added to the flow system to destroy the Mn-XO complex and allow the Al-XO complex to be determined in the second detection cell at 550 nm. A similar methodology was used for (iii) using eriochrome black T (EB) to determine the combined Ca and Mg concentration at 540 nm. EDTA was added to destroy the Ca-EB complex and allow the Mg-EB complex to be determined also at 540 nm. The different rate of reaction with XO were utilized for (ii). The signal recorded in the first cell at 560 nm was due to the Fe-XO complex while that recorded in the second cell at 550 nm was due to the combined absorption of the Fe-XO and Al-XO complexes. The full details of each method are presented along with the linear ranges and detection limits. The methods were tested on synthetic and real samples (soil extracts, sedimentary rocks). High accuracy and good precision were obtained with RSD of 1-6.5%. The sampling frequency was up to 32 samples/h.
Sedimentary Environmental Spectrophotometry Sample preparation Complexation Segmented flow Kinetic

"Online Coated Columns For The Spectrophotometric Determination Of Metals By Continuous-flow Analysis"
Anal. Chim. Acta 1995 Volume 308, Issue 1-3 Pages 378-385
Yuri A. Zolotov, Irina M. Maksimova, Elena I. Morosanova* and Andrei A. Velikorodny

Abstract: Online coated microcolumns and capillary tubes were evaluated for the separation and pre-concentration of metal ions by continuous-flow analysis. Xylenol orange, 1-(2'-pyridylazo)-2-naphthol and (p-sulfophenylazo)-2'-sulfo-4'-nitrodiazoaminobenzene disodium salt (Cadion) were immobilized on reversed-phase silica (C16, C8, phenyl, C1) packed into microcolumns (2.5 cm x 2 mm i.d.) or on capillary tubes (10 m x 2 mm i.d.) with hydrophobic inner surfaces (C6, C-phenol, C1). The optimum conditions for the maximum retention of reagent were determined. The adsorption and acid desorption of metal ions from coated microcolumns and capillaries were studied and procedures for the determination of Cd, Co, Cu and Fe(III) in the range 0.08-30 µM were suggested using spectrophotometric detection. Preconcentration factors of up to 9 and 19 were achieved with coated microcolumns and capillaries, respectively.
Spectrophotometry Column Immobilized reagent Optimization Preconcentration Silica

"Detection Of Flow Injection Analysis With PH Gradient Acousto-optic Tunable Filter Based Spectrophotometry"
Anal. Chim. Acta 1996 Volume 319, Issue 3 Pages 315-324
Celio Pasquini, Jian Lu, Chieu D. Tran* and Sergey Smirnov

Abstract: A spectrophotometer based on an acousto-optic tunable filter is described in which the visible region (390-650 nm) could be scanned at 300 nm/s. The fast scanning capability of this instrument allowed it to be used in FIA systems with acid-base indicator mixtures to monitor the pH vs. time profile. The recorded spectra of the indicators were converted to pH by a partial least squares multivariate calibration technique. The spectrometer was used in FIA systems to characterize the behavior of chemical systems as a function of pH, for example, (i) to determine the pKa of weak acids and (ii) to study complex formation between Fe(III) and sulfosalicylic.
Spectrophotometry Acousto optic tunable filter pH gradient Multivariate calibration Partial least squares

"Flow Injection Assisted Optical Sensor For Determination Of Iron(II) And Iron(III) In Natural Water"
Anal. Chim. Acta 1997 Volume 343, Issue 3 Pages 191-197
A. C. Lopes da Concei&ccedil;&atilde;o*, M. T. Tena, M. M. Correia dos Santos, M. L. Sim&otilde;es Gon&ccedil;alves and M. D. Luque de Castro

Abstract: The FIA method for determining Fe(III) and total iron [Fe(II) plus Fe(III)] was based on the spectrophotometric detection of the Fe(III)-SCN complex retained in a flow cell packed with Dowex-1. A sample volume of 2 mL containing 80-500 ng/ml total Fe at pH 2 was inserted into a 0.01 M HNO3 carrier stream (1.3 ml/min) and split into two equal fractions (L1 and L2). The L1 fraction was merged with 0.25 M ammonium thiocyanate/0.01 M HNO3 reagent stream (1.3 ml/min) and the mixture was propelled through the packed flow cell. The retained Fe(III)-SCN was detected at 480 nm. The L2 fraction was propelled through an oxidation column consisting of DEAE Sephadex saturated with Folin-Ciocalteu's reagent where Fe(II) was oxidized to Fe(III). The total Fe(III) was determined as described for fraction L1. The calibration graphs for Fe(III) and total Fe were linear for 80 (detection limit) to 500 ng/l. The method was applied to the analysis of natural waters. The average recoveries for 0.1-0.4 µg/l Fe(II) and 0.35-0.5 µg/l total Fe from spiked waters were 103 and 101%, respectively. An approach for speciation of iron (as Fe(II) and Fe(III)) based on integration of retention of the Fe(III)-SCN complex with detection using a conventional spectrophotometer is proposed here. The device (namely, a flow-cell packed with an exchange resin) has been coupled to a flow injection manifold with inner-coupled injection valves which enables discrimination between Fe(M) and Fe(II) taking advantage of a redox minicolumn housed in the loop of one of the valves. The method thus proposed has good selectivity with a determination limit of 80 µg L-1 and affords a determination range of 80-500 µg L-1 for Fe(II) plus Fe(III). Application to synthetic and real samples containing both the oxidation states of iron lead to average recoveries of 103% and 101% for Fe(II) and total iron (Fe(II)+Fe(III)), respectively, thus showing the usefulness of the overall approach.
Ground Spectrophotometry Sensor Sephadex Oxidation column Speciation Dowex Flowcell Solid phase detection

"Evaluation Of Natural Computation Techniques In The Modeling And Optimization Of A Sequential Injection Flow System For Colorimetric Iron(III) Determination"
Anal. Chim. Acta 1997 Volume 348, Issue 1-3 Pages 143-150
J. de Graciaa, M. L. M. F. S. Saraviab, A. N. Ara&uacute;job, J. L. F. C. Limab, M. del Vallec and M. Pochd,*

Abstract: The present study shows and gives evidence of the applicability of natural computation techniques in the modeling and optimization of a sequential injection flow system of anal. for colorimetric iron(III) determination in water samples. The reaction with thiocyanate is used as reagent color. A neural network consisting of two hidden layers, each one formed by eight neurons, was used to model the system. Optimization of the system in terms of sensitivity, linearity and sampling rate was carried out by using jointly the neural network and genetic algorithms. The latter were used with a set of 50 crossed and mutated chromosomes over 100 generations. In the system thus developed, 140 µL of sample and 70 µL of reagent were sequentially introduced into the holding coil and propelled toward the detector at a flow of 5 mL/min. The system gave a sampling rate of 110 samples per h. A comparison of the results obtained in the anal. of six samples with those obtained using the reference method (atomic absorption spectrophotometry) showed the high quality of results provided.
Spectrophotometry Neural network Modeling Optimization Sequential injection Computer Method comparison

"Simultaneous Dermination Of Iron (II) And Iron(III) By Flow Injection Analysis. A Mathematical Simulation Of The Detector Response"
Anal. Chim. Acta 1997 Volume 348, Issue 1-3 Pages 101-112
Milko Novi, Marjana Novi*, Jure Zupan, Nadja Zafran and Boris Pihlar

Abstract: A mathematical model for the description of the detector signal obtained in flow injection asynchronous merging zone technique (FIA-AMZ) is proposed. FIA-AMZ is based on the separate injection of a sample and an appropriate reagent in such a way that both injected solutions are covered only partly. The resulted detector signal consists of two consecutive peaks whose heights are proportional to the concentration of the detectable component present in the sample and another component which becomes detectable after the reagent has been added. The detector signals (the concentration profiles of the analytes) are described by a modified Gauss curve, which proved to be better than a combination of Gauss-Lorentz curves. The conversion of undetectable to detectable form of the analyte is described by a sigmoidal function the slope of which corresponds to the frontal dispersion of the added reagent and to the reaction kinetics. The model is tested on the system for the simultaneous spectrophotometric determination Fe2+ and Fe3+. It is shown that fitting of the experimental curves with a model function enables the optimization of the experimental conditions at applied FIA manifold, and consequently the simultaneous determination of concentrations of Fe2+ and Fe3+ ions in a single measurement.
Simulation Modeling Simultaneous analysis Speciation

"Simultaneous Flow Injection Determination Of Iron(II) And Iron(III) With Opto-electrochemical Detection"
Anal. Chim. Acta 1997 Volume 354, Issue 1-3 Pages 43-50
B. Haghighi and A. Safavi*

Abstract: A two line manifold flow injection system with opto-electrochemical detection (simultaneous optical and electrochemical detection) is described for the simultaneous determination of Fe(II) and Fe(III). A modified Z-type flow cell is operated simultaneously as an optical flow cell for the spectrophotometric determination of Fe(III) by monitoring the absorbance of the sulfosalicylic acid-Fe(III) complex at 505 nm and as an electrochemical flow cell for amperometric monitoring of the current due to the oxidation of Fe(II) to Fe(III) at potential of +1.0 V vs. SCE. The optical and electrochemical signals are recorded simultaneously by two recorders. The calibration graphs are linear in the ranges 1 x 10^-6-4 x 10^-4 M for Fe(III) and 1 x 10^-5-3 x 10^-3 M for Fe(II). The 3s limits of detection of Fe(III) and Fe(II) are 4.3 x 10^-7 and 5.6 x 10^-6 M, respectively. The relative standard deviation of 16 determinations of 4 x 10^-5 M of Fe(III) and 1 x 10^-4 M of Fe(II) are 1.00% and 1.39%, respectively. Up to 75 samples per hour can be determined. The effects of several common ions on the determination of Fe(II) and Fe(III) are studied, showing that the method is relatively free from interferences. The method is applied to the simultaneous determination of Fe(II) and Fe(III) in spiked tap water.
Optoelectrochemistry Speciation Simultaneous analysis

"Determination Of Iron(III) In Pharmaceutical Samples Using Dialysis In A Sequential Injection Analysis System"
Anal. Chim. Acta 1997 Volume 357, Issue 1-2 Pages 141-149
J. F. van Staden*, H. du Plessis and R. E. Taljaard

Abstract: The use of membranes for online sepns. in flow-through dialyzers as part of flow systems is extremely useful for automated sample preparation Iron (III) was separated from a sample matrix by dialysis in a sequential injection system. The dialyzed iron was complexed with tiron and the resulting complex was monitored spectrophotometrically at 667 nm. The influence of various parameters, including pump speed for both the donor and recipient streams, sample volume, reagent volume, dialysis time and the effect of multiple flow reversals, on dialysis efficiency was studied. The system was feasible for the determination of iron in pharmaceutical samples which are usually turbid and contain undissolved organic particles. The system is fully computerized and is able to monitor iron(III) in samples at a frequency of 8 samples per h with a relative standard deviation of <1.50 in the linear calibration range (100-1000 mg L-1). The 3s detection limit was 45.0 mg L-1. Although the sample frequency of the proposed sequential injection system is much lower than that of conventional flow injection systems, the volume of sample used is much smaller and the consumption of reagents is much lower, which is more cost effective. Using the feature of multiple flow reversals, the percentage dialysis can be improved to up to 4.5, which compares well with the 4 obtained with conventional flow injection anal.
Pharmaceutical Spectrophotometry Computer Dialysis Sequential injection

"Use Of A Sequential Injection Technique To Evaluate The Effect Of Mixing Chambers On Zone Penetration"
Anal. Chim. Acta 1998 Volume 367, Issue 1-3 Pages 111-121
T. McCormack and J. F. van Staden*

Abstract: The simple chemical and fast rate of the complexation reaction between tiron and iron(III) were used to evaluate the effect four mixing chambers of various volumes (1.2-4.0 mL) have on the degree and reproducibility of zone penetration within a sequential injection (SI) system. As a consequence of this study a fully computerized SI system for the spectrophotometric determination of iron(III) in mine waters is proposed. Using a 1.2 mL mixing chamber placed before the detector, the method is able to analyze 24 samples per h with an average relative standard deviation of 0.28%. The calibration graph is linear between 0 and 200 mg/L with a 3s detection limit of 0.03 mg/L.
Mine Spectrophotometry Sequential injection Mixing chamber Zone penetrating Complexation

"Flow Injection Standard Subtraction Method For The Determination Of Iron(III) Based On Its Catalytic Effect And Inhibition Of EDTA"
Anal. Chim. Acta 1998 Volume 374, Issue 2-3 Pages 303-307
Tsuyako Watanabea, Norio Teshimaa, Shigenori Nakanob and Takuji Kawashimaa,*

Abstract: A new approach for the flow injection catalytic determination of 10^-6 M levels of iron(III) is proposed. This method is based on the catalytic effect of iron(III) on the oxidative coupling of p-anisidine with N,N-dimethylaniline to form a blue compound (λmax=735 nm) in the presence of hydrogen peroxide and 1,10-phenanthroline as an activator, and the inhibitory effect of EDTA on the iron(III)-catalyzed reaction. The concentration. of iron(III) can be determined from only two flow signals which are obtained by injecting the iron(III) and iron(III) plus EDTA solutions into the flow lines without a calibration graph for iron(III); this procedure may be called standard subtraction. The proposed method permits the anal. of 12 samples per h (24 peaks per h) and was successfully applied to the determination of iron in standard iron ore samples.
Iron Spectrophotometry Kinetic Catalysis EDTA Indirect Differential detection Calibration

"Simultaneous Determination Of Traces Of Iron(II) And Iron(III) Using Differential Pulse Anodic Stripping Voltammetry In A Flow-through Configuration On A Glassy Carbon Electrode"
Anal. Chim. Acta 1998 Volume 376, Issue 3 Pages 325-330
J. F. van Staden* and M. C. Matoetoe

Abstract: Iron(II) and iron(III) complexes of pyrophosphate can be determined simultaneously at pH 9. The peak potentials used were -0.8 and 0.5 V for Fe(III) and Fe(II), respectively. Linear calibration plots over the range 10^-6-10-3 mol L-1 were obtained. Detailed iron-couple cyclic voltammetric studies, sample handling procedures, possible interferences and applications of the method to real samples are described. Detection limits of 10^-8 mol L-1 and a relative standard deviation of <4% (n = 14) were achieved at a concentration. of 1 x 10^-6 mol L-1 for both iron species.
Electrode Voltammetry Speciation pH Interferences

"Metal Speciation By Flow Injection Analysis"
Talanta 1983 Volume 30, Issue 11 Pages 841-844
B. P. Bubnis, M. R. Straka and G. E. Pacey

Abstract: A two-channel flow-through switching valve incorporated in the manifold of the system permits determination of two oxidation states of an element. Addition of an appropriate oxidant or reductant is so timed as to allow complete conversion into a single oxidation state, so that measurement before and after the addition gives the concentration. of one and the sum of both species; thus, Fe(II) and Fe(III) are determined with 1,10-phenanthroline and Cr(III) and Cr(VI) with diphenylcarbazide, the absorbances being measured at 512 and 540 nm, respectively. When a 30 µL injection loop is used, rectilinear response is obtained for 0.5 to 30 ppm of Fe and 0.5 to 40 ppm of Cr. The coefficient of variation for each metal is ~1%. At 10 ppm of Fe, there is interference from 15 ppm of Ni, 50 ppm of Zn and 70 ppm of Cu. By increasing the injection-loop volume to 100 µL, it should be possible to lower the detection limit to 0.05 ppm of Fe. The error for total Cr is <2.0%, but is higher for Cr(III) and Cr(VI) individually. The method allows 180 injections to be made in 1 h.
Industrial Water Spectrophotometry Interferences Speciation

"Diode-array Detectors In Flow Injection Analysis. Mixture Resolution By Multi-wavelength Analysis"
Talanta 1987 Volume 34, Issue 12 Pages 987-993
M. Blanco*, J. Gene, H. Iturriaga, S. Maspoch and J. Riba

Abstract: In the use of diode-array spectrophotometry for multi-component determination by flow injection analysis, aspects considered are(I) the recording of reproducible spectra at max. sensitivity and(II) the mathematical processing of the spectral data to determine the various components. Three data processing procedures are assessed, viz: (a) a linear simultaneous-equation system, (b) a multi-component analysis computation program (Hewlett-Packard), and (c) graphical multi-wavelength linear regression analysis. The test analysis was simultaneous determination of Fe(II) and Fe(III) with 1,10-phenanthroline - sulfosalicylic acid reagent with measurements at 486 and 510 nm. Data processing procedures (b) and (c) yielded similar and satisfactory results.
Spectrophotometry Calibration Computer Multicomponent Speciation

"Simple Unsegmented Flow Configurations For Simultaneous Kinetic Determinations"
Talanta 1991 Volume 38, Issue 3 Pages 291-294
M. Romero-Saldana, A. Rios, M. D. Luque De Castro and M. Valcarcel,

Abstract: Two unsegmented flow manifolds were described for use in the determination of two analytes by flow injection analysis, based on their different rates of reaction with the same reagent. The determination of Fe(III) and Co(II) was based on displacement from complexation with EGTA by 4-(2-pyridylazo)resorcinol (described); detection was at 510 nm. Calibration graphs were rectilinear for, e.g., 1 to 5 µg mL-1. Good results were obtained for 1 to 4 µg mL-1 of each metal in mixtures. The coefficient of variation (n =11) were 2.4 and 3.6% for Fe(III) and Co(II), respectively, for 2 µg mL-1 of each metal. The sampling rate was 25 h-1.
Complexation Kinetic

"Simultaneous Determination Of Iron(III) And Vanadium(V) By Use Of A Kinetic - Spectrophotometric And Rapid Mixing Flow System"
Talanta 1991 Volume 38, Issue 10 Pages 1159-1162
Hong-Bin He, Yun-Xiang Ci*, Wen-Bao Chang and Wen-Ling Gong,

Abstract: Food sample (2 g) was heated with 20 mL of 67% HCO3 - 70% HClO4 (1:1) until almost dry and diluted to 25 mL with 0.01 M HCl. Sample solution was merged with chromotropic acid solution and KBrO3 with use of a pump before reaction in a flow cell and detection at 420 nm. The flow system (illustrated) employs a rapid sample and reagent introduction manifold, in which valves and carrier streams are omitted without decreasing the precision or increasing the sample consumption relative to FIA. Satisfactory results were obtained in the simultaneous determination of Fe(III) by its color reaction and VV by its catalytic effect. Calibration graphs were rectilinear from 0.15 to 15 µg mL-1 of Fe(III) and from 3 to 700 ng mL-1 of VV; corresponding coefficient of variation (n = 10) were 0.6 and 2%. Recoveries were 98% in raisins, milk powder and biscuits.
Food Spectrophotometry Catalysis Kinetic

"Investigation Of The Composition Of Complexes And The Stoichiometry Of Non-complex Reactions By Flow Injection Method"
Talanta 1993 Volume 40, Issue 7 Pages 969-974
Jingfu Liu and Huichang Ma*,

Abstract: A spectrophotometric flow injection technique was developed (diagram given) for the determination of the composition of colored complexes by the Asmus method (cf., J. Anal. Chem., 1960, 178, 104). Application of the technique is exemplified by the investigation of the chromogenic reaction between cyanide and pyridine-barbituric acid, and the determination of the compositions of Fe(III)-Tiron complexes formed in media of pH 5.6 (blue), 5.7-6.9 (purple) and 7 (red).
Spectrophotometry Complexation Stoichiometry Tiron

"Preconcentration Of Iron(III), Cobalt(II) And Copper(II) Nitroso-R Complexes On Tetradecyldimethylbenzylammonium Iodide-naphthalene Adsorbent"
Talanta 1995 Volume 42, Issue 3 Pages 337-344
Bal K. Puri and Sanjay Balani

Abstract: Iron, cobalt and copper form colored water soluble anionic complexes with disodium 1-nitroso-2-naphthol-3-6-disulphonate (nitroso R-salt). The anionic complex is retained quantitatively as a water insoluble neutral ion associated complex (M-nitroso R-TDBA) on tetradecyldimethylbenzylammonium iodide on naphthalene (TDBA+I--naphthalene) packed column in the pH range of: Fe(III): 3.1-6.5, Co: 3.4-8.5 and Cu 5.9-8.0 when their solutions are passed individually over this adsorbent at a flow rate of 0.5-5.0 ml/min. The solid mass consisting of an ion associated metal complex along with naphthalene is dissolved out of the column with 5 mL dimethylformamide/chloroform and metals are determined spectrophotometrically. The absorbance is measured at 710 nm for iron, 425 nm for cobalt and 480 nm for copper. Beers law is obeyed in the concentration range 9.2-82 µg of iron, 425 nm for cobalt cobalt and 3.0-62 µg of copper in 5 mL of final DMF/CHCl3 solution. The molar absorptivities are calculated to be Fe: 7.58 x 10^3, Co: 1.33 x 10^4 and Cu: 4.92 x 10^4 M 1 cm-1. Ten replicate determinations containing 25 µg of iron, 9.96 µg of cobalt and 3.17 µg of copper gave mean absorbances 0.677, 0.450 and 0.490 with relative standard deviations of 0.88, 0.98 and 0.92%, respectively. The interference of large number of metals and anions on the estimations of these metals has been studied. The optimized conditions so developed have been employed for the trace determination of these metals in standard alloys, waste water and fly ash samples.
Alloy Industrial Waste Spectrophotometry Preconcentration

"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.
Environmental Spectrophotometry Catalysis Micelle Speciation

"Catalytic Kinetic Simultaneous Determination Of Iron, Silver And Manganese With The Kalman Filter By Using Flow Injection Analysis Stopped-flow Spectrophotometry"
Talanta 1998 Volume 45, Issue 6 Pages 1123-1129
Ying-Zhi Ye*, Hong-Yan Mao and Ya-Hua Chen

Abstract: A catalytic differential kinetic method with Kalman filter for the simultaneous determination of multi-component is described. The oxidation of Rhodamine B (RB) by K periodate in a slightly acid solution is a slow reaction. But Fe(III), Ag(I) or Mn(II) has a differential catalytic effect on the oxidation reaction of RB in the presence of 1,10-phenanthroline as the activator. So Fe, Ag and Mn can be simultaneously determined by measuring the decreasing absorbance of the dye (RB) at 555 nm. A flow injection analysis stopped-flow spectrophotometric system with a microcomputer performs the determinations This method was applied to determining Fe, Ag and Mn in alloy samples with satisfactory results.
Alloy Spectrophotometry Kalman filter Catalysis Kinetic Simultaneous analysis Stopped-flow Computer Indirect Multicomponent

"Speciation Of Metals In Solution By Flow Injection Analysis. 2. Determination Of Iron(III) And Iron(II) In Mineral Process Liquors By Simultaneous Injection Into Parallel Streams"
Analyst 1984 Volume 109, Issue 7 Pages 843-846
Thomas P. Lynch, Nicholas J. Kernoghan and John N. Wilson

Abstract: Two parallel streams, with simultaneous sample introduction by coupled synchronized injection valves, are analyzed colorimetrically. Bivalent Fe is determined as its 1,10-phenanthroline complex at 508 nm and Fe(III) as its complex with SCN- at 475 nm. With 20 µL samples, the working ranges are 0.5 to 180 ppm and 0.5 to 120 ppm for Fe(III) and Fe(II), respectively, although in each instance the calibration graphs are curvilinear. For max. stability, samples and standard solution should be prepared in aqueous 1% (v/v) HCl. Tolerance limits are listed for 19 species. A novel application is described of the simplex optimization procedure in minimizing the interference of Cu(II) in the determination of Fe(III). For 80 ppm each of Fe(II) and Fe(III), the coefficient of variation are 0.56 and 0.81%, respectively (n = 40). Results are presented for Fe(II) and Fe(III) in HCl extracts of three geological samples. The sampling rate is 120 h-1. (For Part I see Anal. Abstr., 1985, 47, 2H51).
Geological Water Process liquor Sample preparation Spectrophotometry Process control Simplex Optimization Interferences Speciation

"Simultaneous Determination Of Iron(III) And Total Iron By Flow Injection Analysis Using Kinetic Spectrophotometry With Tiron"
Analyst 1988 Volume 113, Issue 10 Pages 1557-1560
Rokuro Kuroda, Tadashi Nara and Koichi Oguma

Abstract: Two configurations are described for the cited determination of Fe. In both systems sample solution is injected into 0.1 M H2SO4 as carrier solution, which merges with reagent solution containing 2 g L-1 of Tiron and 10 mL L-1 of 10% Triton X-100 in acetate buffer (pH 4.5 or 6.0). In one system, the absorbance of the mixture is measured at 560 nm, and the mixture is irradiated at 250 nm and passed through a second flow cell in the same detector, where the absorbance is measured again. The first peak is proportional to Fe(III) content, and the second to total Fe. In the second set-up, the absorbance is measured in a closed system until the sample is completely dispersed; an irradiation coil is introduced into the system, and the second absorbance peak is measured. Again, the first peak corresponds to Fe(III), the second to total Fe. In the first system throughput of samples is 60 h-1, with a precision of 0.4% for Fe(III) and 0.6% for total Fe. Sample throughput in the second system is 30 h-1., with a precision of 1.2% for Fe(III) and 0.6% for total Fe.
Spectrophotometry Kinetic Surfactant Speciation Tiron Triton X

"Simultaneous Determination Of Trace Amounts Of Iron(III) And Titanium(IV) By Flow Injection With Spectrophotometric Detection"
Analyst 1990 Volume 115, Issue 4 Pages 431-434
Shoji Kozuka, Kenichi Saito, Koichi Oguma and Rokuro Kuroda

Abstract: Powdered silicate rock sample was fused with Li2CO3 - H3BO3 (1:1) and the melt was dissolved in 1 M HCl. The solution was injected simultaneously into a carrier stream of 1 M HCl at 2 mL min-1 at two inlet points separated by a Ag reductor column that reduced Fe(III) to Fe(II). The stream was merged with a reagent solution of 0.5% disodium 1,2-dihydroxybenzene-3,5-disulfonate in acetate buffer, pH 4.9, at 2.0 mL min-1 and monitored at 430 nm. The absorption of the first peak represented the total Fe(III) and Ti(IV) content and that of the second, the Ti(IV) concentration. The method was applied in the analysis of reference materials, the results obtained agreed closely with certified values with mean coefficient of variation of 1.0 and 0.87% for Fe and Ti respectively. There was no interference.
Silicate Spectrophotometry Column Buffer Reference material Interferences Reduction column Differential detection

"Studies On The Application Of Photochemical Reactions In A Flow Injection System. 2. Simultaneous Determination Of Iron(II) And Iron(III) Based On The Photoreduction Of The Iron(III)-phenanthroline Complex"
Analyst 1992 Volume 117, Issue 11 Pages 1767-1770
Ren-Min Liu, Dao-Jie Liu and Ai-Ling Sun

Abstract: Sample (100 µL) was injected into the flow stream simultaneously at two points. After the passage of one sample through the photochemical reactor, the absorbances of the two sample plugs were measured at 510 nm. Iron(II) absorbance of the Fe(II) - 1,10-phenanthroline complex from the first peak and the total Fe absorbance from the second peak were obtained. Calibration graphs were rectilinear from 0.1 to 120 ppm of Fe(II) and 0.2 to 120 ppm of total Fe; sample throughput was 40 to 60 h-1. The method was applied to synthetic mixtures of standard Fe(II) and Fe(III) and the catalyst for synthetic ammonia manufacture. The results compared well with those obtained by a dichromate titrimetric procedure. An automated procedure for the simultaneous determination of iron(II) and iron(III) was developed, involving the use of a lab.-built flow-through photochem. reactor in a flow injection system based on the photoredn. of the ion(III)-1,10-phenanthroline complex. Optimum anal. conditions were established. A 100 mm3 sample injection gave linear working ranges of 0.1-120 ppm of iron(II) and 0.2-120 ppm of total iron. The sample throughput was 40-60 h-1. The proposed method was applied to the determination of iron(II) and iron(III) in synthetic mixtures of standard iron(II) and iron(III) and the catalyst for synthetic ammonia manufuture.
Spectrophotometry Speciation Photochemistry Method comparison Simultaneous analysis

"Pyoverdin-doped Sol-gel Glass For The Spectrofluorimetric Determination Of Iron(III)"
Analyst 1995 Volume 120, Issue 2 Pages 431-435
J. M. Barrero, C. C&aacute;mara, M. C. P&eacute;rez-Conde, C. San Jos&eacute; and L. Fern&aacute;ndez

Abstract: Pyoverdin was entrapped in sol-gel glass (details given) and used for the determination of Fe(III). Two methods, viz., continuous-flow and flow injection (FI), were used. In the continuous-flow method, Fe(III) solution in 0.05 M MES buffer of pH 6.5 (buffer A) was pumped (1.8 ml/min) through a flow cell filled with 200 mg of the pyoverdin-doped sol-gel glass (maintained at 4°C). The decrease in the fluorescence intensity was measured at 405 nm (excitation at 330 nm). Regeneration was effected with 1 M HCl. In the FIA method, Fe(III) solution (1 ml) was injected into a stream (1.2 ml/min) of buffer A and passed through the flow cell, and the fluorescence was measured as described above. For the continuous-flow method, the calibration graph was linear from 3 (detection limit) to 300 ng/ml of Fe(III) and the RSD (n = 10) was 3%. For the FIA method, the calibration graph was linear from 20 (detection limit) to 900 ng/ml of Fe(III) and the RSD (n = 10) was 4.5%. The continuous-flow method was applied to tap water and the FIA method to human serum.
Serum Human Water Fluorescence Method comparison Indirect Sol-gel

"Determination Of Formation Quotients By A Flow Injection Procedure"
Analyst 1995 Volume 120, Issue 4 Pages 1175-1179
Roger T. Echols and Julian F. Tyson

Abstract: A flow injection (FI) spectrophotometric method is described for determining formation quotients (equilibrium constants) for metal-ligand reactions of 1:1 stoichiometry. Three chemical systems were studied: (i) the reaction of Fe(III) with salicylic acid; (ii) the reaction of Fe(III) with thiocyanate; and (iii) the reaction of La(III) with methyl thymol blue. The absorbance-time data generated were analyzed by two iterative methods (details given). The FI method greatly simplified the experimental procedure for determining formation quotients compared with that of Job's method or the method of continuous variation, and the iterative methods accounted for absorbance by the ligand at the wavelength monitored.
Spectrophotometry Complexation Equilibrium constants Method comparison

"Determination Of The Oxidation-states Of Iron In Natural-waters A Review"
Analyst 1995 Volume 120, Issue 11 Pages 2655-2663
Simo Pehkonen

Abstract: 92 references
Sea Chemiluminescence Fluorescence Mass spectrometry Spectrophotometry Voltammetry Review Simultaneous analysis Speciation

"Flow Injection Analysis And Cyclic Voltammetry"
Anal. Chem. 1983 Volume 55, Issue 12 Pages 1986-1988
Niels Thoegersen, Jiri Janata, and Jaromir Ruzicka

Abstract: The preliminary study by Janata and Ruzicka (cf. Anal. Abstr., 1983, 44, 3J10) was expanded. A single-line flow injection analysis system (cf. Ruzicka et al., Anal. Chim. Acta, 1981, 134, 55) was used, driven by a gas at very low pressure. The voltammetric cell was connected to an IBM EC225 analyzer. and recorder. With careful selection of flow rate and scan rate, it was possible to obtain either a hydrodynamic (50 mV s-1 scan rate) or a cyclic voltammogram (1 V s-1 scan). Various uses of the technique are considered. As an example, the concentration. profile of a 70 µL sample of 1 mM Fe(III) oxalate injected into a carrier of 0.25 M Na oxalate at pH 4.5 flowing at 0.98 mL min-1 was recorded.
Voltammetry Gradient technique

"Determination Of Chromium(III), Titanium, Vanadium, Iron(III), And Aluminum By Inductively Coupled Plasma Atomic Emission Spectrometry With An Online Preconcentrating Ion Exchange Column"
Anal. Chem. 1986 Volume 58, Issue 13 Pages 2602-2606
Shizuko Hirata, Yoshimi Umezaki, and Masahiko Ikeda

Abstract: A method utilizing a miniature ion-exchange column of Muromac A-1 (Muromac Chemicals, Tokyo) has been developed to increase the sensitivity for aluminum, chromium(III), iron(III), titanium, and vanadium measurements by inductively coupled plasma atomic emission spectrometry (ICPAES). A sample (pH 3.8) is pumped through the column at 6.0 mL min-1, mixing with the buffer solution, and sequentially eluted directly to the nebulizer of the ICP with 2 M HCl acid at 3.0 mL min-1 by using a flow injection analysis (FIA) system. This FIA-ICP method gave signal enhancements that were 34-113 times better than for a conventional continuously aspirated system for the metals studied here. A precision of the technique is better than 5 YO relative standard deviation at the 10 µg L-1 level for aqueous standards, and the sampling rate is 17 samples h-1.
Ion exchange Spectrophotometry Column Preconcentration

"Speciation Of Iron(II) And Iron(III) Using A Dual Electrode Modified With Electrocatalytic Polymers"
Anal. Chem. 1992 Volume 64, Issue 5 Pages 572-575
Andrew P. Doherty, Robert J. Forster, Malcolm R. Smyth, and Johannes G. Vos

Abstract: An amperometric sensor system was demonstrated for the flow injection speciation of Fe(II) and Fe(III) using a dual-electrode assembly of a vitreous carbon electrode modified with electrocatalysts. The sensor consists of two vitreous carbon electrodes (3 mm diameter) shrouded in a teflon block placed in a thin-layer electrochemical flow cell such that the sample plug reaches each electrode simultaneously. The electrodes were modified with 2,2'-bipyridyl - poly(4-vinylpyridine) complexes of Ru and Os, respectively, for the detection of Fe(II) and Fe(III). These electrodes were operated at ~0.12 V vs. SCE and gave quantitative recovery from water samples with ratios in the range 100 to 0.1; interference was only observed in the presence of Cu(II) ions. The construction of a dual sensor for the highly selective speciation anal. for Fe(II) and Fe(III) is demonstrated. The dual sensor is constructed from glassy carbon electrodes modified with the electrocatalytic polymers, [Ru(bipy)2(PVP)10Cl]Cl and [Os(bipy)2(PVP)10Cl]Cl. This approach allows simultaneous detection of Fe(II) and Fe(III) using a flow injection procedure. The modified electrode system exhibited greatly enhanced performance with regard to response, lowering of activation overpotential and absence of electrode fouling. The operational performance of the sensor system exhibited considerable advantage over existing procedures for the speciation anal. for Fe(II) and Fe(III).
Amperometry Electrode Electrode Electrode Speciation Dual detection Interferences

"Use Of Saccharomyces Cerevisiae In Flow Injection Atomic Absorption Spectrometry For Trace Metal Preconcentration"
Anal. Chem. 1994 Volume 66, Issue 9 Pages 1462-1467
Angel Maquieira, Hayat A. M. Elmahadi, and Rosa Puchades

Abstract: Freeze-dried yeast was washed with CHCl3 and hot water, digested with 0.1 M HNO3/HClO4 (1:1) on a steam bath for 30 min. Ethanol was added dropwise and the resulting solution was diluted with water and adjusted to pH 7 with 2 M NaOH. The solution was treated with phosphate buffer solution of pH 5.5, 6.5, 7.5 or 8.5 before the addition of glutaraldehyde-treated controlled pore glass. Immobilization proceeded for 24 h at 4°C under N2, the glass was filtered off and air-dried. Immobilization was unsatisfactory at pH 8.5 and slightly less effective at pH 5.5 than at pH 6.5 or 7.5. Methacrylate columns (4 cm x 2.5 mm i.d.) of the yeast-treated glass were evaluated for the concentration of trace Cd, Zn, Cu(II), Pb(II) and Fe(III) ions from 0.1 M phosphate buffer of pH 6.5. The solution was applied to the column; elution was effected with acid and the metal ions were determined by AAS (details given). Zn and Cu(II) were eluted by 0.1 M HNO3, Pb(II) and Cd by 0.5 M HNO3 and Fe(II) by 0.5 M HClO4/HNO3 (1:1). Linear ranges extended up to 1500 ng/ml (Pb) and the detection limits were 0.1 (Zn) to 8.0 ng/ml (Pb). RSD (n = 10) were 2.6%. The method was used to determine Cu and Cd in sediment.
Environmental Spectrophotometry Preconcentration Controlled pore glass

"Electro-osmosis: A Reliable Fluid Propulsion System For Flow Injection Analysis"
Anal. Chem. 1994 Volume 66, Issue 11 Pages 1792-1798
Purnendu K. Dasgupta and Shaorong Liu

Abstract: The electro-osmotic flow (EOF) pumping system, operated at high potential (± 30 kV maximum), consisted of a polyimide-coated fused-silica capillary (40 cm x 75 µm i.d. x 375 µm o.d.) joined via an electrically-conductive ion-exchange membrane (Nafion 014) to a second capillary (10 cm x 250 µm i.d. x 355 µm o.d.). The EOF pumping system was coupled to a single-line FIA system (illustrated) for the determination of Fe(III) in 10 mM HNO3 using 10 mM xylenol orange in 50 mM HNO3, with 2 mM Na2B4O7 as pump electrolyte and carrier. The pumping system was also coupled to a twin-line FIA system (illustrated) for the determination of chloride using 13 mM mercuric thiocyanate in methanol/0.5 M ferric nitrate in 0.3 M HNO3 (3:2). Online pre-concentration (based on electro-stacking effects) followed by FIA was performed using 10 µM-bromocresol green in 10 µM-Na2B4O7 with 0.1 M Na2B4O7 as carrier. The stability and reliability of the EOF system was reflected in the good reproducibility of results (the RSD were 0.4-0.8%).
Electroosmotic flow Preconcentration

"Catalytic-fluorimetric Determination Of EDTA And Iron(III) By Flow Injection Analysis. Inhibition Methods"
Fresenius J. Anal. Chem. 1985 Volume 321, Issue 5 Pages 467-470
Fernando L&aacute;zaro, Mar&iacute;a Dolores Luque de Castro and Miguel Valc&aacute;rcel

Abstract: Several methods for the direct determination of EDTA and indirect determination of Fe(II) are described, based on the inhibition by EDTA of the catalytic action of Cu(II) in the oxidation of di-2-pyridyl ketone hydrazone by H2O2, and on a decrease in this inhibitory effect caused by Fe. From 0.4 to 2.0 µg mL-1 and 0.2 to 1.0 µg mL-1 of EDTA were determined by normal and reversed flow injection analysis, respectively, and from 40 to 240 ng mL-1 of Fe(III) was determined by reversed flow injection analysis. Tolerance levels for Hg(II), Zn, Cd, Co(II), Mg, Ca, Sr, Ba, Ni(II), Ti, Mn(II), Cr(III), Sn(II) and Pb(II) are presented.
Fluorescence Catalysis Interferences Reverse Tecator

"Optimization Of Ion-chromatographic Trace Analysis For Heavy And Alkaline-earth Metals By Post-chromatographic Derivatization"
Fresenius J. Anal. Chem. 1987 Volume 327, Issue 5-6 Pages 503-508
Da -ren Yan, und Georg Schwedt

Abstract: Six metal ions (Fe(III), Cu, Zn, Co, Fe(II) and Mn in elution order) can be separated in 2.5 min by HPLC on a glass column (10 cm x 3 mm) packed with the strong-acid silica gel cation exchanger BT V TM (10 µm; Biotronik) and operated with a mobile phase (2 mL min-1) of 0.25 M tartrate (pH 2.45). A mixture containing 11 ions (additionally Pb, Ni, Cd, Ca and Mg) was separated in 24 min by HPLC on a glass column (20 cm x 4 mm) packed with BT V TM and operated with a mobile phase (1.3 mL min-1) of 0.1 M tartrate (pH 3.05). Detection (at 490 nm) followed post-column derivatization (60°C, 0.25 mL min-1) with a reagent containing 1 mM 4-(2-pyridylazo)resorcinol, 2 M NH3 (pH 11) and, for the 11-elements separation, 0.25 mM ZnEDTA. Detection limits were 1 to 2 ppb although, with pre-concentration. of water samples on a column (5 cm x 3 mm) packed with BT V TM, metals in concentration. 1 part in 1012 could be determined.
Water HPIC Spectrophotometry Heated reaction Post-column derivatization Preconcentration Speciation Optimization

"Ion Chromatography Of Gallium, Indium And Thallium With Applications To The Analysis Of Ores"
Fresenius J. Anal. Chem. 1988 Volume 331, Issue 6 Pages 601-606
Daren Yan, Jingan Zhang und Georg Schwedt

Abstract: Gallium, In, Tl(III), Fe(III), Cu(II), Pb(II) and Zn were separated in 15 min by ion chromatography on a Nucleosil 10SA column (22 cm x 4.6 mm) with 0.1 M tartrate - 0.12% NaCl (pH adjusted to 2.25 with HCl) as mobile phase (1.1 mL min-1). After post-column derivatization with 1 mM 4-(2-pyridylazo)resorcinol - 0.5 mM ZnEDTA - 2 M NH3 at pH 11 and 60°C in a 6-m reaction coil, the metals were detected at 495 nm. Rectilinear calibration ranges varied from 0.08 to 8 ppm of Fe(III) to 0.4 to 40 ppm of Tl(III), Ga, In and Pb(II). A described procedure for the simultaneous determination of Ga and In in complex ores was applied to one synthetic and four natural samples, e.g., a silicate, containing 40 ppm to 0.1% of Ga and In. For determination of all seven metals in the synthetic sample the coefficient of variation were 2.8% (n = 7).
Geological HPIC Spectrophotometry Heated reaction Post-column derivatization

"Simultaneous Determination Of Iron(II), Iron(III) And Titanium(IV) By Flow Injection Analysis Using Kinetic Spectrophotometry With Tiron"
Fresenius J. Anal. Chem. 1991 Volume 341, Issue 9 Pages 545-549
Koichi Oguma, Shoji Kozuka, Kazuyuki Kitada and Rokuro Kuroda

Abstract: Two flow injection manifolds are described; both involve the air-oxidation of Fe(II) to Fe(III), which reacts with tiron, the reduction with Ag of Fe(III) to Fe(II), which does not, and the reaction of Ti(IV) (not affected by the Ag) with tiron. Determination of these species in any combinations up to 7 µg mL-1 of Ti(IV), 70 µg mL-1 of Fe(II) and 70 µg mL-1 of Fe(III) are feasible.
Spectrophotometry Kinetic Tiron

"Determination Of Iron(II)-iron(III) And Iron(III)-nickel(II) By Two-component Potentiometric Complexometric Titration"
Fresenius J. Anal. Chem. 1992 Volume 342, Issue 1-2 Pages 54-57
Jolanta Kochana, Katarzyna Madej and Andrzej Parczewski

Abstract: The two-component complexometric potentiometric titration has been applied to the simultaneous determination of Fe(III) and Fe(II), and of Fe(III) and Ni(II) in solution. In each case the two analytes were determined by reading the end-points directly from the titration curve. The end-points are determined in a sense arbitrarily, but they are repeatable and easy to be detected precisely. However, the apparent (found) anal. results are biased. They are effectively correlated with the use of a set of two calibration equations (uncomplete second degree polynomials), which approximately the relationship between found endpoints and true concentrations of analytes in solution The regression coefficients in the equations are determined on the basis of titration data obtained for standard solutions whose compounds correspond to a 22 factorial.
Potentiometry Titrations Simultaneous analysis Calibration

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

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

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

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

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

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

"Mixed Sorbents And Their Use In Continuous-flow Analysis"
Microchim. Acta 1995 Volume 119, Issue 1-2 Pages 81-93
Nataly V. Semenova, Elena I. Morosanova, Igor V. Pletnev, Irina M. Maksimova and Yuri A. Zolotov

Abstract: Mixed sorbents were prepared by immobilization of complexing reagents [e.g., 5-phenylazaoxyquinoline (PAO), xylenol orange (XO), octaethyl porphyrine (OEP)] on silica gel or reversed-phase silica gel and used for the separation of metal ions. Full details of sorbent preparation and their properties are given. Sorbents based on phenyl silica gel modified with PAO and XO were used for the simultaneous determination of Co and Fe(III) or Co and Zn. Sample was passed through a column (3 cm x 2 mm i.d.) of sorbent for 30 and 20 s for Co/Fe(III) and Co/Zn, respectively, followed by washing solution for 130 and 110 s, respectively. The sample stream was mixed with air, acetic/boric buffer of pH 3 and 0.5 mM 4-(2-pyridylazo)resorcinol in a coil (25 cm x 1 mm i.d.) and the absorbance was measured at 505 nm. Similar methods (details given) for determination of Al and Mn(II) or Al, Mn(II) and Fe(III) using a C16 silica gel-PAO-OEP sorbent are described. Calibration ranges, RSD and detection limits are tabulated.
Spectrophotometry Solid phase reagent Complexation Silica gel

"Flow Injection Potentiometric Detection Of Metal-ions Based On Tungsten-oxide Electrode"
Electroanalysis 1997 Volume 9, Issue 2 Pages 141-144
Zuliang Chen, Peter W. Alexander

Abstract: The use of a tungsten oxide electrode for potentiometric flow injection analysis of transition metal ions is described. The effect of a variety of experimental conditions, including the carrier pH, the types of ligands and their concentrations, was studied. It was found that the best sensitivity for the ions tested was obtained using EDTA as a ligand. The electrode exhibited a linear response for Fe3+, Cu2+, Pb2+ and Ca2+ in the range of 2.5 x 10^-4 M to 2 x 10^-3 M using with 1 x 10^-3 M EDTA at pH 5.0 as carrier. The detection limits were found to be between 1 x 10^-5 to 5 x 10^-5 M. Reproducibility for Fe3+ was about 1.7% with a stable baseline potential. The method is based on the use of the FIA system of Alexander et al. (Anal. Lett., 1984, 17, 3 09) for the indirect determination of metals at a tungsten oxide wire electrode after complexation with EDTA. Sample (10 µL) was injected into a stream of 0.5 ml/min 1 mM EDTA with pH adjusted to 5 with 1 mM NaOH and Ag/AgCl as reference electrode. Calibration graphs were linear for 0.25-2 mM Fe3+, Cu2+, Pb2+ and Ca2+ with detection limits of 1, 50, 50 and 10 µM, respectively. In the determination of 1 mM Fe3+, the peak height RSD was 1.7% (n = 10). The effects of varying complexing agent molecule and concentration, carrier pH and flow rate on the determinations were studied. The results are compared with those obtained at a Cu electrode. 20 References
Potentiometry Electrode Voltammetry EDTA Method comparison Optimization Complexation

"Potentiometric Detection Of Metal-ions Separated By Liquid-chromatography Using A Tungsten-oxide Electrode"
Electroanalysis 1997 Volume 9, Issue 11 Pages 818-821
Zuliang Chen *, Peter W. Alexander

Abstract: The use of a tungsten oxide sensor for the potentiometric detection of metal ions separated by liquid chromatography is described. Separation of metal ions such as Fe3+, Fe2+. Cu2+ and Pb2+ was performed by ion chromatography using a mobile phase containing 25 mM sodium tartrate/2 mM ethylenediamine at pH 3.8. Calibration plots were linear in the range 0.5 to 3.5 mM. Potentiometric detection was also applied to ion-interaction chromatography. The results showed that separation of metal ions was improved and the detection limits for the test metals in the range of 0.5-5 nmol were obtained in the presence of sodium citrate/1-octanesulfonic acid at pH 3.0. The potentiometric detection described in this article is shown to base advantages in terms of low cost, simplicity and sensitivity. 23 References
HPIC Electrode Potentiometry Interferences

"Flow Injection System For Simultaneous Determination Of Iron(III) And Iron(II) With A Single Detector And A Single Injection"
Anal. Sci. 1989 Volume 5, Issue 6 Pages 783-784
T. YAMANE and E. GOTO

Abstract: The system incorporates two 15-cm PTFE sample loops (0.5 mm i.d.) separated by a 4-m coil. The test solution is injected simultaneously at the two positions into the carrier stream (H2O), and at the same time an increment of 0.05% ascorbic acid is injected into a 15-cm reagent loop preceding the second sample loop. The stream is then merged with a stream of 1.25 mM 1,10-phenanthroline at pH 5.9 (acetate buffer) in a 1-m reaction coil before passing through a spectrophotometric detector (526 nm). The first sample plug reaching the detector gives a signal due to total Fe, and the second gives a signal for Fe(II) only. Calibration for Fe(II) and Fe(III) is effected separately. For a solution 50 µM in both Fe(II) and Fe(III), the coefficient of variation was 0.9 and 0.8%, respectively.
Spectrophotometry Simultaneous analysis Dual injection Speciation

"Preconcentration, Separation And Multi-elements Determination In Seawater Using A Cellulose-zinc Hydroxide System With Inductively Coupled Plasma Atomic Emission Spectrometry"
Anal. Sci. 1992 Volume 8, Issue 1 Pages 45-50
I. M. M. KENAWY

Abstract: The use of a cellulose-Zn(OH)2 mixture for the determination of traces of Cd(II), Cr(III), Cu(II), Fe(III), Hg(II), La(III), Ni(II), Pd(II), Sn(IV), and vanadate ion in seawater at different pH's was carried out employing the ICP technique. The effects of the concentration. of Zn(II), mass of the cellulose, shaking time, and pH on the pre-concentration were studied. The method is simple and applicable to the trace determination of 10 heavy metals at the ppb level. The effect of alkali and alkaline earth cations on the pre-concentration of the tested metal ions was examined The distribution coefficient Kd is in the range 102.86-106.31 mL/g.
Sea Spectrophotometry Multielement PPB Preconcentration pH Optimization

"Kinetic Behaviour Of Ligand-displacement Reaction Of Iron(II) And Iron(III)-EGTA Complexes With 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol By Flow Injection Analysis And Its Application"
Anal. Sci. 1995 Volume 11, Issue 5 Pages 857-859
B.-N. WANG, G.-N. TANG and L.-Y. DENG

Abstract: Portions of standard Fe(II) or Fe(III) solutions were mixed with 1 mL 1 mM EGTA and 2 mL 0.1 M potassium biphthalate buffer of pH 3.1 (buffer A; preparation details given) and the solution was diluted to 25 mL with water (solution S). A 6 mL portion of 1 mM 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol was mixed with 4 mL buffer A and 8 mL 95% ethanol and diluted to 50 mL with water (solution R). Portions of sample solution S and reagent solution R were pumped into a 6-way injection valve (schematic shown) and the valve was switched to the injection position. Both solutions were propelled synchronously into a stream of buffer A (2.4 cm/min) and mixed rapidly in a chemical reaction block (48 cm). The mixture was carried to the flow cell, the flow was stopped and the absorbance was measured every 10 s at 556 nm. The calibration graph was linear up to 30 µg Fe(II) and Fe(III)/25 mL solution. The rate constants for both Fe(II) and Fe(III) were calculated (details given) and the method was used to determine both valence states in synthetic mixtures using multivariate calibration (details given).
Spectrophotometry Chemometrics Rate constants Multivariate calibration Speciation Stopped-flow Kinetic

"Reversed Micellar Mediated Luminol Chemiluminescence Detection Of Iron(II) And Iron(III) Combined With Online Solvent Extraction Using 8 Quinolinol"
Anal. Sci. 1998 Volume 14, Issue 1 Pages 203-207
Theingi KYAW, Terufumi FUJIWARA, Hidekazu INOUE, Yasuaki OKAMOTO and Takahiro KUMAMARU

Abstract: An enhancement of the chemiluminescence (CL) emission , observed when the iron(II) complex of 8-quinolinol (oxine), Fe(oxine)3, was mixed with a reversed micellar solution of cetyltrimethylammonium chloride in chloroform-cyclohexane (6:5 v/v)-water (1.0 M NaOH) containing luminol and hydrogen peroxide, was investigated in order to develop a method for iron(III) determination based on the direct coupling of on-line solvent extraction with a reversed micellar-mediated CL reaction in a reverse-flow injection system using a microporous Teflon membrane filter for phase separation. In the CL process, uptake of the complex by reverse micelles and its subsequent decomposition occurs easily, followed by an iron(III)-catalyzed luminol reaction. In the on-line process, iron(III) was extracted from an aqueous solution into chloroform via complex formation with oxine. Upon mixing the reversed micellar luminol solution with the extract stream in a flowcell of a CL monitor, the produced CL signal was measured. A detection limit of 5 ng mL-1 Fe(III) and a linear calibration containing iron(II) and iron(III), total iron, Fe(II)+Fe(III), was measured asthe peak height in the presence of the hydrogen peroxide used to oxidize iron(II) to iron(III) prior to solvent extraction, while only iron(III) could be determined in the absence of hydrogen peroxide.
Chemiluminescence Reverse micelle Complexation 8-Hydroxyquinoline Speciation Solvent extraction Reverse Teflon membrane Phase separator Optimization

"Investigation Into Low-cost Flow Injection Analysis"
Anal. Proc. 1989 Volume 26, Issue 2 Pages 48-49
J. F. Tyson

Abstract: An inexpensive detection system was contructed (details given) for spectrophotometric detection in flow injection analysis. A flow cell was designed that incorporated optical-fiber light guides and stainless-steel sample inlet tubes set in a Perspex block, and the detector consisted of a photodiode and a simple amplifier. The system was applied in the determination of Fe(III) with use of ferron, KSCN or Variamine blue RT salt (C. I. 37240). An inexpensive detection system was constructed (details given) for spectrophotometric detection in flow injection analysis. A flow cell was designed that incorporated optical-fiber light guides and stainless-steel sample inlet tubes set in a Perspex block, and the detector consisted of a photodiode and a simple amplifier. The system was applied in the determination of Fe(III) with use of ferron, KSCN or Variamine blue RT salt (C. I. 37240).
Spectrophotometry Optical fiber Flowcell Detector Photodiode Low cost

"Flow Injection Analysis As A Tool For Metal Speciation"
Am. Lab. 1984 Volume 16, Issue 7 Pages 17-18
Pacey, G.E.;Bubnis, B.P.

Abstract: The usefulness of flow injection analysis in automated systems (with pump programming and 'packed-bed' reaction coils) is described for the rapid processing of large numbers of samples. The importance of metal speciation in environmental and toxicological studies is emphasized and, as an example, a flow injection method for determination of Fe(II) and Fe(III) with use of 1,10-phenanthroline and spectrophotometry at 512 nm is described; it was suitable for application in the range 5 to 30 ppm of each species.
Environmental Spectrophotometry Spectrophotometry Pump programming Speciation Review

"The Synergistic Catalytic Effect Of Metal-cations On Kinetic Reactions And Its Application To Determination Of Iron Oxidation-states"
Chem. Anal. 1995 Volume 40, Issue 5 Pages 815-821
Ronghuan, H.;Jianhua, W.

Abstract: Iron(II) and iron(III) catalyzed hydrogen peroxide/chromotropic acid kinetic reactions were studied by the stopped FIA technique. The concept of the synergistic catalytic coefficient (D) was defined. By introducing this coefficient into the previously established procedure for the simultaneous determination of a binary mixture of metal cations in a kinetic reaction, the deviation of the absorbance from the additivity rule could be effectively eliminated, and the linear concentration ranges were enlarged. The selectivity of the kinetic systems, in addition, was also improved remarkably. The iron oxidation states in wastewater and several simulated samples have been determined. The results are satisfactory. (9 references)
Waste Spectrophotometry Catalysis Kinetic Stopped-flow Speciation

"High-speed Flow Injection Determinations Of Oxidative Agents In Aqueous-solutions Based On Reaction With An Online Generated Leuco Dye"
Chem. Tech. 1990 Volume 42, Issue 7 Pages 304-307
MU&Ecirc;LLER H. ; HANSEN E. H.

Abstract: In a FIAstar 5020 automatic analyzer. (Tecator) with motor-driven injector loop (60 µL), streams (2 mL min-1) of aqueous thionine violet solution (0.2 mg mL-1) and of EDTA solution (3 g in 100 mL of water, diluted to 200 mL with acetate buffer of pH 4.7) were combined and passed through a glass reaction coil (1 m x 2 mm) under a 250-W high-pressure Hg lamp to reduce the dyestuff to its leuco form. Sample solution [e.g., Cr2O72-, Fe(CN)63-, VO3-, S2O82- or Fe3+] was injected into the stream, and the absorbance was measured at 600 nm in a Corning 252 flow-through photometer with a Hellma 178.012 QS flow-through cell (10 mm; 18 µL). Up to 180 samples h-1 can be analyzed. The limit of detection is ~1 µM. As H2O2 reacts only at concentration. of >10 to 100 mM, the determination of, e.g., 10 µM-S2O82- is possible in a 150-fold excess of H2O2.
Spectrophotometry Automation Tecator Injector EDTA Buffer pH Detection limit

"Comparison Of Stirring And Vortex Mixing For The Extraction Of Available Nutrients From Soil Using A Laboratory Robot"
Commun. Soil Sci. Plant Anal. 1996 Volume 27, Issue 9-10 Pages 2213-2220
Bunnell, A.M.;Langan, P.A.;Quigley, M.N.;Reid, W.S.

Abstract: Soil was dried at 50°C and sieved through a 2 mm screen. Portions (10 ml) of the dried soil plus 1 mL of activated C were shaken with 50 mL of a solution comprising 5 kg sodium acetate trihydrate and 1.6 l anhydrous acetic acid in 50 l water of pH 4.8±0.5 (Morgan solution), and filtered. Further extractions were performed robotically using vortex or paddle stirring using 2 mL of dried soil and 10 mL of extraction solution, and similar soil:extractant ratios with 3-6 mL of soil. Using continuous-flow analysis, Al, Cu, Ca, K, Mg, Zn, Mn(II) and Fe(III) were determined by ICP-AES, and nitrate and phosphate by colorimetry (no details given). Robotic paddle stirring was shown to efficiently aid the extraction of the analytes, irrespective of the actual soil:extractant volumes used.
Environmental Spectrophotometry Sample preparation Robot

"Simultaneous Determination Of Iron(III), Iron(II), Copper(II) And Zinc(II) In Water By Ion Chromatography With Post-column Derivatization"
Fenxi Ceshi Xuebao 1993 Volume 12, Issue 3 Pages 16-21
Wang Shengming

Abstract: Water was passed through a column of Dionex CS-2 with a mixed complexing agent solution of sulfosalicylic acid, tartaric acid and oxalic acid, and an eluent of protonated ethylenediammonium ion. The separated ions were treated with 4-(2-pyridylazo)resorcinol in a post-column reactor before spectrophotometric detection at 500 nm. The method was used to analyze environmental water and high-purity water.
Water Environmental HPIC Spectrophotometry Post-column derivatization

"Determination Of Iron(II) And (III) By Flow Injection Analysis"
Fenxi Huaxue 1992 Volume 20, Issue 1 Pages 88-90
Chen, D.;Cai, R.X.;Zeng, Y.E.

Abstract: A 360 µL synthetic sample was injected into a flow injection analyzer. (illustrated) and carried at 2.4 mL min-1 to a splitter. One carrier stream was reacted with a reagent stream containing aqueous 0.005% of the 2,6-dichloro-4-sulfophenylazo derivative of arsenazo I (I) of pH 4, before detection of the Fe(III) - I complex at 618 nm. The other carrier stream was reacted with a stream of 0.25% o-phenanthroline (II) of pH 3 before detection of the Fe(II) - II complex at 512 nm. The reagent stream flow-rates were 0.6 mL min-1 and a 1 m reaction tube (0.5 mm i.d.) was used. The coefficient of variation were 5%. In the determination of 25 mg of Fe(III) and Fe(II), tolerance levels were 1 mg of Mn(II), 2 mg of Zn(II), 5 mg of Sn(IV), 0.1 mg of Mo(VI) and 0.2 mg of Co(II), together with 1 mg of Fe(III) and 0.5 mg of Fe(II) in the presence of the other analyte ion. The sampling rate was 120 h-1.
Spectrophotometry Speciation Sample splitting Interferences

"Determination Of Iron In Drinking Water And Pharmaceuticals By A First-derivative Stop-flow Method"
Fenxi Huaxue 1994 Volume 22, Issue 7 Pages 695-697
Wang, Z.B.;Zheng, Z.Z.;Jin, M.

Abstract: Drugs or tap water were treated with acetic acid/sodium acetate buffer of pH 5.7, triethylenetetramine and 21 mM tetramethyl-p-phenylenediamine and diluted with water. The solution was injected into an FIA system at 7.9 ml/min to mix with a stream of 1.2% H2O2 at 7.9 ml/min. The streams were programmed to flow for fixed time of 40 s then stop for 45 s, before entering a reactor (13.8 cm long) and detection at 565 nm. Five-fold of Cu(II) did not interfere. The calibration graph was linear for 4-40 ng/ml of Fe(III) with a detection limit of 1.92 ng/ml. Recovery was 98.7-101% with RSD of 2.5%.
Water Pharmaceutical Spectrophotometry Interferences Stopped-flow

"Construction And Test Of An Automated Flow Injection Stopped-flow Kinetic Analyser"
Fenxi Huaxue 1995 Volume 23, Issue 5 Pages 551-553
Huang, H.P.;Cai, R.X.;Lin, Z.X.;Zeng, Y.E.

Abstract: The design and construction of the cited flow injection analyzer. are described. An Apple-II microcomputer is used to control the loading and sampling injection, start and stop of the pump, collection and process of data as well as display via a program written in BASIC. The performance of the analyzer. was checked with the Fe(III)/thiocyanate system using a fixed-time method and with the V(V)-micellar catalyzed system using an initial rate method.
Spectrophotometry Complexation Computer Micelle Apparatus Stopped-flow Kinetic

"Kinetic-simultaneous Spectrophotometric Determination Of Iron(II) And Iron(III) By Flow Injection Stopped-flow Technique"
Fenxi Huaxue 1995 Volume 23, Issue 9 Pages 1017-1021
Tang, G.N.;Wang, L.J.;Wang, B.N.

Abstract: Weakly acidic sample (24 µL) was carried at 2.1 ml/min by a stream of 0.1 M sodium acetate/0.1 M acetic acid buffer of pH 5.6 to react with 5% Tiron in a reactor (48 cm long); while flow was stopped measurement of absorbance at 556 nm was taken, readings were taken at 5, 10, 20, 30 and 60 s. Beer's law was obeyed for 30 µg/ml of Fe(II) and Fe(III). For 15 µg/ml of Fe(II) and 10 µg/ml of Fe(III), RSD (n = 6) were 3.2 and 3.9%, respectively. The sampling frequency was 20 runs/h. The method was used to analyze synthetic samples.
Spectrophotometry Stopped-flow Kinetic Speciation Tiron

"Flow Injection Kinetic Spectrophotometric Determination Of Iron(III) And Aluminum(III)"
Fenxi Huaxue 1996 Volume 24, Issue 10 Pages 1166-1169
Chen, Y.P.;Cai, R.X.;Zeng, Y.E.

Abstract: The method proposed for simultaneous determination of Fe and Al is based on the formation of the colored ternary complex 5-bromo-salicylfluorone (I)-hexadecyltrimethylammonium bromide (II)-Fe (or Al). Portions (2 ml) of ethanolic 0.1 µg/ml I were mixed with 2 mL 5 mM II and 5 mL acetate buffer of pH 3.5 and the mixture was diluted to 25 mL with water. After thermostatting at 30°C, portions of reagent and standard solutions (containing Fe:Al in ratio 1:1) were injected into a flow injection system (schematic shown) at 2 ml/min. The mixed solution was transferred to a spectrophotometer and the absorbance of the complex was measured at 568 nm vs. a reagent blank. Calibration graphs were linear up to 15 and 30 µg/25 ml solution, respectively, for Fe and Al. Recoveries were 94-104%. Many co-existing cations did not interfere but EDTA, fluoride, phosphate and perchlorate interfere.
Spectrophotometry Interferences Kinetic

"Flow Injection Stopped-flow Kinetic Method Based On Differential Catalytic Reaction For Simultaneous Determination Of Fe And Mo"
Fenxi Kexue Xuebao 1998 Volume 14, Issue 2 Pages 148-150
Li Jianping, Chen Youjun

Abstract: The catalytic effects of Fe(III) and Mo(VI) on the reaction between hydrogen peroxide and O-aminophenol were studied. A stopped-flow kinetic spectrophotometric method based on the differential rate of catalytic reactions for the simultaneous determination of Fe(III) and Mo(VI) is proposed. The linear range is 0.5~15 µg/mL for Mo(VI) and 0.1~2.5 µg/mL for Fe(III). Most common ions do not interfere. The method has been used for the determination of Fe(III) and Mo(VI) in mixture samples.
Spectrophotometry Kinetic Stopped-flow Catalysis Simultaneous analysis Interferences

"Flow Injection Spectrophotometric Analysis Of Iron Speciation In Natural Water"
Huanjing Huaxue 1989 Volume 8, Issue 4 Pages 35-40
Xu, Quan; Yuan, Xiushun

Abstract: Iron speciation in water was studied using the flow injection-spectrophotometric method. The color-development reaction of Fe2+ and 1,10-phenanthroline was used. Under optimum conditions, Fe3+ was reduced by solid ascorbic acid for the determination of total Fe before the samples were injected. Beer's law was applicable within 0-2.5 ppm ranges of Fe(II); a detection limit of 0.02 ppm was obtained. The relative error is ±0.05 ppm when the concentration of Fe(II) and Fe(III) is 1 ppm. The relative standard deviation for 2 ppm Fe2+ is 0.5% in five measurements. The method can be used at a rate of 250 injections/h. Fe(II) and Fe(III) were determination in aqueous phases and in suspension matter in rainwater and tapwater and lake water with satisfactory results.
Rain Lake Water Spectrophotometry Injection technique Speciation Optimization

"Flow Injection Methods For Determination Of Iron(III)"
Indian J. Chem. A 1981 Volume 20, Issue 11 Pages 1051-1053
Leggett, D. J.; Chen, N. H.; Mahadevappa, D. S. (SFS)

Abstract: The relative merits of flow injection methods for the determination of Fe(III) by complex formation with b-resorcylic acid (BRA), salicylic acid (SA), sulfosalicylic acid (SSA), and KSCN were examined by a simplified flow-injection app. with a single channel manifold. Sampling rates of the order of 250/h have been achieved. The thiocyanate and BRA methods are sensitive for the determination of Fe(III). A modified SSA method (Ogawa, K.; Tobe, N., 1966) was used for estimating Fe(III) in ferrous-ferric mixtures The effects of flow parameters and interferences on the flow-injection determination of Fe(III) were also studied. (SFS)
Spectrophotometry Review Interferences Method comparison

"Automated Stopped-flow / Unsegmented Solution-storage Analyzer"
Int. Lab. 1981 Volume 11, Issue 1 Pages 32-45
Malmstadt, H. V.; Walczak, K. M.; Koupparis, M. A. (SFS)

Abstract: An automated stopped-flow/unsegmented solution-storage analyzer provides rapid automatic aliquating, mixing, and sequential transfer of solutions to a storage coil. Various lengths of storage coil are used for specific analyzes in order to provide the desired delay times and sample conditioning cell. The analyzer can be used to advantage with analytical methods that require a 10^-30 s or longer delay time to reach equilibrium or for single-point reaction-rate methods. The analyzer was illustrated by equilibrium-method determination of Fe(III) and ascorbic acid and by determining P and protein N by single-point reaction-rate methods. (SFS)
Review Computer Stopped-flow

"Flow Injection Analysis Of Water. 1. Automatic Preconcentration Determination Of Sulfate, Ammonia And Iron(II)/iron(III)"
J. Autom. Methods Manag. Chem. 1993 Volume 15, Issue 4 Pages 141-146
J. S. COSANO, M. D. LUQUE DE CASTRO, and M. VALC&Aacute;RCEL

Abstract: A simple flow injection manifold (illustrated) is described for the sequential determination of sulfate, NH4+ and Fe2+/Fe3+ in industrial water. For the determination of sulfate, a turbidimetric method using BaCl2 as derivatizing reagent was used. For NH4+, the Berthelot reaction (i.e., the reaction between hypochlorite and phenol in the presence of NH4+ in a basic medium) was used and the absorbance of the colored product was measured at 636 nm. For the speciation of Fe, Fe2+ was determined by treating a portion of sample solution with 1,10-phenanthroline and the absorbance of the orange complex formed was measured at 510 nm. For the determination of total Fe another portion of sample solution was passed through a copperized-cadmium redox column to reduce Fe3+ to Fe2+ followed by reaction with 1,10-phenanthroline. The concentration. of Fe3+ was calculated by difference. A micro-column of a suitable ion-exchange material was used for the online pre-concentration. of each analyte prior to injection. Results are tabulated. The system may be fully automated.
Water Spectrophotometry Turbidimetry Preconcentration Speciation

"Flow Injection Analysis Of Water. 2. Integrated System For Automatic Multi-determination"
J. Autom. Methods Manag. Chem. 1993 Volume 15, Issue 4 Pages 147-150
J. S. COSANO, M. D. LUQUE DE CASTRO, and M. VALC&Aacute;RCEL

Abstract: The automation of an integrated flow injection system (see previous abstract) for the determination of ammonia, sulfate and Fe2+/Fe3+ in industrial water is described. The system was designed for the determination of individual analytes in a large batch of samples, as manual selection of parameters and units for each individual analyte is required.
Water Multidetection

"Flow Injection Analysis Of Iron In Rain Water With Thiocyanate And Surfactant"
J. Autom. Methods Manag. Chem. 1997 Volume 19, Issue 2 Pages 45-50
A. N. TRIPATHI, S. EHIKHALIKAR, and K. S. PATEL

Abstract: Filtered rain water (5 ml) was oxidized with 0.2 mL concentrated HNO3 and a portion (370 µL) was injected into a stream (4 ml/min) of water which merged with reagent solutions of 1.3 M ammonium thiocyanate, 0.07% cetylpyridinium chloride and 0.05 M HCl/0.05 M H2SO4 (1:1) which were aspirated through tubes of 1.14, 0.51, 0.51 and 0.38 mm diameter, respectively. The optimum coil length of the merging zone was 30 cm (0.5 mm diameter). Sample throughput was 90/h at 4 ml/min flow rate. The optimal rise, injection and delay times were 1, 15 and 25 s, respectively. Detection was at 490 nm. No interference was observed. The detection limit was 8 ppb Fe and the calibration graph was linear for 30-3000 ppb. The RSD (n = 6) at 300 ppb was 0.9%. The results agreed with those obtained by AAS. To determine Fe(III) only, sample was analyzed before oxidation.
Rain Spectrophotometry Speciation Method comparison Optimization Surfactant Interferences Merging zones

"Determination Of Reaction Stoichiometries By Flow Injection Analysis. A Laboratory Exercise"
J. Chem. Educ. 1986 Volume 63, Issue 6 Pages 552-553
Angel Rios, Dolores Luque de Castro and Miguel Valcarcel

Abstract: A laboratory experiment is described for the determination of reaction stoichiometries using a photometric method for the calculation of complex-formation and redox-reaction stoichiometries. The method is based on a closed-loop configuration
Spectrophotometry Education Stoichiometry Closed loop

"Determination Of Pyritic Sulfur In Coal Or Iron(III) In Aqueous Solutions By Flow Injection Analysis"
J. Coal Qual. 1985 Volume 4, Issue 1 Pages 68-71
Whitaker, M.J.; Bryant, M.F.

Abstract: The simple automated method described for determining pyritic S involves initial acid digestion of the sample to oxidize pyritic Fe to Fe(III), and use of NH4SCN solution as the carrier stream and color reagent for Fe(III). About 60 samples can be analyzed in 1 h for 5 to 150 ppm of Fe(III) (0.05 to 1.7% of pyritic S for 1-g samples); the coefficient of variation is <1%. A computer capable of collecting several signals simultaneously is used in conjunction with software by which data are plotted, sample peak-height values can be edited, and laboratory reports are prepared.
Coal Sample preparation Spectrophotometry Computer

"Speciation Of Iron In A Closed-loop System By Multidetection With One Detector"
Quim. Anal. 1987 Volume 6, Issue 3 Pages 314-320
Rios, A.;Luque De Castro, M.D.;Valcarcel, M.

Abstract: NA
Closed loop Multidetection Speciation

"Simultaneous Determination Of Iron And Vanadium By Catalytic Spectrophotometry In A Flow Injection System"
Shaanxi Shifan Daxue Xuebao (Ziran Kexue Ban) 1998 Volume 26, Issue 4 Pages 66-69
Liu Xiuping, Zhang Zhiqi, Chen Shirong

Abstract: A flow injection catalytic spectrophotometry is described for the simultaneous determination of iron(III) and vanadium(V). It is based on the different catalytic behavior of iron(III) and vanadium(V) to decoloration reaction between potassium bromate and victoria blue B in different media and chemometric method CPA matrix is employed. This method has been applied to determination of iron(III) and vanadium(V) binary mixture in the range of 1:2~40:1 (concentration. ratio) with average recoveries of 95.5% and 103.5%, respectively. for iron(III) and vanadium(V).
Spectrophotometry Catalysis Simultaneous analysis Chemometrics

"Flow Injection As An Aid To Element Speciation"
Spectrosc. World 1990 Volume 2, Issue 1 Pages 32-34
McLeod, C.W.;Wei, J.

Abstract: The use of flow injection analysis with atomic spectroscopic detection is outlined for the speciation of elements. The determination of Fe(II) and Fe(III), Cr(III) and Cr(VI), and of inorganic mercury and methylmercury are presented as examples.
Speciation

"Semiautomatic Method For Determination Of Iron(II) And Iron(III) By Using Flow Injection And A Coulometric Monitor"
Sumitomo Tokushu Kinzoku Giho 1984 Volume 7, Issue 1 Pages 33-37
Kikui, Fumiaki; Hayakawa, Tetsuji (SFS)

Abstract: The method involves monitoring Fe3+ by using a coulometric monitor with a C electrode at 0.26 V vs. NHE and an auxiliary electrode with K4Fe(CN)6-K3Fe(CN)6-KNO3-NH4OH electrolyte. The method was used for monitoring FeCl3 etching solutions containing Co, Cr, and Ni. For determining total Fe the divalent ions were 1st oxidized by boiling with H2O2. (SFS)
Industrial Coulometry Simultaneous analysis

"Optosensors And Reflection Spectroscopy In The Flow Analysis Of Water"
Zavod. Lab. 1996 Volume 62, Issue 1 Pages 1-6
Shvoeva, O.P.;Dedkova, V.P.;Savvin, S.B.

Abstract: Methods of determining heavy metals in water using flow sensor systems are described. The methods are based on the concentration of metal ions in flow cells containing fibrous material or fabric discs with immobilized organic reagents. Two types of sensor are proposed: carrier discs with previously immobilized reagent (colored discs); and white carrier discs with immobilization of the reagent during the flow regime. Color changes were detected by diffuse reflectance spectroscopy (NIR spectrometry) after passage of sample through the cells at 10 ml/min. The optimum carriers, reagents and operating conditions are presented for U(VI), Pd(II), Co(II), Cu(II), Ni(II), Fe(III) and Cr(III). The sensor systems formed the basis for the OSA-TM optical sensor analyzer. which can be used to determine Co, U, Pd, Ni, and Cr in fresh water.
Environmental Spectrophotometry Sensor Optosensing Optimization Immobilized reagent Optical fiber

"Determination Of Iron(III) By Spectrophotometric Flow Injection Analysis"
J. Anal. Chem. 1985 Volume 40, Issue 10 Pages 1859-1865
Kuznetsov, V.V.

Abstract: Fertilizers of superphosphate type are analyzed for ~2.3 to 3% of Fe2O3. The carrier stream, supplied from a Mariotte bottle at 3 mL min-1, is 40 mM in Na sulfosalicylate; its pH is 2 (HCl) or 9 (aqueous NH3) when determining 1 to 5 or 10 to 50 µg mL-1 of Fe, respectively. The 70-cm glass mixing coil has i.d. of 0.5 mm; 10 µL samples of acid extracts of the fertilizers can be injected at a rate of 200 samples h-1. The absorbance is measured at 490 nm (at pH 2) or 420 nm (pH 9); a 40 µL (2-cm) flow-through cell is used. The absorbance signal is digitized and the peak heights are printed automatically.
Commercial product Spectrophotometry

"Continuous-flow Analysis. Determination Of Iron In Technological Solutions"
J. Anal. Chem. 1992 Volume 47, Issue 7 Pages 1211-1217
Rodionova, T.V.;Beklemishev, M.K.;Dracheva, L.V.;Zolotov, Y.A.

Abstract: A flow diagram is given of an automated continuous-flow analysis (CFA) system for the spectrophotometric determination of Fe(II) and Fe(III) with sulfosalicylic acid or 1,10-phenanthroline at 505 nm or with SCN- at 480 nm; samples can be injected at rates of 180, 100 and 140 h-1, respectively. The determination of Fe by CFA with SCN- is more sensitive than by flow injection analysis. The method was used to determine 0.05 to 0.1 µg mL-1 of Fe in technological solution with coefficient of variation of 3 to 12%.
Industrial Spectrophotometry Speciation

"Flow Injection Determination Of Iron(III)"
J. Anal. Chem. 1993 Volume 48, Issue 3 Pages 509-512
Gur'ev, I.A.;Lazareva, O.P.;Zyuzina, L.F.

Abstract: Principles for the selection of flow conditions and composition in the flow injection determination of oxidizing agents are described. The principles were applied to the determination of Fe(III) in magnetites; optimum conditions are described.
Magnetite Optimization

"Flow Injection Iodometric Determination Of Oxidants"
J. Anal. Chem. 1994 Volume 49, Issue 6 Pages 579-582
Gur'ev, I.A.;Zyuzina, L.F.;Lazareva, O.P.

Abstract: The method is based on the oxidation of KI and the reaction of the iodine formed with Na2S2O3. The analyte containing H2O2 was mixed with the reagent comprising a mixture of 1 M KI, 50% H2SO4 and (NH4)2MoO4 catalyst. Portions (50-100 µL) of 0.1 M iodine, the prepared analyte and a 1 mM standard solution were successively injected into a 0.3 ml/min flow of 0.1 M Na2S2O3. The mixture, after passing through a 307 mm long reaction spiral entered a potentiometric cell with Pt indicator electrode and a Ag/AgCl auxiliary electrode. The RSD was ~0.03. A similar procedure was used for the determination of chromate and Fe(III).
Potentiometry Electrode Electrode Catalysis

"Expert Multi-syringe Flow-injection System For The Determination And Speciation Analysis Of Iron Using Chelating Disks In Water Samples"
Anal. Chim. Acta 2004 Volume 524, Issue 1-2 Pages 79-88
Carmen Pons, Rafael Forteza and V&iacute;ctor Cerd&agrave;

Abstract: A novel expert multi-syringe flow-injection system has been developed. This system, which is able to choose for itself the best strategy to quantify the analyte, has been applied to the spectrophotometric determination, pre-concentration and speciation analysis of iron. The determination of the lowest iron concentrations benefits from the retention of the analyte on a chelating disk (iminodiacetic acid groups) which has been placed in a laboratory-made methyl methacrylate cylindrical device. A three-way solenoid commutation valve allows the deviation of the flow towards the chelating disk to follow the pre-concentration schemes when necessary. Ammonium thiocyanate was used as the chromogenic reagent for iron(III). Total iron can be determined by on-line oxidation of iron(II) to iron(III) with a hydrogen peroxide stream. A mass calibration was feasible in the wide range from 0.019 to 3 µg. The detection limit (3sb/S) was 19 ng. The repeatability (RSD), calculated from 11 replicates using 3 mL injections of a 0.5 mg L-1, was 2%. When pre-concentration was not required, two linear calibration graph between 0.1 and 20 mg L-1 and between 0.2 and 35 mg L-1 for the determination of iron(III) and total iron, respectively, were obtained. The proposed technique has been validated by replicate analysis (n=3) of a certified reference material of water with satisfactory results. The use of chelating disks offers several advantages over the conventional resin.
Sea NWRI TMDA-54.3 Spectrophotometry Preconcentration Multicommutation Multisyringe Method comparison Expert system

"An Intelligent Flow Analyser For The In-line Concentration, Speciation And Monitoring Of Metals At Trace Levels"
Talanta 2004 Volume 62, Issue 5 Pages 887-895
Carmen Pons, Manuel Mir&oacute;, Eduardo Becerra, Jos&eacute; Manuel Estela and V&iacute;ctor Cerd&agrave;

Abstract: An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents.The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimized physical and chemical variables, linear analytical curves over the ranges 0.025-0.5 or 2.0-40 mg L-1 Fe were attained. The 3s detection limit, the repeatability at the 0.5 mg L-1 level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng mL-1 Fe, 2.5%, 58.6 and 22 h-1, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination. A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required.
Water Water Sea Speciation Interferences Expert system Method comparison Preconcentration

"A Novel Chemical Image Sensor Consisting Of Integrated Microsensor Array Chips And Pattern Recognition"
Meas. Sci. Technol. 2003 Volume 14, Issue 7 Pages 1040-1046
He Huiqi, Xu Gaixia, Ye Xuesong and Wang Ping

Abstract: A novel chemical image sensor developed for liquid component analysis is proposed in this paper; using it, pH values ranging from 1 to 12 and six kinds of metal ion, namely Cu2+, Fe2+, Fe3+, Ca2+, Zn2+, and Mg2+, can be detected qualitatively and quantitatively. The sensor applies the principles of optical chemistry and microfabrication technology to detect the ion concentrations in the solution, and has the advantages of high sensitivity, reduced contamination, a lower sample volume required, and the capability of detecting several indices at one time. Moreover, three multivariate data analysis methods are suggested in the paper for treating the raw data acquired from the microbeads, and predicting the results. The study demonstrates that the principal component analysis is capable of classifying six kinds of cation with success. Both partial least-squares regression (PLS) and artificial neural networks (ANN) can be used to compute the pH values quantitatively; furthermore, the PLS method has the advantage of requiring fewer iteration steps than the ANN approach.
Partial least squares Neural network Microfluidic

"Optical Fibre Reflectance Sensor For The Determination And Speciation Analysis Of Iron In Fresh And Seawater Samples Coupled To A Multisyringe Flow Injection System"
Anal. Chim. Acta 2005 Volume 528, Issue 2 Pages 197-203
Carmen Pons, Rafael Forteza and V&iacute;ctor Cerd&agrave;

Abstract: A novel optical fiber reflectance sensor coupled to a multisyringe flow injection system (MSFIA) for the determination and speciation analysis of iron at trace level using chelating disks (iminodiacetic groups) is proposed. Once iron(III) has been retained onto a chelating disk, an ammonium thiocyanate stream is injected in order to form the iron(III)-thiocyanate complex which is spectrophotometrically detected at 480 nm. Iron(III) is eluted with 2 M hydrochloric acid so that the chelating disk is regenerated for subsequent experiments. The determination of total iron is achieved by the on-line oxidation of iron(II) to iron(III) with a suitable hydrogen peroxide stream. A mass calibration was feasible in the range from 0.001 to 0.25 µg. The detection limit (3sb/S) was 0.001 µg. The repeatability (RSD), calculated from nine replicates using 1 mL injections of a 0.1 mg/l concentration, was 2.2%. The repeatability between five chelating disks was 3.6%. The applicability of the proposed methodology in fresh and seawater samples has been proved. The proposed technique has been validated by replicate analysis (n = 4) of certified reference materials of water with satisfactory results.
Sea NWRI TMDA-54.3 LGC 6010 Spectrophotometry Sensor Reference material Speciation Chelation Optical fiber

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

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

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

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

"Second Chemiluminescence Behavior Of Fe2+, Fe3+ And Cr3+ In The Luminal-KMnO4 System"
Anal. Sci. 2006 Volume 22, Issue 4 Pages 621-625
Hong Qun Luo, Li Na Li And Nian Bing Li

Abstract: A novel flow injection chemiluminescence (CL) method has been developed for the determination of three metal ions, namely Fe2+, Fe3+ and Cr3+, based on the second CL (SCL) signal of the mixture of luminal with KMnO4 in a sodium hydroxide medium by the catalysis of Fe2+, Fe3+ or Cr3+. The possible CL mechanism of the systems, the influencing factors, and the optimum conditions for the reactions were investigated based upon the kinetic curve of the CL reaction, CL spectra, UV-visible spectra and some other experiments. Under the optimum conditions, the SCL intensity was directly proportional to the concentration of these metal ions in solution in the range of 0.10 - 100.00 mg L-1 for Fe2+, 0.50 - 7.50 and 7.50 - 200.00 mg L-1 for Fe3+, 0.01 - 0.25 and 0.25 - 10.00 mg L-1 for Cr3+. The detection limits (3 s/s) were 9.87 x 10^-6 g l-1, 2.71 x 10^-6 g L-1 and 5.25 x 10^-7 g L-1 for Fe2+, Fe3+ and Cr3+, respectively.
Chemiluminescence Optimization Interferences