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

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NWRI TMDA-54.3

Citations 6

"Reversed Flow Injection And Sandwich Sequential Injection Methods For The Spectrophotometric Determination Of Copper(II) With Cuprizone"
Anal. Chim. Acta 2003 Volume 486, Issue 2 Pages 227-235
Paolo Rumori and Victor Cerdà

Abstract: Two new flow methods, flow injection analysis (FIA) and sequential injection analysis (SIA), for the spectrophotometric determination of Cu(II) in water at trace levels have been developed and optimized. Both methods are based on the reaction with oxalic acid bis(cyclohexylidene hydrazide) (cuprizone) in alkaline media. The two procedures have been developed for the final aim to compare their performances and to offer new rapid heavy metals analysis tools, avoiding the use of extraction steps. A detailed study of the physico-chemical parameters affecting the systems performances has been carried out. The reversed FIA and sandwich SIA approaches offered the best sensitivity. In both cases, an extremely good linearity has been obtained within the range 0.06-4 µg mL-1 (correlation coefficient r=0.9999), whereas the observed detection limits were 0.013 and 0.004 µg mL-1, for FIA and SIA, respectively. Furthermore, due to the great similarity of the diffusion zones in the reaction slugs, our approach offers the opportunity to compare the two methods in analogous conditions. This SIA method, besides keeping its typical reagent saving features, offered analytical performances equivalent to those of FIA. To obtain these results, an original 'stop-flow like' method was successfully employed in the SIA approach. Both methods were validated by analysis of real water samples, after copper addition, and certified reference samples of fortified and waste waters.
Copper(II) Spectrophotometry Reverse Sequential injection Sandwich technique Optimization Interferences Stopped-flow

"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 Víctor Cerdà

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.
Iron(2+) Iron(III) Spectrophotometry Preconcentration Multicommutation Multisyringe Method comparison Expert system

"Antimony Determination And Speciation By Multisyringe Flow Injection Analysis With Hydride Generation-atomic Fluorescence Detection"
Anal. Chim. Acta 2005 Volume 530, Issue 1 Pages 113-120
N.V. Semenova, L.O. Leal, R. Forteza and V. Cerdà

Abstract: A new analytical procedure for determination of inorganic antimony and speciation of antimony(III) and antimony(V) is presented. For this purpose, a software-controlled time-based multisyringe flow injection system, which contains a multisyringe burette provided with a multi-port selection valve, was developed. Hydride generation-atomic fluorescence spectrometry was used as a detection technique. A 0.3% (w/v) reducing sodium tetrahydroborate solution, hydrochloric acid (2 M), an antimony solution and a pre-reducing solution of 10% (w/v) KI and 0.3% (w/v) ascorbic acid are dispensed simultaneously into a gas-liquid separation cell with further propulsion of the reaction product into the flame of an atomic fluorescence spectrometer using argon flow. A hydrogen flow was employed to support the flame. The linear range and the detection limit (3sb/S) of the proposed technique were 0.2-5.6 µg L-;1 and 0.08 µg L-;1, respectively. A sample throughput of 18 samples per hour (corresponding to 80 injections per hour) was achieved. The relative standard deviation for 18 independent measurements was 4.6%. This technique was validated by means of reference solid and water materials with good agreement with the certified values. Satisfactory results for speciation of Sb(III) and Sb(V) by means of the developed technique were obtained.
Antimony(3+) Antimony(5+) Fluorescence Multisyringe Speciation Automation Optimization Interferences Method comparison

"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 Víctor Cerdà

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.
Iron(2+) Iron(III) 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 Víctor Cerdà

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

"Speciation Analysis Of Inorganic Arsenic By A Multisyringe Flow Injection System With Hydride Generation–atomic Fluorescence Spectrometric Detection"
Talanta 2006 Volume 69, Issue 2 Pages 500-508
L.O. Leal, R. Forteza and V. Cerdà

Abstract: In this study, a new technique by hydride generation-atomic fluorescence spectrometry (HG-AFS) for determination and speciation of inorganic arsenic using multisyringe flow injection analysis (MSFIA) is reported. The hydride (arsine) was generated by injecting precise known volumes of sample, a reducing sodium tetrahydroborate solution (0.2%), hydrochloric acid (6 M) and a pre-reducing solution (potassium iodide 10% and ascorbic acid 0.2%) to the system using a multisyringe burette coupled with one multi-port selection valve. This solution is used to pre-reduce As(V) to As(III), when the task is to speciate As(III) and As(V). As(V) is determined by the difference between total inorganic arsenic and As(III). The reagents are dispensed into a gas-liquid separation cell. An argon flow delivers the arsine into the flame of an atomic fluorescence spectrometer. A hydrogen flow has been used to support the flame. Nitrogen has been employed as a drier gas (Fig. 1). Several variables such as sample and reagents volumes, flow rates and reagent concentrations were investigated in detail. A linear calibration graph was obtained for arsenic determination between 0.1 and 3 µg l-;1. The detection limit of the proposed technique (3sb/S) was 0.05 µg l-;1. The relative standard deviation (RSD) of As at 1 µg l-;1 was 4.4 % (n = 15). A sample throughput of 10 samples per hour was achieved. This technique was validated by means of reference solid and water materials with good agreement with the certified values. Satisfactory results for speciation of As(III) and As(V) by means of the developed technique were obtained.
Arsenic(3+) Arsenic(5+) Fluorescence Speciation Volatile generation Multisyringe Interferences