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
Website: @unf

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Classification: Water -> purified

Citations 7

"Dual Wetting-film Multi-syringe Flow Injection Analysis Extraction - Application To The Simultaneous Determination Of Nitrophenols"
Anal. Chim. Acta 2001 Volume 438, Issue 1-2 Pages 103-116
Manuel Miró, Andreu Cladera, José Manuel Estela and Víctor Cerdà

Abstract: A dual wetting-film extraction/back-extraction system based on a multi-syringe flow injection analysis (MSFIA) set-up coupled to additional burettes and solenoid valves is proposed. The system performs on-line analyte extraction from an aqueous medium to an organic solvent based on the differential flow velocities of the aqueous and organic phases into PTFE tubing, which is due to the formation of a thin and pseudo-stationary organic film adhered to the inner walls of the extraction coil. The pre-concentrated analytes are eluted into a small eluting solution segment and conducted to a diode-array spectrophotometer for analysis. The peak maximum spectrum is used for the simultaneous determination of different analytes by using multi-component analysis with multi-linear regression (MLR). This dual system is applied to the multi-component determination of 2, 3- and 4-nitrophenol. By using 8 mL of sample and 88 µL of 1-chloroburane in 1-octanol (66/34, v/v) as organic phase, a sample throughput of 11 analyzes per hour can be obtained. The detection limits for 2-, 3- and 4-nitrophenol are 0.11, 0.46 and 0.07 muM, respectively, and the relative standard deviations are less than 4%.
2-Nitrophenol 3-Nitrophenol 4-Nitrophenol Spectrophotometry Extraction Multisyringe Simultaneous analysis Preconcentration

"Determination Of Trace Amounts Of Iron In Highly Purified Water By Ion-exchanger Phase Absorptiometry Combined With Flow Analysis"
Analyst 1992 Volume 117, Issue 9 Pages 1501-1506
Ushio Hase and Kazuhisa Yoshimura

Abstract: Water sample containing 0.01 to 2 µg L-1 of Fe was pre-concentrated at 2.5 mL min-1 for 15 min on the column and for a sample containing 1 to 10 µg L-1 pre-concentration was at 1 mL min-1 for 5 min. Iron was eluted from the pre-concentration column with carrier solution (16.6 mL of anhydrous acetic acid, 14.9 mL of NH3 solution and 25 mL of buffer solution adjusted to pH 4.2 to 4.3 with 6 M HCl) and introduced directly into the sample carrier stream (schematic diagram of flow-analysis system given). At the same time 4,7-diphenyl-1,10-phenanthrolinedisulfonate solution was introduced into the reagent carrier stream and the attenuance was measured at 550 nm; as attenuance decreased, the desorbing solution containing 4 M NaNO3 - acetone was added. Iron was determined from the calibration graph. Detection limit was 0.01 µg L-1 for 80 mL of water. Results agreed well with those obtained by electrothermal vaporization - ICP-MS. The absorbance of a colored species sorbed on an ion-exchanger was measured directly to determine trace amounts of Fe, using flow anal. The method was more sensitive than the corresponding solution-phase method by a factor of 100. For the determination of Fe in highly purified water, the sensitivity was further increased by online pre-concentration. The system blank could be reduced by passing the carrier solutions through respectively online purifying columns. After the sample had been introduced onto a small cation-exchange column, the Fe concentrated on the column was eluted with an acetate carrier solution, and then mixed with the other carrier stream which contained a pulse of 4,7-diphenyl-1,10-phenanthroline disulfonate (DPPS) reagent solution The colored Fe-DPPS complex, formed in the stream, was introduced into a flow-through cell, the light path of which had been partly filled with anion exchanger. The increase in attenuation due to the sorption of the colored complex was measured continuously. The detection limit was 0.01 µg/L, when an 80 mL water sample was used.
Iron Ion exchange Spectrophotometry Preconcentration Column Method comparison Solid phase detection Resin

"Adsorption-concentration Of Ion Associate Formed Between Molybdosilicate And Malachite Green On A Miniature Filter: Its Application To Trace And Ultratrace Determination Of Silicon"
Analyst 1995 Volume 120, Issue 10 Pages 2605-2611
Joko P. Susanto, Mitsuko Oshima and Shoji Motomizu

Abstract: A spectrophotometric method for Si determination (as silicate), based on an adsorption-concentration procedure, is described. Portions (30 ml) of standard silicate solution were mixed with 0.5 mL 1.7 M H2SO4 and 0.5 mL 0.52 M molybdate and the solution was left for 20 min. A 1 mL portion of 0.34 mM Malachite Green in 6.1 M H2SO4 was added and the mixture was left to stand for 35 min. The solution was filtered through a cellulose nitrate membrane filter (5 mm diameter; pore size 1 µm) under suction. The ion associate and the membrane filter were then dissolved in 1 mL methyl Cellosolve and the absorbance of the resulting solution was measured at 627 nm by using a previously described flow injection system (Susanto et al., Ibid., 1995, 120, 187). The calibration graph was linear up to 9 ng/ml of Si and the detection limit was 0.5 nM. The RSD (n = 6) was 4.3%. The method was applied to the analysis of Si in purified water.
Silicon Spectrophotometry Ultratrace Cellulose nitrate Ion pair formation Precipitation

"Speciation Analysis Of Chromium(III) And Chromium(VI) Using Flow Injection Analysis With Fluorometric Detection"
Analyst 1998 Volume 123, Issue 5 Pages 1005-1009
Evangelos K. Paleologos, Spyros I. Lafis, Stella M. Tzouwara-Karayanni and Miltiades I. Karayannis

Abstract: A relatively simple, sensitive, selective, automatic fluorometric method for the simultaneous determination of Cr(III) and Cr(VI) by flow injection analysis (FIA) was developed. The method is based on the selective oxidation of the nonfluorescing reagent 2-(α-pyridyl)thioquinaldinamide (PTQA), which with Cr(VI) yields an intensely fluorescent product (λex = 360 nm; λem = 500 nm). Cr(III) is oxidized online to Cr(VI) with sodium metaperiodate and the Cr(VI) is subsequently treated with PTQA. Fluorescence due to the sum of Cr(III) and Cr(VI) is measured and Cr(III) is determined from the difference in fluorescence values. The effects of various anal. parameters, such as acidity, flow rate, sample volume, temperature, reagent concentration and interfering species, were studied. Kinetic studies using both the stopped-flow technique and the FIA procedure were used to study and optimize the oxidation conditions for Cr(III) from its oxidation efficiency. The calibration graphs were rectilinear in the ranges 0.1-10 µg mL-1 for Cr(VI) and 0.1-1.0 µg mL-1 for Cr(III). The method was successfully verified by performing recovery experiments of Cr in several standard reference materials (peach leaves, sediments and tea), and it was applied to the speciation analysis of Cr(III)-Cr(VI) in environmental waters (mineral, tap and distilled water), a food sample (tomato juice) and synthetic mixtures. Up to 30 samples per h can be analyzed with a relative standard deviation of ~0.1-2%.
Chromium(III) Chromium(VI) Fluorescence Speciation Stopped-flow Kinetic Reference material Indirect Interferences Optimization

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

Abstract: Solid sorbent extraction using a microcolumn in an automated system was successfully coupled with a graphite furnace for atomic absorption spectrometry. Bonded silica with octadecyl functional groups (C-18 reversed phase material) was used in a 15 µL conically shaped microcolumn as a sorbent for the metal complexes formed online with Na diethyldithiocarbamate. Column elution was performed with an EtOH eluent into a PTFE capillary used for eluate storage and transfer into the graphite tube. With a sample loading time of 60 s and direct introduction of the eluate portion containing the highest analyte concentration. into the graphite tube, an enrichment factor of ~20 was realized. Effective elimination of contamination by the closed system and online purifn. of the complexing agent together with highly selective separation of trace metals from alkaline and earth alkaline elements allowed the determination of ultratrace metals in seawater and deionized water. Using only 3 mL of sample, detection limits for Cd, Co, Cu, Pb, and Ni of 0.8, 12, 17, 6.5, and 36 ng/L, respectively, was achieved.
Cadmium Cobalt Copper Lead Nickel Spectrophotometry Sample preparation C18 Preconcentration Ultratrace Solid phase extraction

"Ultratrace Determination Of Phosphate Ion Based On Filtration-dissolution And Flow-through Spectrophotometric Measurement"
Anal. Sci. 1995 Volume 11, Issue 1 Pages 155-160

Abstract: A 10^-40 mL portion of standard 3 mM phosphate solution was treated with 1 mL mixed reagent solution (containing 60 µM-Malachite Green, 0.12 M molybdate and 2.75 M HCl) for 5 mL phosphate standard solution. The mixture was left for 5 min and was filtered, under suction through a membrane filter. The filter was washed with 10 mL water, the filter and its contents were dissolved in 1 mL Methyl Cellosolve and the absorbance of the solution was measured at 627 nm by the flow injection technique (details given). The calibration graph was linear from 18 pg/ml to 1 ng/ml of P in 40 mL sample and the detection limit was 3 pg/ml. As(V) severely interfered with the determination. The method was applied to the determination of phosphate in purified water.
Phosphate Spectrophotometry Interferences Ultratrace

"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 Miró, Eduardo Becerra, José Manuel Estela and Víctor Cerdà

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.
Iron Iron(III) Speciation Interferences Expert system Method comparison Preconcentration