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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Citations 1

"Determination Of Arsenic(III) And Arsenic(V) By Flow Injection Hydride-generation Atomic Absorption Spectrometry Via Online Reduction Of Arsenic(V) By Potassium Iodide"
Anal. Chim. Acta 1997 Volume 343, Issue 1-2 Pages 5-17
Steffen Nielsen and Elo H. Hansen

Abstract: The flow injection method for the determination of total As was based on the online reduction of As(V) to As(III) by ascorbic acid/KI reagent. Sample (100 µL) in a 4 M HCl carrier stream (9.5 ml/min) containing 0.5% ascorbic acid and 1% KI was propelled through a reaction coil (150 cm x 0.5 mm i.d.) at 140°C and a cooling coil (75 cm x 0.5 mm i.d.) at 10°C and then merged with 0.05 M NaBH4 (1.6 ml/min). The mixture was passed to a gas-liquid separator and arsine and H2 were swept to the atomizer cell (at 900°C) by an Ar carrier stream. The absorption signal for As was recorded at 193.7 nm. The same flow manifold was used for the selective detection of As(III) by using a carrier stream of 0.03 M HCl which did not contain the reducing reagents. The detection limits were 37 ng/l for total As and 111 ng/l for As(III). The RSD (n = 10) for 5 µg/l total As and As(III) were Calibration graphs were linear for 0.1-10 µg/l total As. The method was validated by analyzing certified drinking water using the multiple standard additions calibration procedure. A volume-based flow injection (FI) procedure is described for the determination and speciation of trace inorganic arsenic, As(III) and As(V), via hydride generation-atomic absorption spectrometry (HG-AAS) of As(III). The determination of total arsenic is obtained by online reduction of As(V) to As(III) by means of 0.50% (w/v) ascorbic acid and 1.0% (w/v) potassium iodide in 4 M HCl. The combined sample and reduction solution is initially heated by flowing through a knotted reactor immersed in a heated, thermostatted oil bath at 140°C, and subsequently, for cooling the reaction medium, a knotted reactor immersed in a water bath at 10°C. By using the very same volume-based FI-HG-AAS system without the heating and cooling reactors, and employing mild hydrochloric acid conditions, As(V) is not converted to arsine, thereby allowing the selective determination of As(III). The injected sample volume is 100 µl while the total sample consumption per assay is 1.33 ml, and the sampling frequency is 180 samples per hour. The detection limit (3s) for the online reduction procedure was 37 ng L-1 and at the 5.0 µg L-1, the relative standard deviation (RSD) was 1.1% (n=10) by calibrating with As(III) standards; by calibrating with As(V) standards the detection limit was 33 ng L-1 and the RSD was 1.3% (n=10). For the selective determination of As(III) the detection limit was 111 ng L-1 and the RSD was 0.7% (n=10) at 5.0 µg L-1. Both procedures are most tolerant to potential interferents. Thus, without impairing the assay, interferents such as Cu, Co, Ni and Se could, at a As(V) level of 5 µg L-1, be tolerated at a weight excess of 2000, 30000, 200 and 200 times, respectively. The assay of a certified drinking water sample by means of multiple standard addition (five levels; each three replicates) was 9.09±0.05 µg L-1 (certified value 9.38±0.71 µg l-1). 11 References
Arsenic(3+) Arsenic(5+) Spectrophotometry Volatile generation Standard additions calibration Reference material Heated reaction Redox Speciation Interferences Knotted reactor Volatile generation FIAS-400