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Quantitative Trace-Level Speciation of Arsenite and Arsenate in Drinking Water by Ion Chromatography

Quantitative Trace-Level Speciation of Arsenite and Arsenate in Drinking Water by Ion Chromatography

Rebecca L Johnson, Joseph H Aldstad 3rd

Analyst. 2002 Oct;127(10):1305-11.

PMID: 12430600

Abstract:

We describe an improved method for the determination of inorganic arsenic in drinking water. The method is based on comprehensive optimization of the anion-exchange ion chromatographic (IC) separation of arsenite and arsenate with post-column generation and detection of the arsenate-molybdate heteropoly acid (AMHPA) complex ion. The arsenite capacity factor was improved from 0.081 to 0.13 by using a mobile phase (2.0 mL min(-1)) composed of 2.5 mM Na2CO3 and 0.91 mM NaHCO3 (pH 10.5). A post-column photo-oxidation reactor (2.5 m x 0.7 mm) was optimized (0.37 microM potassium persulfate at 0.50 mL min(-1)) such that arsenite was converted to arsenate with 99.8 +/- 4.2% efficiency. Multi-variate optimization of the complexation reaction conditions yielded the following levels: 1.3 mM ammonium molybdate, 7.7 mM ascorbic acid, 0.48 M nitric acid, 0.17 mM potassium antimony tartrate, and 1.0% (v/v) glycerol. A long-path length flow cell (Teflon AF, 100-cm) was used to measure the absorption of the AMHPA complex (818 +/- 2 nm). Figures of merit for arsenite/arsenate include: limit of detection (1.6/0.40 microg L(-1)): standard error in absorbance (5.1 x 10(-3)/3.5 x 10(-3)); and sensitivity (2.9 x 10(-3)/2.2 x 10(-3) absorbance units per ppb). Successful application of the method to fortified surface and ground waters (100 microL samples) is also described.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AS23118	Multi Anion Standard 2 for IC			Price
AS23121	Multi Anion Standard 1 for IC			Price

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