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ARSENIC SPECIATION ANALYSIS IN GROUND WATER BY IC-HG-AFS
Citation:
Xu, N., J. Hong, C. Su, R T. Wilkin*, AND J. Smieja. ARSENIC SPECIATION ANALYSIS IN GROUND WATER BY IC-HG-AFS. Presented at 58th ACS Southwest Regional Mtg, Austin, TX, November 03 - 06, 2002.
Impact/Purpose:
To inform the public.
Description:
The determination of low levels of arsenic draws concern more than ever today, because of the possible legislative changes in the drinking water limit. The toxicity of arsenic depends upon its chemical form. Arsenite is the most toxic form, 25 to 50 times more toxic than arsenate and several hundred times more toxic than the methylated forms; therefore, it is necessary to have an analytical method that can separate these species and detect them individually for their toxicity assessment. A method has been developed to separate and analyze four arsenic species of concern in ground water monitoring: arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The four arsenic species are first separated by an ion chromatograph (IC), then reacted to form arsenic hydride through a hydride generation (HG) apparatus, and finally detected by an atomic fluorescence spectrometer (AFS). The detector utilizes a boosted discharge hollow cathode lamp as an excitation source, and a chemically generated hydrogen diffusion flame for atomization of the hydride. The system is very sensitive and is able to quantify arsenic at 5 microgram per liter and analyze arsenic at lower levels semi-quantitatively. It has been used to evaluate subsurface permeable reactive barriers for situ treatment of arsenic in ground water, to study the effect of pH on the adsorption and speciation of arsenic onto iron oxides of various types, and to study the abiotic reduction of arsenate by carboxylic acids.