Separation of arsenic species in aqueous solutions and optimization of determination by graphite furnace atomic absorption spectrometry

A procedure was developed for the separation and independent determination of nanogram quantities of As(V), As(III), dimethylarsinic acid (DMAA) and phenylarsonic acid (PAS) in aqueous solutions. Arsenic species were collected one by one from the same sample solution by adsorbing them onto different metal-loaded activated charcoals (MC*). First PAS was selectively separated by adsorption onto CeC+, which was filtered out. As(V) in the filtrate was collected next, by adsorption onto LaC*, which also was filtered out. In a third step, As(III) in the filtrate was separated from DMAA by APDC coprecipitation, where Fe3+ acted as carrier, and the precipitate was bound onto activated charcoal. Finally, DMAA in the filtrate was collected onto ZrC*. The adsorbed arsenic species were removed from MC*'s for measurement by graphite furnace atomic absorption spectrometry (GFAAS): PAS was removed from CeC* with 7.0% NE4OH and the other arsenic species were removed from MC* with 12.8% HNO3. The GFAAS procedure was optimized so that all four arsenic species could be measured under the same conditions. Ni-modifier proved to be the most suitable of several chemical matrix modifiers tested. The detection limits for various arsenic species were in the range 0.04-0.13 mu g/l. (C) 2000 Elsevier Science B.V. All rights reserved.