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 p henylarsonic acid (PAS) in aqueous solutions. Arsenic species were collecte d one by one from the same sample solution by adsorbing them onto different metal-loaded activated charcoals (MC*). First PAS was selectively separate d by adsorption onto CeC+, which was filtered out. As(V) in the filtrate wa s 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 copre cipitation, 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 gr aphite furnace atomic absorption spectrometry (GFAAS): PAS was removed from CeC* with 7.0% NE4OH and the other arsenic species were removed from MC* w ith 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 detec tion 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.