Separation of microgram quantities of As(v), As(III) and organoarsenic species in aqueous solutions and determination by energy dispersive X-ray fluorescence spectrometry

A procedure was developed for the separation and independent determination of microgram quantities of As(III), As(V), dimethylarsinic acid (DMAA) and phenylarsonic acid (PAS) in aqueous solution. The arsenic species were collected one by one from the same sample solution, by adsorbing them onto metal-loaded activated charcoal (MC*). PAS was separated by adsorption onto VC* and As(V) remaining in the filtrate was collected onto LaC*. The LaC* was filtered out and As(III) in the filtrate was separated by 1-pyrrolidinecarbodithioic acid, ammonium salt (APDC) coprecipitation, where Fe3+ acted as carrier and the precipitate was bound onto activated charcoal. Finally DMAA in the filtrate was collected onto ZrC*. Arsenic concentration in the metal-loaded activated charcoal was measured directly by energy dispersive X-ray fluorescence spectrometry (EDXRF). The detection limits for all four arsenic species were-better than 0.02 mg L-1. The amount of unadsorbed arsenic was determinated by vapour generation atomic absorption spectrometry (VGAAS) or graphite furnace atomic absorption spectrometry (GFAAS).