Speciation of arsenic using solid phase extraction cartridges

Various solid phase extraction (SPE) cartridges were investigated for speci ation of arsenite [As(III)], arsenate [As(v)], monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Cartridges containing different types of s orbent materials were tested for arsenic retention and elution characterist ics. Alumina cartridges were found to completely retain all thr four target arsenic species, and are suitable for removal and preconcentration purpose s. For speciation analysis, different arsenic species were separated on the basis of their selective retention on and elution from specific cartridges . DMA was retained on a resin-based strong cation exchange cartridge and el uted with 1.0 M HCl. MMA and As(v) were both retained on a silica-based str ong anion exchange cartridge and sequentially eluted with 60 mM acetic acid (for MMA) and 1.0 M HCl [for As(v)]. As(III) was not retained on either ca rtridge and remained in solution. Arsenic species in solution and those elu ted from the cartridges were subsequently quantified by using flow injectio n with hydride generation atomic fluorescence spectrometry (FI-HGAFS) and h ydride generation atomic absorption spectrometry (FI-HGAAS). A detection li mit of 0.05 mug L-1 arsenic in water sample was achieved using HGAFS. An ap plication of the method was demonstrated at a drinking water treatment faci lity. As(III) and As(v) species were determined in water at various stages of treatment. The method is suitable for routine determination of trace lev els of arsenic in drinking water to comply with more stringent environmenta l regulations.