A Hydride Generation Atomic Absorption Technique for Arsenic Speciation

Based on an investigation of hydride generation responses in solutions of various acidities containing nanogram quantities of arsenite [As(III)], arsenate [As(V)], monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA) a sensitive analytical method for the accurate determination of inorganic and organic As species in aqueous solutions was developed. After a pH‐selective reduction, the arsenic species were condensed in a U‐tube filled with a gas chromatographic packing immersed in liquid N2. The species were then separated by slow warming of the trap and measured with an atomic absorption spectrophotometer. The arsines from inorganic As (III) were selectively generated from a solution buffered at a pH of 6.0. The solution of then further acidified to a pH corresponding to 2 M HCl and analyzed for As(V). A second sample aliquot, buffered at pH 1.5 with oxalic acid, was used for the quantitative determination of [As(III) + As(V)], MMAA and DMAA.