Determination of dimethylarsinic acid by hydride generation gas phase molecular absorption spectrometry

A method is described for the determination of dimethylarsinic and monomethylarsonous acids. The procedure involves NaBH4 reduction of the arsenic compounds to the corresponding gaseous arsines. After generation, the hydrides are collected in a liquid nitrogen trap. They are revolatilized and carried to the flow cell where they are measured by gas phase molecular absorption spectrometry (GPMAS). Various parameters affecting the production and collection of the arsines, such as the sample volume, generation conditions, and analyte retention and volatilization are discussed. The spectra obtained over a wide range of wavelengths, allows the reactions which take place during arsine generation, retention and revolatilization and their effects on the analytical signal to be studied. The quality parameters (detection limits, precision and accuracy) for two arsenic species are reported.