Spectrophotometric determination of arsenic and antimony by the silver diethyldithiocarbamate method

When sodium tetrahydroborate(III) is used for hydride generation in the spectrophotometric determination of arsenic as a complex with silver diethyldithiocarbamate, significant antimony interference may occur. This can be overcome by reading the absorbance at a wavelength other than the absorption maximum or both elements can be determined by reading at two wavelengths. The use of oxidising acids for the digestion of sediment, soil and plant material for arsenic and other metals is not suitable for antimony. This can be overcome by adding a reducing agent in the later stages of digestion and allows both arsenic and antimony to be determined simultaneously on the same digest.