Spectrophotometric-isotope dilution determination of arsenic in soils and rock

Arsenic in soil and rock samples may be determined in part-per-million concentrations using a radiochemical-isotope dilution method. Arsenic in the sample plus added As⁷⁶ tracer is separated as arsine and determined spectrophotometrically as a molybdenum blue complex. The As⁷⁶ activity in the absorbing solution allows corrections for chemical losses. A lower limit of 1 ppm is determinate in a 0.5-g sample.