Determination of Arsenate, Methanearsonate, and Dimethylarsinate in Water and Sediment Extracts

A method is described for separating and measuring arsenate, methanearsonate, and dimethylarsinate in water and sediment extracts. The arsenicals were separated by differential elution from a column of cation exchange resin; and the separates were subsequently analyzed by the arsine method. Standard arsenical solutions separated well, and 97, 93, and 95% of arsenate, methanearsonate, and dimethylarsinate, respectively, were recovered in the effluents. The method was tested with pond sediments previously treated in the laboratory with known levels of arsenicals. Recovery varied from 80 to 98%.