DETERMINATION OF TRACE LEVEL ARSENIC(III), ARSENIC(V), AND TOTAL INORGANIC ARSENIC BY DIFFERENTIAL PULSE POLAROGRAPHY

Speciation of As(III), As(V), total inorganic arsenic (As(tot)) was achieved by differential pulse polarography. As(III) was determined directly in 1 M HCIO4 or 1 M HCl. Total inorganic arsenic was measured in either of these supporting electrolytes after prereduction of electroinactive As(V) with a boiling solution of NaHSO3. As(V) was evaluated by difference. The efficiency of reduction ranged from 93% to 109% for concentrations of As(V) ranging from 24 ppb to 4.9 ppm. Standard deviations for the procedure were less than 5.2%. The detection limit in the HCIO4-HS03- reduction medium was 20 ppb; in HCI-HSO3- it was 7 ppb. Relative errors for the determinations of As(III) and As(tot) ranged from 0% to 19.2%. Interferences from Pb, Sn, Tl were accounted for by a blank determination employing Ce(IV); interference from the breakdown of monomethylarsonic acid (MMA) during the preliminary reduction was not significant at concentrations of MMA which normally occur in natural waters. © 1979, American Chemical Society. All rights reserved.