Abstract
The on-site speciation analysis of inorganic arsenic at the μg · l-1 level by anodic stripping voltammetry with a gold film microelectrode was described. As(III) was deposited on a gold film working electrode at -0.4 Vvs.Ag/AgCl for 5 min in 1.2 mol · l-1 hydrochloric acid; the deposit was then anodically stripped in the potential range from -0.4 to 0.9 Vvs.Ag/AgCl at a scan rate of 5 V · s-1. As(V) was chemically reduced to As(III) with sodium thiosulfate and the total inorganic arsenic was determined under the above voltammetric conditions. The original As(V) concentration in the sample was calculated by difference. The calibration curves prepared with As(III) and As(V) standard solutions were linear up to at least 20 μg · l-1 and passed through the origin, with relative standard deviations of 2∼5% for 5 μg · l-1 arsenic (n=5). The detection limits (3σ, n=10) of As(III) and As(V) for a deposition time of 5 min were 0.1 and 0.3 μg · l-1, respectively. The proposed method was applied to the on-site speciation analysis of inorganic arsenic in groundwater in Saitama Prefecture. The time required for the on-site analysis was 20 min.
