Speciation and Analysis of Arsenic(III) and Arsenic(V) by Electrochemical Hydride Generation Spectrophotometric Method

A simple method was developed for speciation and spectrophotometric determination of inorganic As(III) and As(V) using an electrochemical hydride generation technique. For speciation of As(III) and As(V), a graphite rod was used as cathode to reduce As(III) to AsH3, the rod was then replaced with a tin-lead alloy wire for reducing As(V) to AsH3. The spectrophotometric determination was based on the reaction of AsH3 with silver diethyl dithiocarbamate to give an absorbing complex at 510 nm. Under the optimized conditions, the calibration curves were linear over the ranges of 0.1 - 5 mu g ml(-1) for As(III) and 0.5 - 4.0 mu g ml(-1) for As(V). The concentration detection limits of 0.02 and 0.06 mu g ml(-1) were achieved for As(III) and As(V), respectively. The relative standard deviations for five replicate speciation and determination of 3.0 mu g ml(-1) As(III) and As(V) were 0.8 and 7.2%, respectively. The accuracy and recovery of the method were evaluated by analyzing tap water spiked with As(III) and As(V).