Sequential spectrophotometric determination of inorganic arsenic species by hydride generation from selective medium reactions and colour bleaching of permanganate

A simple spectrophotometric method is presented for the sequential determination of inorganic arsenic (As) species in one sample. It is based on the sequential arsine generation from As(III) and As(V) using selective medium reactions, collection of the arsine generated in an absorbing solution containing permanganate and ethanol at 5 °C and subsequent reduction of permanganate by arsine. The decrease in permanganate absorbance at 524.2 nm is monitored for As determination. The acetic acid/sodium acetate and HCl mediums were used for selective arsine generation from As(III) and remaining As(V) in one solution, respectively. The effect of interferences and their possible mechanisms were discussed. Interferences from transition metal ions were removed by using a Chelex 100 resin. Under optimized conditions, the established method is applicable to the determination of 3–30 μg of each arsenic species. Good recoveries (96–102%) of spiked artificial sea water, tap water and standard mixtures of As(III) and As(V) were also found. The method is simple, accurate, precise and environmental friendly.