VOLTAMMETRIC DETERMINATION OF AS(III) IN AN AQUEOUS ZWITTERIONIC COMPLEXING MEDIUM

The polarographic behaviour and determination of As(III) in aqueous co mplexing electrolytes (bicine buffer solutions) of pH values varying f rom 1.13-11.96 have been investigated at 25-degrees-C (direct current and differential pulse polarographic techniques). Using DC polarograph ic measurements, it was shown that reduction of As(III) takes place al ong one or three waves depending upon the pH value of the solution. Mi crocoulometric experiments have been performed at the limiting region of the different waves obtained at different pH values. Cyclic voltamm ograms were recorded using a HDME to investigate the nature of reducti on. Schemes for the mechanism of reduction occurring at the DME have b een deduced. Kinetic parameters and wave characteristics for the reduc tion of As(III) have been calculated. A method for DPP determination o f As(III) in bicine buffer solution of pH 1.41 is reported. The detect ion limit of the method is 6.60 x 10(-8) M As(III).