ADSORPTIVE VOLTAMMETRIC DETERMINATION OF ORTHOPHOSPHATE AT A GLASSY CARBON ELECTRODE

A simple, rapid and sensitive method for the adsorptive voltammetric determination of trace amounts of orthophosphate is described. In order to obtain a flat background current curve, the conditions for the preparation of a glassy carbon electrode and the voltammetric measurements are optimized. Orthophosphate is accumulated as heteropoly blue on the pretreated glassy carbon electrode in an aqueous acidic molybdate solution containing vanadate and acetone at −0.2 V vs. the saturated calomel electrode (SCE) for 150 s with stirring, and then the reduced complex is reoxidized during a positive-going scan at a rate of 50 mV s−1 to 0.2 V vs. SCE. Only one distinct peak is found at around 0.01 V vs. SCE. The calibration graph is linear over the 1 × 10−7to 1 × 10−6mol dm−3 concentration range of orthophosphate and passed through the origin, with a relative standard deviation (n = 6) of 4.3% for 5 × 10−7mol dm−3. The detection limit (3σ) was 1 × 10−8mol dm−3 (1.0 ng cm−3). Arsenate, which forms heteropoly acid wi...