Reductive differential-pulse adsorptive stripping voltammetric determination of molybdenum as 12-molybdophosphoric acid or as molybdic acid at a hanging mercury drop electrode

Abstract

Molybdenum(VI) has been determined by differential-pulse adsorptive stripping voltammetry in a pH 2 phosphate buffer utilising the strong adsorption of 12-molybdophosphoric acid at a hanging mercury drop electrode. Using a 1 min accumulation time calibration graphs are rectilinear up to the 7 × 10^–7M molybdenum level. Coefficients of variation at the 7 × 10^–8M level were typically <2% for five determinations. A clearly defined stripping peak was observed at the 5.6 × 10^–9M level with 2 min accumulation.

Molybdenum(VI) can be accumulated as molybdic acid from 10^–2M sulphuric acid and 10^–2M pH 4 acetate buffer solutions but the signal sizes are only one-fortieth of that obtained with phosphate buffer.