Square wave catalytic stripping voltammetry of molybdenum complexed with dihydroxynaphthalene

Abstract

Abstract A procedure is described for the determination of molybdenum using square wave catalytic stripping voltammetry in the presence of 2,3-dihydroxynaphthalene (DHN) and bromate. Linear scan voltammetry revealed that Mo(VI) forms a 1:2 complex with DHN and undergoes a one-electron reduction at the hanging mercury drop electrode. This reduction is reversible and especially suitable for square wave voltage modulation. A large enhancement of the peak current (500 ×) is observed upon the addition of bromate. The optimum conditions were 1 × 10 −3 M DHN, 3 × 10 −2 M bromate, pH 4.7, and an adsorption potential of −0.05 V. For an adsorption time of 1 min, the relative standard deviation for the measurement of 5 × 10 −12 M Mo(VI) was ±4% ( n = 7), and the detection limit was determined as 6 × 10 −12 M. The peak current was linear with the concentration of Mo(VI) from 1 × 10 −11 to 1 × 10 −9 M. The linear range could be extended with shorter adsorption times or a non-stirring adsorption mode.