Determination of molybdenum in the presence of 2-(2-benzothiazolylazo)-p-cresol by catalytic-adsorptive stripping voltammetry.

Abstract

The adsorptive collection of the molybdenum (VI) complexed with 2-(2-benzothiazolylazo)-p-cresol (BTAC) coupled with the catalytic current of the adsorbed complex at a static mercury drop electrode yields an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental conditions were: a stirred acetate buffer 0.2 M (pH 3.5) as supporting electrolyte, a BTAC concentration of 1.0 x 10(-6) M as ligand, and a concentration of 0.1 M potassium nitrate as the oxidizing agent. In addition, a preconcentration potential of -0.080 V vs Ag/AgCl (3 M KCl), equilibration time of 15 s, a frequency of 30 Hz, a scan increment of 2 mV, a pulse amplitude of 0.050 mV, and a drop area of 0.032 cm2 were used. The cyclic voltammogram was recorded using a staircase wave with a scan rate of 100 mV/s. The forward scan starts at the initial potential of -0.080 V and is reversed at -0.90 V. Using the catalytic current at approximately -0.55 V the response to the Mo(VI) was found to be linear over a concentration range of 1.0-10.0 microg/L. The limit of detection is as low as 6.2 x 10(-10) M with 4 min of preconcentration time. The possible interference of other trace ions was investigated. The merits of this procedure are demonstrated using of reference samples.