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

The adsorptive collection of the molybdenum (VI) complexed with 2-(2-benzot hiazolylazo)-p-cresol (BTAC) coupled with the catalytic current of the adso rbed complex at a static mercury drop electrode yields an ultrasensitive vo ltammetric procedure for the determination of molybdenum. Optimal experimen tal 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 concen tration of 0.1 M potassium nitrate as the oxidizing agent. In addition, a p reconcentration potential of -0.080 V vs Ag/AgCl (3 M KCl), equi libration time of 15 s, a frequency of 30 Hz, a scan increment of 2 mV, a pulse ampli tude of 0.050 mV, and a drop area of 0.032 cm(2) were used. The cyclic volt ammogram 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 reverse d at -0.90 V. Using the catalytic current at similar to -0.55 V the respons e to the Mo(VI) was found to be linear over a concentration range of 1.0-10 .0 mu g/L. The limit of detection is as low as 6.2 x 10(-10) M with 4 min o f preconcentration time. The possible interference of other trace ions was investigated. The merits of this procedure are demonstrated using of refere nce samples.