ULTRATRACE DETERMINATION OF MOLYBDENUM IN THE PRESENCE OF 2-(2'-THIAZOLYLAZO)-P-CRESOL BY CATALYTIC-ADSORPTIVE STRIPPING VOLTAMMETRY

The adsorptive collection of the molybdenum (VI) complex of 2-(2'-thiazolylazo-p-cresol (TAC), coupled with the catalytic current of the adsorbed complex, yields an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental conditions were found with the use of a stirred acetate buffer (pH 2.9) supporting electrolyte, a TAC concentration of 1.0 x 10(-5) M, and a concentration of 0.1 M potassium nitrate. In addition, a preconcentration potential of -0.13 V (vs. Ag/AgCl), equilibrium time of 30 seconds, and an anodic scan rate of 200 mV/s from -0.93 to -0.20 was used. A catalytic effect was observed when nitrate was present. The response was found to be linear over a concentration range of 0.0 to 12.0 mug L-1 Mo (VI). For a preconcentration time of 3 minutes, the detection limit was found to be 11 pM. Possible interferences by anions and other trace metals were investigated. The interference by copper may be masked by CDTA, and sequential determination with molybdenum is possible. The merits of the procedure are demonstrated in the analysis of sea and mineral water.