KINETIC THERMOMETRIC DETERMINATION OF MO(VI) IN VEGETABLES BY ITS CATALYTIC EFFECT ON THE REACTION BETWEEN HYDROGEN-PEROXIDE AND THIOSULFATE ION

A new kinetic thermometric method for the determination of molybdenum based on the catalytic effect of molybdate ion on the reaction between thiosulphate and hydrogen peroxide in 0.03 M acetic acid is reported. The proposed method is quite sensitive and selective: the linear range of the calibration graph is from 5 to 60 ng ml-1, while the relative standard deviation for 40 ng Mo(VI) per ml is 1.1% (n = 9). The presence of foreign ions does not detract from the sensitivity of the method. The method was applied to the determination of molybdenum traces in various vegetables including dry beans, pumpkin and unpodded peas.