DIRECT AND SECOND DERIVATIVE SPECTROPHOTOMETRIC DETERMINATION OF MOLYBDENUM (VI) IN FOOD STUFFS AND IN ALLOY STEELS USING 2- HYDROXY-3-METHOXY BENZALDEHYDE THIOSEMICARBAZONE (HMBATSC)

A rapid, simple, sensitive and selective spectrophotometric method is developed for the determination of molybdenum (VI) in aqueous dimethyl formamide (DMF). Molybdenum (VI) forms a yellow coloured complex with 2-hydroxy-3-methoxy benzaldehyde thiosemicarbazone in the pH range 1.0-6.0. The complex shows maximum absorbance at 375nm and in the pH range 1.0-2.0. However, at this wave length, the reagent shows considerable absorbance. At 385nm, the complex shows large absorbance while the reagent blank shows negligible absorbance. Hence, analytical studies are carried out at 385nm and at pH 1.5 against reagent blank. Beer's law is obeyed in the range 0.24-4.32 µg ml-1. The molar absorptivity and Sandell's sensitivity forthe coloured solution are found to be 2.3 x 10-4 1 mol-1 cm-1 and 0.0042 µg cm-2 respectively. The interference effect of various diverse ions has been studied. The complex shows 1:1 [Mo (VI): HMBATSC] stoichiometry with a stability constant 2.35 x 106. The standard deviation of the method in the determination of 2.396 µg ml-1 of Mo(VI) is calculated as ± 0.0012. A second order derivative spectroscopic method is developed for the determination of molybdenum(VI), which is more sensitive than the zero order method.. The developed method has been employed for the determination of molybdenum (VI) in food stuffs and in alloy steels. The results are in excellent agreement with the certified values