Direct and Derivative Spectrophotometric Determination of Cobalt(II) Using 3,5-Dimethoxy-4- hydroxybenzaldehydebenzoylhydrazone (DMBBH)

Abstract

A rapid, simple, sensitive and selective spectrophotometric  method has been developed for the determination of Cobalt (II) using
newly synthesized Chromogenic reagent 3,5-Dimethoxy-4- hydroxybenzaldehydebenzoylhydrazone(DMBBH) in cationic surfactant
of C-Tab-(5%) (micellar medium). Cobalt (II) forms a Orange coluored  water-soluble complex with 3,5-Dimethoxy-4-  ydroxybenzaldehydebenzoylhydrazone( DMBBH) in the pH range 5.0-9.0. Thecomplex shows maximum absorbance at lmax 439 nm and in the pH range 5.0-6.0. At lmax 439 nm, the complex shows maximum absorbance while the reagent blank shows negligible absorbance. Hence,analytical studies are carried out at lmax 439 nm and at pH 6.0(Phosphate buffer) against reagent blank. Beer's law is obeyed in the range 0.2946 to 3.5358μg/mL and the optimum concentration rangeobtained from ringbom plot is 0.5893 - 2.9465μg/mL of Coobalt (II). The  molar absorptivity and Sandell's sensitivity for the coloured solution are found to be 2.685 x 104L mol-1cm-1 and 0.001862-μg.cm-2 respectively. The interference effect of various diverse ions has been studied. The complex shows 1:2 [Co (II): DMBBH] stoichiometry with stability  constant 11.24x1010 obtained from job’s method. The standard deviation of the method in the determination of Copper (II) is 0.0005and the Relative standard deviation is 0.05. First and second order derivative spectroscopic method is developed at lmax 500 nm and 512 nm  respectively for the determination of Cobalt (II), which is more sensitive than the zero order method. The developed method has been used for the determination of Cobalt (II) in Soil samples and Vitamin B12 samples. The results are in good agreement with the certified values.