STUDIES ON SPECTROPHOTOMETRIC-CATALYTIC DETERMINATION OF TRACE AMOUNTS OF METALS .3. SPECTROPHOTOMETRIC DETERMINATION OF TRACE AMOUNTS OF COBALT BASED ON CATALYTIC-OXIDATION OF GALLOCYANIN BY HYDROGEN-PEROXIDE

A highly sensitive method has been developed for the determination of trace amounts of cobalt based on the catalytic action of cobalt on the oxidation of Gallocyanin (GAL) by hydrogen peroxide. Since GAL was oxidized to decolorized product in the presence of cobalt in weakly alkaline solution, difference of absorbance (ΔE) between reagent blank and sample solution was used to determine cobalt by the fixed time method, the absorbance being measured at the absorption maximum of GAL (520 nm). A linear relationship was obtained between AE and concentration of cobalt in the range between 0.2 and 2.4 ng/ml under the following conditions; In this method, an apparent molar absorptivity was 1.6×l07(l/mol.cm). Among diverse metal ions, 300 times of iron(III) and 2000 times of chromium (III) interfers with the determination. Amounts of 100 times of nickel do not interfer. The coefficient of variation of the analytical result was 4.6%, Present method was succesfully applied to the determination of trace cobalt in lake water. © 1978, The Chemical Society of Japan. All rights reserved.