Kinetic-catalytic determination of iodide using the gallocyanine hydrogen peroxide redox reaction

Highly selective and sensitive method was developed for the determination o f iodide at ultra trace levels. The method is based on the catalytic effect of iodide on the oxidation of gallocyanine by hydrogen peroxide. The react ion was monitored spectrophtometrically by measuring the decrease in absorb ance of the dye for 0.5 - 4.0 min from initiation of the reaction. The plot of decreasing in absorbance at 625 nm us. reaction time showed that the ca libration curve is linear in the range of 0.0010 - 0.500 mu g/ml with a lim it of detection, of 0.0005 mu g/ml. The relative standard deviations for te n replicate analyses of 0.010 0.100 and 0.400 mu g/ml of iodide are 2.8%, 2 .1% and 1.7%, respectively. The influences of more than forty ions for the determination of iodide were completely studied. The method was applied for the determination of iodide in real samples. The mechanism of the reaction is discussed.