Inhibition Kinetic Spectrophotometric Determination of Microamounts of Iodide

Based on the inhibition action of microamounts of iodide ion on the catalytic reaction of nitrite on oxidation of methyl red by potassium bromate in dil.H3PO4 medium,a new method of inhibition kinetic spectrophotometric determination of trace amounts of iodide was proposed.Linear relationship between values of ΔA (difference of absorbances of the inhibition reaction system and the catalytic reaction system) and concentration of iodide ion was kept in the range within 0.66 mg·L-1 of solution.Detection limit (3Sb/K) found was 7.5×10-6g·L-1.Samples of table salt and kelp were analyzed by the proposed method for contents of iodide,giving values of recovery and RSD′s (n=6) in the ranges of 99.7%-100.1% and 1.4%-2.2% respectively.