Colorimetric method for estimation of methyl iodide residues of Jowar (sorghum) and rice

Abstract A new colorimetric method based on the catalytic action of iodide on oxidation of As(III) by Ce(IV) has been developed for the estimation of methyl iodide residues on grains. Methyl iodide residues, in methanolic KOH, are converted to potassium iodide which acts as a catalyst in the timed oxidation of As(III) by Ce(IV). Unreduced eerie salt is measured colorimetrically and the iodide in the sample is calculated. The method is sensitive in the range 0.01 to 0.1 μg iodide.