A SENSITIVE KINETIC ASSAY FOR THE DETERMINATION OF IODINE IN FOODSTUFFS

A spectrophotometric kinetic assay is presented for the determination of iodine present in foodstuffs. Incineration of organic matter was accomplished in successive steps with KOH and ZnSO4. Quantitation of iodine was based on measurement of iodide-catalysed reduction of Ce(IV) to Ce(III) by As(III). The reaction was continuously monitored at 370 nm and initial velocity, i.e. rate of decrease in absorbance was plotted against concentration of iodine. The method showed good reproducibility. Recovery of iodine added to different foods ranged from 94% to 102% with a mean and standard deviation of 97 +/- 3.3%. The method provides a detection limit of 0.4 ng and a sensitivity of 40 pg. The method is also applicable for the determination of iodine in serum, urine and other biological materials.