Colorimetric determination of total iodine in foods by iodide-catalyzed reduction of Ce+4.
An earlier acid digestion determination of iodine in foods was modified to provide an improved detection limit and to allow for the analysis of a greater variety and larger amounts of foods. The organic material in the sample was oxidized overnight by concentrated nitric acid, followed by digestion in a mixture of concentrated sulfuric and 70% perchloric acid. The iodine was determined by an automated colorimetric method based on the iodide-catalyzed reduction of Ce+4 by As+3. The method had an average relative standard deviation of 3.1% for the samples analyzed, and a detection limit of 0.1 ng/mL in the digested solution and 5 ng/g in a 2 g sample prior to digestion. The recovery of added iodine ranged from 90.3 to 101.3%, using external standards. Samples analyzed included NBS Standard Reference Material 1549, and composites of a variety of dairy products, meat, eggs and fish, cereals, and potatoes. The iodine detected in these samples ranged from 9 ng/g for the potato group to 3360 ng/g for the standard reference material.
D001322:Autoanalysis; D002384:Catalysis; D002563:Cerium / Q000032:analysis*; D003124:Colorimetry; D005504:Food Analysis; D007454:Iodides; D007455:Iodine / Q000032:analysis*; D010084:Oxidation-Reduction
D007454:Iodides; D002563:Cerium; D007455:Iodine