Iodine is an essential micronutrient in human growth and is very important for iodine supplementation metabolism. Deficiency of iodine causes serious delay in neurological development, goiter and hypothyroidism. 1) Table salts are iodized with iodate or iodide to serve as a source of iodine. The iodized salt is recognized as the method of choice and the most successful strategy for the prevention of iodine deficiency disorders. The recommended concentration of iodate in salts is 40 ppm.2) Iodine is an effective germicide for a wide range of microorganisms. Iodine is often used in conjunction with complexing nonionic surfactants or polymers (iodophors) in disinfectants that are used in dairies, laboratories and food processing plants. In addition to this iodine finds applications as dietary supplements, catalysts, pharmaceutical preparations, stabilizers and in photography. Iodine is also used in the production of motor fuels, high purity metals and in cloud seeding. The varied applications of iodine have made the determination of iodine very important.Several methods of iodine determination have been proposed, including selective electrodes, 3) X-ray fluorescence (XRF), 4) inductively coupled plasma mass spectrometry (ICP-MS). 5,6) Trace levels of iodide have been determined by the catalytic effect usually on the cerium(IV)-arsenic(III) reaction. 7,8) Other reactions catalyzed or inhibited by iodide have also been described. 9,10) Precipitation as silver iodide, dissolution in potassium cyanide, and determination of silver in the complex by atomic absorption spectrometry has been used for the indirect determination of iodide in a flow system.11) Sensitive extraction photometric methods based on ion-pair formation with methylene blue, 12) or with brilliant green 13) are well known. Recently methods based on the oxidation of leuco xylene cyanol FF 14) or thionin 15) with iodate are reported. Several spectrophotometric methods have been reported for the determination of periodate and iodate. [16][17][18][19][20] El-Shahawi 21) used the ion-associate of periodate with amiloride hydrochloride for simultaneous spectrophotometric determination of periodate and iodate by liquid-liquid extraction. Most of the reported methods are not sensitive enough or require complicated and expensive instruments.There is a need for the determination of iodine species in table salts and pharmaceutical samples. The developed method should be sensitive, simple and reliable. This paper describes a spectrophotometric method for the determination of iodine species like iodide, iodine, iodate and periodate. The method involves the oxidation of iodide to ICl 2 Ϫ in the presence of iodate and chloride in acidic medium.22) The formed ICl 2 Ϫ bleaches the dye methyl red. The decrease in the intensity of the colour of the dye is measured at 520 nm. The system obeys Beer's law in the concentration range 0-3.5 mg of iodide in an overall volume of 10 ml. The developed method can be applied directly to samples containing iodide and iodine and after p...
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