Spectrophotometric Determination of Iodine in Table Salt by Oxidation Coloration of Benzidine

Based on the color reaction of potassium iodate with benzidine in HCl medium,a spectrophotometric method for the determination of iodine in table salt was proposed.Linearity range of the method was found between 100-1 400 μg·L-1,at 45 ℃ in a water bath and with addition of 1.00 mL of 2.0 mol·L-1 HCl and 0.80 mL of 0.42 g·L-1 benzidine solution.The absorption maximum was at the wavelength of 425 nm and the apparent molar absorptivity found was 1.4×105L·mol-1 ·cm-1.The proposed method was used in the determination of iodine in table salt,giving the values of recovery and RSD (n=7) in ranges of 97.5%-101.2% and 0.9%-1.9%,respectively.