ABSTRACT

A novel method for the determination of iodine in food by the sodium nitrite-iodine-starch system has been studied. In an acidic sodium chloride medium, potassium iodide can be quantitatively reduced by sodium nitrite to form I2, then a blue complex with a maximum absorption wavelength of 580 nm is formed by I2 and starch. A new method for the indirect determination of iodide content is established. The various effect factors on the determination of iodide by the sodium nitrite-iodine-starch system are investigated in detail. The results show that in the optimal conditions, a good linear relationship is obtained between the potassium iodide content and the absorbance of the blue complex within the potassium iodide concentration of 16.00~38.40 μg/mL, and the linear regression equation is A=-0.4358+0.0293C (μg/mL). This proposed method had been successfully applied to determine iodine in kelp, and the recovery yields of the standard addition test are 96.1%~103.7%.