Determination of Iodine in Salt by Crystal Violet-Oxalic Acid System Spectrophotometry

A new spectrophotometric method for the determination of trace amount of iodine is established.The oxalic acid reacts with potassium iodine in acidic medium,giving rise to I3-that can oxidize crystal violet selectively.The absorbance increases proportionally to the amount of potassium iodine.The effects of temperature,crystal violet,hydrochloric acid and reducing agent on measurement results are investigated.The best experimental conditions are found out that crystal violet is 0.5mL,hydrochloric acid is 0.5 mL and oxalic acid is 1.5 mL,the temperature is room temperature.The method is simple and with wide linear range.The relative standard deviation is less than 3%;the recovery is from 97.20% to 102.8%.The determination result of iodine in food is accurate and reliable.