结晶紫-草酸体系光度法测定食盐中的碘

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

在酸性介质中,过量的草酸还原 IO3^-得到 I3^-,I3^-继续氧化结晶紫,且反应前后吸光度的差值与碘酸根的浓度成正比。建立起结晶紫-草酸体系光度法测定微量碘的新方法。考察了温度、结晶紫、盐酸、还原剂用量对测定结果的影响,确定了最佳实验条件为室温、结晶紫0.5 mL、盐酸0.5 mL、还原剂1.5 mL。该法操作简便、线性范围宽、RS＜3%、回收率在97.20%-102.8%。利用它测定食品中碘含量结果准确、可靠。

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 0.5 mL,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.