碱灰化砷铈催化分光光度法测定鲜奶及奶粉中碘含量

Measurement of iodine content in milk and milk powder by As^(3+)-Ce^(4+) catalytic spectrophotometrywith dry ashing of sample preparation

目的建立一个奶及其制品中碘的测定方法。方法使用碳酸钾、硫酸锌、氯酸钾、氯化钠混合碱性助剂于550℃灰化样品4 h,用水溶解灰份后取上清砷铈催化分光光度法测定碘含量。根据光密度值的对数与碘含量成线性关系计算样品中的碘含量。结果检测范围为5~250 ng碘;标准曲线的平均相关系数为0.999 4;精密度:测定样品碘含量为86.0μg/L、163.6μg/L、213.1μg/L时,其变异系数(CV)分别为2.9%、4.4%、6.8%(n=6);准确度:对低、中、高3种不同碘含量的尿样加碘标回收率分别为96.8%、94.9%、100.4%(n=6),平均回收率为97.4%。结论本方法适宜于奶及制品中总碘的测定。

Objective To set up a new method for determination of milk iodine in a range of 5 ～ 250 ng by As^3＋ - Ce^4＋ catalytic spectrophotometry with dry ashing of samples in KClO3 - ZnSO4, - KaCO3 - NaCl. Methods The mixture of milk or dissolved milk powder and the solution of KClO3 - ZnSO4 and K2CO3 - NaCl is heated in dry bath at 105℃ for around 3 hours, then heated by a adjustable electric heater at 300 ～ 600 W until all black fog is completely released, transferred into muffle furnace for ashing at 550 ℃ for 4 hours. The dissolved ash is measured by As^3＋ -Ce^4＋ catalytic speetrophotometry. Results This testing covers iodine ranged from 5 ng to 250 ng. The relevanee coefficient of standards is 0.9994. The coefficients of variation are 2.9%, 4.4% and 6.8% （ n = 6） respectively when 86.0μg/L, 163.6μg/L and 213.1μg/L of the iodine contents of samples are tested. The average reeovery is 97.4% （94.9% ～ 106.0%）. Conclusions This method is suitable to measuring milk iodine and easier to be performed with better precision and accuracy.