碘离子选择电极测定果蔬、药剂中Vc含量

Study on Determination of Vitamin C in Vegetables, Fruits and Medicaments by Iodide-selective Electrode

提出用碘离子选择电极测定维生素C与碘在乙醇溶液中发生氧化还原反应时定量释放出游离碘离子溶液中的电位以测定样品中Vc含量的方法。在 0 .1mol·L- 1 KNO3,pH =2 .0～ 6 .0溶液中 ,维生素C的浓度对数值在 10 - 5～ 10 - 1 mol L范围内与电位显示良好的线性关系 ,检测下限为 5×10 - 6 mol L ,回归方程为 ,相关系数为 ,回收率为 92 %～ 10 3% ,相对标准偏差为 2 .3% ,能满足食品、制药及营养研究等行业对Vc的测定。

It had been already found that the ascorbic acid could be reduced by iodine saluted with alcohol to release free iodine ion,which could be responded by iodide-selective electrode. A mixed solution of 0.1mol/L KNO 3 with pH 2.0～6.0 was used as the electrolyte, The change of Vc concentration logarithm with potential was linear in the range of 5.0×10 -6 ～1.0×10 -1 mol/L, and detection limits was 5×10 -6 mol/L. Inthe range,the calibrated equation was Y=57.4x-24.4,the linear correlation coefficient r=0.9998. This method had been used for the determination of trace ascorbic acid in medicaments, fruitand drinks etc.and recovery ranged in 92 %～103 %. And the RST was less then 2.9 %.