枸杞中二氧化硫残留量测定的不确定度分析

Evaluation of Uncertainty in Determination of Sulfur Dioxide Residue in Fructus Lycii

本文根据不确定度评定要求,参照标准《食品安全国家标准食品中二氧化硫的测定》(GB 5009.34-2016),对枸杞中二氧化硫进行检测并对测定结果进行不确定度评估,确立影响因素。结论:碘标准滴定溶液所消耗的体积及重复性是本实验不确定度的主要影响因素,为减少上述两个因素带来的影响:一方面,要降低碘标准滴定溶液所消耗体积产生的不确定度,如为避免肉眼观察颜色变化来判定终点对碘标准滴定溶液所消耗体积产生的误差,可以考虑通过设备(如电位滴定仪)进行终点判断;另一方面,如称样一定要准确,天平选用应是稳定性好、误差小的,确保称量的准确性。

According to GB 5009.34-2016"Determination of Sulfur Dioxide in Food",the uncertainty in measurement of sulfur dioxide in fructus lycii was evaluated in this article.The results showed that:The specific sources of uncertainty were the calibration of iodine standard solution and the repeated determination of samples.In order to reduce the influence of the above two factors,on the one hand,it is necessary to reduce the uncertainty caused by the volume consumed by the iodine standard titration solution.For example,in order to avoid the great influence caused by human visual observation errors,It can be considered to judge the end point through equipment(such as potentiometric titrator);on the other hand,in order to reduce the uncertainty caused by repeatability,it is necessary to control the operation error as much as possible.For example,the weighing sample must be accurate.The balance selection should be stable and the error should be small,so as to ensure the accuracy of weighing.