基于GUM法和控制图法评定烟草中淀粉含量测定的不确定度

Uncertainty evaluation for determination of starch content in tobacco based on GUM method and control chart method

本研究分别基于《测量不确定度表示指南》规定的方法(GUM法)和控制图法对连续流动法测量烟草中淀粉含量的不确定度进行评定。结果表明:取扩展因子k=2,置信概率为95%,GUM法和控制图法评定烟草中淀粉含量分别为4.23%±0.10%和4.26%±0.54%,控制图法评定结果较大。采用GUM法建立不确定度模型,不确定度由样品质量测定、含水率测定、前处理稀释定容过程、浓度测定、测定重复性组成,其中测定重复性是最大不确定度分量。综合2种方法,推荐已确定不确定度主要来源的实验室采用控制图法进行实验室质控水平的长期评定。

According to GUM method and control chart method,uncertainty for determination of starch content in tobacco by continuous flow method was evaluated.The results showed that when the expansion factor(k)was two and the confidence probability was 95%,the content of starch was 4.23%±0.10%and 4.26%±0.54%by GUM method and control chart method respectively,the evaluation results by control chart method was larger.The model for uncertainty was established by GUM method.The uncertainty of measurement was composed of sample weight determination,water content determination,dilution and volume fixation in sample pretreatment,concentration determination and repeatability of determination.The repeatability was the main sources of the uncertainty.By comprehensive consideration of the two methods,it is recommended for laboratories which have identified main sources of uncertainty to evalute long-term quality control by utilizing control chart method.