微量分光光度法测定饮用水中硫酸盐的不确定度研究

The uncertainty in determination of sulfate in drinking water measured by micro-spectrophotometry

目的对微量分光光度法测定饮用水中硫酸盐含量的不确定度进行评定。方法依据JJF1059.1-2012《测量不确定度评定与表示》建立数学模型,分析和识别不确定度来源,运用不确定度传播律对饮用水中硫酸盐的微量分光光度法进行不确定度评定。结果用微量分光光度法测定饮用水中硫酸盐含量,测量结果为49.5mg/L,合成标准不确定度为0.95mg/L。取包含因子k=2,置信水平约为95%,扩展不确定度为1.9mg/L。结论线性回归产生的不确定度分量最大,其次是标准系列溶液的配制过程,取样体积带来的不确定度分量最小。实际工作中,提高校准曲线线性相关性和避免使用较小容量器皿配制标准系列溶液,可大幅减小测量结果的不确定度。

Objective To assess the uncertainty in determination of sulfate in drinking water measured by micro-spectrophotometry. Methods According to Evaluation and Expression of Uncertainty in Measurement（JJF1059.1-2012）,the mathematical model was established to analyze and identify the source of uncertainty.The uncertainty of sulfate in drinking water determined by micro-spectrophotometry was assessed using law of propagation of uncertainty. Results The concentration of sulfate in drinking water sample determined by micro-spectrophotometry was 49.5mg/L.The combined standard uncertainty was 0.95mg/L.The expanded uncertainty was 1.9mg/L using a coverage factor k of 2with the confidence of approximately 95%. Conclusions Linear regression is found to be the biggest contribution to uncertainty,followed by the preparation of standard solution,the contribution of sample volume is the smallest.In practical work,the uncertainty of results can be significantly reduced by improving the linear correlation of the calibration curve and avoiding the use of small capacity vessels for preparation of standard solutions.