分光光度法测定水中氨氮的不确定度评定

Evaluation of uncertainty for determination of ammonium nitrogen in water by spectrophotometer

目的对分光光度法测定水中氨氮含量的不确定度的来源及其对测量不确定度的影响进行分析。方法利用相对标准不确定度进行测量不确定度的评定。过程采用直观的因果图,建立有效的数学模型,利用相对标准不确定度分量进行测量不确定度评定,并在氨氮测定含量为5.5μg/mL 的水样中获得其相对合成标准不确定度为4.77%。结论水样中氨氮含量测定的测量不确定度影响因素中,校准曲线斜率引起的不确定度最大,占3.69%,其次是测定时吸光度值和体积引起的不确定度,占3.03%。

Objective To study the sources and influluences of uncertainty for determination of ammonium nitrogen in water.Method Using the related standard uncertainty to evaluate uncertainty in measurement.Process Making use of the cause and effect diagram to analyse uncertainty, the mathematical model of the related standard uncertainty was established which consists of terms of uncertainty component and a result of related combined standard uncertainty 4.77% was obtained in determination of a water sample with ammonium nitrogen 5.5μg/ml.Conclusion In the influence factors of uncertainty in determination of ammonium nitrogen in water,the uncertainty of slope in calibration curve was the best,it was 3.69%.The uncertainty of absorbance and volume for determination of ammonium nitrogen was following, it was 3.03%.