紫外分光光度法测定渔业水体中总氮含量的测量不确定度评定OA

As an important index to judge water quality and eutrophication degree of water body,the accuracy of total nitrogen measurement results is particularly important.To determine the uncertainty of total nitrogen content in fishery water bodies,this paper measures the total nitrogen content in fishery water bodies according to HJ 636-2012"De-termination of Total Nitrogen in Water Quality Alkaline Persulfate Digestion Ultraviolet Spectrophotometry Method",and evaluates the measurement uncertainty of total nitrogen content in accordance with JJF1059.1-2012.A measure-ment model was established to analyze the sources of uncertainty in the determination of total nitrogen by alkaline po-tassium persulfate digestion ultraviolet spectrophotometry.The results show that the main sources of measurement un-certainty can be divided into three categories:the uncertainty introduced by repeated measurements of samples,the uncertainty introduced by the sample during the determination of nitrogen content(including the uncertainty intro-duced by potassium nitrate standard stock solution,the uncertainty introduced by the preparation process of potassium nitrate standard working solution,the uncertainty introduced during the transfer of testing points for the total nitrogen standard curve,the uncertainty introduced during the fitting of the total nitrogen standard curve,and the uncertainty introduced during the precision measurement of total nitrogen by the testing instrument),and the uncertainty intro-duced during the sampling,digestion,and volumetric processes of the samples.By evaluating the measurement uncer-tainty of the measurement process,it is found that the measurement result of total nitrogen content of the sample in this fishery water body sample can be reported as ρ=(0.96±0.06)mg/L(k=2).The uncertainty of sample re-peated measurement and the uncertainty introduced by the fitting of total nitrogen standard curve are the main sources of measurement uncertainty,accounting for 89.56%of all uncertainty sources.The results of this study can clarify the uncertainty in key steps of total nitrogen determination and the methods to reduce the uncertainty,provide refer-ence for reducing the error of laboratory determination of total nitrogen,and also provide reference for the measure-ment uncertainty evaluation of other indexes in fishery water.[Chinese Fishery Quality and Standards,2025,15(1):48-57].