微量分光光度法测定饮用水中亚硝酸盐氮检测结果的有效性评估

Assessment on Validity Nitrite-nitrogen Results in Drinking-water by Micro-spectrophotometry

目的通过分析新型微量分光光度法测定饮用水中亚硝酸盐氮的不确定度及其影响因素,进行不确定度分析评定,从而评估该法检测结果的有效性。方法利用亚硝酸盐与对氨基苯磺酰胺重氮化,再与盐酸N-(1-萘)-乙二胺产生偶合反应,生成紫红色的偶氮染料的原理,采用自主研制的能够自动进样、自动计算结果、自动清洗的微量自动分析仪及其配套的分析试剂盒,对饮用水中的亚硝酸盐氮进行测定。结果在0.001 mg/L^0.2 mg/L浓度内呈线性关系,工作曲线为A=3.0065m+0.0049,相关系数r=0.9999,检出限为0.001 mg/L。采用该法测定实际水样,并对测定结果进行不确定度分析。当k=2(95%置信概率),测量结果为(0.072±0.002)mg/L。结论微量分光光度法测定饮用水中亚硝酸盐氮的不确定度主要来源于标准系列的配制过程。在测量时注意合理选择标准物质,准确配制标准溶液,做好标准曲线。同时要控制适宜的环境温度,维护好仪器,从而减少测量不确定度,提高测量结果的准确性。合成不确定度较小,证明该仪器运行稳定,处于较好的可控状态,检测结果有效。

Objective To analyze the factors influencing the uncertainty of nitrite-nitrogen in drinking water detected by micro-spectrophotometry in order to assess the validity of results. Methods Based on the reaction of nitrite with sulfanilic amide and N- 1- naphthalethylenediamine to form a kind of violet red azo dye,nitrite nitrogen was quantified by a trace automatic analyzer matched with colorimetric assay kits. The action of sampling,calculating and cleaning samples in the analyzer could be done automatically. Results There was a good linear relationship between the concentrations of nitrite nitrogen in the range of 0. 001 mg / L ~ 0. 2 mg / L with the absorbance.The working curve was y = 3. 0065 x ＋ 0. 0049,and the correlation coefficient was r = 0. 9999. The detection limit was 0. 001 mg / L. In detecting actual samples and analyzing the uncertainty of results,the result of the sample was（ 0. 072 ± 0. 002） mg /L when k = 2（ 95% confidence probability）. Conclusions According to the results in this study,the uncertainty was mainly from standard curve fitting. More attention should be paid to a rational selection of standard substance,accurate preparation of standard solution and standard curve. At the same time,temperature should be suitably controlled,instruments should be in good condition,so as to reduce the uncertainty of measurement,improve the accuracy of results. The equipment has been proved running stably and in good control with small synthetic uncertainty,and the detected result was effective.