水中氨氮纳氏法测定时样品前处理方法的质量控制研究

A Study on the Quality Control of Sample Pretreatment in Nesslerization Method for the Examination of Ammonia Nitrogen in Water

纳氏试剂分光光度法测定水中氨氮通常采用絮凝沉淀或蒸馏的前处理方法。通过对不同浓度的实际样品和标准样品进行检测比较2 种前处理方法的适用情况,发现絮凝沉淀方法更适用于地表水。但絮凝过程中的pH 条件和沉淀后处理的实验条件决定了检测结果的准确性和真实性。针对pH 值、沉淀后分离方式、过滤材质的选择等实验条件进行了具体的比较分析,并进行了过滤材质的准确度、前处理方法的准确度和精密度比较。研究结果表明,pH 为10.5~11.0 时,絮凝效果最好;经5 次洗涤后,部分定性滤纸满足分析要求;0.45μm 滤膜较滤纸更适合低浓度地表水分析。研究结论可为相关实验检测提供数据参考和理论支持。

Floc precipitation or distillation is usually used in sample pretreatment for examining ammonia nitrogen in water by Nessler reagent spectrophotometry. The applicability of those two pretreatment methods was compared through detecting the actual samples and standard samples in various concentrations. It was found that the floc precipitation method was more suitable for surface water. However, the pH condition and post-precipitation treatment would determine the accuracy and authenticity of the results. The specific conditions such as pH value, post-precipitation separation, filter material, and etc. were compared and analysed. The findings showed that the flocculation effect would be the best when pH value was at 10.5 ~ 11.0. Some of qualitative filter paper could meet the analytical requirement after being washed for five times. Filter membrane in size of 0.45 μm would be more suitable for analysing surface water in low concentration other than filter paper. The conclusion could provide data reference and theoretical support for relevant experimental tests.