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采用预蒸馏纳氏试剂吸光光度法测定污水中的氨氮，以Ｈ３ＢＯ３ 溶液作吸收剂时，有色胶体的稳定性较差，加入ＮａＯＨ溶液可提高胶体的稳定性。当ＮａＯＨ 溶液（１ ｍｏｌ／Ｌ）与Ｈ３ＢＯ３ 溶液（２ ％） 的体积相同时，有色胶体稳定时间最长。加入胶体保护剂聚乙烯醇（ＰＶＡ） 可进一步提高胶体的稳定性和测定准确度。对Ｈ３ＢＯ３ ，ＮａＯＨ 和ＰＶＡ 的影响规律进行了研究，提出了最佳实验条件：以２％ Ｈ３ＢＯ３ 溶液作吸收液，１ ｍｏｌ／ＬＮａＯＨ 溶液１０ ｍＬ，罗谢尔盐溶液１．００ ｍＬ，５％ 聚乙烯醇０．１６ ｍＬ，纳氏试剂１ ．００ ｍＬ，反应１０ ｍｉｎ。该方法的最低检出限为０．０１５ ｍｇ／Ｌ，回收率为９８ ．６％ ～１０３％ ，适用于环保站、化工厂进行的常规分析
Pretreatment Nessler reagent absorbance spectrophotometry for the determination of ammonia nitrogen in wastewater, H3BO3 solution as absorbent, the colloidal colloid stability is poor, adding NaOH solution can improve the stability of colloids. When the volume of NaOH solution (1 mol / L) and H3BO3 solution (2%) are the same, the color colloid has the longest stability time. Adding colloidal protective agent polyvinyl alcohol (PVA) can further improve the colloidal stability and determination of accuracy. The influence of H3BO3, NaOH and PVA was studied. The optimal experimental conditions were as follows: 2% H3BO3 solution as absorbent, 10 mL of 1 mol / L NaOH solution, 1.00 mL of Rochelle salt solution, 0.16 mL of vinyl alcohol, Nessler reagent 1. 00 mL, the reaction 10 min. The method has the lowest detection limit of 0.015 mg / L and the recovery rate of 98. 6% ~ 103%, suitable for environmental protection stations, chemical plants for routine analysis