连续流动注射分光光度法测定饮用水中氨氮

Analysis on determination of ammonia nitrogen in drinking water by continuous flow injection spectrophotometry

目的基于改进的贝特洛反应,建立连续流动注射分光光度法测定饮用水中氨氮的方法。方法样品通过连续流动注射分析仪被带入连续流动的载流液中,氨氯化生成一氯胺,一氯胺与水杨酸反应生成5-氨基水杨酸盐,进一步发生氧化和氧化耦合反应,生成绿色络合物,在660 nm波长处测量其吸光度。结果氨氮的线性范围为0.02~2.00 mg/L,方法检出限为0.003 8 mg/L,在本底浓度为0.031 mg/L水源水和0.021 mg/L出厂水中分别加入0.02、0.10和0.18 mg/L 3种不同浓度的氨氮标准溶液,连续测定6次,水源水的相对标准偏差分别为2.80%、0.21%、0.12%,出厂水的相对标准偏差分别为3.80%、0.34%和0.37%。不同浓度的实际水样加标回收率在90.0%~110.0%之间。测定结果与国标方法(纳氏试剂分光光度法)比较差异无统计学意义(t=2.09,P>0.05)。结论本方法具有较高的准确度和精密度,相比于普通的分光光度法具有操作简便,分析速度快,适合于大批量测定饮用水中的氨氮。

Objective To established a method to detect ammonia nitrogen in drinking water with continuous flow injection spectrophotometry based on the modified Bertolo reaction.Methods The sample was brought into the continuous flow liquid by continuous flow injection analyzer.Ammonia chlorination forms monochloramine,and monochloramine reacts with salicylic acid to form 5-aminosalicylic acid,then oxidation and oxidation coupling were reacted to form green complex.The absorbance of sample was measured at the wavelength of 660 nm.Results The curve of ammonia nitrogen was linear in the concentration range of 0.02-2.00 mg/L,and the detection limit was 0.0038 mg/L.0.02,0.10 and 0.18 mg/L ammonia nitrogen standard solutions were added to the source water and Ex-factory water with background concentration of 0.031 mg/L and 0.021 mg/L,respectively,value of RSD found were 2.8%,0.21%,.12%for source water and 3.8%,0.34%,0.37%for Ex-factory water with 6 detection continuously.The recovery of water samples with different concentrations were in the range of 90.0%-110%.The test results showed there was no significant difference(t=2.09,P>0.05)between this method and the national standard method(Nessler’s reagent spectrophotometry).Conclusion The method has high accuracy and precision,and operation is simple and fast compared with common spectrophotometry,and it is more suitable for largescale determination of ammonia nitrogen in drinking water.