顶空-气相色谱法测定城镇生活污水中氨氮方法改进

Improvement of HS-GC for determination of ammonia nitrogen in urban domestic sewage

利用甲醛在弱碱性条件下会与铵盐反应生成中间产物CO_(2),在一定浓度范围内CO_(2)含量与铵盐含量成正比,建立了顶空-气相色谱(HS-GC)测定城镇生活污水中NH_(3)-N的方法。对影响测定结果的参数进行了优化。结果显示,甲醛最优加入量500μL,平衡时间10min,反应温度40℃,所得的CO_(2)峰面积达到最高值。优化后标准曲线方程y=1.01x-0.0262,相关系数r=0.9996,精密度RSD 0.55%~1.53%,加标回收率98.7%~105.46%,满足检测需求。与《水质氨氮的测定纳氏试剂分光光度法》HJ 535-2009比,本文方法准确度较高。实际样品验证,某污水厂的生活污水排放口NH_(3)-N均值为15.8mg·L^(-1),RSD 1.18%,该方法既具备了准确快速,干扰小,覆盖面广,二次污染较低等优势,尤其适合于基质复杂的NH3-N批量快速分析。

A method for the determination of ammonia nitrogen in urban domestic sewage by headspace gas chromatography(HS-GC)was established based on the fact that formaldehyde reacts with ammonium salt to produce intermediate product CO_(2)under weakly alkaline conditions,and the content of CO_(2)is directly proportional to the content of ammonium salt in a certain concentration range.The parameters affecting the determination results were optimized.The results show that the optimal amount of formaldehyde is 500μL.The peak area of CO_(2)reached the highest value when the equilibrium time was 10min and the reaction temperature was 40℃.The optimized standard curve method y=1.01x-0.0262,the correlation coefficient r=0.9996,and the precision RSD 0.55%~1.53%,and the recovery rate of standard addition is 98.7%~105.46%,which meets the detection requirements.Compared with the determination of ammonia nitrogen in water quality Nessler reagent spectrophotometry HJ 535-2009,the accuracy of this method is higher.The actual sample verification shows that the average value of ammonia nitrogen at the domestic sewage outlet of a sewage plant is 15.8mg·L^(-1),RSD 1.18%.This method has the advantages of accuracy and rapidity,small interference,wide coverage and low secondary pollution.It is especially suitable for batch rapid analysis of ammonia nitrogen with complex matrix.