气相分子吸收光谱法测定水中氨氮干扰因素的研究

气相分子吸收光谱法测定成分复杂氨氮实际样品时,干扰因素造成测定结果不准确,而现有的标准方法和文献对干扰物质的研究不全面,制约了仪器的应用。该文系统地开展干扰因素的研究,提出干扰因素的消除方法,用加标回收率验证消除的有效性。结果表明,亚硫酸盐、硫化物等还原性物质对测定产生负干扰;石油烃、N,N-二甲基甲酰胺(DMF)等挥发性有机物、有机胺类以及亚硝酸盐对测定产生正干扰。根据不同干扰类型,通过加入适量酸性重铬酸钾溶液、在酸性条件下加热煮沸、预蒸馏等方法可消除干扰,消除干扰后加标回收率为84%~120%。生活污水、石化企业废水等6种典型水样消除干扰后,气相分子吸收光谱法和纳氏试剂分光光度法测定氨氮有较好的可比性,干扰消除方式有效。

Determination of Ammonia Nitrogen Interference Factors in Water by Gas-Phase Molecular Absorption Spectrometry

When the actual sample of complex ammonia nitrogen is determined by gas-phase molecular absorption spectrometry,the interference factors cause the measurement results to be inaccurate,and the existing standard methods and literature do not comprehensively study the interfering substances,which restricts the application of the instrument.In this paper,the study of interference factors is carried out systematically,the elimination method of interference factors is proposed,and the effectiveness of elimination is verified by the standard recovery rate.The results show that reducing substances such as sulphites and sulfide have negative interference on the determination.Volatile organic compounds and organic amines,such as petroleum hydrocarbons,N,N-dimethylformamide(DMF),and nitrites have positive interference on the determination.Depending on the type of interference,the interference can be eliminated by adding an appropriate amount of acidic potassium dichromate solution,or heating and boiling under acidic conditions,or pre-distillation,and the recovery rate after eliminating interference is 84% to 120%.After the interference of 6 typical water samples such as domestic sewage and petrochemical enterprise wastewater is eliminated,the gas-phase molecular absorption spectroscopy and the Nessler''s reagent spectrophotometric determination of ammonia nitrogen have good comparability,and the interference elimination method is effective.