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用对硝基苯胺作为重氮化试剂,以N-(1～萘基)乙二胺为偶联剂的偶氮染料法测定了水中NO_2~-的含量。研究了重氮化试剂用量与重氮化时间的关系、偶联试剂用量与展色时间的关系以及1:1盐酸加入量对消光值的影响,并比较了52种化合物或离子分别对于对硝基苯胺和对氧基苯磺酸为重氮化试剂的干扰实验。实验表明,在最大吸收波长530毫微米下,用1厘米比色池测定0.0081毫克/升NO_2~-水溶液,消光值为0.010。测定0.800毫克/升NO_2~-水溶液,相对标准偏差为0.21%。检测灵敏度比以对氡基苯磺酸为重氮化试剂的要高17%。颜色在两小时以内稳定。离子和化合物的干扰情况除Mg~(++)及Hg~(++)外,两种方法完全一样。本实验证明,Hg~(++)及Mg~(++)与对硝基苯胺形成络合物而发生干扰,加入少量含-SO_3H的化合物完全可以隐蔽克服该干扰。
The content of NO 2 - in water was determined by azo dye method using p-nitroaniline as diazotization reagent and N- (1-naphthyl) ethylenediamine as coupling agent. The relationship between the amount of diazotization reagent and the diazotization time, the relationship between the amount of coupling reagent and the development time, the effect of 1: 1 hydrochloric acid addition on the extinction ratio were studied. The effects of the amount of diazotization reagent on the extinction time, Aniline and p-oxybenzene sulfonic acid as diazotization reagent interference experiments. Experiments show that at a maximum absorption wavelength of 530 nm, with a 1 cm colorimetric cell determination of 0.0081 mg / L NO 2 - - aqueous solution, the extinction value of 0.010. Determination of 0.800 mg / L NO2 ~ - aqueous solution, the relative standard deviation of 0.21%. The detection sensitivity is 17% higher than the diazotization reagent for radon-based benzenesulfonic acid. Color stable within two hours. Interferences between ions and compounds Except Mg ~ (++) and Hg ~ (++), the two methods are exactly the same. This experiment proved that Hg ~ (++) and Mg ~ (++) and p-nitroaniline formation of complex interference, adding a small amount of -SO_3H containing compounds can completely conceal the interference.