摘要：

利用紫外分光光度法测定水中的NO₃ ^--N时，S₂O₃ ^2-的存在会使测定结果出现很大的正偏差，且S₂O₃ ^2-浓度越高干扰程度越大。为了保证含有S₂O₃ ^2-水样中NO₃ ^--N测定结果的准确性并提出消除干扰的方法作为参考，先测定了不同浓度S₂O₃ ^2-对NO₃ ^--N测定结果的干扰程度，而后在NO₃ ^--N初始质量浓度为10 mg/L，S₂O₃ ^2-质量浓度为100 mg/L的条件下，以加入盐酸、加入Ba²⁺、臭氧吹脱和加入过硫酸钾4种方法对S₂O₃ ^2-进行掩蔽排除。实验发现，加入盐酸对S₂O₃ ^2-的干扰有一定的排除能力，排除干扰的比例为30.599%，效果较差；加入Ba²⁺排除干扰的效果最差，排除比例仅有17.409%；利用臭氧吹脱方法取得了较好的排除效果，干扰的排除比例达到了54.752%，相较于前2种方法有了较大的提高，但仍不能够将干扰完全排除；加入过硫酸钾的效果最好，干扰的排除比例可达91.248%，基本不影响NO₃ ^--N的测定。

关键词: NO₃ ^--N, 硫代硫酸根, 干扰排除, 过硫酸钾, 紫外分光光度法

Abstract:

When NO₃ ^--N in water is measured by UV spectrophotometry，thiosulfate ions will cause great positive deviation to the measurement results. Higher thiosulfate ions concentration leads to the greater interference degree. In order to ensure the accuracy of NO₃ ^--N measurement results in water samples containing S₂O₃ ^2- and put forward the method of eliminating interference as a reference，the interference degree of different concentrations of thiosulfate ions on the measurement error of NO₃ ^--N was firstly determined. Then，under the condition that the initial mass concentration of NO₃ ^--N and thiosulfate ions were 10 mg/L and 100 mg/L，respectively，hydrochloric acid，Ba²⁺，ozone stripping and potassium persulfate were introduced to eliminate the measurement error. It was found that the addition of hydrochloric acid could eliminate the interference of thiosulfate ions in some degree，and the proportion of eliminating interference was inefficient only 30.599%. The effect of adding Ba²⁺ to eliminate interference was the worst，and the proportion of eliminating interference was only 17.409%. While the approach of ozone stripping achieved better elimination effect，and the elimination proportion reached 54.752%. It was greatly improved compared with the first two methods，but it was still unable to eliminate the interference thoroughly. The highest proportion of eliminating interference of 91.248% was realized when potassium persulfate was added. Basically，it had no effect on NO₃ ^--N determination.

Key words: NO₃ ^--N, thiosulfate, interference elimination, potassium persulfate, ultraviolet spectrophotometry

中图分类号: 

• X832