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极谱法测定NO_3~-离子,人们研究较多的是先将NO_3~-离子还原为NO_2~-,然后借助催化体系通过测定NO_2~-离子来换算NO_3~-的含量。近来,直接测定NO_3~-离子也有报道,在硫酸钾的存在下,利用硝酸根与铀离子的催化反应,以微分脉冲极谱法测定NO_3~-离子的含量。但NO_2~-,HPO_4~(2-)离子干扰严重,必须预先除去。本文通过实验,发现在醋酸铀酞-尿素体系中,大量的NO_2~-离子存在,不干扰NO_3~-的直接测定。应用该法测定了四种天然水样品,测定结果及回收率均较为满意。
Polarographic determination of NO_3 ~ - ions, the more people research is the first reduction of NO_3 ~ - ions to NO_2 ~ -, and then through the catalytic system by measuring NO_2 ~ - ions to convert NO_3 ~ - content. Recently, direct determination of NO 3 - ions has also been reported. The catalytic reaction of nitrate and uranium ions in the presence of potassium sulfate was used to determine the content of NO 3 - ions by differential pulse polarography. However, the interferences of NO_2 ~ -, HPO_4 ~ (2-) ions are serious and must be removed beforehand. In this paper, we found that a large amount of NO 2 - ions exist in uranyl acetate-urea acetate system without any interference with the direct determination of NO 3 -. Four kinds of natural water samples were determined by this method, and the results and recovery rates were satisfactory.