气相分子吸收光谱法测定水中氨氮的干扰去除研究

Research on Removing Interference During Ammoniac Nitrogen Detection in Water by Using Gas-phase Molecular Absorption Spectrometry

气相分子吸收光谱法测定酸性和还原性物质的氨氮水样时,酸性物质和还原性物质会消耗次溴酸盐氧化剂使得氨氮转化率降低,从而使测定结果偏低。考察了酸度、还原性物质对气相分子吸收光谱法测定水中氨氮的影响及干扰消除。酸度为0.1%、0.5%时对测定无影响,酸度增加至1.0%、5.0%时,结果偏低,需调节样品酸碱性后分析;还原性物质使测定结果偏低,采用酸性重铬酸钾消解样品后分析,相对标准偏差为2.8%、1.1%,加标回收率为100%、98%。

When using the gas-phase molecular absorption spectrometry to determine the ammonia nitrogen in water samples containing reducing and acid substances,the reducing and acid substances will consume the hypobromate oxidant and reduce the conversion rate of ammonia nitrogen,resulting in low determination results.The impact of acidity and reducibility was discussed in the determination of ammonia nitrogen in water samples by using gas-phase molecular absorption spectrometry.The results showed that the ammonia nitrogen determination was not affected when the concentration of acid is 0.1%and 0.5%,but increased to 1.0%,5.0%.The result was lower than the true value,and the pH of water samples should be adjusted to neutral.It was found that the presence of reducing agents could result in a lower ammonia value.A new analytic method was applied,using potassium dichromate to consume reducing agents before the determination of ammonia concentration.The samples RSD were 2.8%and 1.1%,and the recovery rate were 100%and 98%.