水质样本中亚硝酸根离子^(15)N同位素丰度测定

Determination of ^(15)N Isotope Abundance of Nitrite Ion in Water Samples

基于高分辨气体同位素质谱技术,建立了水质样本中亚硝酸根离子^(15)N同位素丰度的检测方法。取2 mL样本(亚硝酸根离子含量≥10 mg/L)、5 mg碘化钾和1 mL乙酸,反应生成^(15)NO,将生成的^(15)NO引入高分辨气体同位素质谱仪中,检测质量数为30和31的离子流强度,根据2种同位素峰强度计算得到^(15)N同位素丰度。测试结果表明,当样本中亚硝酸根离子浓度≥10 mg/L时,误差均小于0.3%,相对标准偏差均小于2%,同时水质中硝酸根离子的存在对测试亚硝酸根离子中^(15)N同位素丰度没有影响。方法适用的^(15)N同位素丰度范围为0.365%~99%。该方法可为样本中亚硝酸根离子^(15)N同位素丰度提供准确可靠的检测方法。

An isotopic abundance measurement method for ^(15)N of nitrite ions in water samples was developed based on high-resolution gas isotopic mass spectrometry.A 2 mL sample(with nitrite ion content≥10 mg/L),5 mg potassium iodate and 1 ml acetic acid were taken to react and form ^(15)NO.The generated ^(15)NO was introduced into the high-resolution gas isotopic mass spectrometer to measure the ion flow with mass numbers 30 and 31.^(15)N isotopic abundance was calculated from the intensity of the two isotopic peaks.The test results showed that when the concentration of nitrite ions in the sample was≥10 mg/L,the errors were less than 0.3%,relative standard deviation were less than 2%,while the presence of nitrate ions in the water did not affect the ^(15)N isotopic abundance in the nitrite ions.The method was applicable to a ^(15)N isotopic abundance range of 0.365%~99%.The method could accurately and reliably measure ^(15)N isotopic abundance of nitrite ions in samples.