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首页> 中文期刊> 《质谱学报》 >质谱准确测定高丰度15N2的计算方法

质谱准确测定高丰度15N2的计算方法

         
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摘要

近年来,稳定同位素质谱(IRM S)在农业、生态、环境以及地质资源中的应用越来越广泛.在氮素研究过程中,稳定同位素质谱仪主要测定的是15 N自然丰度或15 N富集较低的气体样品,在测定高丰度的15 N2时,质谱仪自动计算出的结果在精确度和准确度上,都有很大的偏差.为了探究造成这种现象的原因,利用(NH4)2 SO4与NaBrO溶液反应产生N2,精确地配制了10、25、50、70、99.14 atom%的15 N2系列高丰度气体样品,利用M A T-253稳定同位素质谱仪测定气体样品的15 N2丰度,并采用推导出的3种不同的公式:15 N atom%=11+2 I28 I29×100、15 N atom%=I29+2 I302(I28+I29+I30)×100和15 N atom%=I292 I30+2×100计算15 N2系列样品的丰度,并与仪器给出的结果进行对比.结果表明,在测定15 N atom%≥10 atom%的N2样品丰度时,质谱仪计算机软件计算出的15 N丰度结果并不准确,必须采用公式进行人工计算.公式15 N atom%=11+2 I28 I29×100和15 N atom%=I29+2 I302(I28+I29+I30)×100只适用于计算丰度约为10 atom%的N2样品的15 N丰度,并要求以m/z 28、29和30的峰面积代入公式进行计算;而当N2样品15 N atom%≥10 atom%时,均可采用公式15 N atom%=2 I29 I30+2×100计算15 N2的丰度.该方法可为质谱测定高丰度15N2提供准确可靠的计算方法.%Stable isotope ratio mass spectrometers (IRMS ) have been more and more widely used in the agricultural , ecological , environmental studies and geological resources ,among them , gas IRMS is mainly used to measure the natural or low enriched 15 N abundance samples in the process of nitrogen research .However ,in terms of determination of high abundance of 15 N2 ,it was found that the given results of the automatic calculation of mass spectrometer calculator had a great deviation in precision , especially in accuracy .In order to explore the causes of above problem ,10 ,25 ,50 ,70 and 99.14 atom% series of high abundance gas samples of 15 N2 were prepared precisely according to the method that ammonium sulfate and sodium bromate solution could pro-duce N2 by reaction .Then ,m/z 28 ,29 and 30 of the 15 N2 samples were determinated by MAT-253 IRMS .In this study ,three different formulas for calculating the abundance of 15 N2 samples were deduced ,respectively as 15 N atom% = 11+2 I28 I29 × 100 ,15 N atom% =I29 +2 I302(I28 + I29 + I30 ) × 100 and 15 N atom% = I292 I30 +2 × 100 .Finally ,the datas of m/z 28 ,29 and 30 of 15 N2 samples were put into the three formulas for calculating the abundance of the samples .The result showed that ,formulas 15 N atom% = 11+2 I28 I29 × 100 and 15 N atom% =I29 +2 I302(I28 + I29 + I30 ) × 100 were suitable for calculation of the 15 N2 abundance about 10 atom% ,and formula 15 N atom% = 2 I29 I30 +2 × 100 was applicable to calculate the abundance higher than 10 atom% of 15 N2 samples .For all of three formulas ,adopting the peak areas of m/z 28 ,29 and 30 to calculate the abundance were more accurate than using the peak heights ,because the amplification of receivers of m/z 28 ,29 and 30 were different ,so magnifications were to be converted to the same level just at the artificial calculation .The receiving cups in the actual measurement process were different from the theory ,the larger the differences ,the greater the deviation from the results .How-ever ,the peak areas were high resistance to the same multiple cases ,so there was no error amplification factor .In addition ,the abundance of N2 was larger ,the combination probability of 15 N was higher ,and the ion current intensity of m/z 30 was stronger ,so the calculation of high abundance 15 N2 samples were mainly determined by the intensity of m/z 30 . T herefore , the results of the automatic calculation of mass spectrometer calculator without m/z 30 were wrong .As a result ,using the m/z 28 ,29 and 30 of 15 N2 and the three abundance calculation formulas deduced in this paper could obtain the accurate 15 N2 abundance ,which provides an accurate and reliable calculation method for the mass spectrometric determination of high abundance 15 N2 in the future .

著录项

  • 来源
    《质谱学报》 |2017年第6期|664-670|共7页
  • 作者

    杨帆; 孙晓丽; 王曦; 曹亚澄; 张金波; 蔡祖聪;

  • 作者单位

    南京师范大学地理科学学院,江苏南京 210023;

    中国科学院南京土壤研究所,土壤与环境分析测试中心,江苏南京 210008;

    中国科学院南京土壤研究所,土壤与环境分析测试中心,江苏南京 210008;

    南京师范大学地理科学学院,江苏南京 210023;

    中国科学院南京土壤研究所,土壤与环境分析测试中心,江苏南京 210008;

    南京师范大学地理科学学院,江苏南京 210023;

    江苏省地理环境演化国家重点实验室培育建设点,江苏南京 210023;

    江苏省地理信息资源开发与利用协同创新中心,江苏南京 210023;

    虚拟地理环境教育部重点实验室(南京师范大学),江苏南京 210023;

    南京师范大学地理科学学院,江苏南京 210023;

    江苏省地理信息资源开发与利用协同创新中心,江苏南京 210023;

    虚拟地理环境教育部重点实验室(南京师范大学),江苏南京 210023;

  • 原文格式 PDF
  • 正文语种 chi
  • 中图分类 质谱分析;
  • 关键词

    质谱; 高丰度15N2; 计算公式;

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