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徐丽, 邢蓝田, 王鑫, 李中平, 毛俊丽. 元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定[J]. 岩矿测试, 2018, 37(1): 15-20. DOI: 10.15898/j.cnki.11-2131/td.201701130005
引用本文: 徐丽, 邢蓝田, 王鑫, 李中平, 毛俊丽. 元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定[J]. 岩矿测试, 2018, 37(1): 15-20. DOI: 10.15898/j.cnki.11-2131/td.201701130005
Li XU, Lan-tian XING, Xin WANG, Zhong-ping LI, Jun-li MAO. Study on the Optimal Reaction Temperature and Sampling Weight for Measurement of Carbon and Nitrogen Isotope Ratio by Elemental Analyzer-Isotope Ratio Mass Spectrometer[J]. Rock and Mineral Analysis, 2018, 37(1): 15-20. DOI: 10.15898/j.cnki.11-2131/td.201701130005
Citation: Li XU, Lan-tian XING, Xin WANG, Zhong-ping LI, Jun-li MAO. Study on the Optimal Reaction Temperature and Sampling Weight for Measurement of Carbon and Nitrogen Isotope Ratio by Elemental Analyzer-Isotope Ratio Mass Spectrometer[J]. Rock and Mineral Analysis, 2018, 37(1): 15-20. DOI: 10.15898/j.cnki.11-2131/td.201701130005

元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定

Study on the Optimal Reaction Temperature and Sampling Weight for Measurement of Carbon and Nitrogen Isotope Ratio by Elemental Analyzer-Isotope Ratio Mass Spectrometer

  • 摘要: 沉积有机质的碳氮稳定同位素值是进行古气候、古环境及生态系统研究不可或缺的主要研究手段,目前碳氮同位素主要利用元素分析仪-同位素比值质谱(EA-IRMS)系统来测定。EA-IRMS测定过程中的反应温度及样品进样量直接影响反应物在测试中的燃烧程度,从而影响测试数据的精度。本文利用EA-IRMS技术,以标准样品为参考,在不同转化温度下测试碳氮同位素值,研究保证测试精度的最佳反应温度条件;同时,通过分析不同含氮量样品的检测限,明确了样品含氮量与最低检测限之间的关系,确定了精确测定氮同位素值的最低进样量。结果表明:反应温度对测试精度有显著影响,在碳同位素测定时,将反应温度设定为900℃或以上时测试精度均能达到±0.2‰;氮同位素测定时,反应温度须设定为950℃时测试精度才能达到±0.3‰。实验得出样品含氮量与检测限之间的线性相关性为R2=0.873,开展氮同位素测定时可根据此关系来判断和控制进样量。

     

    Abstract: Carbon and nitrogen isotopes are essential tools to study paleoclimate, palaeoenvironment, and ecosystem. At present, carbon and nitrogen isotopes are commonly determined by Elemental Analyzer-Isotope Ratio Mass Spectrometer (EA-IRMS). Reaction temperature and sampling weight directly affect the burning of samples, and thus affect analytical precision. Using EA-IRMS technology and taking standard samples as references, the carbon and nitrogen isotope values were determined at different conversion temperatures to study the optimum reaction temperature, in order to ensure the accuracy of the analysis presented in this paper. At the same time, by analyzing the detection limits of samples with different nitrogen contents, the relationship between the nitrogen content of the sample and the lowest detection limit was determined and thus the lowest quantity of samples for accurate determination of nitrogen isotopes were also defined. The results show that reaction temperature has a significant effect on analytical precision. Analytical precision of carbon isotope is less than ±0.2‰ when the reaction temperature is either 900℃ or higher than 900℃, but the precision of nitrogen isotope can reach ±0.3‰ only when the reaction temperature is no lower than 950℃. The linear relationship between nitrogen content and detection limit was expressed as R2=0.873 according to the data. According to this relationship, the sample introduction quantity can be determined and controlled when analyzing nitrogen isotope.

     

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