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幔源流体活动区天然气中微量H2是研究幔源H2同位素组成的最佳样品,但受目前测试技术的限制,能准确测试同位素组成的H2浓度下限仍然有待继续降低。前人研究表明,当H2浓度低于1.5%时,测试结果的误差较大,可信度较低,这可能与载气进样时在进样针孔附近发生了随机分馏有关。为了避免这种随机分馏,文章提出了一种利用压差进样的方法,即利用饱和NaC l溶液增加样品瓶内的压力实现进样。实验结果表明,利用这种进样方法,不同浓度条件下,H2同位素组成测试值的极差与标准偏差都随H2浓度的增加而减小,统计得到的绝对误差与仪器的误差范围相当。因此,该进样方法可以有效避免微量H2在进样过程中发生的随机分馏,提高测试结果的精度和可信度。同时表明可以对现有设备进行合理改造,挖掘仪器的测试潜能。
The trace amount of H2 in the natural gas of the mantle source fluid activity zone is the best sample for studying the composition of the mantle source H2 isotope. However, due to the limitation of the current test technique, the lower limit of the H2 concentration capable of accurately testing the isotopic composition still needs to be further reduced. Previous studies have shown that when H2 concentration is lower than 1.5%, the error of the test result is larger and the reliability is lower, which may be related to the random fractionation of the carrier gas injection hole around the injection hole. In order to avoid this random fractionation, the paper presents a method of using differential injection, which is to use saturated NaC l solution to increase the pressure in the sample bottle for injection. The experimental results show that using this injection method, the range and standard deviation of the H2 isotope composition test values decrease with the increase of H2 concentration under different concentrations, and the absolute error of the statistics is comparable to the error range of the instrument. Therefore, the injection method can effectively avoid the random fractionation of trace H 2 during injection and improve the accuracy and reliability of the test results. At the same time shows that the existing equipment can be a reasonable transformation, mining test potential of the instrument.