三氧化二铝PLOT柱气相色谱法分离氢同位素自旋异构体

摘要

氢同位素核自旋异构体正-仲态比例影响氢同位素的低温物性,有必要对其比例进行测定.本文利用活性三氧化二铝多孔层开管(Porous Layer Open Tubular,PLOT)柱实现了正-仲氢同位素(氕、氘)的基线分离,发展了一种可在液氮温度下测定同核分子正-仲态比例的色谱分析技术.研究结果表明,与传统三氧化二铝填充柱相比,高效PLOT柱实现了正、仲氕(o-H2、p-H2)以及正、仲氘(o-D2、p-D2)的基线分离(分离度Rs大于1.5),当流量为5 mL·min?1时,分离度Rs(p-H2,o-H2)=6.9,Rs(o-D2,p-D2)=1.8.正仲态分离度与进样量、流量均有关系.根据峰面积的积分结果,常温(298 K)下正、仲氕比例为2.77:1,正、仲氘比例为1.78:1,与理论测算值基本符合.HD与o-H2实现了部分分离,Rs(o-H2,HD)=0.5,根据理论预测,实现HD与o-H2的基线分离(Rs达到1.5),理论塔板数需要达到3.9×105.%Background:The cryogenic properties of hydrogen isotopes are affected by ortho-para ratio of the homonuclear molecules (H2, D2, T2).Purpose:It is necessary to determine the ortho-para ratio.Methods:A cryogenic elution chromatographic method for determination of the ortho-para ratio is established, in which an activated alumina porous layer open tubular (PLOT) column with 30 m×0.53 mm×20μm was applied for separation of the spin isomers.Results:The isomers were well separated at base line (the resolutionRs>1.5) at temperature of liquid nitrogen (78 K), compared with the conventional packed columns. When the Neon carrier rate is 5 mL·min?1, the resolution of ortho-para protiumRs (o-H2, p-H2) and ortho-para deuteriumRs(o-D2, p-D2) is 6.9, 1.8, respectively. Conclusion:The resolution is affected by sample content and flow rate. According to integration of peak areas, the ortho-para rate at 300 K for protium and deuterium is 2.77:1, 1.78:1, respectively, which is in accordance with the theoretical results. Partial separation is obtained between ortho-H2 and HD, and the resolutionRs (o-H2, HD) reached 0.4, theoretical plates of 3.9×105 should be required to achieve the baseline separation (Rs=1.5).