Determination of hydrogen isotopes and isomers by different deactivated alumina PLOT columns

To determine residual H2 and D2 concentrations in high purity HD, gas chromatography was used to separate the hydrogen isotopes in a 5 A molecular sieve porous layer open tubular (PLOT) column cooled in a slowly warmed dewar. It took more than 15 min to produce one chromatogram in which a platform existed between o-H2 and p-H2, and resolution between o-D2 and p-D2 was hardly investigated. In this study, to improve thermal stability of the column oven, the column is designed to be immersed in pure liquid nitrogen instead of a mixture of liquid nitrogen and isopentane. Several alumina PLOT columns under different deactivation conditions are used to separate the hydrogen isotopes at 78 K. Results show that the sulfate deactivated column performs higher elution resolution than the chloride deactivated column. The platform was decreased in a 15 m sodium sulfate deactivated column; o-H2 and p-H2 was baseline separated within 1 min; o-H2: p-H2 = 72:28 according to peak areas. o-D2 and p-D2 was separated in less than 2 min in the same column, the ratio o-D2:p-D2 = 67:33. Relative short analysis time would help reduce the platform. Residual concentrations of high purity HD (HD = 96%) were determined within 3 min in a 15 m sulfate deactivated column modified by magnesium sulfate.