阳离子取代基对离子液体气相色谱固定相保留性能的影响

Effects of substituted functional groups of cations on retention performance of ionic liquid stationary phases in gas chromatography

以双-三氟甲烷磺酰亚胺离子([NTf_2]-)、三氟甲基磺酸根离子([TFO]^-)和六氟磷酸根离子([PF_6]^-)为阴离子,合成了含有丙基、丁基、壬基、乙苯基或氰甲基等阳离子取代基的聚合乙烯基咪唑基离子液体固定相,制备了13种离子液体石英毛细管色谱柱。考察了离子液体固定相结构与色谱柱Mc Reyno lds常数、热稳定性和测试化合物保留行为之间的构效关系,研究了阳离子取代基对固定相保留性能的影响规律;同时考察了测试化合物保留指数随温度变化的规律。结果表明,所合成的离子液体固定相具有较强的极性,其保留性能不仅与阳离子取代基的性质密切相关,而且受取代基结构和阴离子影响明显;在考察的温度范围内,测试化合物的保留指数变化规律与传统色谱固定相完全相同。

Thirteen stationary phases comprising a polyvinyl imidazolium ionic liquid（ IL） in which cations containing propyl,butyl,nonyl,ethyl-phenyl,or cyan methyl functional groups are paired with bis（ trifluoromethanesulfonyl） imide（ [NTf2]--）,trifluoromethanesulfonate（ [TFO]--）,and hexafluorophosphate（ [PF6]--） were synthesized and directly coated inside capillary fused silica tubing for use in gas chromatography. The relationship between the structure of the ILs and the McReynolds constant,thermal stability,and retention behavior of the test compound on the prepared fused silica columns was examined and discussed. The influence of the cationic substituents on retention performance of stationary phases was also studied. The variation in the retention index of the test compound with temperature was also investigated.The results indicated that the synthesized ILs have strong polarity,and that their retention performance is closely related to not only the properties of the cationic substituent but also the structure of the substituted groups and the anion. In the temperature range investigated,the variation in the retention index of the tested compounds was the same as that of conventional chromatographic stationary phases.