Binary Stationary Phase Of CB[7] And IL For Gas Chromatography

Specific molecular recognition and high thermal stability offers cucurbit[n]urils as ideal candidates for stationary phases in gas chromatography(GC). But their poor solubility in common organic solvents often leads to poor column efficiency, which greatly limits their use in the field. Ionic liquids are known for their highly solubilizing ability for diverse materials and good film-forming ability on the inner wall of fused silica capillaries, and might be helpful in solving the aforementioned problem with CB[n]. In this work, we present a facile strategy by integrating cucurbit[7]uril(CB[7]) with a guanidinium-based ionic liquid(GBIL) into a binary stationary phase to achieve high separation performance for analytes of interest.This work contains the following three sections:Firstly, CB[7]-IL capillary columns were prepared by static coating approach and characterized by column efficiency, McReynolds constants andAbraham solvation system constants, respectively. As a result, CB[7]-IL column presents high column efficiency up to 4363 plates/m, and shows moderate polarity. Besides, Abraham system constants indicated its multiple molecular interactions including H-bond basicity, dipole-dipole, dispersion,π/nonbonding electronic interaction and H-bond acidity, which were helpful in predicting the possible retention mechanism.Secondly, a large number of analytes including alkanes, esters, alcohols, aldehydes,alkyl halides and aromatic compounds were selected as probes and separated on the CB[7]-IL, CB[7] and IL columns, respectively. Comparison of the separation results on the binary stationary phase and neat stationary phases revealed thespecific separation performance of the binary phase and its advantages over the neat phases.Thirdly, the specific selectivity of the IL stationary phase found in the above work interested us to further explore its separation performance and retention mechanism by employing analytes of varying polarity. It was interesting to find its strong retention behaviour for both nonpolar n-alkanes and polar alcohols, which was not reported for a polar GC stationary phase. This new finding regarding the amphiphilic selectivity of the GBIL phase is of great value in scientific research and applications.