Preparation and Application of Imidazole-based Ionic Liquid and Amide Bipolar Groups Co-embedded Hydrophilic C18 Silica Gel Stationary Phase
In this work,octadecyl-modified silica chromatographic stationary phases with amide and imidazole-based ionic liquid bipolar groups co-embedded were prepared by stepwise bonding and two stationary phases with different anionic coordinations(Sil-IL-AMC18-Cl and Sil-IL-AMC18-Tf2N)were prepared by ion-exchange,which were characterized by means of infrared spectroscopy and elemental analysis.Both stationary phases showed C=C stretching vibration peaks and C=N bending vibration peaks on the imidazole ring at 1460 and 661 cm‒1,and asym-metric and symmetric stretching vibration peaks of—CH at 2927 and 2856 cm‒1,which proved the bonding of amino-imidazole ionic liquid.And the original 919 cm‒1 of primary amine N—H out-of-plane deformation vibration peak dis-appeared,indicating that octadecanoyl chloride is bonded with amino.The results of elemental analysis showed that Sil-IL-AMC18-Cl contained 3.07%of nitrogen,16.73%of carbon and 3.07%of hydrogen,and Sil-IL-AMC18-Tf2N contained 2.88%of nitrogen,15.98%of carbon and 2.95%of hydrogen,which indicated that Sil-IL-AMC18-Cl and Sil-IL-AMC18-Tf2N chromatographic stationary phases were prepared.The chromatographic separation modes and performance of Sil-IL-AMC18-Cl and Sil-IL-AMC18-Tf2N stationary phases were investigated,and the results showed that:(1)the two stationary phases had higher column efficiency than commercial C18 columns in the reversed-phase chromatographic mode(RPLC);(2)since the stationary phase has a bipolar group,it has a stronger hydrophilic ability compared to the traditional hydrophilic modified C18 silica stationary phase,and thus hydrophilic chromato-graphic mode(HILIC)can be realized;(3)simultaneous separation of hydrophilic and hydrophobic substances in mixed reversed-phase/hydrophilic(RPLC/HILIC)chromatographic mode.It was found that Sil-IL-AMC18-Cl stationary phase had stronger hydrophilic properties compared to Sil-IL-AMC18-Tf2N stationary phase,so in the HILIC chromatographic mode Sil-IL-AMC18-Cl stationary phase was used for the separation of 8 base nucleosides,which could realize the baseline separation of this kind of strong hydrophilic substances,and the RSD of the injection repeatability was 0.03%—0.25%(n=9);in the RPLC chromatographic mode,Sil-IL-AMC18-Tf2N stationary phase was used for the separation of 6 anilines,which not only could realize the baseline separation,but also improved the peak trailing problem of anilines,and the RSD of the injection repeatability was 0.05%—0.10%(n=9).
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