A novel mixed-mode monolithic stationary phase based on bonding of 4,5-imidazoledicarboxy acid to the surface of an organic-silica hybrid monolith was prepared and characterized. Satisfactory characteristics in terms of mechanical stability, permeability and reproducibility of the resultant monolithic column were achieved. A typical per aqueous chromatographic behavior was observed in water-rich mobile phases. The resultant monolithic column was applied for the efficient resolution of various polar and hydrophilic compounds under per aqueous or reversed-phase chromatographic conditions, which successfully demonstrated its suitability for the analysis of these polar compounds in highly aqueous mobile phases. The highest column efficiency obtained for the amines was 149 000 N m−1. The experimental results showed that the mixed-mode mechanism of hydrophobic and ion-exchange interactions was involved in the separation under the given conditions. The successful applications suggested that the mixed-mode organic-silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar compounds, achieving various target separations.
Green chromatography techniques using low-toxic mobile phase are getting increasingly attention in recent years. The core is developing stationary phases that possess adequate retention and separation under the mobile phase of high content water. Using thiol-ene click chemistry, an undecylenic acid-bonded silica stationary phase (UAS) was prepared in a facile manner. Elemental analysis (EA), solid-state 13 C NMR spectroscopy and Fourier transform infrared spectrometry (FT-IR) confirmed the successful preparation of UAS . The synthesized UAS was employed for per aqueous liquid chromatography (PALC), which uses little organic solvent during separation. Due to the hydrophilic carboxy, thioether group and hydrophobic alkyl chains of the UAS, various categories of compounds (including nucleobases , nucleosides , organic acids and basic compounds) with different properties can achieve enhanced separation under the mobile phase of high content water compared with commercial C18 and silica stationary phases. Overall, our present UAS stationary phase shows excellent separation ability toward highly polar compounds and meets the requirements of green chromatography.
Ye Shu,Tong Chen,Tao Liu,Hechen Xu,Jinjin He,Zhihui Cai,Wanning Zhu,Zihan Zhao,Jun Jiang
In this paper, the surface modification of spherical silica was sequentially grafted with functional groups including imidazole, amide and sulfonic acid. The novel surface polymerization type stationary phases (SPs) for hydrophilic interaction liquid chromatography (HILIC) were obtained in three procedures. Elemental analysis, Fourier transform infrared spectroscopy, transmission scanning electron microscopy, Brunauer Emmett Teller and Barrett Joyner Halenda were carried out for the characterization of the SPs. The bonding rate of the functionalized group (1-acrylamide propyl sulfonic) was calculated to be 2.02 μmol/m 2 . Positive outcomes were attained for the surface grafting of the SPs. The effect of various chromatographic conditions on the retention time of various analytes was investigated on high performance liquid chromatography. The dual retention mechanism of hydrophilic interaction and ion exchange mechanism of the prepared SPs was confirmed. The polymeric HILIC SPs had more abundant functionalized groups on the surface, which provided superior hydrophilic properties, ion exchange and thus higher selectivity. Compared with the C 18 column, the resolution of the HILIC column was better. The HILIC SPs were used for the separation of sulfonamides and flavonoid natural components, and had achieved better baseline separations. In addition, the HILIC mode was used for the separation of the extract of the Fructus Ligustri Lucidi , in which the quality markers had satisfactory peak shape and baseline separation. In conclusion, the prepared surface polymeric SPs were competent for the analysis of polar components and applicable to complex samples.
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