Chitosan/polyacrylic acid/octadecene double-crosslinked network hydrogel functionalized porous silica microspheres for multimode liquid chromatographic separation.

In this study, chitosan (CS) and polyacrylic acid (PAA) were used to construct a double-crosslinked network hydrogel, which was employed as the functional material for silica microspheres to prepare a CS/PAA hydrogel modified liquid chromatographic stationary phase. During preparation, octadecene (ODE) was introduced into the CS/PAA hydrogel to improve its hydrophobicity and separation ability. The electrostatic interaction between the amino group of CS and the carboxyl group of PAA effectively prevented the swelling of the CS/PAA hydrogel, which ensured the successful application of the obtained CS/PAA hydrogel@SiO2 in chromatographic analysis. Polar nucleosides/bases and B-vitamins were selectively separated using hydrophilic interaction liquid chromatography. Hydrophobic polycyclic aromatic hydrocarbons and alkylphenols were effectively separated through reversed-phase liquid chromatography. Moreover, the effective separation of aromatic positional isomers and chiral enantiomers was achieved. This study confirms the potential application of the CS/PAA hydrogel in chromatographic separation. What is noteworthy is that the method developed in this study also provides a feasible strategy to solve the swelling issue associated with the hydrogel-based liquid chromatographic stationary phase.

Hydrophobic/hydrophilic separation performance evaluation of a mixed-mode ionic liquid embedded stearyl thioglycolate functionalized silica stationary phase.

In this work, a novel imidazolium ionic liquid embedded multifunctional chromatographic stationary phase (Sil-AVI-ST) was synthesized by the radical-mediated thiol-ene click reaction. A wide range of samples including hydrophilic sulfonamides, vitamins and nucleosides/bases as well as hydrophobic phthalates, bisphenols, alkylphenols and steroid hormones were selected to evaluate the separation ability of the newly obtained Sil-AVI-ST. As expected, an efficient separation of the above tested analytes was successfully achieved in different chromatographic modes. It was proved that multiple stationary phase-analyte interaction forces promoted the selective separation. The Sil-AVI-ST column provided multiple retention mechanisms, enabling the efficient separation of diverse analytes with different polarity. More importantly, embedding a polar ligand (1-allyl-3-vinyl-imidazolium) could improve the separation efficiency of long-chain alkyl bonded stationary phases for hydrophilic analytes, and the developed Sil-AVI-ST column could also realize the detection of hydrophobic analytes under water-rich conditions, which is impossible for the conventional hydrophobic columns. Therefore, the newly prepared Sil-AVI-ST stationary phase has a good practical application potential.

Hydrophobic and hydrophilic selectivity of a multifunctional carbonyldiimidazolium/dodecyl modified silica stationary phase.

In this work, a new strategy of simultaneously grafting two different functional ligands onto the silica surface was adopted to prepare a carbonyldiimidazolium/dodecyl dual-functionalized silica stationary phase (Sil-CDI-DD) by recycling the discarded commercial C18 columns as the raw materials. A full characterization of the waste silica-C18, the calcined silica, the acidified silica and the new packing materials was done to explore the feasibility of recycling the waste chromatographic columns. Hydrophobic and hydrophilic selectivity of the obtained Sil-CDI-DD was specifically investigated, and retention mechanisms in reversed-phase and hydrophilic interaction chromatography modes were discussed. The experimental results showed that the perfect combination of carbonyldiimidazolium and long-chain alkyl groups commendably enhanced the separation selectivity and efficiency of the versatile Sil-CDI-DD, which could provide multiple interaction sites for diverse target analytes, thereby contributing to the favorable resolution of hydrophilic nucleosides/nucleobases and weak polar environmental endocrine disruptors, including alkylphenols, bisphenols, steroid hormones and phthalates.

Innovative preparation of ureido/dodecyl dual-functionalized silica as a versatile mixed-mode stationary phase for high-resolution chromatographic separations.

Developing a versatile stationary phase to achieve the purpose of efficiently separating various target analytes is of great significance. In this work, ureido/dodecyl dual-functionalized silica (Sil-Ur-DD) was synthesized and employed as a new mixed-mode stationary phase for high-resolution chromatographic analysis. It was observed that multiple interactions, including hydrophobic, hydrophilic, hydrogen bonding, electrostatic and π-π interactions, contributed to the retention. Nucleosides and nucleobases could be effectively determined in hydrophilic interaction chromatography mode, and the separation performance of the Sil-Ur-DD was found to be even superior to that of the commercial XAmide column. Environmental endocrine disruptors, including alkylphenols, bisphenols, steroid hormones and phthalates, were more favorably separated in reversed-phase chromatography mode with highly aqueous mobile phases compared with the commercial C18-silica column. The experimental results indicated that the combined effect of ureido and long-chain alkyl groups obviously enhanced separation efficiency and selectivity. More significantly, the proposed method concerning the preparation of an efficient separation material with powerful separation ability is economical and environmentally friendly, which provides a proven and effective way for the recycling and utilization of the discarded chromatographic packing materials, thereby showing a good application prospect.