Immobilization of two dendritic organic phases onto silica and their molecular shape recognition for polycyclic aromatic hydrocarbons, tocopherols and carotenoid isomers

Yuanyuan Li; Shaorong Li; Yongli Wu; Yulong Ma; Wenxin Ji; Yonggang Sun; Keren Shi

doi:10.1016/j.aca.2023.342156

Immobilization of two dendritic organic phases onto silica and their molecular shape recognition for polycyclic aromatic hydrocarbons, tocopherols and carotenoid isomers

Anal Chim Acta. 2024 Feb 1:1288:342156. doi: 10.1016/j.aca.2023.342156. Epub 2023 Dec 22.

Authors

Yuanyuan Li¹, Shaorong Li², Yongli Wu², Yulong Ma², Wenxin Ji², Yonggang Sun², Keren Shi²

Affiliations

¹ State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University, Yinchuan, 750021, China; College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China. Electronic address: liyuanyuan_abc@sohu.com.
² State Key Laboratory of High-Efficiency Utilization of Coal and Green Chemical Engineering, Ningxia University, Yinchuan, 750021, China; College of Chemistry and Chemical Engineering, Ningxia University, Yinchuan, 750021, China.

PMID: 38220288
DOI: 10.1016/j.aca.2023.342156

Abstract

Background: Molecular shape selectivity, based on the size and shape parameters of the molecule, such as length and planarity, is a separation process that can be used for compounds with restricted shapes, such as isomers. The separation of geometric isomers is challenging because these compounds have similar physicochemical properties but differ slightly in molecular shape. The ability to separate and quantify these isomers is important in high performance liquid chromatography (HPLC), which is one of the most widely used techniques in separation science today, because the shape of the molecule has a strong influence on biological processes.

Results: We prepared symmetrical discoidal dendrimeric organomolecule gelators (G_SDM) and o-phenylenediamine-derived low-molecular-weight dendrimeric organomolecule gelators (G1) and bonded them to silica surfaces. The dendritic organic compound-grafted silica (SiO₂@G_SDM and SiO₂@G1) was used as HPLC stationary phases for the separation of shape-restricted isomers of polycyclic aromatic hydrocarbons (PAHs), carotenoids and tocopherols. The two phases exhibit a very high molecular shape selectivity compared to the commercially available alkyl phases. There are differences in molecular shape selectivity between the two stationary phases. Changes in the chemical structure of dendritic organic compounds can alter the orientation of the molecules, as well as changes in the molecular recognition ability. It was found that SiO₂@G_SDM has high molecular linear selectivity for PAHs at different temperatures, even at 50 °C. The planar selectivity of SiO₂@G_SDM was better for triphenylene and o-terphenyl benzenes compared to SiO₂@G1.

Significance: This separation behavior may be attributed to the combined effect of weak interaction centers, which allowed the effective separation of bioactive and shape-restricted isomers through multiple interactions. Furthermore, SiO₂@G_SDM showed better separation of tocopherols and carotenoids, suggesting that the backbone and ordered structure of organic molecular gelators is an effective way to improve the shape selectivity of the molecules, whereas the molecular orientation of the functional groups influences the separation mechanism of the shape-restricted isomers.

Keywords: Dendritic organic molecular gelators; High performance liquid chromatography; Mixed-mode stationary phase; Molecular shape selectivity; Separation of structural isomers.