Chiral stationary phases based on superficially porous silica for enantioseparation of chiral drugs

Bezhan Chankvetadze, Institute of Physical and Analytical Chemistry, Tbilisi State University, I. Chavchavadze Ave 1, 0179 Tbilisi, Georgia

The advantages of superficially porous silica (SPS) over fully porous silica (FPS) for achiral and chiral separations in liquid phase have been extensively documented. These advantages include significantly higher chromatographic efficiency, a marked shift to higher optimal flow rates and limited dependence of column performance on a mobile phase linear velocity. The higher efficiency of columns made with SPS particles is probably due to the more uniform particle-size distribution of SPS particles compared to their fully porous analogues resulting in higher radial homogeneity of columns packed with SPS and to the shorter diffusion path available to analytes. These same characteristics are responsible for the limited dependence of column performance on the mobile phase linear velocity, minimizing both the eddy diffusion term (A term) and also the mass-transfer coefficient (C term) to the height equivalent to a theoretical plate (HETP) as detailed in the van Deemter equation. Realizing the minimum HETP value and maintaining it at even higher mobile phase flow rates makes SPS columns suited for high-speed separations.
Since polysaccharide esters and phenylcarbamates are recognized to be the most successful chiral selectors for the separation of enantiomers in liquid phase techniques such as high-performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC), nano-chromatography and capillary electrochromatography (CEC), their combination with SPS seems logical for the preparation of highly efficient chiral stationary phases (CSP).
This presentation summarizes our recent studies on the preparation of polysaccharide-based chiral stationary phases (CSPs) for separation of enantiomers in HPLC [1-2], SFC, nano-LC and CEC [3]. Various effects based on superficially porous structure of silica are reported and discussed in detail.

References:
[1] L. Bezhitashvili, A. Bardavelidze, A. Mskhiladze, A. Volonterio, M. Gumustas, S. Ozkan, T. Farkas, B. Chankvetadze, J. Chromatogr. A, 1571 (2018) 132-139.
[2] N. Khundadze, S. Pantsulaia, C. Fanali, T. Farkas, B. Chankvetadze, J. Chromatogr. A, 1572 (2018) 37-43.
[3] G. D´Orazio, R. Kakava, A. Volonterio, S. Fanali, B. Chankvetadze, Electrophoresis, 38, 2017, 1932-1938.