Shedding light on mechanisms leading to convex-upward van Deemter curves on a cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral stationary phase

Simona Felletti; Chiara De Luca; Giulio Lievore; Tatiana Chenet; Bezhan Chankvetadze; Tivadar Farkas; Alberto Cavazzini; Martina Catani

doi:10.1016/j.chroma.2020.461532

Shedding light on mechanisms leading to convex-upward van Deemter curves on a cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral stationary phase

J Chromatogr A. 2020 Sep 12:1630:461532. doi: 10.1016/j.chroma.2020.461532. Online ahead of print.

Authors

Simona Felletti¹, Chiara De Luca¹, Giulio Lievore¹, Tatiana Chenet¹, Bezhan Chankvetadze², Tivadar Farkas³, Alberto Cavazzini⁴, Martina Catani⁵

Affiliations

¹ Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari 46, 44121 Ferrara, Italy.
² Institute of Physical and Analytical Chemistry, School of Exact and Natural Sciences, Tbilisi State University, Chavchavadze Ave 3, 0179 Tbilisi, Georgia.
³ Phenomenex Inc., 411 Madrid Ave., Torrance, CA 90501, United States.
⁴ Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari 46, 44121 Ferrara, Italy. Electronic address: cvz@unife.it.
⁵ Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, via L. Borsari 46, 44121 Ferrara, Italy. Electronic address: ctnmtn@unife.it.

PMID: 32950816
DOI: 10.1016/j.chroma.2020.461532

Abstract

An unusual convex-upward van Deemter curve was observed for the more retained enantiomer of a chiral sulfoxide (2-(benzylsulfinyl)benzamide) on a cellulose tris(4-chloro-3-methylphenylcarbamate)-based chiral stationary phase (CSP), prepared on silica particles of 1000 Å pore size. In contrast, the firstly eluted enantiomer of the same molecule exhibited the traditional convex-downward van Deemter curve. A detailed kinetic and thermodynamic investigation has revealed that this unusual phenomenon, which however has already been observed in chiral chromatography, originates when the adsorption of the compound is very strong and the solid-phase diffusion negligible. Experimentally, the intraparticle diffusion of the more retained enantiomer of the sulfoxide was found to be one order of magnitude smaller than that of the first eluted one. Overall, this translates into very little longitudinal diffusion (b-term of van Deemter curve) accompanied by high solid-liquid mass transfer resistance (c-term). Finally the comparison with another, differently-substituted chiral sulfoxide (whose enantiomers both exhibit traditional van Deemter curve behavior) has allowed to correlate these findings to the specific characteristics of the molecule.

Keywords: Chiral liquid chromatography; Enantiomers separation; Mass transfer adsorption isotherms; Polysaccharide chiral stationary phase; van Deemter curve.