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Mechanistic studies on the separation of cations in zwitterionic ion chromatography

journal contribution
posted on 2023-05-16, 14:26 authored by Cook, HA, Gregory Dicinoski, Paul HaddadPaul Haddad
Electrostatic ion chromatography, also known as zwitterionic ion chromatography, has been predominantly used for the analysis of anions. Consequently, separation mechanisms proposed for this technique have been based on anion retention data obtained using a sulfobetaine-type surfactant-coated column. A comprehensive cation retention data set has been obtained on a C18 column coated with the zwitterionic surfactant N-tetradecylphosphocholine (which has the negatively and positively charged functional groups reversed in comparison to the sulfobetaine surfactants), with mobile phases being varied systematically in the concentration and species of both the mobile-phase anion and cation. A retention mechanism based on both an ion exclusion effect and a direct (chaotropic) interaction with the inner negative charge on the zwitterion is proposed for the retention of cations. Despite the relatively low chaotropic nature of cations compared with anions, the retention data shows that cations are retained in this system predominantly due to a chaotropic interaction with the inner charge, analogous to anions in a system where the C18 column is coated with a sulfobetaine-type surfactant. The retention of an analyte cation, and the effect of the mobile-phase anion and cation, can be predicted by the relative positions of these species on the Hofmeister (chaotropic) series.

History

Publication title

Journal of Chromatography A

Volume

997

Issue

1-2

Pagination

13-20

ISSN

0021-9673

Department/School

School of Natural Sciences

Publisher

Elsevier Science BV

Place of publication

Amsterdam, Netherlands

Rights statement

The definitive version is available at http://www.sciencedirect.com

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the chemical sciences

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