Contributions to reversed-phase column selectivity. II. Cation exchange

Marchand, D. H.; Carr, P. W.; McCalley, David V.; Neue, U. D.; Dolan, J. W.; Snyder, L. R.

Abstract

The contribution of cation exchange to solute retention for type-B alkylsilica columns (made from high-purity silica) has been examined in terms of the hydrophobic-subtraction (H-S) model of reversed-phase column selectivity. The relative importance of cation exchange in the separation of ionized bases by reversed-phase chromatography (RPC) varies with (a) column acidity (values of the column cation-exchange capacity C), (b) mobile-phase pH and buffer concentration, and (c) the nature of the buffer cation. The effects of each of these separation variables on cation retention were examined. The contribution of cation exchange (and other ionic interactions) to solute retention is represented in the H-S model by properties of the solute (κ') and column (C), respectively. Values of κ' for 87 solutes have been examined as a function of solute molecular structure, and values of C for 167 type-B alkylsilica columns have been related to various column properties: ligand length (e.g., C 8 vs. C 18 ) and concentration (μmol/m 2 ), pore diameter (nm), and end-capping. These results contribute to a more detailed picture of the retention of cationic solutes in RPC as a function of separation conditions. While previous work suggests that the ionization of type-B alkylsilica columns is generally negligible with mobile-phase pH

• Journal Article Type: Article
• Publication Date: Oct 7, 2011
• Journal: Journal of Chromatography A
• Print ISSN: 0021-9673
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 1218
• Issue: 40
• Pages: 7110-7129
• DOI: https://doi.org/10.1016/j.chroma.2011.07.085
• Keywords: HPLC, reversed-phase, column selectivity, hydrophobic-subtraction model, cation-exchange, retention mechanism
• Public URL: https://uwe-repository.worktribe.com/output/970097
• Publisher URL: http://dx.doi.org/10.1016/j.chroma.2011.07.085