Issue 1, 2024

Cation/anion-exchange mode switching chromatography utilizing pH-responsive mixed charge polymer-modified silica beads

Abstract

The separation capacity of a column typically remains constant. By applying stimuli-responsive materials to the stationary phase, the separation capacity in a single column can be tuned; however, the separation mode is not completely switched. In this study, we aimed to develop a cation/anion-exchange mode switching chromatography approach, in which the monomer ratio is adjusted, enabling the surface charge to become either negative or positive in response to mobile phase pH. Three types of beads were prepared, each modified with a pH-responsive mixed-charge polymer combining a cationic monomer, a pH-responsive carboxylic acid monomer, a neutral monomer, and a cross-linking monomer. The composition ratio of the cationic monomer to the pH-responsive carboxylic acid monomer was set at 1 : 2 so that the cation-exchange mode occurs at a pH above the pKa and the anion-exchange mode occurs below the pKa. At a pH below the pKa, the retention factor of the negatively charged compound increased. In contrast, at a pH above the pKa, the retention factor of the positively charged compound increased, confirming the charge switching on the bead surface. Switching to the cation- and anion-exchange mode enabled the separation of five basic antidepressants and acidic non-steroidal anti-inflammatory drugs, respectively. Utilizing a pH-responsive mixed-charge polymer, we attributed a cation/anion-exchange mode to a single column.

Graphical abstract: Cation/anion-exchange mode switching chromatography utilizing pH-responsive mixed charge polymer-modified silica beads

Supplementary files

Article information

Article type
Paper
Submitted
15 iyn 2023
Accepted
02 noy 2023
First published
03 noy 2023
This article is Open Access
Creative Commons BY license

Mol. Syst. Des. Eng., 2024,9, 56-62

Cation/anion-exchange mode switching chromatography utilizing pH-responsive mixed charge polymer-modified silica beads

T. Kaku, K. Deura, T. Yoshii, D. Citterio and Y. Hiruta, Mol. Syst. Des. Eng., 2024, 9, 56 DOI: 10.1039/D3ME00100H

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