Counter-ionic Effect on the Separation of Water-soluble Compounds Applying a Hydrophilic Stationary Phase Bonded with a Zwitter-ionic Polymer

Abstract

A novel hydrophilic stationary phase bonded with a zwitter-ionic polymer for HPLC was synthesized. The stationary phase, in combination with a mobile phase containing various salts, was evaluated for its ability to separate water-soluble compounds, such as nucleobases, nucleosides and glycosides. The retention of a large majority of the solutes, except for cytosine, was increased by adding anti-chaotropic ions to the mobile phase. These results suggested that the retention of solutes depended on the thickness of the hydration layer on the stationary phase. In the zwitter-ionic polymer adsorbent, the formation of the hydration layer and the ionicity of the zwitter-ionic group on the stationary phase will be controlled by the properties of the ions added to the mobile phase.

Retention characteristics of water‐soluble compounds on water‐holding adsorbents with immobilized zwitterionic copolymers having different ionicities

“…Analyte anions having a lower hydration property tend to associate directly with the cation sites of the zwitterionic functional group. Further, we previously confirmed that the hydrating water content was governed by the association of anions in the mobile phase with the cation sites on the adsorbent . Increasing the acetonitrile proportion in the mobile phase resulted in a higher retention of organic acids and a lower retention of benzylamine.…”

“…However, changing the pH and/or buffer of the mobile phase might greatly change the retention of solutes because of its weak ionic functional groups. Therefore, the effect of the counter‐ion on the functional group of the zwitterionic adsorbent was evaluated . Adding strong chaotropic anions to the mobile phase decreased the retention of hydrophilic solutes and also changed the selectivity of separation.…”

Control of the Electrostatic Effect on DAM-adsorbent for the Water-soluble Compounds by HPLC

“…The difference in the water content was caused by a counter ionic effect in the acetate solution. 11 The retention curves of solutes were similar to the curve of hydrating water at pH above 5. From this result, the main retention force on the DAM-adsorbent was thought to be a partition interaction with the hydration layer.…”

Fundamental Properties of Packing Materials for Liquid Chromatography

“…The wide range of hydrophobicity, ionic characterization, and steric hindrance has been used for chromatography in a variety of applications, such as bioactive compounds [86][87][88][89][90][91], natural products, foods, drugs, and fine chemicals [92][93][94], including polychlorinated biphenyls, alkylphenols, and parabens, PAH, and phthalate [95,96]. An interesting approach was proposed for applications in drug delivery using drug ILs [97].…”

“…An interesting approach was proposed for applications in drug delivery using drug ILs [97]. They were used for extraction of bioactive compounds in plants [88], and also as extraction solvents, for separation and preconcentration in chromatography [86]. Analytical methods using sphingosine 1-phosphate modulators in various biological matrices were reviewed including sample processing and chromatography [89].…”