Effect of nature of electrolytes on retention and selectivity in hydrophilic interaction liquid chromatography.

Affiliation

Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, AB, T6G 2G2, Canada. Electronic address: [Email]

Abstract

This work investigates the selectivity and retention changes on four classes of HILIC columns upon addition of 1-20 mM electrolyte. The effect of four electrolytes (Na+Cl-, Na+ClO4-, Na+PF6-, and Na+CF3CO2-) were tested on neutral, cationic, anionic, and zwitterionic analytes under HILIC conditions (70-90% ACN). These electrolytes alter the retention and selectivity on silica, zwitterionic and diol columns through ion exchange and ionic screening mechanisms. Neutral analytes were unaffected by addition of 1-20 mM electrolyte, indicating minimal change to the retentivity of the water layer. Cationic and anionic analytes increase and decrease in retention, respectively (Na+PF6- ≈ Na+ClO4- > Na+CF3CO2- > Na+Cl-). Chaotropic electrolytes accumulate at the mobile phase/water layer interface, enhancing the ion exchange and ionic screening effects of the mobile phase electrolyte. Altering the buffer cation (Li+, Na+, K+) caused small but statistically significant changes in retention.

Keywords

HILIC,Ion exchange,Ionic repulsion,Liquid chromatography,Method development,