Mixed-mode reversed-phase and ion-exchange separations of cationic analytes on polybutadiene-coated zirconia

Yue Hu, Xiqin Yang, Peter W. Carr

Research output: Contribution to journalArticle

50 Scopus citations

Abstract

The retention and selectivity of the chromatographic separation of basic (cationic) analytes on a polybutadiene-coated zirconia (PBD-ZrO2) stationary phase have been studied in greater detail than in previous studies. These separations are strongly influenced by the chemistry of the accessible surface of zirconia. In the presence of buffers which contain hard Lewis bases (e.g., phosphate, fluoride, carboxylic acids) zirconia's surface becomes negatively charged due to adsorption of the buffer anion at the hard Lewis acid sites. Consequently, under most conditions (e.g., neutral pH), cationic analytes undergo both hydrophobic and cation-exchange interactions. This mixed-mode retention process generally leads to greater retention factors for cations relative to those on silica-based reversed phases despite the lower surface areas of the zirconia phase, but, more importantly, adsorption of hard Lewis bases can be used to control the chromatographic selectivity for cationic analytes on these zirconia-based stationary phases. In contrast to our prior work, here we show that when mixed-mode retention takes place, both retention and selectivity are easily adjusted by changing the type of hard Lewis base buffer anion, the type of buffer counter-ion (e.g., sodium, potassium, ammonium), the pH, and the ionic strength of the eluent as well as the type and amount of organic modifier.

Original languageEnglish (US)
Pages (from-to)17-29
Number of pages13
JournalJournal of Chromatography A
Volume968
Issue number1-2
DOIs
StatePublished - Aug 30 2002

Keywords

  • Cationic drugs
  • Lewis acid-base interactions
  • Mixed-mode retention
  • Mobile phase composition
  • Polybutadiene
  • Silanophilic interactions
  • Stationary phases, LC
  • Zirconia

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