title: Effect of amine counterion type on the retention of basic compounds on octadecyl silane bonded silica-based and polybutadiene-coated zirconia phases.
abstract: In a previous paper, we compared the mixed-mode retention characteristics of cationic solutes on octadecyl silane-bonded silica (ODS) and polybutadiene-coated zirconia (PBD-ZrO2) phases. It is well recognized that both reversed-phase and ion-exchange interactions contribute to the retention of cations on ODS phases. The reversed-phase interaction results from the bonded hydrocarbon chain; the ion-exchange interaction originates in the ionized residual silanol groups. These two types of interactions also exist on the PBD-ZrO2 phase. The polybutadiene contributes to the reversed-phase interaction and the ionized zirconol, but primarily, the adsorbed Lewis base anions, such as phosphate or fluoride, contribute to the ion-exchange interaction. We have shown that on ODS phases, reversed-phase interactions are much more important, whereas the opposite is true of PBD-ZrO2 phases. In this work, we investigate the effect of several amine mobile phase counterions on the retention of cationic solutes on ODS and PBD-ZrO2 phases. The effects of the chain length and the type of amine (1 degree, 2 degrees, 3 degrees) counterion on the retention of basic compounds were studied. In contrast to older studies of type A silica-based phases, the results show that the chain length and type of the amine blocker do not have a large effect on the retention of basic compounds with the newer type B silica-based materials. However, on the PBD-ZrO2 phase, very striking differences in retention were observed with different amine counterions. We show that the molecular geometry of the amine counterion has a significant effect on the retention of basic solutes on the PBD-ZrO2 phase.
authors.affiliation: Department of Chemistry, Smith and Kolthoff Hall, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, USA.
authors.forename: Xiqin
authors.initials: X
authors.lastname: Yang
authors.forename: Jun
authors.initials: J
authors.lastname: Dai
authors.forename: Peter W
authors.initials: PW
authors.lastname: Carr
mesh_terms: D000588:Amines / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D002412:Cations; D002852:Chromatography, Ion Exchange / Q000379:methods*; D020724:Elastomers; D011108:Polymers / Q000737:chemistry*; D012821:Silanes / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000588:Amines; D002070:Butadienes; D002412:Cations; D020724:Elastomers; D011108:Polymers; D012821:Silanes; C028834:polybutadiene; D015040:Zirconium; C028541:zirconium oxide