Retention behavior of basic compounds on alkylphosphonate-modified magnesia-zirconia composite stationary phase in RPHPLC

The chromatographic properties of an alkylphosphonate-modified magnesia-zir conia composite stationary phase have been investigated by reversed-phase h igh-performance liquid chromatography wi ih bas ic com pounds as probes. Th e influence of organic modifier composition and mobile phase pH was studied . The new stationary phase, similar to a silica-based reversed-phase statio nary phase, has hydrophobic properties, but greater pH stability. Use of th e phase results in more symmetric peaks for basic compounds. A possible mechanism of retention of basic solutes on the new stationary ph ase is discussed. The chromatographic behavior of the basic solutes depends mainly on hydrophobic interactions between the solutes and the hydrophobic moiety of the stationary phase. Bronsted acidic and basic sites on the sur face of the new stationary phase play an important role in the retention of ionized solutes by ion-exchange interaction. Promising separations of some basic compounds have been achieved by use of methanolic TRIS buffer, pH 10 .0, as the mobile phase.