Characterization of polybutadiene-coated zirconia and comparison to conventional bonded phases by use of linear solvation energy relationships

This paper describes the use of linear solvation energy relationships (LSERs) to thermodynamically characterize retention on a reversed-phase type material based on polybutadiene (PBD)-coated zirconia. Retention data were obtained for a large set of judiciously selected test solutes on four PBD phases (carbon loads varying from 1.5 to 5.6% by weight) in various methanol-water mobile phases. Based on the LSERs, the free energy of retention was dissected into contributions from cavity formation/dispersive interactions, dipolar interactions, and hydrogen bond (HE) donor-acceptor interactions, The PBD-zirconia phases were compared to conventional silica-based bonded reversed phases. As is the case with conventional bonded phases, the solute's size and HE acceptor basicity are the predominant retention determining factors, and on the whole, PBD-zirconia phases closely resemble conventional chemically bonded reversed phase materials. Interestingly, the solute's basicity has a larger effect on its retention on the PBD-zirconia phase than on conventional bonded phases, so relative to their behavior on conventional phases, strong hydrogen bases and highly dipolar analytes, when compared to nonpolar solutes, are less strongly retained on PBD-zirconia than on conventional phases. PBD-zirconia and conventional phases are so similar that there should be little difficulty in transferring separation methods between phases.