The Retention Behavior of Acidic, Basic and Neutral Pharmaceuticals on the Deactivated Polybutadiene Zirconia Phase
Reversed zirconia-based stationary phases belong among interesting alternatives of widely used RP silica
phases. Zirconia displays specific surface properties, which are responsible for a unique retention mechanism. Furthemore,
it is necessary especially for acidic analytes to add a strong Lewis base to the mobile phase mainly to improve
the separation efficiency. However, commonly recommended strong Lewis base buffers are not volatile and therefore are
incompatible with a mass spectrometric detection.
A novel RP zirconia-based stationary phase with deactivated Lewis acid sites of zirconia was introduced to enable the use
of volatile additives (acetate, formate) despite their low Lewis basicity. It is reported on the influence of surface deactivation
on chromatographic behavior of acidic, basic and neutral analytes in this paper. The influence of variables such as pH
levels, Lewis base type, its concentration and temperature were studied. The results were compared with the undeactivated
stationary phase. In general, around 2.5-fold stronger retention of compounds was observed on the deactivated phase.
Moreover, some variances in retention and selectivity were observed for both acidic and basic analytes when using different
Lewis bases. For these reasons the properties of deactivated and unmodified phases under the same conditions were
partly diverse and consequently the selectivity was similar but not identical.
Keywords: Deactivated polybutadiene-coated zirconia, HPLC, Lewis base additives, Local anaesthetics, Mass detection, Metal
oxide stationary phases, Mixed-mode retention, NSAIDs, Ondansetron, Pharmaceutical analysis, Zirconia-based stationary phases
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