The development of a stable ZRO2-based reversed-phase chromatographic support

Although silica-based bonded phases are extra-ordinarily useful for a wide range of applications in reversed-phase HPLC, their use is primarily limited to pH's between 2 and 8 due to the hydrolytic instability of both the silica support particle and the silozane bond used to anchor the non-polar active group. The authors are interested in the development of reversed-phase chromatographic supports which are stable at extreme pH's while retaining the desirable mechanical and physical properties of an inorganic support such as silica gel. In this paper the development of a stable reversed-phase HPLC support based on porous microparticulate ZrO2 spherules is discussed. A variety of methods of modifying the inorganic surface though covalent attachment of non-polar ligands (e.g., organosilanes) were investigated and are briefly discussed. The silanized-ZrO2 reversed-phases were evaluated and found to be very unstable. The stability of these supports will be considered within the context of the stability of silanized metal oxides in general. Adsorption of polymers onto the ZrO2 surface was investigated as a means of producing a reversed-phase support, and this work is also discussed. The stability of reversed-phases produced by polymer adsorption was assessed under extreme conditions (e.g., pH 14 at 100 degrees C) using a variety of methods, including determination of carbon load, measurement of dissolved support in the column effluent by ICP-ES, surface techniques (e.g., ESCA) and changes in retention of non-polar test solutes. The results of these experiments are discussed with particular emphasis on the inadequacy of chromatographic retention measurements as a means of demonstrating the stability of polymer-coated reversed-phase supports. The results of the chromatographic evaluation of the polymer coated ZrO2 reversed-phases will be shown with an emphasis on some novel applications