The Characterisation of Chemically Bonded Chromatographic Stationary Phases by Thermogravimetry

Abstract

This paper details a simple thermogravimetric procedure to determine the amount of ligand present on silica based chemically bonded stationary phases for HPLC and CEC. The weight loss observed from stationary phases between 150 and 600 °C was found to be directly proportional to carbon loading of the phase. Weight loss at lower temperatures was due to the removal of weakly bound solvent. The use of temperatures higher than 600 °C resulted in the condensation of surface silanol groups resulting in an artificially elevated carbon loading result. The procedure has been applied to a range of commercially available HPLC stationary phases and the results obtained for the carbon loading for each phase was within 3% of the value reported by the manufacturer. The data presented demonstrates that the procedure is accurate and precise over a rage of carbon contents typically observed for commercially available HPLC phases and is applicable to a range of silica supports and hydrophobic ligands.