Phosphorimetry and its potential for the study of surface heterogeneity of chromatographic silica-based stationary phases

Phosphorimetry was applied to the study of silica-based chromatographic phase surface heterogeneity by determining the phosphorescence response of a phenanthrene probe as a function of loading on underivatized silica and reversed and ion-exchange phases. The phosphorescence response was used to "titrate" and estimate the number of strong adsorption sites on underivatized silica. By incorporating covalent vs. ionic heavy atom/ion enhancers onto derivatized silicas, it was demonstrated that the probe molecules adsorb at residual silanols at lower loadings but associate with alkyl chains at higher loadings. Suggestions for further phosphorimetric studies are given.