Fluorescence characterization of acid-base interaction and mobility at Chromatographic interfaces

Chromatographic surfaces are investigated by means of fluorescent probes (aza-aromatic compounds and anthroic acids). From absorption and fluorescence spectra the acid-base equilibria and types of binding at the interfaces are determined. The different surface acidities are given in terms of pH equivalents, which cover a range of more than three ΔpH units. The rotational mobility of probe molecules on reversed phase materials is measured to get a more detailed understanding of the chromatographic separation mechanism. The rotational correlation time is calculated from fluorescence anisotropy and decay time measurements.