Surface Heterogeneity Characterization by Nonlinear Perturbation Method in NP Chromatography

A novel approach to characterize the surface heterogeneity of polar adsorptive material under NP mode is proposed. The method relies in the determination of a few nonlinear perturbation peaks of strong MP modifiers, recorded after equilibration of the adsorptive surface with a weak component (hexane, heptane, dichloromethane). This approach has been proven to be able to investigate phenomena that take place at rare sites present on stationary phases, i.e. the isotherm region that firstly saturates. It has been demonstrated that, on an immobilized cellulose-based CSP, adsorption of 2-propanol is best modelled by a single Langmuir isotherm, while for EtOAc a BiLangmuir isotherm is necessary. Analogous results for adsorptions of the alcohol and the ester on polar surfaces were obtained via Attenuated Total Internal Reflection Infrared Spectroscopy.