Determination of rate constants for heterogeneous mass transfer kinetics in liquid chromatography.

The heterogeneity of the stationary phase surface leads to undesired peak broadening and tailing in chromatography. In order to properly characterize the interactions between the solute molecules and the surface of the stationary phase, the determination of the equilibrium isotherm is usually necessary by overloading the column. In this study we show that measurements made in the linear range of the isotherm can also be utilized to estimate the heterogeneity of the stationary phase. When one studies the peak shape obtained after injecting a small (analytical) amount of sample, the peak shape parameters can be correlated with the kinetic rate constants. The peak of a mildly polar solute, phenol, was measured in reversed-phase HPLC under various conditions and kinetic information was obtained regarding the heterogeneity of interactions.