Performance of idealized column structures under high pressure.

We have examined the influence of the longitudinal temperature and pressure gradients in columns operated under very high pressures on the coefficients of the van Deemter equation under the idealized condition of complete radial uniformity. These gradients change the diffusion coefficients over the length of the column, and the equation takes a new form, where the classical linear C-term is replaced by more complex forms that capture the effects of these axial gradients. The details of the derivations are shown and the implications are discussed.

Implications of column peak capacity on the separation of complex peptide mixtures in single- and two-dimensional high-performance liquid chromatography.

Column peak capacity was utilized as a measure of column efficiency for gradient elution conditions. Peak capacity was evaluated experimentally for reversed-phase (RP) and cation-exchange high-performance liquid chromatography (HPLC) columns, and compared to the values predicted from RP-HPLC gradient theory. The model was found to be useful for the prediction of peak capacity and productivity in single- and two-dimensional (2D) chromatography.

Moment analysis of mass-transfer kinetics in C18-silica monolithic columns.

The moment analysis of elution peak profiles based on new moment equations provides information on the mass-transfer characteristics of C(18)-silica monolithic columns. The flow rate dependence of the HETP data was analyzed using the generalized van Deemter equation, after correction of these data by subtraction of the external mass-transfer contribution to band broadening. Kinetic parameters and diffusion coefficients related to the mass-transfer processes in monolithic columns were derived by taking advantage of the different flow velocity dependence of their contributions to band broadening.