Theoretical Investigation of Dual-Mode Gradient Elution Chromatography Considering Simultaneous Variations in the Column Temperature and Solvent Composition

Abstract

This article presents the theory of dual-mode gradient elution chromatography considering simultaneous spatial and temporal changes in the column temperature and mobile phase composition. In this technique, both solvent and temperature gradients propagate independently along the axial coordinate of the chromatographic column. The mathematical model of the underlying process contains nonlinear convection-dominated partial differential equations for mass, volume fraction of the solvent, and energy, coupled with algebraic or differential equations. The linear solvent strength retention model and the modified van’t Hoff retention behavior are utilized for expressing coefficients of Henry’s, nonlinearity, axial dispersion, and heat conductivity as functions of temperature and solvent composition. An extended high-resolution semidiscrete finite volume method is utilized for the numerical approximation of model equations. Numerous case studies have been conducted to assess the column performance for a variety of operating conditions. The benefits of dual-mode gradient elution, influencing the propagation speeds of concentration profiles, are thoroughly explored compared to that of isocratic operation. The results show a significant reduction in the retention time and a better performance of the column. Outcomes of this study will be useful for optimizing the model parameters and for further improving the process performance.