The evolution and implications of the concentration profiles of an analyte in porous adsorbent particles packed in a capillary electrochromatography column operated in the analytical mode

Abstract

In this work, a mathematical model is constructed and solved to describe the propagation and dispersion of the mass wave of an analyte in a capillary electrochromatography (CEC) column packed with porous adsorbent particles and operated in the analytical mode. The evolution and dynamic behavior of the isoconcentration contours of the concentration of the analyte in the pores of the particles are presented in order to demonstrate the significant impact that the velocity of the intraparticle electroosmotic flow (EOF) encountered in CEC systems could have in reducing the overall intraparticle mass transfer resistance. It is shown that under both unretained and retained conditions the intraparticle EOF causes a significant departure in the spherical symmetry of the isoconcentration contours of an analyte in the pores of spherical porous adsorbent particles. The asymmetric isoconcentration contours clearly indicate how the intraparticle EOF leads to highly resolved and evenly distributed mass waves of an analyte in the effluent stream of the CEC column and provide efficient separation performance. Furthermore, comments are presented that describe the conditions that could be encountered in CEC systems which could significantly increase the overall intraparticle mass transfer resistance as well as the mass transfer resistance in the interstitial channels for bulk flow and lead to inefficient separation performance.