Band-broadening in capillary zone electrophoresis with axial temperature gradients

Abstract

It is widely accepted that Joule heating effects yield radial temperature gradients in capillary zone electrophoresis (CZE). The resultant parabolic profile of electrophoretic velocity of analyte molecules is believed to increase the band-broadening via Taylor-Aris dispersion. This typically insignificant contribution, however, cannot explain the decrease in separation efficiency at high electric fields. We show that the additional band-broadening due to axial temperature gradients may provide the answer. These axial temperature variations result from the change of heat transfer condition along the capillary, which is often present in CZE with thermostating. In this case, the electric field becomes nonuniform due to the temperature dependence of fluid conductivity, and hence the induced pressure gradient is brought about to meet the mass continuity. This modification of the electroosmotic flow pattern can cause significant band-broadening. An analytical model is developed to predict the band-broadening in CZE with axial temperature gradients in terms of the theoretical plate height. We find that the resultant thermal plate height can be very high and even comparable to that due to molecular diffusion. This thermal plate height is much higher than that due to radial temperature gradients alone. The analytical model explains successfully the phenomena observed in previous experiments.

Electrokinetic transport of charged solutes in micro‐ and nanochannels: The influence of transverse electromigration

“…At kw,1 (corresponding to half channel width w = 30 nm), H ek is so small compared to the plate height due to diffusion H D = 2D/U num (to be demonstrated in Fig. 7) [35,41] that the accuracy of the ratios between the two modes are doubtable. We, therefore, exclude the data points at kw,1 in Fig.…”

Microchip electrophoretic separation for the fast diagnosis of Anaplasma phagocytophilum infection in cattle

“…It also creates a temperature gradient radial to the microchannel and inconsistent temperature distribution along the axial direction. This gradient contributes to zone spreading of the DNA peaks in electropherograms [19][20][21]. Consequently, determining the optimum electric field strength is very important for fast A. phagocytophilum separation.…”

Preparative capillary zone electrophoresis using a dynamic coated wide‐bore capillary

“…Adsorption onto the capillary wall is not significant, as indicated by the peak asymmetry factor being ,1 regardless of the capillary diameter. Thus, the decrease in efficiencies in wide-bore capillary is due to Joule heating [42][43][44]. Nonetheless, the horse and bovine cytochrome c peaks were well resolved (R s .2.0), and as will be shown in Section 3.2 the band broadening under preparative conditions is dominated by other factors.…”