Numerical study of radial temperature gradient effect on separation efficiency in capillary electrophoresis

Joule heating effect is one of the factors that can decrease the separation efficiency in capillary electrophoresis. A mathematical model, including the Poisson–Boltzmann equation, the modified Navier–Stokes equation and the energy equation, is used to calculate temperature and velocity distributions in the capillary under different capillary inner radii, heat transfer coefficients and solution concentrations. By substituting the velocity distributions under these conditions into two different expressions for the thermal plate height, various effects on the thermal plate height and separation efficiency in capillary electrophoresis are analyzed. It is found that at the same electrical field strength, larger capillary radius, lower heat transfer coefficient and higher solution concentration can lead to a larger thermal plate height and therefore lowering the separation efficiency. The results of the separation efficiency based on the two different expressions agree well with each other.