INFLUENCE OF THERMAL VARIATION OF DIFFUSION-COEFFICIENT ON NONEQUILIBRIUM PLATE HEIGHT IN CAPILLARY ZONE ELECTROPHORESIS

A numerical algorithm is developed by which the radial profiles of temperature and mobility in an electrophoretic capillary can be computed from the steady-state equation of heat conduction. To determine these profiles accurately, the viscosity at any temperature is calculated to four significant figures from an expression different from the commonly used Andrade equation. The profiles so computed are used in a theory derived here, which addresses the impact of the thermal variation of diffusion coefficient on the axial dispersion of analyte ions in capillary zone electrophoresis. The magnitude of this dispersion is expressed as the non-equilibrium plate height. The numerical computation of this plate height indicates that this variation becomes significant only when the difference in temperature between the capillary center and wall exceeds ca. 5°C. The plate heights computed here can differ by more than a factor of two from those based on the Andrade equation, even when the variation of the diffusion coefficient is ignored. These differences originate from the relative inaccuracy of this equation. © 1990.