THERMAL-MODEL OF CAPILLARY ELECTROPHORESIS AND A METHOD FOR COUNTERACTING THERMAL BAND BROADENING

Thermal band broadening is known to be caused by the temperature dependence of ionic mobility. This dependence also strongly influences the temperature of the capillary by providing positive feedback between the temperature and power density. Previous thermal models of capillary electrophoresis have not fully considered this "autothermal effect". We show that it always causes a capillary to run hotter than is predicted by a constant conductivity model; temperature excursions two times greater are typical. We propose that the thermally induced parabolic distortion of the migration velocity can be countered with an opposing Poiseuille (pressure-driven) flow. Dispersion calculations indicate that it may be possible to obtain plate numbers in excess of 106 m-1 even in very large bore (400 μm) capillaries. © 1990.