RAMAN-SPECTROSCOPIC MEASUREMENT OF SPATIAL AND TEMPORAL TEMPERATURE-GRADIENTS IN OPERATING ELECTROPHORESIS CAPILLARIES

Steady-state and transient intracapillary temperature gradients are measured by Raman microthermometry during capillary zone electrophoresis. The axial temperature gradient away from a heat sink extends for several millimeters, depending upon the contact of the capillary and heat sink. In free-air convection, small radial gradients, 2-4 degrees C from the center of the lumen to the wall, are observed at 0.85 kW/cm(3). The temperature profile is adequately described by a parabola. With forced cooling, the center-wall temperature difference is less than 1 degrees C. The time to steady-state temperature after power-on is found to be 20 s. The measurements are compared to the results of heat transport calculations.