METHODS FOR CALCULATING THE INTERNAL TEMPERATURE OF CAPILLARY COLUMNS DURING CAPILLARY ELECTROPHORESIS

The internal temperature, the buffer viscosity and the efficiency of heat removal from a silica capillary can be calculated by measuring the differential electroosmostic mobility at a low voltage and a high voltage. The calculated temperature is plotted vs the power generated by the electrophoretic instrument and yields a linear relationship when the power is below 3.0 W. The temperature can also be calculated using the conductivity of the solution. The two methods provide the same temperature, which compares well with literature values. A rule of thumb for a quick calculation of internal temperatures is that a power of 0.1 W increases the internal temperature by 1.1-degrees-C for natural convection cooling and 0.6-degrees-C for forced air cooling. The efficiency of heat removal, indicated by the slope of the line, is dictated by the heat transfer between the outer wall of the column and the surrounding environment, and not by the inside diameter of the column. The proper choice of buffer and the counter cation will lead to a lower internal temperature. The type of cation used in the buffer will influence the electroosmotic mobility; greater mobilities are observed in sodium buffers compared to potassium buffers.