Spatially resolved temperature measurements in electrophoresis capillaries by Raman thermometry

Local temperatures inside a 75-microns-i.d. capillary under electrophoresis conditions are measured noninvasively with a Raman microprobe. The method is based on the temperature dependence of the water O-H stretch equilibrium between weakly bent and strongly bent hydrogen bonded species. With calibration against a known temperature standard, this technique is shown to be capable of obtaining spatially resolved intracapillary temperature measurements with an accuracy of +/- 1.0 degree C and a precision of +/- 0.1 degree C. Intracapillary temperatures ranging from 25 to 70 degrees C are observed over the range of buffer compositions and electric fields used. Differences between local temperatures and average capillary temperatures are observed at all operating conditions. The difficulty of an accurate theoretical description of heat dissipation under CE conditions is discussed.