Diffusion as a tool of measuring temperature inside a capillary.

Application of capillary electrophoresis (CE) to temperature-sensitive biomolecular interactions requires knowledge of the temperature inside the capillary. The simplest approach to finding temperature in CE employs a molecular probe with a temperature-dependent parameter. Up until now only spectral parameters of molecular probes were utilized for temperature measurements in CE. The arbitrary nature of spectral parameters leads to several inherent limitations that compromise the accuracy and precision of temperature determination. This paper introduces the concept of finding temperature in CE through the measurement of a nonspectral parameter of the molecular probeits diffusion coefficient. Diffusion is a fundamental property of molecules that depends only on the molecular structure of the probe, the nature of the environment, and the temperature. It is ideally suited for temperature measurements in CE if an approach for measuring the diffusion coefficient in a capillary with high precision is available. This work first develops an approach for measuring the diffusion coefficient in a capillary with a relative standard deviation of as low as 2.1%. It is then demonstrated that such precise measurements of the diffusion coefficient could facilitate accurate temperature determination in CE with a precision of 1 degrees C. This new method was used to study the effect on temperature of different amounts of joule heat generated and different efficiencies of heat dissipation. The nonspectroscopic nature of the method makes it potentially applicable to nonspectroscopic detection schemes, for example, electrochemical and mass spectrometric detection.