NMR thermometry

M. E. Lacey, A. G. Webb, J. V. Sweedler 2000, (Monitoring temperature changes in capillary electrophoresis with nanoli-ter-volume NMR thermometry), Anal. Chem. 72(20), 4991. 

In principle, a resonance frequency or difference in frequencies can be employed to perform NMR thermometry. The accuracy of temperature measurement depends on the accuracy of the thermocouple (0.2°C) in the NMR spectrometer. Generally, a precision of better than 0.2°C has been reported with these NMR thermometry measurements. Individual calibration plots may not be required when using aqueous buffers. Proper calibration procedures should be adopted with nonaqueous buffers and in the presence of organic modifiers. 

Fig. 2. (left) Graph of electrical current vs. time during a CE-NMR thermometry experiment, (right) Corresponding plot of intracapillary temperature vs. time. The peak in the temperature corresponds to the passage of the lower conductivity NaCl solution through the NMR coil. (Reprinted with permission from ref. 24, Copyright 2000 American Chemical Society.)... 

A knowledge of the electrolyte temperature is important in CE as temperature changes in the electrolyte influence precision, accuracy, separation efficiency, and method robustness [7,14,32], During the past two decades, a considerable amount of research has been conducted toward electrolyte temperature measurements in CE [1,14,19,21,32 2], Early methods have included using the variation of electroosmotic mobility (eieof), electrophoretic mobility (p-ep), and electrical conductivity (k) to measure temperature [38,39], More recently, techniques such as external thermocouples [21], Raman thermometry [19,40], NMR spectroscopy [32,35], thermochromic probes [41], and the variation in fluorescence response [42] have been used to measure temperatures. Most of these methods require the modiflcation of the existing instrument and/or the purchase of additional equipment. 

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