When you perform a Variable Temperature (VT) NMR experiment, the displayed temperature is not necessarily the actual sample temperature. When you need to know the actual temperature, with a high degree of accuracy, it is important to calibrate the sample temperature, relative to the displayed temperature.
The common method to perform this calibration is to observe the chemical-shift separation between the OH resonances and CHn resonances in either Methanol or Ethylene Glycol (generally Methanol is used for low-temperature calibration, and Ethylene Glycol is used for temperatures above ambient). The temperature dependence of this shift has been well-studied, and a variety of conversion methods have been reported to enable the determination of sample temperature.
You can dowanload this xls file (nmr-tempcal), which allows easy determination of either (a) temperature from measured shift separation, or (b) predicition of peak shifts for a particular temperature (created by Rich Shoemaker). The use of this spreadsheet is simple. There are fields to enter temperature (calculating the chemical shift separation), and fields to enter peak-separation (calculating the temperature). A variety of solvent systems are included.
REF: Link
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