The C-13 NMR signals of tris(trimethylsilyl)methane show a strong linear temperature dependence of the chemical shifts, which can be used to measure the true internal temperature of a sample during measurement of DNMR C-13 NMR spectra. See: Sikorski, W. H.; Sanders, A. W.; Reich H. J. Magn. Reson. Chem. 1998, 36, S118-S124.
Amount needed: 0.10%-0.15% of 1:10 13C labeled:unlabeled (TMS)3CH (2-4 µl in 3.0 mL solvent).
Different solvents show similar slopes in the delta vs T plot, but different intercepts, so each solvent needs to be calibrated. The equations below are used to calculate the temperature (in deg C) from the difference in chemical shift (ppm) between the Me and CH signals.
The graph below shows some calibration curves (y axis in Hz at 75 MHz,360 MHz proton frequency).
