Temperature dependence of the 1H chemical shift of tetramethylsilane in chloroform, methanol, and dimethylsulfoxide
The chemical shift of tetramethylsilane (TMS) is usually taken to be zero. However, it does vary slightly with temperature, having obvious implications for studies of temperature effects on chemical shifts. In this work, we measure the variation in the chemical shift of TMS with temperature in three solvents, CDCl 3, CD 3OD, and DMSO- d6, relative to the resonant frequency of 3He gas, which can be reasonably assumed to be temperature independent. In all three solvents, the average temperature coefficient over a wide temperature range is about -6 × 10 -4 ppm/°C, a factor of five smaller than that previously reported in the literature. Data are included for 3He resonance frequencies over a temperature range of -110 to +180 °C, along with new measurements of volume magnetic susceptibilities of the three solvents and estimates of their temperature dependence. A novel method is used to provide temperature measurement via 2H resonances of methanol and ethylene glycol samples, which can concurrently be used for field/frequency locking.