Bruker NMR, User Manual

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Advanced Operation
Z33085_2_002 21
Figure 5.5: Temperature shift values filled in.
For many NMR applications (for instance, Bio-NMR in aqueous solutions) an estimate of the
slope (be aware of the fact that the slope can have negative or positive sign!) of the
temperature dependency and the knowledge of the offset (absolute temperature correction)
are sufficient (the necessary temperature range might be rather small) to create an .xml file. It
is off course also possible to determine the correct slope automatically.
Selection of NMR Thermometer Compounds
The simplest compound for the NMR Thermometer is fully deuterated methanol used as a
NMR solvent. While the deuterium signal of the methyl group is used for the field lock, the
deuterium signal of the hydroxyl group is used for the NMR Thermometer. The deuterium
chemical shifts of commonly used organic NMR solvents like CDCl
3
, acetone-d
6
and DMSO-
d
6
are virtually independent on the sample temperature. In that case, deuterated methanol
could be placed in a capillary or mixed with the solvent.
The chemical shift of water strongly depends on the temperature. For samples in aqueous
solutions, a deuterated organic small molecule can be added as a thermometer compound.
Details will be described in the following section.
The compounds listed in the table below have been tested and can be considered.
Figure 5.6: Suggested compounds for the NMR Thermometer and samples in aqueous solution (D2O 5
– 100%), their properties and estimated concentration. Fully deuterated DSS and TSP are currently not
available but will be synthesized on Bruker’s request at small amounts only for internal tests.
5.2