Trimethylsilyl propanoic acid (TMSP or TSP) is a chemical compound containing a trimethylsilyl

Trimethylsilyl

A trimethylsilyl group is a functional group in organic chemistry. This group consists of three methyl groups bonded to a silicon atom [−Si3], which is in turn bonded to the rest of a molecule...

 group. It is used as internal reference in the NMR spectrum nuclear magnetic resonance

Nuclear magnetic resonance

Nuclear magnetic resonance is a physical phenomenon in which magnetic nuclei in a magnetic field absorb and re-emit electromagnetic radiation...

 for aqueous solvents (e.g. D₂O). For that use it is often deuterated (3-(trimethylsilyl)-2,2',3,3'-tetradeuteropropionic acid or TMSP-d4). Other internal references that are frequently used in NMR experiments are DSS

DSS (NMR Standard)

DSS is a chemical compound used in proton- and carbon-related NMR spectroscopy as a calibration standard, similar to tetramethylsilane , but with much higher water solubility...

 and tetramethylsilane

Tetramethylsilane

Tetramethylsilane is the chemical compound with the formula Si4. It is the simplest tetraorganosilane. Like all silanes, the TMS framework is tetrahedral...

.