There are many sensitivity standards. Wilmad Product No. The lack of consensus about Reference Standards results largely from the conflicting interests of various instrument and probe manufacturers and users of NMR Spectrometers. In addition to sensitivity, the other commonly measured performance criterion is spectrometer resolution. Resolution affects your ability to discern closely spaced resonances.
Poor resolution can also reduce apparent sensitivity, since peak broadening reduces signal height.
The most commonly used sensitivity and resolution standards are listed in the table at the end of this report. Because spectrometers must maintain stability through long-term accumulations, there are standards, usually consisting of small concentrations of biological molecules stabilized against microbial degradation, that are used to define resolution stability and multiple pulse sensitivity. Examples include 0.002M Cholesterol Hydrochloride for 1 H spectrometry or 0.1M Sucrose for 13 C spectrometry. Since many nuclei are studied proton decoupled, reference standards are also available for decoupled and, sometimes, undecoupled sensitivity, so you can measure instrument performance in the mode that most closely matches your experiments. There are now sensitivity standards for indirect detection, too.