The relaxation delay

The relaxation delay is one of the basic NMR parameters. Optimising the relaxation delay can help improve the appearance of your spectra and increase the accuracy of your integrals. In this post its impact on 1D ¹H spectra is shown.

NORD: No Relaxation Delay NMR spectroscopy

No Relaxation Delay (NORD) NMR spectroscopy is a method for making the acquisition of NMR spectra less time consuming. By modification of the pulse sequences and careful ordering of the experiments it is possible to eliminate the most time consuming part, the relaxation delay.

NOAH supersequences

Much of the time taken to acquire multi-dimensional NMR spectra is consumed by the relaxation delay. NOAH (NMR by Ordered Acquisition using ¹H-detection) is a method developed to interleave several experiments and use a single relaxation delay for the whole group, thereby reducing the time taken to acquire a series of experiments.

ASAP - Acceleration by Sharing Adjacent Polarization

NMR is a non destructive technique and so reducing acquisition time can be used either to increase sample throughput, or to lower the detection limit. To lower the detection limit a given amount of time is used to acquire a greater number of scans than would normally be acquired. A relatively recent method for reducing acquisition time is ASAP (Acceleration by Sharing Adjacent Polarization)¹. The ASAP technique speeds acquisition by greatly reducing the length of the relaxation delay.

Signal-to-noise, pulse width and the relaxation delay

In the previous post I reported data showing signal-to-noise increased in a less than linear fashion with increasing number of scans. In fact, the increase was much less than the expected square root increase. To further probe this relationship I have recorded a series of experiments with an increasing number of scans and measured the signal-to noise in each.