Fail-Safe Non-Uniform Sampling (NUS)

NUS is an acquisition technique applicable for nD NMRexperiments in which a certain amount of increments in the indirect dimension(s) are skipped during acquisition followed by a post-acquisition data reconstruction. When used correctly, this saves time without compromising data quality. The optimal settings depend on the sample under investigation and are setby SmartDriveNMR in automation.

SmartDriveNMR Fail-Safe NUS
With the 1D Proton spectrum and the structure (if available) as the input (1) a conservative upper limit for the amount of sampling (NUS%) is estimated (2) e.g. 49%. Now the acquisition of the 2D experiment is started with a significantly lower NUS% than the conservative estimate e.g. 15%. The acquisition continues, increasing the NUS% step by step until the spectrum reaches a high quality and is free of artefacts without passing the conservative estimate (3).

SmartDriveNMR Results

Active decision making on-the-fly saves experiment time – simply considering the structure alone might have demanded an HSQC in both cases.

Top part of figure - SmartDriveNMR: Multiplets are well separated and straightforward to assign → in mode OPTime: no HSQC will be acquired.

Bottom part of figure - SmartDriveNMR: Multiplets overlap in the CH/CH2 region, HSQC will improve confidence → in mode OPTime: HSQC will be setup.

Fig1. SmartDriveNMR

Optimized 1D 13C Acquisition

To acquire 1D 13C spectra manually with a good signal to noise ratio (S/N) without wasting measurement time some experience is needed because depending on the probe head design of the NMR sensor at use the 13C sensitivity relative to the 1H sensatory can vary significantly. SmartDriveNMR has access to these information and can deduce the proper number of scans (NS) individually for each sample.

  1. From the 1D 1H experiment NS is estimated conservatively for 1D 13C taking the probe head design and its includes on the 13C sensitivity relative to the 1H into account. In this example NS is set to 1024
  2. At acquisition time S/N is determined after some scans (256 in this example) and compared to the desired S/N set by SmartDriveNMR
  3. If the desired S/N is not reached yet, the acquisition is prolonged with increased NS – subsequently the new S/N is determined
  4. This procedure is repeated until the desired S/N is reached, then the acquisition is terminated (in this example at an NS of 600)
SmartDriveNMR Optimized 1D 13C Acquisition