Non-uniformly sampled Maximum Quantum spectroscopy

Abstract: Maximum-Quantum (MaxQ) NMR is an approach that exploits the simple lineshape (a singlet) of the highest possible coherence quantum order for a given spin system to help resolving the interpretation of the spectrum of complex mixtures. In this setup, resolution in the indirect, multiple-quantum, dimension is crucial, and it may be linked to a long duration of the signal acquired along this axis. We explored if this boundary on the length of the indirect dimension could not necessarily translate into extended experimental times by applying Non-Uniform Sampling (NUS) schemes in conjunction with Recursive Multi-Dimensional Decomposition (R-MDD) data processing. The actual value of the MaxQ order depends on the size of the spin system, so that for a mixture several MQ correlation spectra must be recorded to detect all possible molecular fragments. As the sparseness of the MQ datasets vary dramatically in going from higher (sparser) to lower (denser) coherence orders, the optimal compressing conditions and the fidelity of NUS/R-MDD scheme may vary along the series of MQ spectra. The NUS-MaxQ approach is demonstrated on the aromatic region of the 1H spectrum of a mixture of 10 simple aromatic molecules. [Copyright &y& Elsevier]