Implementing SPAM into STMAS: A net sensitivity improvement in high-resolution NMR of quadrupolar nuclei

Abstract: Gan and Kwak recently introduced two new tools for high-resolution 2D NMR methods applied to quadrupolar nuclei: double-quantum filtering in STMAS (DQF–STMAS) and the soft-pulse added mixing (SPAM) idea. Double-quantum filtering suppresses all undesired signals in the STMAS method with limited loss in sensitivity. With SPAM, all pathways are added constructively after the second hard-pulse instead of using a single pathway as previously. Here, the sensitivity, advantages and drawbacks of DQF–STMAS are compared to 3QMAS. Additionally, SPAM can be included into DQF–STMAS method, resulting in a net sensitivity gain with respect to 3QMAS of ca. 10–15. [Copyright &y& Elsevier]