MQMAS NMR: Experimental Strategies and Applications

In this article, we give a general description of the fundamental principles of the MQMAS experiment. It is followed by an extensive discussion of strategies for maximizing the sensitivity and the detection of pure-phase spectra, including the shifted echo, z-filter, and SPAM methods, as well as the approaches for avoiding the folding of frequencies in F1 domain (TPPI and States methods). The processing and interpretation of the MQMAS spectra are explained, including the shearing transformation and referencing. The methods used for quantitative analysis of the MQMAS spectra, and the analysis of the distribution of quadrupolar and chemical shift parameters are described, as well. Several MQMAS-based methods for studying the heteronuclear correlations are reviewed, involving cross polarization, INEPT, TEDOR, and REDOR. Finally, we highlight the representative applications of MQMAS NMR in chemistry, materials science, and biology. Keywords: MQMAS NMR; pure-phase MQMAS spectrum; shifted echo; whole echo; z-filter; split-t1 method; quantification of MQMAS spectra; MQMAS-HETCOR; CPMG-MQMAS