**1. Introduction**

278 Advanced Aspects of Spectroscopy

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In the early to mid-90's, NMR studies were being published that recognized the power of magic angle spinning (MAS) to increase resolution in materials that were not strictly solids by averaging differences in magnetic susceptibility and residual dipolar coupling inherent in these samples. The method of utilizing MAS for non-solid materials to produce liquid-like NMR lines was termed High-Resolution Magic Angle Spinning (HR-MAS). A few of the first HR-MAS examples included investigation of resins for combinatorial chemistry,[1] solvent swollen polystyrene gels,[2] and lipid systems.[3] Then in 1996, Maas *et al.* [4] advanced the field of HR-MAS NMR by adding a magnetic field gradient along the magic angle (see Figure 1). Like high resolution solution NMR, this gradient improved sensitivity and resolution with the ability to more easily select coherence pathways and by reducing indirect dimension (*t1*) noise.[4]

There are currently commercially available HR-MAS probes with magic angle gradients from companies like Bruker BioSpin Corporation (Billerica, MA),[5] Agilent Technologies (Santa Clara, CA),[6] JEOL USA, Inc. (Peabody, MA),[7] and Doty Scientific, Inc. (Columbia, SC).[8] In addition to magic angle gradients, many of these probes also have a deuterium (2H) lock channel, allowing improved ease of shimming and long term stability. With the emergence of commercially available probes, HR-MAS NMR has become more popular in the last few years, especially in the biological and biomedical fields. This popularity is mainly due to the heterogeneous nature of tissues and cells that are well suited for HR-MAS. Multiple HR-MAS NMR studies involving different tissue biopsies, like brain, kidney, liver, and muscle tissues for metabonomics studies, as well as identification of abnormal tissues (*i.e.* cancerous tissues) have been reported.[9-11] HR-MAS NMR has also been applied to the characterization of foodstuffs, including the assignment of metabolites in tomatoes and apples, the study of biopolymers in fruit cuticles, quantification of *n*-3 fatty acids content in different fish species, and tracking the chemistry of coffee beans during the

© 2012 Alam and Jenkins, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

roasting process.[12, 13] These types of biological and foodstuff HR-MAS NMR investigations highlight the diverse range of information that can be obtained.

The application of HR-MAS NMR to material science was initially focused almost exclusively on the analysis of solid-phase (*i.e.* utilizing support resins) organic and peptide synthesis, or analysis of combinatorial solid-phase results. In these studies, the material was swollen in appropriate solvents such that the mobility of the attached ligands was increased, allowing high resolution NMR spectra to be obtained. The application of HR-MAS to solid state synthetic chemistry remains an active area of research, but will not be discussed in detail. The readers are encouraged to consult several very extensive reviews in this area.[14- 16] In comparison to the numerous HR-MAS NMR studies on biological and solid-phase synthetic chemistry systems, there are fewer examples that focus on the use of this technique to material science. This chapter will review the application of HR-MAS NMR to a wide range of systems, including ceramics, zeolites, liquid crystals, ionic liquids, and surface modified nanoparticles.
