Steven Dec - Comparison of the 1H NMR Analysis of Solids by the CRAMPS and MAS-Only Techniques

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      Publication Details (including relevant citation   information):

      S.F. Dec;  C.E. Bronnimann;  R.A. Wind and G.E. Maciel,   Journal of  Magnetic Resonance,   82, 454 (1989).

      Abstract:

      1H NMR spectra are reported on eight representative   solid samples, including pure powdered crystalline samples,   synthetic organic polymers, a silica gel, HY zeolite, and a   lignite. Spectra were obtained by the following three approaches:   (1) single pulse on a static sample, (2) CRAMPS, and (3) single   pulse with magic-angle spinning (MAS-only). The MAS-only results   were obtained as a function of MAS speed. Although the MAS-only   technique is capable of achieving a significant degree of line   narrowing, even with modest MAS speeds, MAS-only spectra of the   general quality of the apparently undistorted high-resolution   1H spectra obtained by the CRAMPS technique are not   obtained at the highest MAS speeds examined (21 kHz for a   polymethylmethacrylate sample), unless the   1H-1H dipolar interactions in the sample   are rather weak, as with silica gel or a zeolite. Thus, caution   should be exercised in interpreting 1H MAS-only   spectra, especially if CRAMPS results are not available as a   calibration.

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