Magic-angle spinning sample preparation

N. J. Waters, S. Garrod, R. D. Farrant, J. N. Haselden, S. C. Connor, J. Connelly, J. C. Lindon, E. Holmes and J. K. Nicholson, High-resolution magic angle spinning H-l NMR spectroscopy of intact liver and kidney Optimization of sample preparation procedures and biochemical stability of tissue during spectral acquisition, Anal. Biochem., 2000, 282, 16-23. 

We report (i) isomorphous substitution of boron, by secondary synthesis, into silicalite and into highly siliceous (Si/Al>400) ZSM-5 and (ii) an improved direct synthesis of zeolite (Si,B) -ZSM-5. The chemical status of B in die boronated products depends upon reaction conditions. Careful control of the concentration of the base, the borate species and of die duration of treatment, allows the preparation of samples containing only 4-coordinated B or a mixture of 3- and 4-coordinated B in various relative concentrations. The products were characterized by magic-angle-spinning (MAS) NMR and infrared (IR) spectroscopies and by powder x-ray diffraction (XRD). 

The experimental results which lead to these conclusions are summarized In Table I. Elemental analyses, conducted by a commercial laboratory, are presented In the form of a ratio of the relative numbers of atoms of C, H, N, and 0 normalized to 3 carbon atoms per monomer unit. IR spectra were obtained In-house using a Perkin Elmer 298 IR spectrophotometer. Solid probe magic angle spinning NMR experiments were performed at the National Bureau of Standards. All of these analyses were performed on bulk (l.e. pyrolyzed In batches of lg) samples of 485,000 average molecular weight ultrapure PAN prepared In a tube furnace evacuated by a mechanical vacuum pump, and are reported on In detail elsewhere.(13) Table I also summarizes electrical conductivity and optical absorption experimental results obtained using thin films of PAN solution cast In dlmethylformamlde. 

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