Magic Angle Spinning Techniques Research Articles

The use of solid 13C nuclear magnetic resonance for the characterization of cholesterol and bilirubin pigment composition of human gallstones

The new magic-angle spinning and cross polarization techniques for obtaining a 13C solid NMR spectrum are applied to the characterization of human cholesterol, mixed cholesterol-pigment, calcium bilirubinate and bilirubin pigment gallstones. The stones divide into two general classes: the cholesterol stones and the bilirubin pigment stones. The cholesterol stones are very similar to each other whereas the bilirubin pigment stones exhibit considerably more variation in spectral features. The importance of other material and polymerization in the bilirubin pigment stones is discussed.

Prospects for carbon-13 nuclear magnetic resonance analysis of solid fossil-fuel materials

Because of excessive line broadening in solids due to magnetic dipole—dipole interactions and chemical shift anisotropies, and because of long spin-lattice relaxation times, standard continuous wave (CW) or pulse Fourier transform techniques do not normally yield structurally informative 13C n.m.r. spectra from solid samples. However, the techniques of dipolar decoupling, cross polarization and magic-angle spinning show great promise for routine 13C n.m.r. studies of solids. Applications of these techniques to analysis of anthracite, lignite and algal coal samples, and to oil shale and kerogen samples, are discussed. It is shown that cross-polarization spectra obtained with dipolar decoupling display chemical shift anisotropy which interferes with attempts to distinguish the resonances of aromatic and aliphatic carbons. However, with magic-angle spinning the distinction can be made. Prospects and potential difficulties with applications of these techniques are discussed.