Carbon-1 3 magic-angle spinning

Table 1. Structural carbon distribution (%) of the humic acids extracted from soil horizons, adopted from Xing (2001). The distribution was calculated from solid state 13C Cross-Polarization Magic-Angle-Spinning (CP/MAS) NMR spectra. Chemical shift assignment for carbon functional groups alkyl 0-50 ppm O-alkyl 50-117 ppm aromatic 107-165 ppm.

NMR spectra of solids, and thus soil, are obtained by what is called magic angle spinning. The spectra obtained have broader absorption features than NMR spectra of components in solution or liquids. Numerous NMR experiments such as 3H—13C heteronuclear chemical shift correlation (HETCOR), which identifies which hydrogen atoms are attached to which carbon atoms, can also be carried out on solid samples. A great deal of useful information about the structure of components in soil can thus be obtained from NMR investigations [5,6],... 

The 13C NMR study utilized cross polarization-magic angle spinning (CP-MAS) with spin counting. The elemental and functional group analyses provided input for a series of analytical constraints calculations that yield an absolute upper limit for the amount of aromatic carbon and most probable estimates of both aromatic and non-carboxyl aliphatic carbon in each sample. Spin counting experiments demonstrate that less than 50% of the... 

Figure 4. The influence of magic angle spinning on the SL cross polarization time constant. In the PlP-cured epoxy the time constant for the nonprotonated carbons increases by about 50% for = 1-3 kHz while those of the protonated carbons are virtually unchanged over this range.

Figure 6. Magic angle spinning, high-power proton decoupling, FT C-13 NMR spectrum of cured, carbon-black-loaded polyisoprene at ambient temperature, FT of normal FID without proton enhancement.

Figure 9. C-13 NMR spectra of a 60/40 emulsion SBR/polijbutadiene rubber blend (a) solid, cured, carbon black filled at 100°C (b) same as Sample a but using magic angle spinning at ambient temperature.

The experimental design was to study both the carbon-13 and proton relaxation as a function of temperature for both polymer and solvent, and to extend these to as high a polymer concentration as the available equipment permitted. Inasmuch as the mechanical properties of polymers can be affected considerably by small amounts of diluents, we would ultimately like to approach the bulk polymer state, where use of strong dipolar decoupling and magic angle spinning are necessary. ... 

Figure 4. Carbon-13 cross-polarization, magic-angle spinning NMR spectra from an acrylic-melamine (A) and acrylic-urethane (B) coating. (Reproduced with permission from ref. 28. Copyright 1986 Elsevier Sequoia.)...

Ripmeester, J.A. Ratcliffe, C.I. (1988). Low-temperature cross-polarization/magic angle spinning carbon-13 NMR of number solid methane hydrates structure, cage occupancy, and hydration. J. Phys. Chem., 92, 337-339. 

K. J. D. MacKenzie and R. H. Meinhold, A Mg magic-angle spinning nuclear magnetic resonance study of the thermal decomposition of magnesium carbonate. /. Mater. Sci. Lett, 1993,12,1696-1698. 

Fig. 13.9 Carbon-13 solid-state NMR spectra of poly(ethylene) (a) cross-polarization magic angle spinning (CP/MAS), (b) progressive saturation, and (c) Torchia T, experiment.

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