Nuclear magnetic resonance spectroscopy of soils and related materials. Relaxation of 13C nuclei in cross polarization nuclear magnetic resonance experiments |
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| Authors: | Michael A Wilson Ronald J Pugmire David M Grant |
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| Institution: | Departments of Chemistry and Fuels Engineering, University of Utah, Salt Lake City, UT 84112, U.S.A. |
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| Abstract: | Relaxation of 13C nuclei in a peat, a soil, and three soil fractions have been investigated in order to improve structural resolution and to investigate quantification of various carbon types. Rotating frame spin lattice relaxation times (T1?'s) and transverse relaxation times (T2′'s) are similar to those observed for coals. T2′'s of carbons in different magnetic environments differ sufficiently that spectra can be obtained containing only nonprotonated carbon and methyl substituents if a 40 μsec delay without decoupling is inserted into the pulse programme before data acquisition (dipolar dephasing). Provided quantitative data is obtained in simple cross polarization experiments and allowance is made for loss in signal intensity of nonprotonated carbon during dipolar dephasing, then the fraction of aromatic carbon which is protonated in the samples can be determined. |
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