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Carbon-13 solid-state NMR of soil organic matter--using the technique effectively
Solid-state 13 C CPMAS NMR offers many options for characterizing carbon in soil organic matter (SOM). Its effectiveness, however, is often limited by a poor understanding of the techniques, and lack of hands-on access and training opportunities for students. Of nearly 250 modern NMR systems in Cana...
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Published in: | Canadian journal of soil science 2001-01, Vol.81 (3), p.255-270 |
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Main Author: | |
Format: | Article |
Language: | English |
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Citations: | Items that cite this one |
Online Access: | Get full text |
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Summary: | Solid-state
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C CPMAS NMR offers many options for characterizing carbon in soil organic matter (SOM). Its effectiveness, however, is often limited by a poor understanding of the techniques, and lack of hands-on access and training opportunities for students. Of nearly 250 modern NMR systems in Canada, approximately one is genuinely available for SOM studies, and there is poor communication between NMR operators and SOM users. While quantitative reliability can be addressed to some extent by multiple contact-time experiments or single-pulse (Bloch decay) spectra, it is also important to consider the effects of spectrometer background, spinning sidebands (especially with higher magnetic fields) and processing operations such as line-broadening, phasing and baseline correction. In many studies, more consideration needs to be given to instrument specifications, the type of information needed, and whether sample fractionation or pretreatment should be used. Structural information can be greatly enhanced by dipolar-dephasing and sideband suppression sequences. Sequences based on relaxation differences can reveal pools of carbon with different structures. Data analysis can be enhanced by principal component analysis, spectrum deconvolution and difference spectra. Studies of xenobiotics and C metabolism can be greatly aided by
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C-labeling. However, a key limitation to SOM applications remains the gap in culture and expectations of the users. Key words: Soil organic matter,
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C CPMAS NMR, Bloch decay, dipolar dephasing, spinning sidebands |
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ISSN: | 0008-4271 1918-1841 |
DOI: | 10.4141/s00-074 |