PMID: 11931426Apr 5, 2002Paper

Solid-state carbon-13 nuclear magnetic resonance of humic acids at high magnetic field strengths

Journal of Environmental Quality
Karl J DriaPatrick G Hatcher

Abstract

Use of solid-state 13C nuclear magnetic resonance (NMR) spectroscopy has become commonplace in studies of humic substances in soils and sediments, but when modern high-field spectrometers are employed, care must be taken to ensure that the data obtained accurately reflect the chemical composition of these complex materials in environmental systems. In an effort to evaluate the quality of solid-state 13C NMR spectra obtained with modern high-field spectrometers, we conducted a series of experiments to examine spectra of various humic acids taken under a variety of conditions. We evaluate conditions for obtaining semiquantitative cross polarization magic angle spinning (CPMAS) 13C NMR spectra of humic acids at high magnetic field and spinning frequency. We examine the cross polarization (CP) dynamics under both traditional and ramp CP conditions on Cedar Creek humic acid. Fitted equilibrium intensities from these CP dynamic studies compare to within 3.4% of the intensities determined from a Bloch decay spectrum of the same sample. With a 1-ms contact time, ramp CP and traditional CP spectra were acquired on this sample and were found to compare to within 5.4% of the Bloch decay spectrum; however, the signal-to-noise ratio per hou...Continue Reading

Citations

Dec 5, 2012·Environmental Science & Technology·Perry J Mitchell, Myrna J Simpson
Feb 3, 2012·Journal of Agricultural and Food Chemistry·Marcus FostonArthur J Ragauskas
Sep 11, 2008·Analytical Sciences : the International Journal of the Japan Society for Analytical Chemistry·Pellegrino Conte, Anne E Berns
Apr 17, 2007·Ecotoxicology and Environmental Safety·Christopher M HurdzanOlli H Tuovinen
Jul 18, 2017·The Science of the Total Environment·Jun-Jian WangMyrna J Simpson

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