title: High-field 13C solid-state NMR studies of stream humic and fulvic acids with fast magic-angle spinning.
abstract: Standard samples of stream humic and fulvic acids have been studied by high-resolution 13C solid-state NMR. The spectra have been recorded at a high (9.4 T) magnetic field using 1H-13C cross-polarization (CP) and proton high-power decoupling (HPDEC) with fast (up to 15 kHz) magic-angle spinning (MAS). The widths of the spectral lines decrease with increasing spinning rate. This is probably due to the overlap of spinning sidebands with resonances at low speeds and to a more effective averaging of anisotropic broadening at high speeds. However, fast MAS modulates the CP signal intensities, making quantitative analysis very difficult.
authors: Department of Chemistry, University of Aveiro, Portugal.
authors: J
authors: J
authors: Rocha
authors: E
authors: E
authors: Santos
authors: J D
authors: JD
authors: de Jesus
authors: A C
authors: AC
authors: Duarte
mesh_terms: D001578:Benzopyrans / Q000737:chemistry*; D002247:Carbon Isotopes; D006812:Humic Substances / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy
chemical_list: D001578:Benzopyrans; D002247:Carbon Isotopes; D006812:Humic Substances; C005023:fulvic acid