Acquisition Parameters: Liquid State 13C NMR Spectra. Samples were obtained from the International Humic Substances Society in the H+-saturated form. For liquid state NMR analysis, 300 mg of sample was added to deionised and distilled water, titrated to pH 6 with 1 N NaOH, and freeze dried. The freeze dried sodium salt was redissolved in 1.5 ml H2O and 1.5 ml D2O. Liquid state 13C NMR spectra were recorded on a Varian 300 MHz NMR spectrometer at a carbon resonance frequency of 75.4 MHz using a 10 mm broadband probe (30-122 MHz), modified to be free of background carbon signal. Acquisition parameters included a 50,000 Hz spectral window and 0.2 second acquisition time. The inverse gated decoupled spectra (quantitative) were acquired using a 90° pulse angle and 12.0 second pulse delay. The continuous WALTZ decoupled spectra (nonquantitative) were acquired using a 45° pulse angle and 1.0 second pulse delay. The following links will display JPEG images of individual spectra.
Solid State CP/MAS 13C NMR Spectra of Elliot Silt Loam Soil and Florida Pahokee Peat: Solid state cross polarization/magic angle spinning (CP/MAS) 13C NMR spectra were recorded on a Chemagnetics CMX-200 NMR spectrometer at a carbon resonance frequency of 50.3 MHz, using a 7.5 mm ceramic probe (reduced 13C background) with zirconium pencil rotors. Acquisition parameters included a 30 KHz spectral window, 17.051-millesecond acquisition time, 5.0 millesecond contact time, 0.5 second pulse delay and spinning rate of 5 KHz. The following links will display JPEG images of individual spectra.
