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Solvent Systems for the Isolation of Organic Components from Soils

Chemical and Environmental Sciences, Univ. of Limerick, Ireland

View larger version (35K): [in a new window]   Fig. 1. Diffusion ordered spectroscopy spectrum of the International Humic Substances Society peat humic acid standard in D2O after the addition of 5 µL ethanoic acid (after Simpson, 2002).

View larger version (26K): [in a new window]   Fig. 2. Cross polarization magic angle spinning 13C-nuclear magnetic resonance spectra for humic acids (HAs) isolated from a silty clay grassland soil by the International Humic Substances Society procedure at pH 7 (1), 10.6 (2), or 12.6 (3), and for the HA precipitated from dilute solution at pH 2 from the extract at pH 12.6 (spectrum 4) and subjected to the resin in tandem separation procedure. Spectra 5, 6, and 7 are for fulvic acids, and 8, 9, and 10 are for the XAD-4 (styrenedivinylbenzene) acids from the pH 7, 10.6, and 12.6 extracts, respectively, and fractionated by the resin in tandem process. Spectrum 11 is for the XAD-4 neutrals.

View larger version (16K): [in a new window]   Fig. 3. Cross-polarization–total sideband suppression (CP/TOSS) 13C nuclear magnetic resonance spectra of humic acids (HAs) isolated in 0.1 M NaOH at pH 12, and in 0.1 M NaOH + 6 M urea after prior exhaustive extractions at pH 7 and at 10.6. CON = amide, COO = carboxyl, Arom-C = aromatic carbon; OC = oxygen alkyl carbon; alipha. = aliphatic carbon.

View larger version (10K): [in a new window]   Fig. 4. Cross polarization magic angle spinning 13C NMR spectrum of the residual organic materials not extracted from soil in base + 6 M urea.

View larger version (7K): [in a new window]   Fig. 5. A hypothetical representation of associations between dimethylsulfoxide and the carboxyl, phenolic, and other hydroxyl functional groups in humic substances. R represents the remainder of the humic structures stretching from the complexed carboxyl and phenolic or other hydroxyl functional groups; represents an aromatic functionality.