Summary
Two humic and one fulvic acid were hydrolyzed with hot 6M HCl and a combination of 12M and 0.5M H2SO4. Effects of acid hydrolysis on the chemical structures of the humic materials were assessed by comparing liquid-state13C NMR spectra of hydrolyzed with those of unhydrolyzed humic substances. Hydrolysis with 6M HCl was found to be more efficient for removing ptoteinaceous materials and carbohydrates than was hydrolysis with 12M-0.5M H2SO4. The latter appeared to better preserve the structural integrity of the humic materials, especially in the lower aliphatic region (0–50 ppm). Hydrolysis with the two acids increased the aromaticity of the humic materials, in part by removing proteinaceous components and carbohydrates. It also lowered the CO2H content of two out of three humic preparations, probably because of acid decarboxylation. The data presented demonstrate the great potential of13C NMR spectroscopy for structural research on humic materials.
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Schnitzer, M., Preston, C.M. Effects of acid hydrolysis on the13C NMR spectra of humic substances. Plant Soil 75, 201–211 (1983). https://doi.org/10.1007/BF02375565
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DOI: https://doi.org/10.1007/BF02375565