HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Preston, C. M. Articles by Schnitzer, M. Search for Related Content PubMed Articles by Preston, C. M. Articles by Schnitzer, M. Agricola Articles by Preston, C. M. Articles by Schnitzer, M.

Effects of Chemical Modifications and Extractants on the Carbon-13 NMR Spectra of Humic Materials¹

ABSTRACT

Carbon-13 NMR was used to study the effects of methylation, 6M HCl hydrolysis and 6M HCl hydrolysis followed by methylation on two humic acids (HA's) and one fulvic acid (FA), as well as the effect of extraction by 0.5M NaOH vs. 0.1M HCl on an FA. Spectra of methylated HA's and FA's indicate that almost all CO₂H groups are attached to aromatic structures, and that phenolic OH's are significant functional groups. These spectra also exhibit fine structure in the 127- to 131-ppm region, possibly due to benzenecarboxylic acid-type structures, which have been proposed as major building blocks of humic materials. Other sharp signals are observed in the 133- to 146-ppm region, due to C-substituted carbons in aromatic or heterocyclic rings. Carbon-13 NMR spectra of hydrolyzed HA's and FA indicate, in agreement with chemical analyses, that 6M HCl hydrolysis removes all amino acids, most carbohydrates and increases the aromatic C content (aromaticity) of the residues. Carbon-13 NMR spectra of FA extracted by 0.5M NaOH and 0.1M HCl are similar.

¹ Contribution No. 1375 from the Chemistry and Biology Res. Inst., Res. Branch, Agriculture Canada, Ottawa, Ontario, Canada K1A OC6.

² Research Scientist, Nitrogen Fixation, and Program Leader, Soil Nitrogen and Organic Matter, respectively.

Received for publication February 10, 1983. Accepted for publication November 1, 1983.

This article has been cited by other articles:

				B. Chefetz, M. J. Salloum, A. P. Deshmukh, and P. G. Hatcher Structural Components of Humic Acids as Determined by Chemical Modifications and Carbon-13 NMR, Pyrolysis-, and Thermochemolysis-Gas Chromatography/Mass Spectrometry Soil Sci. Soc. Am. J., July 1, 2002; 66(4): 1159 - 1171. [Abstract] [Full Text] [PDF]