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Surface-Enhanced Raman Spectroscopy of Chernozem Humic Acid and Their Fractions Obtained by Coupled Size Exclusion ChromatographyPolyacrylamide Gel Electrophoresis (SEC-PAGE)

Volume 60, Number 1 (Jan. 2006) Page 48-53

Sanchez-Cortes, S.; Corrado, G.; Trubetskaya, O.E.; Trubetskoj, O.A.; Hermosin, B.; Saiz-Jimenez, C.

A humic acid extracted from a chernozem soil was fractionated combining size exclusion chromatography and polyacrylamide electrophoresis (SEC-PAGE). Three fractions named A, B, and C+D, with different electrophoretic mobilities and molecular sizes (MS), were obtained and subsequently characterized by thermochemolysis and surface-enhanced Raman spectroscopy (SERS). The data confirmed that fraction A, with the higher MS, was more aliphatic than fractions B and C+D and, in turn, fractions with lower MS (B and C+D) denoted an enrichment in lignin residues. These structural features explain conformational changes when varying the pH in the humic fraction A and indicated that combination of the two techniques is a good approach for characterizing humic substances.