Tandem size exclusion chromatography polyacrylamide gel electrophoresis ofhumic acids

Humic acids (HAs) from four soils were fractionated by size exclusion chrom atography (SEC) on Sephadex G-75. Three fractions were obtained in all humi c acids, collected and assayed by polyacrylamide gel electrophoresis (PAGE) . The unfractionated HA from each soil was used as reference. Each chromato graphic fraction formed one electrophoretic zone corresponding closely to o ne band of the reference sample with some admixture of the fractions preced ing or following. The results indicate that fractionation of HAs by tandem SEC-PAGE can be successfully used for obtaining fractions of reduced polydi spersity and different electrophoretic mobilities. Pyrolysis/methylation-ga s chromatography-mass spectrometry of the full size preparations:of HA and fractions with exactly defined molecular size and electrophoretic mobility showed a different distribution in humic components mainly lipids, lignin d erivatives and N-containing compounds.