Characterization of humic acid size fractions by SEC and MALS

Latahco silt-loam humic acid was separated on a preparatory scale by size e xclusion chromatography (SEC) on a gravity-fed Sepharose column. Four fract ions from this separation were collected and further analyzed, along with w hole humic acid, by high-performance SEC coupled with a multi-angle light s cattering (MALS) detector. A detailed characterization of the radius of gyr ation across the elution profile of each fraction by MALS demonstrated that the preparative column generally separated the humic acid according to dif ferences in molecular size. Furthermore, a comparison of elution profiles o btained on the whole humic acid with UV and refractive index detectors reve aled the presence of a non-aromatic low molecular weight component. (C) 199 9 Elsevier Science Ltd. All rights reserved.