Characterizing dissolved organic matter in aquatic environments by size exclusion chromatography coupled with multiple detectors.

Size exclusion chromatography (SEC) is one of the most commonly used techniques to detect the molecular weight (MW) of dissolved organic matter (DOM) in aquatic environments. The significant improvement and focus of this method have been the application of multiple detectors, which contribute to providing fundamental physicochemical properties of various MW fractions. This study has coupled SEC with multiple detectors to simultaneously detect ultraviolet absorbance, fluorescence, dissolved organic carbon, and dissolved organic nitrogen of different MW fractions. The detection limits for the organic carbon and nitrogen detectors were 0.20 μg C L-1 and 0.14 μg N L-1, respectively. Furthermore, we gave an interpretation of the nature and evolution of DOM in surface water based on the comparison and analyses of the combined chromatogram obtained from multiple detectors. Fractions assigned as hydrophobic humic-like substances, hydrophilic humic-like substances, low-MW microbial extracellular metabolites and low-MW hydrophobic protein-like substances were first established in this study and attributed to the presence of a fluorescence detector. We believe that the developed method provides in-depth knowledge of the structure and composition of DOM and could be used as a potential analytical tool in environmental organic chemistry, humus chemistry and supramolecular chemistry.