Determination of relative molecular weights of fluorescent components in dissolved organic matter using asymmetrical flow field-flow fractionation and parallel factor analysis

Dissolved organic matter in aquatic systems is of variable structure and composition. Asymmetrical flow field-flow fractionation coupled to UV/vis diode array and fluorescence detectors (AF4–DAD–EEM) was used to assess the size and optical properties of dissolved organic matter. The results were analyzed using parallel factor analysis (PARAFAC) and statistical fractogram deconvolution to correlate fluorescing components with molecular weight fractions. This coupling, which is shown for the first time in this work, is a powerful method capable of revealing novel information about the size properties of PARAFAC components. Tyrosine/polyphenol-like fluorescence (peak B) was significantly correlated (p < 0.05) with the smallest size group (relative molecular weight = 310 ± 10 Da), microbial humic-like and terrestrial visible humic-like fluorescence (peaks M, C, A) with the intermediate size group (1600 ± 150 Da), and terrestrial fulvic-like and tryptophan/polyphenol-like fluorescence (peaks A and T) with the largest size group (4300 ± 660 Da).

Typical fractogram and deconvolution fractions for leachate DOM (top) showing EEMs captured at (1) low, (2) intermediate and (3) high molecular weight. The peak label is based on Coble's nomenclature (1996).Figure optionsDownload as PowerPoint slideHighlights
► Correlation between fluorescing components with molecular weight fractions.
► Size- and sample-dependencies of PARAFAC components are found.
► Tyrosine-like constituents are smaller in size than the humic-like constituents.