SEPARATION OF MOLECULAR-SIZE CLASSES OF AQUATIC HUMIC SUBSTANCES USING ULTRAFILTRATION AND DIALYSIS

A procedure for separating aquatic humic substances into discrete mole cular size fractions by the combined use of ultrafiltration and dialys is was tested. The molecular size distributions of separated fractions were examined by application of samples to a gel filtration chromatog raphy column. Variations in the elution patterns observed for the sepa rated fractions of small and intermediate molecular size were largely consistent with predicted effects of separation procedures. In contras t, humic substances of large molecular size were not separated effecti vely by dialysis using dialysis membranes of large molecular weight cu t-off. Small quantities of humic material of large molecular size were observed in most of the ultrafiltrates. This phenomenon may have been an artefact of filtration and/or the result of reconfiguration of mat erial after separation.