Isolation and characterization of natural organic matter from lake water: Two different adsorption chromatographic methods

Aquatic humic solutes were isolated from lake water by two different methods: non-ionic sorbing solid (XAD technique) and weakly basic anion exchanger (DEAE cellulose). The DEAE procedure removed from the fresh water sample at natural acidity 80% of the DOC as humic solutes. This was practically equal to the total amount of the three organic acids obtained directly by the XAD-8 resin at preadjusted acidity (pH 2) and of the acidic solutes obtained by a specific anion exchanger in connection with the XAD-8 column. The acidic gross character of the humic solutes obtained by the DEAE procedure was similar to the combined character of the four distinct acidic fractions obtained at pH 2 by different adsorbents. The structural composition of humic solutes obtained by the DEAE isolation procedure appears to be a given combination of the various hydrophobic and hydrophilic acidic solutes obtained at pH 2 by the XAD technique. It is likely the acidic treatments connected to the isolation and fractionation of organic solutes by the XAD technique can be to some extent coincidental, especially from the structural chemistry point of view. However, aquatic humic solutes (especially so-called fulvic and humic acids) modelled by the XAD technique are in some degree real, rather than accidental products of the isolation method. (C) 1997 Elsevier Science Ltd.