Specific Interactions of Organic Substances in Size-Exclusion Chromatography

Size-exclusion experiments of alcohols, mono- and dicarboxylic acids, aromatic acids, and amino acids were conducted. Two columns with different gel packings (TSK HW 50 S and TSK G2000SW) were used to determine the influence of the gel core structure on the elution volume of organic substances. Neither for the polymer based gel nor for the silica based gel specific interactions, especially hydrophobic interactions, could be neglected. For both alcohols and monocarboxylic acids the elution volume increased with an increasing number of carbon atoms. It was found that aromatic compounds interacted strongly with both gels. Whereas alcohols were not affected by differences in ionic strength between sample and eluent, the elution volume of carboxylic acids was strongly influenced. In combination with a multidetector system (UV absorption, fluorescence, dissolved organic carbon, electrical conductivity) changes in the chromatographic behavior of these compounds due to differences in ionic strength between sample and eluent were used to interpret size-exclusion results from natural organic matter and ligninosulfonic acids. Since most of the substances used in this work do not absorb UV light nor do they have any fluorescent capabilities, a continuous-flow DOC detector was used to record the chromatograms.