Specific interactions of organic substances in size-exclusion chromatography

Size-exclusion experiments of alcohols, mono- and dicarboxylic acids, aroma tic acids, and amino acids were conducted. Two columns with different gel p ackings (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. Neit her for the polymer based gel nor for the silica based gel specific interac tions, especially hydrophobic interactions, could be neglected. For both al cohols and monocarboxylic acids the elution volume increased with an increa sing number of carbon atoms. It was found that aromatic compounds interacte d strongly with both gels. Whereas alcohols were not affected by difference s in ionic strength between sample and eluent, the elution volume of carbox ylic acids was strongly influenced. In combination with a multidetector sys tem (UV absorption, fluorescence, dissolved organic carbon, electrical cond uctivity) changes in the chromatographic behavior of these compounds due to differences in ionic strength between sample and eluent were used to inter pret size-exclusion results from natural organic matter and ligninosulfonic acids. Since most of the substances used in this work do not absorb UV lig ht nor do they have any fluorescent capabilities, a continuous-flow DOC det ector was used to record the chromatograms.