High-Performance Liquid Chromatographic Study on Oxidation Products of Lignin and Humic Substances

We describe a convenient method of preparing samples and characterizing the mixture of degradation products obtained from alkaline cupric oxide oxidation of water samples containing lignin and humic substances. The method was applied to one unpolluted humic water sample and a total mill effluent of a kraft pulp mill. The fractions (Mr > 1000) obtained by ultrafi1tration were oxidized and the products (mixtures of degradation products) were analyzed by reversed-phase high-performance liquid chromatography (Spherisorb 5 ODS column). Acetonitrile-0.01 M phosphate buffer (pH 2) was used as the eluent in a gradient system and UV (set at 280 nm) as the detection system. Differences in the chromatograms of the high molecular mass fractions (Mr > 1000) of the samples studied can be used to characterize natural lignin and humic substances of various origins and to distinguish between natural humic matter and lignin compounds formed in the pulp industry.