A new concept for the fractionation of DOM as a basis for its combined chemical and biological characterization

To overcome the problem of non-specific interactions during the preparative fractionation of dissolved organic matter (DOM) for its combined chemical and biological characterization, the concept of standardized fractions (SFs) was developed. The concept is based on the calibration of the fractionation systems with suitable standards for the experimental definition of SFs, and the subsequent preparative fractionation of DOM samples according to the pre-defined SFs. Undesired non-specific interactions can thus be minimized experimentally. It was applied to the fractionation methods size exclusion chromatography (SEC) and multistage ultrafiltration (mst-UF). A brownwater sample and an effluent from a sewage treatment plant were fractionated. The two methods performed rather differently which was evidenced both by the polydispersity of the resulting fractions as well as sum parameter fractionation patterns. Consequently, the interpretation of data obtained from the chemical–physical as well as biological analysis must always consider the limitations and particularities of the fractionation method employed.