Introduction of DEAE Sepharose for isolation of dissolved organic matter

An anion exchange resin, diethylaminoethyl (DEAE) Sepharose ® , was utilized for the isolation of dissolved organic matter (DOM) from fresh waters as an alternative to the discontinued DEAE cellulose. We used the following two chemically distinct model DOM samples to determine the optimized adsorption conditions onto DEAE Sepharose: the International Humic Substances Society’s standard samples, Suwannee River Fulvic Acid (FA) and Pony Lake FA. The optimized conditions consisted of the following: a contact time of 1 h (with shaking), a resin dosage of 1 ml mgC −1 , and a dissolved organic carbon (DOC) concentration range of 1–100 mgC l −1 . In addition, we examined the distribution of the DOM fractions extracted with DEAE Sepharose and DAX-8 from Lake Biwa (Japan) and Scottish river DOM samples. The majority of DOM (70% and 65%) was extracted by both of the resins. As indicated by 1 H NMR, the evapo-concentrate (bulk DOM), the DEAE Sepharose fraction and the DAX-8 fraction from the Scottish DOM sample had substantial similarity in their proton distributions, while those of a clear-colored, low DOC sample (Lake Biwa) showed different NMR spectra. These findings highlight a need to pay more attention to the extraction selectivity of resins for experimentally ‘challenging’ samples.