High‐pressure size exclusion chromatography analysis of dissolved organic matter isolated by tangential‐flow ultrafiltration

Abstract

A 1,000-Dalton tangential-flow ultrafiltration (TFUF) membrane was used to isolate dissolved organic matter (DOM) from several freshwater environments. The TFUF unit used in this study was able to completely retain a polystyrene sulfonate 1,800-Dalton standard. Unaltered and TFUF-fractionated DOM molecular weights were assayed by high-pressure size exclusion chromatography (HPSEC). The weight-averaged molecular weights of the retentates were larger than those of the raw water samples, whereas the filtrates were all significantly smaller and approximately the same size or smaller than the manufacturer-specified pore size of the membrane. Moreover, at 280 nm the molar absorptivity of the DOM retained by the ultrafilter is significantly larger than the material in the filtrate. This observation suggests that most of the chromophoric components are associated with the higher molecular weight fraction of the DOM pool. Multivalent metals in the aqueous matrix also affected the molecular weights of the DOM molecules. Typically, proton-exchanged DOM retentates were smaller than untreated samples. This TFUF system appears to be an effective means of isolating aquatic DOM by size, but the ultimate size of the retentates may be affected by the presence of metals and by configurational properties unique to the DOM phase.The isolation and characterization of aquatic dissolved organic matter (DOM) in both limnological and oceanic environments has been the focus of a number of studies (Aiken et al.

Characterizing the properties of dissolved organic matter isolated by XAD and C-18 solid phase extraction and ultrafiltration

“…Splits of the water samples were isolated by tangential flow ultrafiltration (TFUF) using the methods described in Everett et al (1999). Briefly, filtered and acidified water samples were passed through a tangential-flow UF system (Amicon CH2M) equipped with a 1000 Dalton membrane.…”

“…UF is a physical separation process that segregates based upon size even though matrix effects, e. g., ionic strength and pH influences the efficiency of the method. Molecular weight cutoff ranges for ultrafiltration membranes used to isolate DOM are typically 1 to 3 KDa, and efficiencies range from 20 to 99 % of the total DOM in a whole water sample (McCarthy et al, 1996;Benner et al, 1997;Burdige and Gardner, 1998;Everett et al, 1999;Hedges et al, 2000;Kaiser et al, 2003;.…”

Sources and distribution of organic carbon and nitrogen in the Tagliamento River, Italy

“…For removal of trace metals for 13 C NMR experiments, two solid phase extracted and one ultrafiltered DOM sample (see Fig. 6 D, E, F) were cation-exchanged (Bio-Rad, AG 50W and AG MP-50, Everett et al, 1999). All DOM concentrates were freeze-dried to a powdery solid phase.…”

Distribution of dissolved organic carbon and dissolved fulvic acid in mesotrophic Lake Biwa, Japan

“…Yamada et al (2000) successfully determined the humic substances in river waters by GPC with a fluorescent detector using Aldrich humic acid as a standard. Recently, high-performance sizeexclusion chromatography (HPSEC) has been applied to the characterization of aquatic humic substances (Peuravuori and Pihlaja 1997;Cabaniss et al 2000;Perminova et al 2003) and dissolved organic matter (Everett et al 1999;Minor et al 2002;Muller and Frimmel 2002). HPLC has the advantages for routine analysis in terms of reproducibility, separability, and its applicability to small sample volumes.…”