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The sorption of seven endocrine disrupting chemicals (EDCs) to aquatic colloids was determined by cross-flow ultrafiltration (CFUF) followed by gas chromatography-mass spectrometry (GC-MS). Results show that the colloidal organic carbon normalized sorption coefficient (Kcoc) of EDCs to different aquatic colloids varies by a factor of 6-12 because such colloids are of different origin. Through characterization of colloidal samples, a significant relationship was established between Kcoc values and the molar extinction coefficient of colloids at 280 nm, whereas no other colloidal properties such as elemental ratios were correlated with Kcoc values. The results are consistent with other reports of the importance of the quality of sorbents such as their aromatic carbon content in sorbing various organic pollutants. The presence of a surfactant was found to increase Kcoc values for estrone (El) and 17alpha-ethynylestradiol (EE2). The method was subsequently applied for determining EDC concentrations in field samples, where both conventional and truly dissolved EDCs showed higher concentrations close to sewage outfalls than either upstream or downstream, confirming the sourceconcentration relationship. In addition, the truly dissolved EDC concentrations were lower than the conventional dissolved concentrations, confirming that there were interactions between aquatic colloids and EDCs. It is estimated that between 10 and 29% of EDCs are associated with aquatic colloids. As colloids are highly abundant in rivers and ocean, they will therefore play a significant role in the environmental behavior and fate of EDCs.

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Interactions between pharmaceuticals and aquatic colloids are a key process regulating their environmental fate, but poorly understood. A validated cross-flow ultrafiltration (CFUF) system was used to isolate river colloids and to determine the partition of selected pharmaceuticals between colloidal (>1 kDa but <0.7 microm) and dissolved phases (<1 kDa) by liquid chromatography-tandem mass spectrometry (LC-MS-MS). The kinetics of pharmaceutical binding to colloids was rapid, reaching equilibrium within 5 min. The mass balance of chosen pharmaceuticals through CFUF system was satisfactory for propranolol, sulfamethoxazole, meberverine, carbamazepine, indomethacine, diclofenac, and meclofenamic acid. The partition coefficient normalized to colloidal organic carbon content (Kcoc) varied from 5.45 x 10(4) to 7.54 x 10(5) mL/g for the chosen pharmaceuticals, which are greater than those for endocrine disrupting chemicals (EDCs), suggesting substantially stronger colloidal interactions with pharmaceuticals than with EDCs. Linear relationships were demonstrated between log-Kcoc, and pharmaceutical properties such as log Kow (octanol-water partition coefficient), highlighting the importance of compound hydrophobicity in controlling their binding with colloids. Such a finding is in contrast to that for EDCs whose Kcoc values were independent of their Kow values. The CFUF-LCMS technique has the potential to become a widely applicable tool for quantifying the distribution of emerging organic pollutants between nanoparticles and the dissolved phase.

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