Isolation of Marine Sediment Colloids and Associated Polychlorinated Biphenyls:  An Evaluation of Ultrafiltration and Reverse-Phase Chromatography

Environmental colloids are suspected of having significant effects on nonpolar organic contaminant geochemistry, transport, and bioavailability. However, environmental data on colloid−contaminant interactions is limited because isolating colloids from the dissolved and particulate phases is problematic. In this study, two practical methods using ultrafiltration and reverse-phase chromatography were evaluated for isolating environmentally contaminated marine sediment interstitial water colloids and associated PCBs. In assessing each method, ultrafiltration demonstrated extensive sorption of radiolabeled nonpolar compounds (>90%) and a re-occurring breakthrough phenomena, both of which compromise the method for accurately assessing colloid−PCB interactions. Conversely, C 18 reverse-phase chromatography, performed using laboratory-packed columns, generated reproducible organic carbon-normalized colloidal partitioning coefficients ( K coc ) that agreed with literature and theoretical considerations. Evaluations of sample flow rate and prefiltration size along with potential for C 18 bed saturation indicated that these parameters have only a minor (e.g., less than a factor of 2) effect on the calculated contaminant distribution coefficients. Of the two methods evaluated, reverse-phase chromatography was the most promising for quantifying environmental colloid−PCB interactions.