Centrifugal partition chromatographic extraction of phenols and organochlorine pesticides from water samples

As part of an ongoing evaluation of new sample preparation methods conducted by the U.S. Environmental Protection Agency through the Environmental Monitoring Systems Laboratory - Las Vegas, especially those meethods that minimize waste solvent generation, we investigated the feasibility of using centrifugal partition chromatography (CPC) to extract parts-per-billion levels of phenols and organochlorine pesticides (OCPs) from aqueous samples. In this paper, we report on the optimization of a CPC extraction technique, discuss the effects of five variables (i.e., extraction solvent, sample loading flow rate, volume of displaced extraction solvent, ionic strength, and presence of humic materials in the aqueous sample) on the extraction of 13 phenols and 20 OCPs, and present recovery data for these analytes from spiked reagent water and spiked wastewater samples. Our results indicate that methylene chloride is more effective than hexane in extracting phenols but only slightly better than hexane in extracting OCPs. CPC appears to perform much better than conventional liquid-liquid extraction for phenols but not for OCPs, and our results also show that the target compounds are extracted into a very small volume of solvent, which means that the CPC technique can be used to concentrate such compounds from a relatively large volume of aqueous matrix (e.g., 100 mL) into a small volume of solvent (e.g., 2 mL). Therefore, the CPC technique reduces extraction solvent consumption and eliminates additional sample workup.