A METHOD FOR ESTIMATION OF CHLORINATED BIPHENYLS IN SURFACE WATERS - INFLUENCE OF SAMPLING METHOD ON ANALYTICAL RESULTS

An accurate extraction and measurement procedure to determine chlorinated biphenyls (CBs) in surface waters was developed, and sampling techniques for removing suspended matter (SPM) were investigated. The procedure involved a 10-L batch liquid-liquid extraction directly from the sample bottle to prevent loss due to adsorption to the wall. Exhaustive extraction for recovery measurements was proposed, next to spikes, resulting in an extraction time of 10-45 h. A detection limit lower than 10 pg/kg and a coefficient of variation of 3-9% were obtained. Two sampling techniques to remove SPM were investigated: filtration and continuous-flow centrifugation. Filter clogging and adsorption affected the accuracy of the filtration technique. Insufficient separation of low-density particulate organic matter in continuous-flow centrifuge determined the CB contents measured in centrifugates. Results using these techniques for distribution or bioavailability studies are questionable because freely dissolved CBs and dissolved organic matter (DOM) bound CBs cannot be distinguished. Centrifugation may be applicable to transport studies.