Fully automated robotic method for the screening of polychlorinated biphenyls in used mineral oils

A screening method for the determination of polychlorinated biphenyls (PCBs) in waste mineral oils based on dechlorination by sodium and potentiometric measurement is proposed. The method is fully automated by a robotic station in which the robot performs the neighing of the sample, adds the reagents, develops a liquid-liquid extraction and obtains the chloride concentrations using a chloride-selective electrode. The data are acquired and treated by the computer. The method affords a detection limit of 1 mu g g(-1) chloride and a precision, expressed as relative standard deviation, of 3.2% which corresponds to a detection limit of 12 mu g g(-1) for Aroclor 1242. This detection limit is far below the regulatory limit of 50 mu g g(-1) which establishes whether or not a waste oil is contaminated by PCBs, The sample throughput is 12 h(-1).