Determination of Polychlorinated Biphenyls in Water Using Gas Chromatography–Mass Spectrometry with Extractive Freezing-Out of Analytes

A method for determining polychlorinated biphenyls (PCBs) in waters using preliminary concentration of analytes through extractive freezing-out under the action of centrifugal forces (EFC) is developed. According to the mathematical model of extraction constructed using the three-factorial Box–Behnken plan, the significant factor is the content of acetonitrile in the extraction mixture, and the insignificant factors are the degree of chlorination of PCBs and the concentration of analytes. Analysis of the surface area of this model allows one to establish the region of optimal values of acetonitrile concentration in the range from 14% to 21%. The acetonitrile content of 15% in the extraction mixture ensures the maximum extraction efficiency of seven different PCBs (>92%) in a wide range of their concentrations (from 1.0 to 5000 ng/L). The relative standard deviations of repeatability and reproducibility of the analysis results are in the range from 4.2 to 6.8% and from 5.3 to 8.1%, respectively, at an error in determining the analytes being 10–15%. Petroleum hydrocarbons are not extracted into the acetonitrile extract and do not interfere with the determination of PCBs, which also ensures longer detector operation without loss of sensitivity. Co-extraction of polyaromatic hydrocarbons and organochlorine pesticides does not affect the extraction of PCBs from waters (95–100%) and does not affect the metrological indicators of the determination method.