GC-MS determination of polychlorinated biphenyls in water using extractive freezing-out of analytes

A method for determining polychlorinated biphenyls (PCBs) in water using the method of concentrating analytes through extractive freezing-out under the effect of a centrifugal forces (EFC) has been developed. A mathematical model for analyte extraction using a three-factor Box-Behnken design demonstrated that the content of acetonitrile in the extraction mixture is a significant factor, whereas the degree of PCBs chlorination and the concentration of analytes are insignificant parameters. Analysis of the surface area of the model allowed the determination of the optimal range of the acetonitrile concentration, which fell between 14 and 21%. A 15% content of acetonitrile in the extraction mixture provided maximum extraction efficiency for 7 different PCBs (>92%) across a wide range of analyte concentrations (1.0 – 5000 ng/liter). The relative standard deviations in the repeatability and reproducibility range from 4.2 to 6.8% and 5.3 to 8.1%, respectively, the accuracy of analyte determination being 10 – 15%. Petroleum hydrocarbons were not extracted into the acetonitrile extract and did not interfere with the determination of PCBs, which provided longer operation of the detector without any loss in the sensitivity. Co-extraction of polycyclic aromatic hydrocarbons and chlorinated pesticides did not affect the extraction of PCBs from water (95 – 100%) and did not touch on the metrological indicators of the determination procedure.