A new scheme of dispersive liquid-liquid microextraction of polychlorinated biphenyls having different degrees of chlorination from waters with subsequent identification by gas chromatography coupled with mass spectrometry

Abstract

This study offers a theoretical rationale and experimental validation of extraction of 22 polychlorinated biphenyls (PCBs) having various degrees of chlorination (including five dioxin-like ones: PCB-105, PCB-118, PCB-156, PCB-157, and PCB-167) from waters of various salinity levels by dispersive liquid–liquid microextraction (DLLME) using various extractants and mixtures of aliphatic alcohols for additional dispersion, with subsequent identification by gas chromatography coupled with mass spectrometry. To optimize the conditions of DLLME and of concentrating PCBs of various degrees of chlorination, the experiment was planned via the three-factor Box–Behnken design (response surface methodology). Composition and ratios of components were found for the extractant mixture, and composition of the dispersive agent was optimized. Effective recovery of the 22 congeners from waters with salinity ranging between 1‰ and 22‰ was ensured by an extractant mixture consisting of chloroform, dichloromethane, and carbon tetrachloride and by a dispersive agent composed of acetone, ethyl acetate, ethyl alcohol, and isopropyl alcohol. The newly developed sample preparation scheme is compatible with gas chromatography coupled with mass spectrometry, and limits of detection and quantitation varied as follows: 0.0075–0.0150 and 0.025–0.050 µg/L, respectively. The newly developed assay allows to quantify the analytes at concentrations of 0.025–15 µg/L in waters, with recovery 90–105% and relative standard deviation 4–8%.