Determination of Polychlorinated Biphenyl Enantiomers in Lotus Root and Sediment by Chiral Gas Chromatography-Mass Spectrometry

An enantioselective method was developed for the separation and determination of six chiral polychlorinated biphenyls (PCBs) including PCB 91, 95, 136, 149, 176 and 183 in lotus root, stem, leaf and sediment by gas chromatography-mass spectrometry (GC-MS). After optimization of instrumental parameters for enantiomeric separation and investigation of sample preparation steps including accelerated solvent extraction (ASE) parameters, extraction solvents and cleanup methods, PCB atropisomers were extracted from samples by ASE with n-hexane/acetone (1:1, V/V) at 100 degrees C and 10.3 MPa for 10 min. The extracts were cleaned with sulfuric acid, purified by Florisil solid phase extraction, reconstituted with isooctane after concentration, and detected by GC-MS with Chirasil-Dex and BGB-172 columns. Good linearity was obtained in the concentration range of 0.5-100 mu g L-1 for all analytes. The recoveries of spiked samples at 0.25, 2.5 and 25 mu g kg(-1) were 82.8%-117.0% with relative standard deviations (RSDs) of 1.5%-13.6%. The limits of detection (LOD) and limits of quantification (LOQ) were 0.01-0.02 mu g kg(-1) and 0.025-0.04 mu g kg(-1), respectively. Chiral PCBs were not detected in lotus roots from markets, but higher concentrations were found in lotus root and sediment from a contaminated area. The concentrations of the second-eluted PCB 91, first-eluted PCB 95 and (+)-PCB 136 atropisomers in lotus root, stem and leaf were higher than those of their respective antipodes, while no significant differences between the two enantiomers of PCB 149, 176 and 183 were found.