Pcdfs

All the solvents used for extraction and clean-up procedures were of pesticide residue analysis grade, and were purchased from Duksan (South Korea). Florisil solid-phase exchange cartridges (1000 mg, 6 mL), multi-layer silica-gel columns, and silica-gel dispersed carbon columns (Kanto Chemicals Co., Japan) were utilized for clean-up procedures. ¹³C-labeled standard solutions of PCDDs, PCDFs, PeCBz, HxCBz (Cambridge Isotope Laboratories, USA) and dl-PCBs (Wellington Laboratories, Canada) were used as internal standards. Unlabeled standard solutions and 1,2,4,5-tetrabromobenzene were purchased from AccuStandard (USA).

Carbon-13-labeled and carbon-13-unlabeled polychlorinated dibenzo-p-dioxins (PCDDs) were obtained from Wellington Laboratories Inc. (Guelph, ON, Canada); PCDFs, PCBs, and PBDEs from Cambridge Isotope Laboratories Inc. (Tewkesbury, MA, USA); other ¹³C-labeled and ¹³C-unlabeled POPs from Wako Pure Chemical Industries, Ltd. (Osaka, Japan); and 263 unlabeled pesticides from Kanto Chemical Co., Inc. (Tokyo, Japan).