Determination of PCBs, PCDDs and PCDFs in insulating oil samples from stored Chinese electrical capacitors by HRGC/HRMS

► Chinese PCBs oil (PCB3) was firstly determined by isotope dilution using HRGC/HRMS. ► Homologue and congener profiles of PCBs was firstly reported. ► TriCBs, TetraCBs, and DiCBs were found to be most abundant. ► Twelve PCB congeners account for more than 50% of the total PCBs concentration. ► Detailed concentrations of PCDDs, PCDFs and dioxin-like PCBs were also reported. Homologue and congener profiles of polychlorinated biphenyls (PCBs), polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in commercial PCBs formulations are key information for the source identification of PCBs contamination as well as for the risk assessment caused by potential exposure. The isotope dilution technology in combination with high resolution gas chromatography–high resolution mass spectrometry (HRGC/HRMS) has made the accurate determination of such profiles possible. So far, various commercial PCB formulations except Chinese products have been successfully determined. Two PCBs containing insulating oil samples from stored Chinese electrical capacitors have been determined with the same methodology for comparability. The total concentration PCBs in two oil samples were 790 000 μg g −1 and 720 000 μg g −1, respectively. TriCBs, TetraCBs, and DiCBs were found to be most abundant. Concentration of dioxins contamination in two samples is 650–670 ngTEQ g −1, of which 69–71 ngTEQ g −1 from PCDD/Fs with the predominant congeners of 1,2,7,8-TeCDF; 2,3,7,8-TeCDF; 2,3,4,7,8-PeCDF and 1,2,3,7,8-PeCDF. The contributions of DL-PCBs in total TEQ in both samples were more than 85%. The dioxin-like toxicity in insulating oils contained in electrical capacitors could be considered receive attention as an important dioxins source if such wastes are not managed in an environmentally sound manner.