This standard specifies the determination methods of contents and toxic equivalent quantities (TEQ) of 17 species of 2, 3, 7, 8-substituted polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and 12 species of dioxins and dioxin-like polychlorinated biphenyls (DL-PCBs) in foods.
This standard is applicable to determine the content and TEQ of 17 species of 2, 3, 7, 8-substituted polychlorinated dibenzodioxins, polychlorinated dibenzofurans (PCDD/Fs) and 12 species of DL-PCBs specified in Table A.1 in Appendix A.
2. Principle
Monitor two ions of the target compound through accurately mass measurement with high-resolution gas chromatography-mass spectrometry, under resolution rate of mass spectrum greater than 10,000; obtain the specific response of target compound; exactly determine the content of 2, 3, 7, 8 chlorine substituted PCDD/Fs and DL-PCBs in foods with the isotope labeled compound of target compound as quantitative internal standard through stable isotope dilution; multiply the toxic equivalency factor (TEF)of each target compound with the measured content, accumulate the results, and then obtain the toxic equivalent quantity (TEQ) of the dioxin and dioxin-like compounds in the sample.
3. Reagents and Materials
3.1 Organic solvents
Note: the following organic solvents are pesticide residues, in which, dioxin and dioxin-like compounds shall not be detected after being concentrated by 10,000 times.
3.1.1 Acetone (C3H6O).
3.1.2 N-hexane (C6H14).
3.1.3 Toluene (C7H8).
3.1.4 Cyclohexane (C6H12).
3.1.5 Dichloromethane (CH2Cl2).
3.1.6 Ethyl ether (C4H10O).
3.1.7 Methanol (CH3OH).
3.1.8 N-nonane (C9H20).
3.1.9 Isooctane (C8H18).
3.1.10 Ethyl acetate (CH3COOCH2CH3).
3.1.11 Ethanol (CH3CH2OH).
3.2 Standard solutions
3.2.1 PCDD/Fs standard solution
Note: standard solution specified in EPA 1613-1997 is recommended in this standard, and equivalent standard product may be selected for each laboratory according to specific conditions. The preparation of stock solution, where required, shall be carried out in ventilating cabinet; gas mask shall be provided.
3.2.1.1 Standard solution (CS3WT solution) for calibration and time window determination: solution prepared with nonane and containing natural and isotope labeled PCDD/Fs (quantitative internal standard, purification standard and internal recovery standard); it is used for calibration and corroboration of method, determination of DB5MS capillary column (or equivalent column) time window, and inspection for separation degree of 2, 3, 7, 8-TCDD (see Table B.1 in Appendix B).
3.2.1.2 Standard purification solution: 37C14-2, 3, 7, 8-TCDD solution (with concentration of 40±2μg/L) prepared with nonane.
