GB/T 8381.8-2005 Determination of polychlorobiphenyls (PCBs) in feed - Gas chromatography
1 Scope
This standard specifies a method for the determination of polychlorinated biphenyls (PCBs) in feed using gas chromatography with an electron capture detector.
This standard is applicable to the determination of PCBs in compound feed, additive premixes, and fish meal. The minimum detectable concentration of the method is 0.01 μg/g.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections) to, or revisions, of any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document applies.
GB/T 6682 Water for analytical laboratory use - Specification and test methods
GB/T 14699.1 Feeding stuffs - Sampling
3 Principle
The specimen is extracted with n-hexane, and the extract is subjected to sulfonation with concentrated sulfuric acid, followed by purification through a silica gel column. The purified solution is then analyzed by gas chromatography equipped with an electron capture detector.
4 Reagents and materials
The water used shall meet the requirements for Grade 3 water as specified in GB/T 6682.
4.1 N-hexane: Analytical grade, redistilled in an all-glass apparatus.
4.2 Isooctane: Guaranteed reagent grade.
4.3 Concentrated sulfuric acid: Guaranteed reagent grade.
4.4 Anhydrous sodium sulfate: Guaranteed reagent grade, burned at a temperature of 550°C for 4h, then cooled and stored in a dryer.
4.5 Silica gel: Analytical grade, with particle size of 0.075-0.150 mm (100–200 mesh), dried at 130°C for 16h, then cooled and stored in a dryer.
4.6 PCB reference solution: Take 2.0 mL of the polychlorobiphenyl Aroclor1242 stock solution with a concentration of 187.7 μg/mL, and dilute it to 50 mL with isooctane to prepare a working solution with a concentration of 7.5 μg/mL. Then, take 1 mL, 2.5 mL, and 5 mL of this working solution, respectively, and dilute each to 25 mL to prepare a series of reference solutions with concentrations of 0.30 μg/mL, 0.75 μg/mL, and 1.50 μg/mL for standby. Store at 4°C in a refrigerator, protected from light, with the useful life of 6 months.
4.7 20 g/L sodium sulfate solution: Dissolve 20g sodium sulfate in water and dilute to 1L in a volumetric flask.
5 Apparatus
5.1 Gas chromatograph: Equipped with an electron capture detector.
5.2 All-glass redistillation apparatus.
