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GB/T 34270-2017: Determination of polychlorinated biphenyls and hexachlorobenzene in feeds - Gas chromatography Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid
Similar standardsGB/T 34270-2017: Determination of polychlorinated biphenyls and hexachlorobenzene in feeds - Gas chromatography---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GBT34270-2017 GB NATIONAL STANDARD OF THE PEOPLE'S REPUBLIC OF CHINA ICS 65.120 B 46 Determination of polychlorinated biphenyls and hexachlorobenzene in feeds - Gas chromatography ISSUED ON: SEPTEMBER 7, 2017 IMPLEMENTED ON: APRIL 1, 2018 Issued by: General Administration of Quality Supervision, Inspection and Quarantine of PRC; Standardization Administration of PRC. Table of ContentsForeword ... 3 1 Scope ... 4 2 Normative references ... 4 3 Principle ... 4 4 Reagents and materials ... 5 5 Instruments and equipment ... 6 6 Sampling and specimen preparation ... 6 7 Analysis steps ... 6 8 Result calculation ... 8 9 Repeatability ... 9 Appendix A (Informative) Chinese and English names, molecular formulas and CAS numbers of indicative PCBs and HCB ... 10 Appendix B (Informative) Chromatogram of the indicative PCB and HCB standard working solution ... 11ForewordThis standard was drafted in accordance with the rules given in GB/T 1.1-2009. This standard was proposed by and is under the jurisdiction of the National Technical Committee on Feed Industry of Standardization Administration of China (SAC/TC76). This standard was drafted by the Institute of Quality Standard and Testing Technology for Argo-products of Chinese Academy of Agricultural Sciences. Main drafters of this standard: Fan Li, Qiu Jing, Xu Hongda, Song Rong, Xiao Zhiming, Yang Shuming. Determination of polychlorinated biphenyls and hexachlorobenzene in feeds - Gas chromatography1 ScopeThis standard specifies the gas chromatography method for the determination of indicative polychlorinated biphenyls and hexachlorobenzene in feed. This standard is applicable to the determination of single or multiple contents of indicator polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, PCB180) and hexachlorobenzene (HCB) in compound feed, concentrated feed, additive premix, feed raw materials (except oils and fats) and feed additive copper sulfate. The detection limits of indicative polychlorinated biphenyls and hexachlorobenzene in this standard are both 0.5 μg/kg, and the quantification limits are both 2 μg/kg.2 Normative referencesThe following documents are essential to the application of this document. For referenced documents with dates, only the versions corresponding to the dates are applicable to this document; for referenced documents without dates, the latest versions (including all amendments) are applicable to this document. GB/T 603 Chemical reagent - Preparations of reagent solutions for use in test methods GB/T 6682 Water for analytical laboratory use - Specification and test methods GB/T 14699.1 Feed - Sampling GB/T 20195 Animal feed - Preparation of test samples3 PrincipleThe indicative polychlorinated biphenyls and hexachlorobenzene in the sample are extracted with n-hexane acetone solution and sulfonated with concentrated sulfuric acid, then determined by gas chromatography-electron capture detector (ECD) and quantified by external standard method.4 Reagents and materialsUnless otherwise specified, all reagents are analytically pure and conform to the secondary water specified in GB/T 6682. The preparations used in the test shall be prepared in accordance with the provisions of GB/T 603. In the analysis, high-purity reagents of pesticide residue grade are used, and blank tests are performed. Polychlorinated biphenyls and hexachlorobenzene shall not be detected when the organic reagents are concentrated 10,000 times. 4.1 n-Hexane: Pesticide residue grade. 4.2 Acetone: pesticide residue grade. 4.3 Anhydrous sodium sulfate: It shall be baked at 660 ℃ for at least 6 hours, stored in a sealed container in a desiccator, and used within one month. 4.4 Saturated sodium sulfate solution. 4.5 Concentrated sulfuric acid: a guaranteed reagent. 4.6 N-Hexane acetone solution: 1+1. Take 500 mL of n-hexane and 500 mL of acetone and mix them evenly. 4.7 Indicative polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB118, PCB138, PCB153, PCB180) and hexachlorobenzene standards: with a purity of ≥98.0%. The Chinese names, English names, molecular formulas and CAS numbers of the substances are shown in Table A.1. 4.8 Standard stock solution: Weigh the hexachlorobenzene standard and prepare a 100 μg/mL standard stock solution with n-hexane. Polychlorinated biphenyls are liquid standards and are diluted with n-hexane to 100 μg/mL standard stock solutions. Store at -20 ℃, valid for 6 months. 4.9 Mixed standard stock solution: Take appropriate amounts of hexachlorobenzene and indicative polychlorinated biphenyl standard stock solutions (4.8) respectively, and dilute with n-hexane to a mixed standard stock solution with a concentration of 1 μg/mL; store at -20 ℃, valid for 3 months. 4.10 Diatomaceous earth. 4.11 Microporous filter membrane: 0.22 μm, organic phase. WARNING: Polychlorinated biphenyls are carcinogens and must be handled with safety protection equipment. Weigh about 10 g (accurate to 0.001 g) of the specimen into a mortar, add 1 g of diatomaceous earth (4.10), grind evenly and transfer to a 34 mL ASE extraction cell. Use n-hexane acetone solution (4.6) as the extractant, at a temperature of 100 ℃, under a pressure of 10.3 MPa, preheat for 5 min, and statically extract for 10 min; quickly rinse the sample with 60% of the extraction cell volume of the extractant, and perform accelerated solvent extraction under nitrogen purge for 90 seconds. Collect all the extract and transfer it to a 100 mL pear-shaped flask, rotate and evaporate it under reduced pressure at 35 ℃ until almost dry, and dissolve it with 5 mL of n-hexane. 7.2 Purification Add 1 mL of concentrated sulfuric acid (4.5) for sulfonation, vortex for 30 seconds, centrifuge for 5 minutes, and discard the lower sulfuric acid layer; repeat the above operation until the organic phase is colorless; add 15 mL of saturated sodium sulfate aqueous solution (4.4), shake, let it stand, discard the water phase, and repeat washing until the pH of the water phase is 7. Take the organic phase and blow dry it with nitrogen at 35 °C, make it up to 1 mL with n-hexane, vortex for 30 seconds, filter it with a filter membrane, and then determine it by gas chromatography. 7.3 Determination 7.3.1 Standard curve drawing Accurately measure out an appropriate amount of the indicative PCB or HCB mixed standard stock solution (4.9), dilute it with n-hexane to mixed standard working solutions with a concentration of 0.01 μg/mL, 0.02 μg/mL, 0.10 μg/mL, 0.50 μg/mL, and 1.00 μg/mL for gas chromatography determination. Draw a standard curve with the concentration of each target substance in the above solutions as the abscissa and the corresponding peak area as the ordinate. 7.3.2 Gas chromatography reference conditions Chromatographic column: 50% phenyl 50% methyl polysiloxane capillary gas chromatography column (DB-17MS), with a specification of 30 m×0.25 mm×0.25 μm, or equivalent. Column temperature: Maintain at 60 ℃ for 1 min, raise the temperature to 180 ℃ at a rate of 10 ℃/min, and then increase the temperature to 280 ℃ at a rate of 4 ℃/min and maintain for 10 min. Inlet temperature: 300 ℃; non-split injection, split after 1 min. Electron capture detector (ECD) temperature: 300 °C. Column flow rate: 1.0 mL/min. 7.3.3 Qualitative and quantitative determination Respectively take appropriate amounts of the indicative PCB and HCB mixed standard working solution specified in 7.3.1 and the purified sample solution specified in 7.2 for determination. The chromatographic peak retention time shall be used for qualitative analysis. The relative deviation between the sample and the standard retention time shall not exceed 0.5%. The chromatographic peak signal-to-noise ratio (S/N) of the polychlorinated biphenyls (PCBs) shall be greater than 3. The chromatographic peak area response value is used for quantification of single-point or multi-point calibration. The chromatogram of the indicative PCB and HCB mixed standard working solution is shown in Appendix B.8 Result calculationThe content Xi of indicative PCBs and hexachlorobenzene in the specimen is expressed as a mass fraction, in mg/kg, and is calculated according to formula (1) for the single- point calibration method and formula (2) for the multi-point calibration method: Single-point calibration method: where: m -- Mass of the specimen, in grams (g); Ai -- Peak area of indicative polychlorinated biphenyls or hexachlorobenzene to be detected in the specimen; Asi -- Peak area of indicative polychlorinated biphenyls or hexachlorobenzene in the standard working solution; ci -- Concentration of indicative polychlorinated biphenyls or hexachlorobenzene in the standard working solution, in micrograms per milliliter (μg/mL); V -- The metered volume before injection, in milliliters (mL). The determination result is expressed as the arithmetic mean of parallel determinations, and the result is rounded to three significant figures. Multi-point calibration method:5 Instruments and equipment5.1 Gas chromatograph: It is equipped with an electron capture detector (ECD). 5.2 Analytical balance: The sensitivities are 0.1 mg and 0.01 mg. 5.3 Soxhlet extractor. 5.4 Accelerated solvent extraction (ASE) system: It is equipped with a 34 mL extraction cell. 5.5 Mortar. 5.6 Centrifuge: The speed is >10000 r/min. 5.7 Termovap Sample Concentrator. 5.8 Vortex mixer. 5.9 Ultrasonic cleaner. 5.10 Rotary evaporator.6 Sampling and specimen preparationTake a representative sample according to GB/T 14699.1 and reduce the sample by quartering. Prepare the specimen according to GB/T 20195; grind it, pass it through a 0.45 mm mesh sieve, mix it, put it into a sealed container, and store it at a low temperature away from light for later use.7 Analysis steps7.1 Extraction 7.1.1 Method 1: Soxhlet extraction Weigh about 5 g (accurate to 0.001 g) of the specimen, add 10 g of anhydrous sodium sulfate (4.3), wrap it with filter paper and place it in a Soxhlet extractor; add 100 mL of n-hexane (4.1), and extract for 10 hours (with a reflux rate of 10~12 times per hour); after cooling, transfer the extract into a 100 mL pear-shaped flask, rotate and evaporate it under reduced pressure at 35 °C to near dryness, and dissolve it with 5 mL of n-hexane for purification. 7.1.2 Method 2: Accelerated solvent extraction ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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