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GB 5009.17-2021: Determination of total mercury and organic-mercury in foods Delivery: 9 seconds. True-PDF full-copy in English & invoice will be downloaded + auto-delivered via email. See step-by-step procedure Status: Valid GB 5009.17: Historical versions
Similar standardsGB 5009.17-2021: Determination of total mercury and organic-mercury in foods---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/GB5009.17-2021GB NATIONAL STANDARD OF THE PEOPLE’S REPUBLIC OF CHINA National Food Safety Standard - Determination of Total Mercury and Organic-mercury in Food Issued on. SEPTEMBER 7, 2021 Implemented on. MARCH 7, 2022 Issued by. National Health Commission of the People’s Republic of China; State Administration for Market Regulation. Table of ContentsForeword... 4 1 Scope... 5 Part 1.Determination of Total Mercury in Food... 5 Method 1 -- Atomic Fluorescence Spectrometry... 5 2 Principle... 5 3 Reagents and Materials... 5 4 Instruments and Equipment... 7 5 Analytical Procedures... 7 6 Expression of Analytical Results... 10 7 Precision... 11 8 Others... 11 Method 2 -- Direct Injection Method for Mercury Determination... 11 9 Principle... 11 10 Reagents and Materials... 12 11 Instruments and Equipment... 13 12 Analytical Procedures... 13 13 Expression of Analytical Results... 14 14 Precision... 15 15 Others... 15 Method 3 -- Inductively Coupled Plasma Mass Spectrometry... 15 Method 4 -- Cold Atomic Absorption Spectrometry... 15 16 Principle... 15 17 Reagents and Materials... 16 18 Instruments and Equipment... 17 19 Analytical Procedures... 17 20 Expression of Analytical Results... 18 21 Precision... 19 22 Others... 19 Part 2.Determination of Methyl Mercury in Food... 19 Method 1 -- Liquid Chromatography - Atomic Fluorescence Spectrometry... 19 23 Principle... 19 24 Reagents and Materials... 19 25 Instruments and Equipment... 22 26 Analytical Procedures... 23 27 Expression of Analytical Results... 25 28 Precision... 251 ScopePart 1 of this Standard specifies the methods for the determination of total mercury in food. Part 1 of this Standard is applicable to the determination of total mercury in food. Part 2 of this Standard specifies the methods for the determination of methyl mercury in food. Part 2 of this Standard is applicable to the determination of methyl mercury in aquatic animals and their products, as well as rice and edible fungi. Part 1.Determination of Total Mercury in Food Method 1 -- Atomic Fluorescence Spectrometry2 PrincipleAfter the specimen is heated and digested by acid, in the acidic medium, the mercury in the specimen is reduced to atomic-state mercury by potassium borohydride or sodium borohydride, which is brought into the atomizer by the carrier gas (argon). Under the irradiation of mercury hollow cathode lamp, the ground-state mercury atoms are excited to a high-energy state. When they return from the high-energy state to the ground-state, they emit fluorescence with a characteristic wavelength. The fluorescence intensity is directly proportional to the mercury content, which is quantified by the external standard method.3 Reagents and MaterialsUnless it is otherwise specified, the reagents used in this Method are of top-grade purity, and the water is Grade-1 water specified in GB/T 6682. 3.1 Reagents 3.1.1 Nitric acid (HNO3). 3.1.2 Hydrogen peroxide (H2O2). 3.1.3 Sulfuric acid (H2SO4). 3.1.4 Potassium hydroxide (KOH). 3.1.5 Potassium borohydride (KBH4). analytically pure. 3.1.6 Potassium dichromate (K2Cr2O7). 3.2 Preparation of Reagents 3.2.1 Nitric acid solution (1 + 9). measure-take 50 mL of nitric acid; slowly add it to 450 mL of water; mix it up. 3.2.2 Nitric acid solution (5 + 95). measure-take 50 mL of nitric acid; slowly add it to 950 mL of water; mix it up. 3.2.3 Potassium hydroxide solution (5 g/L). weigh-take 5.0 g of potassium hydroxide; use water to dissolve it and dilute to 1,000 mL; mix it up. 3.3 Standard Substance Mercury chloride (HgCl2, CAS No.. 7487-94-7). purity ≥ 99%. 3.4 Preparation of Standard Solutions4 Instruments and Equipment4.1 Atomic fluorescence spectrometer. equipped with a mercury hollow cathode lamp. 4.2 Electronic balance. with a division value of 0.01 mg, 0.1 mg and 1 mg. 4.3 Microwave digestion system. 4.4 Pressure digester. 4.5 Constant-temperature drying oven (50 °C ~ 300 °C). 4.6 Temperature-controllable electric heating plate (50 °C ~ 200 °C). 4.7 Ultrasonic water bath. 4.8 Homogenizer. 4.9 High-speed pulverizer.5 Analytical Procedures5.1 Pre-treatment of Specimens 5.2 Digestion of Specimens 5.2.1 Method of microwave digestion Weigh-take 0.2 g ~ 0.5 g of solid specimen (accurate to 0.001 g; for samples with relatively more water content, the sampling amount may be properly increased to 0.8 g), or accurately weigh-take 1.0 g ~ 3.0 g of liquid specimen (accurate to 0.001 g). For samples that are difficult to digest, for example, vegetable oils, weigh-take 0.2 g ~ 0.5 g (accurate to 0.001 g). Place it in a digestion tank; add 5 mL ~ 8 mL of nitric acid; put on the lid and let it stand for 1 h. For samples that are difficult to digest, add 0.5 mL ~ 1 mL of hydrogen peroxide; tightly screw the lid; in accordance with the standard operating procedures of the microwave digestion apparatus (please refer to Table A.1 in Appendix A for the reference conditions of microwave digestion), conduct the digestion. After cooling it down, take it out; slowly open the lid of the tank to exhaust air; 5.2.2 Method of pressure tank digestion Weigh-take 0.2 g ~ 1.0 g of solid specimen (accurate to 0.001 g; for samples with relatively more water content, the sampling amount may be properly increased to 2 g), or accurately weigh-take 1.0 g ~ 5.0 g of liquid specimen (accurate to 0.001 g). For samples that are difficult to digest, for example, vegetable oils, weigh-take 0.2 g ~ 0.5 g (accurate to 0.001 g). Place it in a digestion tank; add 5 mL of nitric acid; let it stand for 1 h or overnight. Put on the inner lid; tightly screw the stainless steel enclosure; put it in a constant-temperature drying oven; at 140 °C ~ 160 °C, maintain for 4 h ~ 5 h. 5.2.3 Method of reflux digestion 5.2.3.1 Grains Weigh-take 1.0 g ~ 4.0 g (accurate to 0.001 g) of specimen; place it in a conical flask of the digestion device. Add several glass beads; add 45 mL of nitric acid and 10 mL and sulfuric acid; rotate the conical flask to prevent local carbonization. After installing the condenser pipe, heat it up at a low temperature. When it starts foaming, stop heating. After foaming stops, heat to reflux for 2 h. If the solution turns brown during the heating process, add 5 mL of nitric acid and continue to reflux for 2 h. Conduct digestion, until the sample is completely dissolved, which is generally pale yellow or colorless. After cooling, carefully add 20 mL of water from the upper end of the condenser pipe; continue to heat and reflux for 10 min. After leaving it to cool down, use an appropriate amount of water to rinse the condenser pipe; incorporate the rinsing liquid into the digestive fluid. Filter the digestive fluid through glass wool into a 100 mL volumetric flask; use a small amount of water to wash the conical flask and filter. Incorporate the washing liquid into the volumetric flask; add water to the scale; mix it up for later use. Meanwhile, conduct a blank test. 5.2.3.5 Milk and dairy products Weigh-take 1.0 g ~ 4.0 g (accurate to 0.001 g) of specimen, place it in a conical flask of the digestion device. Add several glass beads and 30 mL of nitric acid; for milk, add 10 mL of sulfuric acid; for dairy products, add 5 mL of sulfuric acid. Rotate the conical flask to prevent local carbonization. The subsequent steps are the same as 5.2.3.1 “After installing the condenser pipe, heat it up with a small fire... Meanwhile, conduct a blank test”. 5.3 Determination6 Expression of Analytical ResultsThe mercury content in the specimen shall be calculated in accordance with Formula(1).7 PrecisionWhen the mercury content in the sample is greater than 1 mg/kg, the absolute difference between two independent determination results obtained under repeatability conditions shall not exceed 10% of the arithmetic mean value. When the mercury content in the sample is less than or equal to 1 mg/kg, and greater than 0.1 mg/kg,8 OthersWhen the mass of the sample is 0.5 g and the constant volume is 25 mL, the detection limit of this Method is 0.003 mg/kg;9 PrincipleAfter the sample is burned at a high temperature and is subject to catalytic pyrolysis, mercury is reduced to elemental mercury. Use gold amalgam for enrichment or directly bring into the detector by carrier gas. At a wavelength of 253.7 nm, measure the atomic absorption signal of mercury, or use a mercury lamp to excite the atomic fluorescence signal of the mercury being detected, which is quantified by the external standard method.10 Reagents and MaterialsUnless it is otherwise specified, the reagents used in this Method are of top-gradepurity, 10.1 Reagents 10.2 Preparation of Reagents 10.3 Standard Substance Mercury chloride (HgCl2, CAS No.. 7487-94-7). purity ≥ 99%. 10.4 Preparation of Standard Solutions 10.4.1 Standard stock solution of mercury (1,000 mg/L). same as 3.4.1. 10.4.2 Standard intermediate solution of mercury (100 mg/L). accurately draw 10.0 mL of the standard stock solution of mercury (1,000 mg/L) in a 100 mL volumetric flask; 10.4.3 Standard working solution of mercury (10.0 mg/L). accurately draw 10.0 mL of the standard intermediate solution of mercury (100 mg/L) into a 100 mL volumetric flask; use nitric acid solution of potassium dichromate (0.5 g/L) to dilute it and reach a constant volume to the scale; mix it up. Store it at 2 °C ~ 8 °C in the refrigerator; keep away from light; it shall remain valid for 1 year.11 Instruments and Equipment11.1 Direct mercury meter. 11.2 Electronic balance. with a division value of 0.01 mg, 0.1 mg and 1 mg. 11.3 Homogenizer. 11.4 High-speed pulverizer. 11.5 Sample boat. nickel boat or quartz boat. 11.6 Carrier gas. oxygen (99.9%) or air; argon-hydrogen mixture (9.1, volume ratio) (99.9%).12 Analytical Procedures12.1 Pre-treatment of Specimens 12.1.1 In terms of grains and beans, take the edible part and evenly crush it, with a particle size of 425 μm or less (equivalent to 40 mesh or more). Put it into a clean polyethylene bottle; seal and store it for later use. 12.1.2 In terms of samples with relatively more water content, for example, vegetables, if necessary, wash and drain them; take the edible part and homogenize it. For samples like aquatic products, meat and eggs, take the edible part and homogenize it. Put it in a clean polyethylene bottle; seal it; store it at 2 °C ~ 8 °C in the refrigerator for later use. 12.2 Determination 12.2.1 Reference conditions of instrument In accordance with the performance of the used direct mercury meter, adjust to the optimum state. The reference conditions of catalytic pyrolysis gold amalgam cold atomic absorption mercury meter are shown in Table B.1 in Appendix B; the reference conditions of catalytic pyrolysis gold amalgam atomic fluorescence mercury meter are shown in Table B.2; the reference conditions of pyrolysis cold atomic absorption mercury meter are shown in Table B.3. 12.2.2 Sample boat purification After the sample ash remaining in the sample boat is cleaned up, adopt the built-in heating program of the instrument or muffle furnace to conduct high-temperature burning (600 °C ~ 800 °C) for more than 20 min to remove the mercury residue. ......Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al. 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