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This standard shall replace GB/T 5009.17-1996 "Method for Determination of Total Mercury in Foods" and 4.6 ‘Methyl Mercury’ of GB/T 5009.45-1996 "Method for Analysis of Hygienic Standard of Fish and Other Aquatic Products".
There have been some significant changes in this standard over GB/T 5009.17-1996 "Method for Determination of Total Mercury in Foods" and 4.6 ‘Methyl Mercury’ of GB/T 5009.45-1996 "Method for Analysis of Hygienic Standard of Fish and Other Aquatic Products".
——the Chinese title of the standard was amend into《食品中总汞及有机汞的测定》;
——the structure of the previous edition was amended according to GB/T 20001.4-2001 "Rules for Drafting Standards--Part 4: Methods of Chemical Analysis";
——the Hydride Generation-Atomic Fluorescence Spectrometry was added as the first method for determination of total mercury;
——4.6 ‘Methyl Mercury’ in GB/T 5009.45-1996 "Method for Analysis of Hygienic Standard of Fish and Other Aquatic Products" was used for the determination of methyl mercury.
This standard was proposed by and is under the jurisdiction of the Ministry of Health of the People's Republic of China.
The first determination method of total mercury in this standard was drafted with the participation of Institute of Food Safety Control and Inspection Ministry of Public Health of the People's Republic of China, Beijing Institute of Food Safety Control and Inspection, Sichuan Provincial Institute of Food Safety Control and Inspection and Beijing Institute of Imported Food Safety Control and Inspection.
Section (I) in the second determination method of total mercury in this standard was drafted by the Shanghai Institute of Food Safety Control and Inspection, the Institute for Nutrition and Food Safety of the Chinese Academy of Preventive Medicine, and the Institute of Food Safety Control and Inspection Ministry of Public Health of the People's Republic of China.
The Section (II) of the second determination method of total mercury in this standard was drafted by the Institute of Food Safety Control and Inspection Ministry of Public Health of the People's Republic of China.
The third determination method of total mercury in this standard was drafted by the Jiangsu Provincial Epidemic Prevention Station.
The determination of methyl mercury in this standard was drafted by the Shanghai Institute of Food Safety Control and Inspection, Jiangsu Provincial Epidemic Prevention Station, Hangzhou Sanitary and Anti-epidemic Station, Institute of Food Safety Control and Inspection Ministry of Public Health of the People's Republic of China, Qinghai Provincial Epidemic Prevention Station and Fujian Provincial Health School.
Chief drafting staffs of the first determination method of total mercury in this standard: Yang Huifen, Huan Liusheng, Mao Hong, Qiang Weiguo, and Yan Jun.
This standard was issued for the first time in 1985, revised for the first time in 1996 and revised now for the second time.
Determination of Total Mercury and Organic-mercury in Foods
食品中总汞及有机汞的测定
1 Scope
This standard specifies various methods for determination of total mercury in foods.
This standard is applicable to the determination of total mercury in various foods.
Atomic fluorescence spectrometry: the detection limit is 0.15μg/kg, the optimal linear range of standard curve is 0μg/L~60μg/L; the detection limit of cold-vapor atomic absorption method: is 0.4μg/kg for pressure digestion method, 10μg/kg for other digestion methods, and 25μg/kg for colorimetry.
METHOD No.1 Atomic Fluorescence Spectrometry
2 Principles
After being heated and digested in acid, the mercury in the test sample will be reduce to the atomic mercury by the potassium borohydride (KBH4) or sodium borohydride (NaBH4) in acid medium and is carried into the atomizer by the carrier gas (argon gas), the mercury atoms at ground state will be activated to the super-high energy state with the irradiation of the hollow-cathode lamp of special mercury; when the mercury atoms are deactivated to the ground state and eradiate out the fluorescent of characteristic wavelength, the fluorescence intensity is proportional to the mercury content and shall be determined by comparing with the standard series.
3 Reagents
3.1 Nitric acid (super pure).
3.2 30% hydrogen peroxide.
3.3 Sulfuric acid (super pure).
3.4 Sulfuric acid + nitric acid + water (1+1+8): Measure 10mL of nitric acid and 10mL sulfuric acid, pour them into 80ml water slowly, cool and blend the liquid.
3.5 Nitric acid solution (1+9): Measure 50mL nitric acid, and pour it into 450mL water and blend the liquid.
3.6 Potash solution (5g/L): Weigh 5.0g potassium hydroxide and dissolve it in water, dilute the solution to 1000mL and blend it.
3.7 Potassium borohydride solution (5g/L): Weigh 5.0g potassium borohydride and dissolve it in 5.0g/L potash solution, dilute the solution to 1000mL and blend it, this reagent will be prepared freshly before use.
3.8 Standard mercury stock solution: Accurately weigh 0.1354g dried mercuric chloride, put it and dissolve in the sulfuric acid + nitric acid water mixed acid (1+1+8), transfer the liquid into a 100mL measuring flask and dilute it to the scale, blend the liquid finally, and every 1mL of this solution is equivalent to 1mg of mercury.
3.9 Standard mercury application solution: Absorb 1mL of standard mercury stock solution (1mg/mL) with pipette and transfer it to a 100mL measuring flask, dilute the solution to the scale with nitric acid solution (1+9) and blend it, and this solution concentration is 10μg/mL. Whereafter, absorb 1mL and 5mL of standard mercury solution (10μg/mL) and transfer them respectively to two 100mL measuring flasks, dilute the solution to the scale with nitric acid solution (1+9) and lend them, the solution concentration respectively are 100ng/mL and 500ng/mL for determining the low concentration sample and high concentration sample so as to draft the standard curve.
4 Instruments
4.1 Dual-channel atomic fluorescence spectrophotometer.
4.2 High-pressure digestion vessel (capacity: 100mL).
4.3 Microwave digestion furnace.
5 Analytical Procedures
5.1 Sample digestion
5.1.1 High-pressure digestion method
This method is applicable to the determination of the total mercury in foods, beans, vegetables, fruits, thin meat, fishes, eggs, milk and milk products.
5.1.1.1 Dry samples of grain and beans: Weight 0.2g~1.00g of dry sample that has been milled, blended and screened through 40 mesh screen, place the sample in a inter polytetrafluoroethylene plastic tank, inject 5mL of nitric acid, blend the mixture and place it overnight, and then inject 7mL of hydrogen peroxide, cover the inner cup, put the tank into one stainless steel housing, fasten and seal the housing. Whereafter, place the slaker into a common drying box and heat it to make temperature rise up to the 120℃, keep it at 120℃ for 2h~3h till the sample is fully digested, and cool the liquid to the room temperature naturally. Quantify digestion solution with nitric acid solution (1+9) to 25mL, and blend the liquid. At the same time, conduct the reagent blank test. Keep the samples for measuring.
5.1.1.2 Stamp and mill the fresh samples of high moisture content of vegetables, thin meat, fishes and eggs into homogenate with pulping machine, weigh 1.00g~5.00g of 1.00g and place it into a inter polytetrafluoroethylene plastic tank, cover the tank with a joint left, put this tank into one 65℃fan-drying oven or general oven and bake the homogenate near to dry, take out the tank, and later, operate according to 5.1.1.1 from "adding 5mL of nitric acid".
