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GB/T 13081-2022 English PDF (GBT13081-2022)

GB/T 13081-2022 English PDF (GBT13081-2022)

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GB/T 13081-2022: Determination of mercury in feeds
This document describes the atomic fluorescence spectrometry, cold atomic absorption spectrometry, and direct injection methods for the determination of total mercury in feeds. This document is applicable to the determination of total mercury in compound feeds, concentrated feeds, concentrate supplements, additive premixed feeds, feed raw materials, and feed additives. Atomic fluorescence spectrometry: When the sample weight is 0.5 g and the constant volume is 50 mL, the method detection limit is 0.6 ¦Ìg/kg and the quantification limit is 3 ¦Ìg/kg. Cold atomic absorption spectrometry: When the sample weight is 2 g and the constant volume is 100 mL, the method detection limit is 3 ¦Ìg/kg and the quantitation limit is 10 ¦Ìg/kg. Direct injection method: When the sample weighing amount is 0.1 g, the detection limit of the method is 0.3 ¦Ìg/kg, and the quantification limit is 1 ¦Ìg/kg.
GB/T 13081-2022
GB
NATIONAL STANDARD OF THE
PEOPLE'S REPUBLIC OF CHINA
ICS 65.120
CCS B 46
Replacing GB/T 13081-2006
Determination of mercury in feeds
ISSUED ON: DECEMBER 30, 2022
IMPLEMENTED ON: JULY 1, 2023
Issued by: State Administration for Market Regulation;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Atomic fluorescence spectrometry (arbitration method) ... 5
5 Cold atomic absorption spectrometry ... 10
6 Direct injection method ... 13
Determination of mercury in feeds
1 Scope
This document describes the atomic fluorescence spectrometry, cold atomic absorption spectrometry, and direct injection methods for the determination of total mercury in feeds.
This document is applicable to the determination of total mercury in compound feeds, concentrated feeds, concentrate supplements, additive premixed feeds, feed raw materials, and feed additives.
Atomic fluorescence spectrometry: When the sample weight is 0.5 g and the constant volume is 50 mL, the method detection limit is 0.6 μg/kg and the quantification limit is 3 μg/kg. Cold atomic absorption spectrometry: When the sample weight is 2 g and the constant volume is 100 mL, the method detection limit is 3 μg/kg and the quantitation limit is 10 μg/kg. Direct injection method: When the sample weighing amount is 0.1 g, the detection limit of the method is 0.3 μg/kg, and the quantification limit is 1 μg/kg. 2 Normative references
The contents of the following documents constitute essential provisions of this document through normative references in the text. For the dated referenced documents, only the versions with the indicated dates are applicable to this document; for the undated referenced documents, only the latest version (including all the amendments) is applicable to this document.
GB/T 6682 Water for analytical laboratory use - Specification and test methods GB/T 20195 Animal feeding stuffs - Preparation of test samples
3 Terms and definitions
There are no terms or definitions that need to be defined in this document. 4 Atomic fluorescence spectrometry (arbitration method)
4.1 Principle
After the sample is digested by acid heating, mercury is reduced to atomic mercury by potassium borohydride (KBH4) in the acidic medium, which is brought into the atomizer by argon gas. Under the irradiation of a special mercury hollow cathode lamp, the ground-state mercury atoms are excited to a high energy state and then deactivated back to the ground state, which emit fluorescence with a characteristic wavelength. Its fluorescence intensity is proportional to the mercury content and can be quantified by the external standard method.
4.2 Reagents or materials
WARNING -- Mercury is highly toxic. Pay attention to ventilation when handling and avoid contact with skin and clothing. All kinds of strong acids shall be handled carefully and shall be handled in a fume hood.
Unless otherwise specified, use only guaranteed reagents.
4.2.1 Water: The second-grade water specified in GB/T 6682.
4.2.2 Nitric acid.
4.2.3 Hydrogen peroxide: The mass fraction is not less than 30%.
4.2.4 Nitric acid solution I: Measure 100 mL of nitric acid, slowly add it to 400 mL of water, and mix well.
4.2.5 Nitric acid solution II: Measure 50 mL of nitric acid, slowly add it to 450 mL of water, and mix well.
4.2.6 Nitric acid solution III: Measure 50 mL of nitric acid, slowly add it to 950 mL of water, and mix well.
4.2.7 Potassium hydroxide solution (5 g/L): Weigh 5 g of potassium hydroxide, dissolve and dilute to 1000 mL with water, and mix well.
4.2.8 Potassium borohydride solution (5 g/L): Weigh 5 g of potassium borohydride, dissolve and dilute to 1000 mL with potassium hydroxide solution (4.2.7), and mix well. Prepare it fresh just before use.
4.2.9 Mercury standard stock solution (1 mg/mL): certified reference material. 4.2.10 Mercury standard intermediate solution (10 μg/mL): Accurately pipette 1 mL of mercury standard stock solution (4.2.9) into a 100 mL volumetric flask, dilute to the mark with nitric acid solution II (4.2.5), and mix well. Transfer the solution to a borosilicate glass bottle and store at 2 ℃~8 ℃. The validity period is 1 month. 4.2.11 Mercury standard working solution (25 ng/mL): Accurately pipette 0.25 mL of mercury standard intermediate solution (4.2.10) into a 100 mL volumetric flask, dilute to the mark with nitric acid solution II (4.2.5), and mix evenly. Prepare it fresh just before use.
4.2.12 Standard series solutions: Accurately pipette 0 mL, 0.10 mL, 0.20 mL, 1.00 mL, 2.00 mL, and 4.00 mL mercury standard working solutions (4.2.11) into 50 mL volumetric flasks respectively, dilute to the mark with nitric acid solution II (4.2.5), mix well to prepare standard series solutions with mass concentrations of 0 ng/mL, 0.05 ng/mL, 0.10 ng/mL, 0.50 ng/mL, 1.00 ng/mL, and 2.00 ng/mL. Prepare it fresh just before use.
4.2.13 High-purity argon: The purity is not less than 99.999%.
4.3 Instruments and equipment
4.3.1 Atomic fluorescence spectrometer: It is equipped with a mercury hollow cathode lamp.
4.3.2 Analytical balance: The sensitivity is 0.0001 g.
4.3.3 High-pressure digestion tank: It is equipped with a 100 mL
polytetrafluoroethylene digestion tube.
4.3.4 Microwave digestion instrument: It is equipped with a 50 mL
polytetrafluoroethylene digestion tube.
4.3.5 Constant temperature drying oven: The temperature control accuracy is ±2 °C. 4.3.6 Ultrasonic cleaner.
NOTE: Glassware and polytetrafluoroethylene digestion tubes need to be soaked in nitric acid solution I (4.2.4) for 24 hours, and then rinsed repeatedly with water.
4.4 Samples
The sample is prepared according to GB/T 20195. The solid sample shall be at least 200 g. It is crushed so that it all passes through an analysis sieve with a pore size of 0.425 mm; it is mixed thoroughly and stored in an airtight container for later use. 4.5 Test procedures
4.5.1 Sample solution preparation
4.5.1.1 High-pressure tank digestion method
Do two experiments in parallel. Weigh 0.5 g~1 g of the sample, accurate to 0.0001 g, place it in a polytetrafluoroethylene digestion tube, add 5 mL of nitric acid (4.2.2), add 8 mL of hydrogen peroxide (4.2.3), close the inner cover, place it into a stainless-steel jacket, and let it stand overnight. Tighten the seal, heat the digestion tank (4.3.3) in a glass bottle and store it at 2 ℃~8 ℃. The validity period is 1 month.
5.2.9 Mercury standard working solution (0.1 μg/mL): Accurately pipette 1 mL of mercury standard intermediate solution (5.2.8), place it in a 100 mL volumetric flask, add the mixed acid solution (5.2.6) to dilute to the mark, and mix well. Prepare it fresh just before use.
5.3 Instruments and equipment
5.3.1 Cold atom mercury analyzer: It is equipped with a 50 mL reducing bottle. 5.3.2 Analytical balance: The sensitivity is 0.0001 g.
5.3.3 Digestion equipment.
NOTE: All glassware needs to be soaked in nitric acid solution I (4.2.4) for 24 hours, and then rinsed repeatedly with water.
5.4 Samples
The sample is prepared according to GB/T 20195. The solid sample shall be at least 200 g. It is crushed so that it all passes through an analysis sieve with a pore size of 0.425 mm; it is mixed thoroughly and stored in an airtight container for later use. 5.5 Test procedures
5.5.1 Preparation of sample solution
Do two experiments in parallel. Weigh 1 g~5 g of the sample, accurate to 0.0001 g, place it in a 250 mL Erlenmeyer flask, add a few glass beads, add 25 mL of nitric acid (5.2.2) and 5 mL of sulfuric acid (5.2.3), and rotate the Erlenmeyer flask to prevent local carbonization. Install the condenser tube, heat over low heat, and stop heating when foaming begins. After foaming stops, reheat and reflux for 2 hours. After cooling, carefully add 20 mL of water from the upper end of the condenser tube, continue to heat and reflux for 10 minutes, cool to room temperature, rinse the condenser tube with an appropriate amount of water, and merge the washing liquid into the digestion liquid. Filter the digestion liquid through glass wool or filter paper into a 100 mL volumetric flask, wash the Erlenmeyer flask and filter with a small amount of water, merge the washing liquid into the volumetric flask, dilute to volume with water, and mix well for later use. At the same time, do a reagent blank test.
If the sample is stone powder, weigh 1 g of the sample, accurate to 0.0001 g, place it in an Erlenmeyer flask, and add a few glass beads; install a condenser tube, add 15 mL of nitric acid (5.2.2) from the upper end of the condenser tube, heat over low heat for 15 min, and cool to room temperature. Rinse the condenser tube with an appropriate amount of water, transfer the digestion liquid into a 100 mL volumetric flask, dilute to It is the same as 4.7.
6 Direct injection method
6.1 Principle
After the sample is dried at high temperature and catalytically pyrolyzed, the mercury is reduced to elemental mercury, which is enriched with gold amalgam or directly brought into the detector through a carrier gas, and the atomic absorption signal of mercury is measured at a wavelength of 253.7 nm, or the atomic fluorescence signal of mercury is detected with excitation by a mercury lamp; it is quantified by external standard method.
6.2 Reagents or materials
WARNING -- Mercury is highly toxic. Pay attention to ventilation when handling and avoid contact with skin and clothing. All kinds of strong acids shall be handled carefully and shall be handled in a fume hood.
Unless otherwise specified, use only guaranteed reagents.
6.2.1 Water: The second-grade water specified in GB/T 6682.
6.2.2 Nitric acid.
6.2.3 5% nitric acid solution: Accurately measure 5 mL of nitric acid (6.2.2), add water to the volume of 100 mL, and mix well.
6.2.4 Mercury standard stock solution (1 mg/mL): certified reference material. 6.2.5 Mercury standard intermediate solution I (100 μg/mL): Accurately pipette 1 mL of mercury standard stock solution (6.2.4) into a 10 mL volumetric flask, dilute to volume with 5% nitric acid solution (6.2.3), and mix well. Transfer to a borosilicate glass bottle and store at 2 ℃~8 ℃. The validity period is 6 months.
6.2.6 Mercury standard intermediate solution II (10 μg/mL): Accurately pipette 1 mL of mercury standard stock solution (6.2.4) into a 100 mL volumetric flask, dilute to volume with 5% nitric acid solution (6.2.3), and mix well. Transfer to a borosilicate glass bottle and store at 2 ℃~8 ℃. The validity period is 1 month.
6.2.7 Low-concentration standard series solution: Accurately pipette the mercury standard intermediate solution II (6.2.6), and dilute it stepwise with 5% nitric acid solution (6.2.3) to obtain low-concentration standard series solutions with mass concentrations of 0 ng/mL, 5.0 ng/mL, 10.0 ng/mL, 20.0 ng/mL, 50.0 ng/mL, 100 ng/mL, and 200 ng/mL.
6.2.8 High-concentration standard series solution: Accurately pipette the mercury standard intermediate solution I (6.2.5), and dilute it stepwise with 5% nitric acid solution (6.2.3) to obtain high-concentration standard series solutions with mass concentrations of 300 ng/mL, 600 ng/mL, 800 ng/mL, 1000 ng/mL, 3000 ng/mL, and 5000 ng/mL.
6.3 Instruments and equipment
6.3.1 Direct injection mercury analyzer.
6.3.2 Analytical balance: The sensitivity is 0.0001 g.
6.3.3 Muffle furnace: The temperature control accuracy is ±20 ℃.
6.3.4 Sample boat: It is made of nickel or quartz, burned in a muffle furnace at 550 ℃±20 ℃ for 1 hour before use, taken out and placed in a desiccator to cool for later use.
6.3.5 Gas: oxygen (the purity is not less than 99.9%) or air; argon-hydrogen mixture (the volume ratio is 9:1, and the purity is not less than 99.9%).
NOTE: All glassware needs to be soaked in nitric acid solution I (4.2.4) for 24 hours, and then rinsed repeatedly with water.
6.4 Samples
The sample is prepared according to GB/T 20195. The solid sample shall be at least 200 g. It is crushed so that it all passes through an analysis sieve with a pore size of 0.425 mm; it is mixed thoroughly and stored in an airtight container for later use. 6.5 Test procedures
6.5.1 Standard curve drawing
Accurately pipette 0.1 mL of the low-concentration standard series solutions (6.2.7) and the high-concentration standard series solutions (6.2.8) respectively into the sample boats. The mercury masses of the low-concentration standard series solutions are 0 ng, 0.5 ng, 1.0 ng, 2.0 ng, 5.0 ng, 10.0 ng, and 20.0 ng; the mercury masses of the high- concentration standard series solutions are 30.0 ng, 60.0 ng, 80.0 ng, 100 ng, 300 ng, and 500 ng. Under the best condition of the instrument, in order from low to high mercury mass, measure the standard series solutions and record the signal response values. Take the mass (ng) of mercury in each series of standard solutions as the abscissa and its corresponding signal response value as the ordinate, and draw low- concentration and high-concentration mercury standard curves, respectively. 6.5.2 Determination
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