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GB 5009.17-2021: Determination of total mercury and organic-mercury in foods
GB 5009.17-2021
GB
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 Contents
Foreword ... 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 ... 25 
29 Others ... 25 
Method 2 - Liquid Chromatography - Inductively Coupled Plasma Mass
Spectrometry... 26 
30 Principle ... 26 
31 Reagents and Materials ... 26 
32 Instruments and Equipment ... 28 
33 Analytical Procedures ... 29 
34 Expression of Analytical Results ... 30 
35 Precision ... 31 
36 Others ... 31 
Appendix A Reference Conditions of Microwave Digestion ... 32 
Appendix B Reference Conditions of Instruments ... 33 
Appendix C Chromatograms of LC-AFS Method ... 35 
Appendix D Chromatograms of LC-ICP-MS Method ... 38 
National Food Safety Standard - Determination of
Total Mercury and Organic-mercury in Food
1 Scope
Part 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 Spectrometry
2 Principle
After 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 Materials
Unless 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.
3.2.4 Potassium borohydride solution (5 g/L): weigh-take 5.0 g of potassium
borohydride; use potassium hydroxide solution (5 g/L) to dissolve it and dilute to 1,000
mL; mix it up. Prepare it right before use.
3.2.5 Nitric acid solution of potassium dichromate (0.5 g/L): weigh-take 0.5 g of
potassium dichromate; use nitric acid solution (5 + 95) to dissolve it and dilute to 1,000
mL; mix it up.
NOTE: this method may also use sodium borohydride as a reducing agent: weigh-take 3.5
g of sodium borohydride; use sodium hydroxide solution (3.5 g/L) to dissolve it and
reach a constant volume of 1,000 mL; mix it up. Prepare it right before use.
3.3 Standard Substance
Mercury chloride (HgCl2, CAS No.: 7487-94-7): purity ≥ 99%.
3.4 Preparation of Standard Solutions
3.4.1 Standard stock solution of mercury (1,000 mg/L): accurately weigh-take 0.1354
g of mercury chloride; use nitric acid solution of potassium dichromate (0.5 g/L) to
dissolve it and transfer to a 100 mL volumetric flask; dilute it to 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 2 years. Or a mercury standard solution certified by the country
and awarded with a standard substance certificate.
3.4.2 Standard intermediate solution of mercury (10.0 mg/L): accurately draw 1.00 mL
a clean polyethylene bottle; seal and store it for later use.
5.1.2 In terms of fresh samples, such as: vegetables, fruits, fish, meat and eggs, wash
and dry them; take the edible part and homogenize it; put it into a clean polyethylene
bottle; seal it; store it at 2 °C ~ 8 °C in the refrigerator for later use.
5.1.3 In terms of milk and dairy products, after homogenizing it, put it into a clean
polyethylene bottle; seal it; store it at 2 °C ~ 8 °C in the refrigerator for later use.
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; use a small amount of water to rinse the inner lid. Place the digestion tank on a
temperature-controllable electric heating plate or in the ultrasonic water bath; at 80 °C,
heat it up or ultrasonically degas for 3 min ~ 6 min to drive off the brown gas. Take out
the digestion inner tank; transfer the digestion solution to a 25 mL volumetric fl...