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GB 5009.12-2023: National food safety standard - Determination of lead in foods
GB 5009.12-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard - Determination of lead in
foods
ISSUED ON: SEPTEMBER 06, 2023
IMPLEMENTED ON: MARCH 06, 2024
Issued by: National Health Commission of the People’s Republic of China;
State Administration for Market Regulation.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Principle ... 4
3 Reagents and materials ... 4
4 Instruments and apparatuses ... 6
5 Analysis steps ... 6
6 Expression of analysis results ... 8
7 Precision ... 9
8 Others ... 9
9 Principle ... 10
10 Reagents and materials ... 10
11 Instruments and apparatuses ... 11
12 Analysis steps ... 12
13 Expression of analysis results ... 13
14 Precision ... 13
15 Others ... 13
Appendix A Microwave digestion heating program ... 14
Appendix B Desalted sample operation steps ... 15
Appendix C Apparatus reference conditions for graphite furnace atomic absorption
spectrometry ... 17
Appendix D Apparatus reference conditions for flame atomic absorption spectrometry
... 18
National food safety standard - Determination of lead in
foods
1 Scope
This Standard specifies the methods for the determination of lead in foods by graphite
furnace atomic absorption spectrometry, inductively coupled plasma mass spectrometry
and flame atomic absorption spectrometry.
This Standard applies to the determination of lead in foods.
Method I – Graphite furnace atomic absorption spectrometry
2 Principle
After digestion treatment, the sample is atomized in a graphite furnace and the
absorbance is measured at 283.3 nm. Within a certain concentration range, the
absorbance value of lead is proportional to the lead content and can be compared
quantitatively with the standard series.
3 Reagents and materials
Unless otherwise stated, the reagents used in this method are guaranteed reagents, and
the water is grade-II water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3).
3.1.2 Perchloric acid (HClO4).
3.1.3 Ammonium dihydrogen phosphate (NH4H2PO4).
3.1.4 Palladium nitrate [Pd(NO3)2].
3.1.5 Ammonium acetate (CH3COONH4).
3.1.6 Sodium acetate (CH3COONa).
3.2 Preparation of reagents
3.2.1 Nitric acid solution (5+95): Measure 50 mL of nitric acid; slowly add it to 950
mL of water; mix well.
3.2.2 Nitric acid solution (1+9): Measure 50 mL of nitric acid; slowly add it to 450 mL
of water; mix well.
3.2.3 Nitric acid solution (1+99): Measure 10 mL of nitric acid; slowly add it to 990
mL of water; mix well.
3.2.4 Sodium acetate solution (2 mol/L): Weigh 164.0 g of sodium acetate; add water
to dissolve; adjust the volume to 1 000 mL.
3.2.5 Ammonium acetate solution (1 mol/L): Weigh 77.1 g of ammonium acetate; add
water to dissolve; adjust the volume to 1 000 mL.
3.2.6 Ammonium dihydrogen phosphate-palladium nitrate solution: Weigh 0.02 g of
palladium nitrate; add a small amount of nitric acid solution (1+9) to dissolve it; then,
add 2 g of ammonium dihydrogen phosphate; after dissolution, use nitric acid solution
(5+95) to adjust the volume to 100 mL; mix well.
3.3 Standard
Lead nitrate [Pb(NO3)2, CAS number: 10099-74-8]: purity >99.99%, or lead standard
solution certified by the state and granted with a reference material certificate.
3.4 Preparation of standard solution
3.4.1 Lead standard stock solution (1 000 mg/L): Accurately weigh 1.598 5 g (accurate
to 0.000 1 g) of lead nitrate; use a small amount of nitric acid solution (1+9) to dissolve
it; transfer it to a 1 000 mL volumetric flask; add water to the mark; mix well.
3.4.2 Lead standard intermediate solution (10.0 mg/L): Accurately draw 1.00 mL of
lead standard stock solution (1 000 mg/L) into a 100 mL volumetric flask; use nitric
acid solution (5+95) to adjust the volume to the mark; mix well.
3.4.3 Lead standard working solution (1.00 mg/L): Accurately draw 10.00 mL of lead
standard intermediate solution (10.0 mg/L) into a 100 mL volumetric flask; use nitric
acid solution (5+95) to adjust the volume to the mark; mix well.
3.4.4 Lead standard series solution: Respectively draw 0 mL, 0.2 mL, 0.5 mL, 1.0 mL,
2.0 mL and 4.0 mL of lead standard working solution (1.00 mg/L) into 100 mL
volumetric flasks; add nitric acid solution (5+95) to the mark; mix well. The mass
concentrations of this lead standard series of solutions are 0 μg/L, 2.0 μg/L, 5.0 μg/L,
10.0 μg/L, 20.0 μg/L and 40.0 μg/L, respectively.
Note: The mass concentration of lead and the concentration of nitric acid solution in
the standard series of solutions can be determined based on the sensitivity of the
instrument, the actual lead content in the sample and different instrument models.
5.1.2 Liquid samples
For samples of soft drinks, alcoholic beverages, condiments, etc., shake well.
5.1.3 Semi-solid samples
Mix well.
5.2 Sample pretreatment
5.2.1 Wet digestion
Weigh 0.2 g ~ 3 g (accurate to 0.001 g) of solid sample or accurately transfer 0.50 mL
~ 5.00 mL of liquid sample into a graduated digestion tube. For samples containing
ethanol or carbon dioxide, first heat at low temperature on an electric hot plate to
remove ethanol or carbon dioxide; add 10 mL of nitric acid and 0.5 mL of perchloric
acid; put a few glass beads; digest it on an adjustable electric furnace (reference
conditions: 120 °C/0.5 h ~ 1 h; heated to 180 °C/2 h ~ 4 h, heated to 200 °C ~ 220 °C).
If the digestion solution is brown, add a small amount of nitric acid and digest until
white smoke is emitted and the digestion solution is colorless, transparent or slightly
yellow. Remove the remaining acid until almost dry; stop digestion; cool and add water
to adjust the volume to 10 mL or 25 mL; mix well and set aside. Do a reagent blank test
at the same time. Alternatively, use an Erlenmeyer flask and perform wet digestion on
an adjustable electric hot plate according to the above operation methods.
Note: The added volume of nitric acid and perchloric acid can be adjusted according to
the actual situation.
5.2.2 Microwave digestion
Weigh 0.2 g ~ 2 g (accurate to 0.001 g) of the solid sample or accurately transfer 0.50
mL ~ 3.00 mL of the liquid sample into the microwave digestion tank. For samples
containing ethanol or carbon dioxide, first heat at low temperature on an electric hot
plate to remove the ethanol or carbon dioxide; add 5 mL ~ 10 mL of nitric acid (the
amount of nitric acid used can be adjusted according to the weighing amount and
properties of the sample); digest the sample according to the operating steps of
microwave digestion. For digestion conditions, refer to Appendix A. After cooling, take
out the digestion tank and remove the remaining acid on the electric hot plate at 140 °C
~ 160 °C until it is almost dry. After the digestion tank cools off, transfer the digestion
solution to a 10 mL or 25 mL volumetric flask; use a small amount of water to wash the
digestion tank 2 ~ 3 times; combine the cleaning mixture in the volumetric flask and
use water to adjust the volume to the mark; mix well and set aside. Do a reagent blank
test at the same time.
5.2.3 Pressure tank digestion
Weigh 0.2 g ~ 2 g (accurate to 0.001 g) of the solid sample or accurately transfer 0.50
mL ~ 5.00 mL of the liquid sample into the digestion inner tank. For samples containing
ethanol or carbon dioxide, first heat at low temperature on an electric hot plate to
remove the ethanol or carbon dioxide; add 5 mL ~ 10 mL of nitric...