GB 5009.12-2023 (GB5009.12-2023) & related versions
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GB 5009.12-2023: PDF in English
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 acid (the amount of
nitric acid used can be adjusted according to the weighing amount and properties of the
sample). Close the inner cover; screw the stainless-steel outer cover tightly; put it in a
constant-temperature drying oven; keep it at 140 °C ~ 160 °C for 4 h ~ 5 h. After cooling,
slowly unscrew the outer tank, take out the digestion inner tank, and place it on an
adjustable electric hot plate to remove the remaining acid at 140 °C ~ 160 °C until it is
almost dry. After cooling, transfer the digestion solution to a 10 mL or 25 mL volumetric
flask; use a small amount of water to wash the inner tank and inner cover 2 ~ 3 times;
combine the cleaning mixture in the volumetric flask; use water to dilute to the mark;
mix well and set aside. Do a reagent blank test at the same time.
Note: High-salt foods such as table salt, soy sauce, pickled foods, hot pot soup bases
and instant noodle salt packets can be desalinated. For details, see Appendix B.
5.3 Determination
5.3.1 Apparatus reference conditions
See Appendix C for apparatus reference conditions.
5.3.2 Preparation of standard curve
In order of mass concentration from low to high, add 10 μL of lead standard series
solution and 5 μL of ammonium dihydrogen phosphate-palladium nitrate solution (the
optimal injection volume and optimal matrix modifier can be determined according to
the instrument used, and samples passing through the solid-phase extraction column do
not need to be added with matrix modifier) into the graphite furnace at the same time,
and measure their absorbance values after atomization. Make a standard curve with the
mass concentration as the abscissa and the absorbance value as the ordinate.
5.3.3 Determination of sample solution
Under the same experiment conditions as the measurement of the standard solution,
inject 10 μL of blank solution or sample solution and 5 μL of ammonium dihydrogen
phosphate-palladium nitrate solution (the optimal injection volume can be determined
according to the instrument used) into the graphite furnace at the same time, which can
be omitted for the sample passing through the solid-phase extraction column; measure
its absorbance value after atomization; compare it quantitatively with the standard
series.
6 Expression of analysis results
The content of lead in the sample is calculated according to Formula (1).
10.2.2 Nitric acid solution (1+9): Measure 50 mL of nitric acid; slowly add it to 450
mL of water; mix well.
10.2.3 Ammonium sulfate solution (300 g/L): Weigh 30 g of ammonium sulfate; use
water to dissolve and dilute to 100 mL; mix well.
10.2.4 Ammonium citrate solution (250 g/L): Weigh 25 g of ammonium citrate; use
water to dissolve and dilute to 100 mL; mix well.
10.2.5 Bromothymol blue aqueous solution (1 g/L): Weigh 0.1 g of bromothymol blue;
use water to dissolve and dilute to 100 mL; mix well.
10.2.6 DDTC solution (50 g/L): Weigh 5 g of DDTC; use water to dissolve and dilute
to 100 mL; mix well.
10.2.7 Ammonia solution (1+1): Take 100 mL of ammonia; add 100 mL of water; mix
well.
10.2.8 Hydrochloric acid solution (1+11): Take 10 mL of hydrochloric acid; add 110
mL of water; mix well.
10.3 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.
10.4 Preparation of standard solution
10.4.1 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.
10.4.2 Lead standard working 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; add nitric acid
solution (5+95) to the mark; mix well.
11 Instruments and apparatuses
Note: All glassware needs to be soaked in nitric acid solution (1+5) or nitric acid
solution (1+4) overnight, rinsed repeatedly with tap water, and finally rinsed
with water and dried.
11.1 Atomic absorption spectrometer: equipped with flame atomizer and accompanied
by lead hollow cathode lamp.
11.2 Analytical balance: The sensitivity is 0.1 mg and 1 mg, respectively.
11.3 Adjustable electric furnace and adjustable electric hot plate.
Appendix B
Desalted sample operation steps
B.1 Sample digestion
B.1.1 Wet digestion
Follow the steps of “Weigh the solid sample...the digestion solution is colorless,
transparent or slightly yellow; remove the remaining acid until almost dry” in 5.2.1;
after cooling, use sodium acetate solution (2 mol/L) to wash the digestion tank 2 ~ 3
times; combine the cleaning mixture in a 25 mL volumetric flask; use sodium acetate
solution (2 mol/L) to adjust the volume to the mark; mix well and set aside (the pH of
the solution after dilution is 4.5 ~ 6.5). Do a reagent blank test at the same time.
B.1.2 Microwave digestion
Follow the steps of “Weigh the solid sample...remove the remaining acid on the electric
hot plate at 140 °C ~ 160 °C until it is almost dry” in 5.2.2; after cooling, use sodium
acetate solution (2 mol/L) to wash the digestion tank 2 ~ 3 times; combine the cleaning
mixture in a 25 mL volumetric flask; use sodium acetate solution (2 mol/L) to adjust
the volume to the mark; mix well and set aside (the pH of the solution after dilution is
4.5 ~ 6.5). Do a reagent blank test at the same time.
B.1.3 Pressure tank digestion
Follow the steps of “Weigh the solid sample... place it on an adjustable electric hot plate
to remove the remaining acid at 140 °C ~ 160 °C until it is almost dry” in 5.2.3; after
cooling, use sodium acetate solution (2 mol/L) to wash the inner tank and inner cover
2 ~ 3 times; combine the cleaning mixture in a 25 mL volumetric flask; use sodium
acetate solution to adjust the volume to the mark; mix well and set aside (the pH of the
solution after dilution is 4.5 ~ 6.5). Do a reagent blank test at the same time.
B.2 Separation of lead
B.2.1 Activation of solid-phase extraction column
Pipette 10 mL of nitric acid solution (1+99) through the column at a flow rate of 5
mL/min; then, use 5 mL of water and 5 mL of ammonium acetate solution (1 mol/L) to
pass through the column at a flow rate of 5 mL/min.
B.2.2 Adsorption and desorption of lead
Take 25 mL of the reagent blank solution and the above sample solution respectively;
pass them through the column at a flow rate of 5 mL/min; then, use 5 mL of ammonium
acetate solution (1 mol/L) to wash the column; then, use 10 mL of water to wash away
......
| Standard ID | GB 5009.12-2023 (GB5009.12-2023) | | Description (Translated English) | (National food safety standards Determination of cyanide in food) | | Sector / Industry | National Standard | | Classification of Chinese Standard | X09 | | Word Count Estimation | 24,243 | | Date of Issue | 2023-09-06 | | Date of Implementation | 2024-03-06 | | Issuing agency(ies) | National Health Commission of the People's Republic of China, State Administration for Market Regulation | | Summary | This standard specifies the method for the determination of cyanide in food. The first method of spectrophotometry is suitable for the determination of cyanide in distilled wine and its preparations, edible alcohol, tapioca flour, packaged drinking water and mineral water. The second method gas chromatography and the third method gas chromatography-mass spectrometry are suitable for the determination of cyanide in liquor, edible alcohol, grain, packaged drinking water and mineral water. The fourth method of ion chromatography is suitable for the determination of cyanide in distilled wine and its prepared wine, edible alcohol, packaged drinking water, mineral water and beverages (with almonds as raw material). The fifth method of flow injection/continuous flow-spectrophotometry is suitable for the determination of cyanide in distilled wine and its preparations, edible alcohol, packaged drinking water and mineral water. |
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