GB 5009.304-2025 PDF English
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National food safety standard - Determination of trivalent chromium and hexavalent chromium in foods
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GB 5009.304-2025: National food safety standard - Determination of trivalent chromium and hexavalent chromium in foods
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB5009.304-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard - Determination of trivalent
chromium and hexavalent chromium in food
Issued on: MARCH 16, 2025
Implemented on: SEPTEMBER 16, 2025
Issued by. National Health Commission of the People’s Republic of China;
State Administration for Market Regulation.
Table of Contents
1 Scope... 3
Part I -- Determination of hexavalent chromium in food... 3
2 Principle... 3
3 Reagents and materials... 3
4 Instruments and equipment... 4
5 Analysis steps... 4
6 Expression of analysis results... 6
7 Precision... 6
8 Others... 6
Part II -- Determination of trivalent chromium in food... 6
9 Principle... 6
10 Reagents and materials... 7
11 Instruments and equipment... 8
12 Analysis steps... 8
13 Expression of analysis results... 9
14 Precision... 10
15 Others... 10
Annex A Reference conditions of inductively coupled plasma mass spectrometry... 11
Annex B Liquid chromatography-inductively coupled plasma mass spectrum of
trivalent chromium and hexavalent chromium standard solutions... 12
National food safety standard - Determination of trivalent
chromium and hexavalent chromium in food
1 Scope
Part I of this Standard specifies the method for the determination of hexavalent
chromium in food.
Part I of this Standard applies to the determination of hexavalent chromium in special
medical purpose formula foods and special medical purpose infant formula foods.
Part II of this Standard specifies the method for the determination of trivalent chromium
in food.
Part II of this Standard applies to the determination of trivalent chromium in special
medical purpose formula foods and special medical purpose infant formula foods.
Part I -- Determination of hexavalent chromium in food
2 Principle
The sample is shaken with an alkaline solution to extract hexavalent chromium, then
centrifuged at high speed and subjected to determination by liquid chromatography-
inductively coupled plasma mass spectrometry.
3 Reagents and materials
Unless otherwise specified, the reagents used in this method are analytically pure, and
the water is grade 1 water specified in GB/T 6682.
3.1 Reagents
3.1.1 Nitric acid (HNO3). concentration ≥ 69 %.
3.1.2 Ammonia (NH3 • H2O). concentration ≥ 25 %.
3.1.3 Sodium hydroxide (NaOH).
3.1.4 Helium (He). helium (≥ 99.995 %).
3.1.5 Argon (Ar). argon (≥ 99.995 %) or liquid argon.
3.2 Reagent preparation
3.2.1 60 mmol/L ammonium nitrate solution. pipette 3.9 mL of nitric acid into 1 L of
water, adjust the pH to 7.0 ± 0.1 with ammonia water.
3.2.2 0.05 mol/L sodium hydroxide solution. weigh 1 g of sodium hydroxide, dissolve
in water and make up to 500 mL.
3.3 Standards
Hexavalent chromium standard solution. 1000 μg/mL, the medium is water, and it is a
reference standard certified by the state and awarded a reference standard certificate.
3.4 Preparation of standard solutions
3.4.1 Hexavalent chromium standard stock solution (10 μg/mL). pipette 1.0 mL of
hexavalent chromium standard solution (1000 μg/mL), place in a 100 mL volumetric
flask, make up to the mark with water, shake well, transfer to a brown reagent bottle,
store at 4 ℃ in the dark, and the validity period is 1 month.
3.4.2 Hexavalent chromium standard working solution (100 μg/L). pipette 1.0 mL of
hexavalent chromium standard stock solution, place in a 100 mL volumetric flask, make
up to the mark with 60 mmol/L ammonium nitrate solution, shake well, transfer to a
brown reagent bottle. Prepare before use.
4 Instruments and equipment
4.1 Liquid chromatography-inductively coupled plasma mass spectrometer (LC-ICP-
MS). it consists of a liquid chromatograph and an inductively coupled plasma mass
spectrometer (with a collision reaction cell).
4.2 Balance. the sensitivity is 0.001 g.
4.3 pH meter. the accuracy is 0.01.
4.4 Water bath oscillator.
4.5 Refrigerated centrifuge. the centrifugal force is not less than 13100 g.
4.6 Aqueous phase needle filter. 0.45 μm mixed cellulose filter membrane.
5 Analysis steps
5.1 Sample preparation
5.1.1 During sample preparation and sample storage, samples shall be protected from
contamination.
5.1.2 After the powdered sample and liquid sample are mixed evenly, they are placed
in a clean container, sealed and labeled, and stored at 4°C for future use.
5.2 Sample pretreatment
Accurately weigh 0.25 g of sample (accurate to 0.001 g), place in a stoppered
polypropylene centrifuge tube, add 5 mL of water and vortex to disperse the sample,
then add 20 mL of sodium hydroxide solution (0.05 mol/L), oscillate and extract in a
25 ℃ water bath for 0.5 h, centrifuge at 10000 r/min for 10 min at 4 ℃, take the upper
centrifugal clear liquid and filter through a 0.45 μm filter membrane, for determination
by liquid chromatography-inductively coupled plasma mass spectrometry. Perform a
blank test at the same time.
5.3 Instrument reference conditions
5.3.1 Liquid chromatography conditions
Chromatographic column. Dionex AG19 guard column (4.1 mm × 50 mm, 10 μm) +
AS19 analytical column (4.1 mm × 250 mm, 10 μm), or anion exchange columns with
equivalent performance.
Column temperature. 25 ℃.
Mobile phase. 60 mmol/L ammonium nitrate, pH = 7.0.
Flow rate. 1.0 mL/min.
Sample injection volume. 50 μL.
5.3.2 Mass spectrometry conditions
See Annex A.
5.4 Plotting of standard curve
Respectively pipette 0 μL, 5 μL, 10 μL, 20 μL, 50 μL, 100 μL, and 200 μL of hexavalent
chromium standard working solution, make up to 1 mL with water, and prepare the
series standard solutions with hexavalent chromium mass concentrations of 0 ng/mL,
0.5 ng/mL, 1.0 ng/mL, 2.0 ng/mL, 5.0 ng/mL, 10.0 ng/mL, and 20.0 ng/mL respectively,
for determination by liquid chromatography-inductively coupled plasma mass
spectrometry. Plot a standard working curve using the peak area of hexavalent
chromium as the ordinate and the concentration of hexavalent chromium as the abscissa.
5.5 Determination of sample solution
Under the same conditions, inject the blank test solution and the sample solution into
the instrument for determination, and calculate the concentration of hexavalent
chromium in the test solution using the standard working curve.
centrifugation, the sample is subjected to liquid chromatography-inductively coupled
plasma mass spectrometry for determination of trivalent chromium. Under this
determination condition, trivalent chromium and hexavalent chromium are converted
in equal amounts, the amount of trivalent chromium measured minus the amount of
hexavalent chromium determined in part I is the trivalent chromium content in the
sample.
10 Reagents and materials
Unless otherwise specified, all reagents used in this method are analytically pure, and
the water is grade 1 water specified in GB/T 6682.
10.1 Reagents
10.1.1 Sodium thiosulfate (Na2S2O3 • 5H2O).
10.1.2 Disodium ethylenediaminetetraacetic acid (EDTA-2Na).
10.1.3 Nitric acid (HNO3). ultra-high purity, concentration ≥ 69 %.
10.1.4 Ammonia (NH3 • H2O). chromatographic purity, concentration ≥ 25 %.
10.1.5 Helium (He). helium (≥ 99.995 %).
10.1.6 Argon (Ar). argon (≥ 99.995 %) or liquid argon.
10.2 Reagent preparation
10.2.1 0.1 mol/L sodium thiosulfate solution. weigh 26 g of sodium thiosulfate, dissolve
in 1000 mL of boiled and cooled water for later use.
10.2.2 60 mmol/L ammonium nitrate solution. pipette 3.9 mL of nitric acid into 1 L of
water, adjust pH to 7.0 ± 0.1 with ammonia water.
10.2.3 20 mmol/L disodium ethylenediaminetetraacetic acid solution. weigh 3.38 g of
disodium ethylenediaminetetraacetic acid, dissolve with ammonium nitrate solution (60
mmol/L) and add water to nearly 500 mL, adjust pH to 9.0 ± 0.1 with ammonia water,
transfer to a 500 mL volumetric flask, and make up to the mark with water.
10.2.4 5 % nitric acid solution. weigh a certain amount of nitric acid that is converted
to 5 g and place in a 100 mL volumetric flask, add water to dilute to the mark.
10.3 Standards
Trivalent chromium standard solution. 1000 μg/mL, the medium is hydrochloric acid,
it is a reference standard certified by the state and awarded a reference standard
certificate.
10.4 Preparation of standard solutions
10.4.1 Trivalent chromium standard stock solution (10 μg/mL). pipette 1.0 mL of
trivalent chromium standard solution (1000 μg/mL), place in a 100 mL volumetric flask,
make up to the mark with hydrochloric acid, shake well, transfer to a brown reagent
bottle, store at 4 ℃ in the dark, and the validity period is 1 month.
10.4.2 Trivalent chromium standard working solution (1000 μg/L). pipette 10.0 mL of
trivalent chromium standard stock solution, place in a 100 mL volumetric flask, make
up to the mark with 60 mmol/L ammonium nitrate solution, shake well, and transfer to
a brown reagent bottle. Prepare before use.
11 Instruments and equipment
Same as Clause 4.
12 Analysis steps
12.1 Sample preparation
Same as 5.1.
12.2 Sample pretreatment
Accurately weigh 0.5 g of sample (accurate to 0.001 g), place in a stoppered
polypropylene centrifuge tube, add 5 mL of 5 % nitric acid solution, oscillate in a 80 ℃
water bath for 1 h, add 5 mL sodium thiosulfate solution (0.1 mol/L) after cooling,
adjust pH to 9.0 ± 0.1 with ammonia water, add 15 mL disodium
ethylenediaminetetraacetic acid solution (20 mmol/L), oscillate in a 80 ℃ water bath
for 1 h, cool to room temperature, add water to make up to 25 mL, centrifuge at 4 ℃
10000 r/min for 10 min, filter through a 0.45 μm filter membrane, and put on the
machine. Perform a blank test at the same time.
12.3 Instrument reference conditions
12.3.1 Liquid chromatography conditions
Same as 5.3.1.
12.3.2 Mass spectrometry conditions
See Annex A.
12.4 Plotting of standard curve
Respectively pipette 0 μL, 12.5 μL, 25 μL, 50 μL, 125 μL, 250 μL, and 500 μL of
trivalent chromium standard working solution, add 5 mL of sodium thiosulfate solution
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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