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GB 5009.33: Evolution and historical versions
| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB 5009.33-2025 | English | 320 |
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National food safety standard - Determination of nitrite and nitrate in foods
| Valid |
| GB 5009.33-2016 | English | 115 |
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National food safety standard - Determination of Nitrite and Nitrate in Foods
| Valid |
| GB 5009.33-2010 | English | 85 |
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National food safety standard -- Determination of nitrite and nitrate in foods
| Obsolete |
| GB/T 5009.33-2008 | English | 479 |
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Determination of nitrite and nitrate in foods
| Obsolete |
| GB/T 5009.33-2003 | English | 319 |
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Determination of nitrite and nitrate in foods
| Obsolete |
| GB/T 5009.33-1996 | English | 239 |
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Method for determination of nitrite and nitrate in foods
| Obsolete |
| GB 5009.33-1985 | English | 199 |
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Method for determination of nitrite and nitrate in foods
| Obsolete |
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GB 5009.33-2025: National food safety standard - Determination of nitrite and nitrate 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/GB5009.33-2025
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standard - Determination of nitrite and
nitrate in foods
Issued on: SEPTEMBER 02, 2025
Implemented on: MARCH 02, 2026
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... 12
12 Procedures... 12
13 Expression of analysis results... 14
14 Precision... 16
15 Others... 16
16 Principle... 17
17 Reagents and materials... 17
18 Instruments and apparatuses... 19
19 Procedures... 19
20 Expression of analysis results... 21
21 Precision... 22
22 Others... 22
23 Principle... 23
24 Reagents and materials... 23
25 Instruments and apparatuses... 24
26 Procedures... 24
27 Result calculation... 25
28 Precision... 26
29 Others... 26
Appendix A Chromatograms of nitrite and nitrate ions... 27
Appendix B Cadmium particle preparation... 28
Appendix C Determination of cadmium column reduction efficiency... 31
National food safety standard
Determination of nitrite and nitrate in foods
1 Scope
This Standard specifies the methods for determining nitrite and nitrate in foods.
Method I of this Standard applies to the determination of nitrite and nitrate in foods
(excluding foods for special medical purposes containing partially hydrolyzed milk
protein, extensively hydrolyzed milk protein, amino acid formulas, and amino acid
metabolism disorder formulas).
Methods II and III of this Standard are applicable to the determination of nitrite and
nitrate in foods.
Method IV of this Standard is applicable to the determination of nitrate in fresh
vegetables and fruits.
Method I - Ion chromatography
2 Principle
After the sample is subject to protein precipitation and fat removal, extraction and
purification, use potassium hydroxide or sodium hydroxide solution as eluent, separate
by anion exchange column, and detect by conductivity detector or ultraviolet detector.
Perform qualitative analysis using retention time, and quantitative analysis the external
standard method.
3 Reagents and materials
Unless otherwise specified, all the reagents in this method are analytical reagents, and
the water is grade-I water specified by GB/T 6682.
3.1 Reagents
3.1.1 Acetic acid (CH3COOH). chromatographic pure.
3.1.2 Potassium hydroxide (KOH).
3.1.3 Sodium hydroxide (NaOH).
3.1.4 α-Amylase. enzyme activity ≥ 1.5 U/mg.
3.2 Preparation of reagents
3.2.1 Acetic acid solution (3%). Measure 3 mL of acetic acid into a 100 mL volumetric
flask; use water to dilute to the mark; mix well.
3.2.2 Potassium hydroxide solution (1 mol/L). Weigh 5.6 g of potassium hydroxide;
dissolve it in freshly boiled and cooled water; dilute to 100 mL; mix well.
3.2.3 Sodium hydroxide solution (1 mol/L). Weigh 4.0 g of sodium hydroxide; add
freshly boiled and cooled water to dissolve it; dilute to 100 mL; mix well.
3.3 Standards
3.3.1 Sodium nitrite standard (NaNO2, CAS No.. 7632-00-0). purity ≥ 99%. Or nitrite
standards that have been certified by the state and granted a standard substance
certificate.
3.3.2 Sodium nitrate standard (NaNO3, CAS No.. 7631-99-4). purity ≥ 99%. Or nitrate
standards that have been certified by the state and granted a standard substance
certificate.
3.4 Preparation of standard solution
3.4.1 Sodium nitrite standard stock solution (100 mg/L). Accurately weigh 0.100 0 g of
sodium nitrite dried to constant weight at 110 ℃~120 ℃; use water to dissolve and
dilute to 1 000 mL; mix well; store in a refrigerator at 2 ℃ ~ 6 ℃. The validity period
is 3 months.
3.4.2 Sodium nitrate standard stock solution (100 mg/L). Accurately weigh 0.100 0 g
of sodium nitrate dried to constant weight at 110 ℃ ~ 120 ℃; use water to dissolve and
dilute to 1 000 mL; mix well; store in a refrigerator at 2 ℃ ~ 6 ℃. The validity period
is 3 months.
3.4.3 Mixed standard intermediate solution of sodium nitrite and sodium nitrate (2.00
mg/L). Accurately transfer 2.00 mL of each of the standard stock solutions of sodium
nitrite and sodium nitrate into 100 mL volumetric flasks; use water to dilute to the mark.
Prepare when necessary.
3.4.4 Mixed standard solution of sodium nitrite and sodium nitrate. Transfer the
intermediate solution of the mixed standard of sodium nitrite and sodium nitrate; add
water to dilute it stepwise to prepare a series of standard solutions with mass
concentrations of 0 mg/L, 0.010 0 mg/L, 0.020 0 mg/L, 0.050 0 mg/L, 0.100 mg/L,
0.200 mg/L, 0.500 mg/L, 1.00 mg/L and 2.00 mg/L. Prepare when necessary.
Note. The range of the standard curve can be adjusted according to the content of
the target analyte in the sample, and it shall include at least 5 concentration
levels (excluding zero).
3.5 Materials
3.5.1 Membrane needle filter. water-based, 0.22 μm.
3.5.2 C18 purification column. 1 mL, or equivalent column. Before use, activate with
10 mL of methanol and 15 mL of water in sequence.
3.5.3 Ag purification column. column capacity 2.0 ion equivalent ~ 2.2 ion equivalent,
or equivalent column. Use 10 mL of water to activate before use.
3.5.4 Na purification column. column capacity 2.0 ion equivalent ~ 2.2 ion equivalent,
or equivalent column. Use 10 mL of water to activate before use.
4 Instruments and apparatuses
4.1 Ion chromatograph. equipped with a conductivity detector and suppressor, or an
ultraviolet detector.
4.2 Food grinder.
4.3 Ultrasonic cleaner.
4.4 Electronic balance. sensitivity, 0.1 mg and 0.01 g.
4.5 Centrifuge. speed ≥ 10 000 r/min.
5 Analysis steps
5.1 Sample preparation and storage
5.1.1 Sample preparation
5.1.1.1 Liquid or semi-solid samples. Take an appropriate amount of sample and mix it
thoroughly by stirring or shaking.
5.1.1.2 Solid powder samples. Take an appropriate amount of sample and mix it
thoroughly by means of shaking or other methods.
5.1.1.3 Cheese. Take an appropriate amount of sample and grind it into a uniform slurry.
To avoid moisture loss, excessive heat shall be avoided during the grinding process.
5.1.1.4 Other solid samples. Take an appropriate amount of sample and crush it into
uniform powder or make it into slurry for later use.
5.1.2 Sample storage
5.1.2.1 Perishable samples such as fruits, vegetables, meat, and aquatic products shall
be stored at -18 ℃ or below.
5.1.2.2 Other samples shall be stored in accordance with the product's storage
conditions.
5.2 Sample extraction
5.2.1 Milk and dairy products, infant formula, infant formula for special medical
purposes, formula for special medical purposes, bird's nest and its products. Weigh 10
g of liquid sample and 1 g ~ 2.5 g of other samples (accurate to 0.01 g); place them in
a 150 mL stoppered conical flask; add 80 mL of water; shake well; sonicate for 30 min
(heat if necessary to dissolve or fully swell); remove and place at room temperature;
quantitatively transfer to a 100 mL volumetric flask; add 2 mL of 3% acetic acid
solution (the amount can be adjusted appropriately according to the precipitation effect);
add water to dilute to the mark; mix well. Transfer the solution into a 250 mL stoppered
iodine flask and place it at 4 ℃ for 20 min; remove the flask and allow it to cool to
room temperature; take a portion of the solution and filter it through filter paper;
centrifuge the filtrate at 10 000 r/min for 15 min; keep the supernatant for later use.
5.2.2 High starch content samples that are easy to gelatinize. Weigh 2.5 g (accurate to
0.01 g) of the sample; place it in a 150 mL stoppered conical flask; add 0.2 g of α-
amylase (the amount of enzyme can be adjusted according to the starch content); add
80 mL of water; shake well; enzymatically hydrolyze at 55 ℃ for 30 min. Follow the
steps in section 5.2.1 starting from "Remove and let stand at room temperature".
5.2.3 Other samples. Weigh 2 g ~ 10 g (accurate to 0.01 g) of the sample; place it in a
150 mL stoppered conical flask; add 80 mL of water; extract by sonication for 30 min;
shake once every 5 min to keep the sample completely dispersed. Place in a 75 ℃ water
bath for 5 minutes; then follow the steps in section 5.2.1 starting from "Remove and let
stand to room temperature".
5.3 Sample purification
Take about 15 mL of the solution prepared in 5.2.1 ~ 5.2.3 and pass it through a 0.22
μm aqueous filter needle filter and a C18 column; discard the first 3 mL (if the chloride
ion concentration is greater than 100 mg/L or the target substance interferes, it is
necessary to pass it through the needle filter, C18 column, Ag column and Na column in
sequence; discard the first 7 mL); collect the eluent for analysis.
5.4 Blank test
Except for not adding a sample, the other operations are the same as those for adding a
sample.
5.5 Apparatus reference conditions
5.5.1 Column. a high-capacity anion exchange column with hydroxide selectivity,
compatible with gradient elution, using a divinylstyrene-ethylstyrene copolymer matrix
and alkanoyl quaternary ammonium salt functional groups, 4 mm × 250 mm (with a
guard column of 4 mm × 50 mm), or an ion chromatography column with equivalent
performance.
5.5.2 Eluent. Potassium hydroxide solution or sodium hydroxide solution, with a
concentration of 6 mmol/L ~ 70 mmol/L. The elution gradients shall be 6 mmol/L for
30 min, 70 mmol/L for 5 min, and 6 mmol/L for 5 min; the flow rate shall be 1.0 mL/min.
When chromatographic interference exists, the following elution methods can be
selected.
Potassium hydroxide solution or sodium hydroxide solution, with a concentration of 5
mmol/L ~ 50 mmol/L. The elution gradients shall be 5 mmol/L for 33 min, 50 mmol/L
for 5 min, and 5 mmol/L for 5 min; the flow rate shall be 1.3 mL/min.
5.5.3 Detector. Conductivity detector, with a detection cell temperature of 35 ℃; or
ultraviolet detector, with a detection wavelength of 226 nm.
5.5.4 Injection volume. 50 μL (can be adjusted according to the content of the analyte
ions in the sample).
5.6 Determination
5.6.1 Preparation of the standard curve
Inject the standard series of working solutions into the ion chromatograph (see
Appendix A, Figure A.1 for the standard chromatograms); plot the standard curve with
the concentration of the standard working solution on the x-axis and the peak height or
peak area on the y-axis.
5.6.2 Determination of sample solution
Inject the blank and sample solutions into the ion chromatograph to obtain the peak
height or peak area of the blank and sample solutions. Obtain the mass concentration
of sodium nitrite or sodium nitrate in the test solution according to the standard curve.
6 Expression of analysis results
The content of nitrite (calculated as sodium nitrite) or nitrate (calculated as sodium
nitrate) in the sample is calculated according to Formula (1).
Where.
X – the content of nitrite (calculated as sodium nitrite) or nitrate (calculated as sodium
nitrate) in the sample, in milligrams per kilogram (mg/kg);
ρ – the mass concentration of nitrite (calculated as sodium nitrite) or nitrate (calculated
as sodium nitrate) in the sample solution used for determination, in milligrams per
liter (mg/L);
ρ0 – the mass concentration of nitrite (calculated as sodium nitrite) or nitrate (calculated
as sodium nitrate) in the blank solution, in milligrams per liter (mg/L);
V – volume of the sample solution, in milliliters (mL);
f – dilution factor of the sample solution;
1 000 – conversion coefficient;
m – sample mass, in grams (g).
When the result is greater than or equal to 1.00 mg/kg, retain 3 significant figures; when
the result is less than 1.00 mg/kg, retain 2 significant figures.
7 Precision
The absolute difference of two independent test results under repeatability cannot
exceed 10% of the arithmetic mean value.
8 Others
8.1 Detection-limit
Nitrite (calculated as sodium nitrite). 0.05 mg/kg for liquid samples (10 g sample
weight), and 0.1 mg/kg for other samples (5 g sample weight).
Nitrate (calculated as sodium nitrate). 0.1 mg/kg for liquid samples (10 g sample
weight), and 0.2 mg/kg for other samples (5 g sample weight).
8.2 Quantitation-limit
Nitrite (calculated as sodium nitrite). 0.1mg/kg for liquid samples (10 g sample weight),
and 0.2mg/kg for other samples (5 g sample weight).
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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