GB 5009.33-2016 English PDF (GB5009.33-2016)

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GB 5009.33-2016: National food safety standard -- Determination of nitrite and nitrate in foods
GB 5009.33-2016
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standard -
Determination of Nitrite and Nitrate in Foods
ISSUED ON. DECEMBER 23, 2016
IMPLEMENTED ON. JUNE 23, 2017
Issued by. National Health and Family Planning Commission of the
People’s Republic of China;
State Food and Drug Administration of the People’s Republic
of China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
Method I Ion Chromatography ... 4 
2 Principle ... 4 
3 Reagents and Materials ... 4 
4 Instruments and Equipment ... 5 
5 Analytical Procedures ... 6 
6 Expression of Analysis Results ... 8 
7 Precision ... 9 
8 Others ... 9 
Method II Spectrophotometry ... 9 
9 Principle ... 9 
10 Reagents and Materials... 10 
11 Instruments and Equipment ... 12 
12 Analytical Procedures ... 15 
13 Expression of Analysis Results ... 17 
14 Precision ... 18 
15 Others ... 18 
Method III Determination of Nitrate in Vegetables and Fruits - UV
Spectrophotometry ... 18 
16 Principle ... 18 
17 Reagents and Materials... 19 
18 Instruments and Equipment ... 20 
19 Analytical Procedures ... 20 
20 Calculation Result ... 21 
21 Precision ... 21 
22 Others ... 21 
Appendix A Chromatogram of Nitrite and Nitrate ... 22
National Food Safety Standard -
Determination of Nitrite and Nitrate in Foods
1 Scope
This Standard specifies the method of determining nitrite and nitrate in foods.
This Standard is applicable to the determination of nitrite and nitrate in foods.
Method I -- Ion Chromatography
2 Principle
Precipitate protein and remove fat from the sample; adopt the corresponding method
to extract and purify; take potassium hydroxide solution as the eluent; adopt anion
exchange column for separation; take conductance detector or UV detector for
detection. Determine the nature with the retention time and quantify with the external
standard method.
3 Reagents and Materials
Unless otherwise indicated, the reagents adopted under this method are of analytical
purity. The water is first-grade water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Acetic acid (CH3COOH).
3.1.2 Potassium hydroxide (KOH).
3.2 Preparation of Reagents
3.2.1 Acetic acid solution (3%). weigh-take 3 mL of acetic acid, place it in 100 mL
volumetric flask. Add water to dilute to the constant volume; mix it up.
3.2.2 Potassium hydroxide solution (1 mol/L). weigh-take 6 g of potassium hydroxide;
dissolve it in cold water that’s newly boiled; dilute to 100 mL; mix it up.
3.3 Standards
volumetric flask; add water to dilute to the constant volume, mix it up. Use filter paper
to filter the solution; take part of the solution, then, centrifuge for 15 min under 10,000
r/min. Reserve the supernatant for later usage.
5.2.2 Meat, egg, fish and other products. weigh-take 5 g (accurate to 0.001 g) of
sample homogenate, place it in 150 mL conical flask with a plug; add 80 mL of water.
Start ultrasonic extraction for 30 min; shake once every 5 min, then, maintain the
completely dispersed solid phase. Place it in water bath at 75 °C for 5 min; take it out
and wait till it reaches the room temperature. Quantitatively transfer it into 100 mL
volumetric flask; add water to dilute to the constant volume, mix it up. Use filter paper
to filter the solution; take part of the solution, then, centrifuge for 15 min under 10,000
r/min. Reserve the supernatant for later usage.
5.2.3 Marinated fish, marinated meat and other marinated products. weigh-take 2 g
(accurate to 0.001 g) of sample homogenate, place it in 150 mL conical flask with a
plug; add 80 mL of water. Start ultrasonic extraction for 30 min; shake once every 5
min, then, maintain the completely dispersed solid phase. Place it in water bath at
75 °C for 5 min; take it out and wait till it reaches the room temperature. Quantitatively
transfer it into 100 mL volumetric flask; add water to dilute to the constant volume, mix
it up. Use filter paper to filter the solution; take part of the solution, then, centrifuge for
15 min under 10,000 r/min. Reserve the supernatant for later usage.
5.2.4 Dairy products. weigh-take 10 g (accurate to 0.01 g) of sample, place it in 100
mL conical flask with a plug; add 80 mL of water, mix it up. Start ultrasonic extraction
for 30 min. Add 2 mL of 3% acetic acid solution, place it under 4 °C for 20 min; take it
out and wait till it reaches the room temperature. Add water to dilute to the constant
volume. Use filter paper to filter the solution; reserve the filtrate for later usage.
5.2.5 Milk powder and cottage cheese. weigh-take 2.5 g (accurate to 0.01 g) of
sample, place it in 100 mL conical flask with a plug; add 80 mL of water, mix it up. Start
ultrasonic extraction for 30 min. Take it out and wait till it reaches the room
temperature. Quantitatively transfer it into 100 mL volumetric flask; add 2 mL of 3%
acetic acid solution. Add water to dilute to the constant volume. Place it under 4 °C for
20 min; take it out and wait till it reaches the room temperature. Use filter paper to filter
the solution; reserve the filtrate for later usage.
5.2.6 Take approximately 15 mL of the above-mentioned reserved solution; adopt
0.22 μm water filter needle filter and C18 column to remove 3 mL of supernatant (if
chloride is >100 mg/L, adopt needle filter, C18 column, Ag column and Na column to
remove 7 mL of supernatant); gather the remaining eluent for detection.
Before the usage of solid phase extraction column, it needs to be activated. The
activation of C18 column (1.0 mL), Ag column (1.0 mL) and Na column (1.0 mL).
before the usage of C18 column (1.0 mL), respectively inject 10 mL of methanol and 15
mL of water; start static activation for 30min. Inject 10 mL of water to Ag column (1.0
mL) and Na column (1.0 mL); start static activation for 30 min.
add 100 mL of water; mix it up. Add 65 mL of ammonia; add water to dilute to 1,000
mL; mix it up. Adjust pH to 9.6~9.7.
10.2.5 Diluent of ammonia buffer solution. weigh-take 50 mL of pH 9.6~9.7 ammonia
buffer solution; add water to dilute to 500 mL; mix it up.
10.2.6 Hydrochloric acid (0.1 mol/L). weigh-take 8.3 mL of hydrochloric acid; add
water to dilute to 1,000 mL.
10.2.7 Hydrochloric acid (2 mol/L). weigh-take 167 mL of hydrochloric acid; add water
to dilute to 1,000 mL.
10.2.8 Hydrochloric acid (20%). weigh-take 20 mL of hydrochloric acid; add water to
dilute to 100 mL.
10.2.9 Sulfanilic acid solution (4 g/L). weigh-take 0.4 g of sulfanilic acid; dissolve it in
100 mL of 20% hydrochloric acid; mix it up. Place it in brown bottle; keep away from
light.
10.2.10 Naphthalene ethylenediamine hydrochloride solution (2 g/L). weigh-take 0.2 g
of naphthalene ethylenediamine hydrochloride; dissolve it in 100 mL of water; mix it
up. Place it in brown bottle; keep away from light.
10.2.11 Copper sulfate solution (20 g/L). weigh-take 20 g of copper sulfate; add water
to dilute it to 1,000 mL.
10.2.12 Cadmium sulfate solution (40 g/L). weigh-take 40 g of cadmium sulfate; add
water to dilute it to 1,000 mL.
10.2.13 Acetic acid solution (3%). weigh-take 3 mL of glacial acetic acid; place it in
100 mL volumetric flask. Add water to dilute to the constant volume; mix it up.
10.3 Standards
10.3.1 Sodium nitrite (NaNO2, CAS No.. 7632-00-0). reference reagents, or standard
nitrite solution supported by Reference Material Certificate.
3.3.2 Sodium nitrate (NaNO3, CAS No.. 7631...