National food safety standard- Determination of total arsenic and abio-arsenic in foods
1 Scope
Part I of this standard specifies the determination method of total arsenic in foods.
Method I and Method II in Part I of this standard are applicable to the determination of total arsenic in foods, while Method III is applicable to the determination of total arsenic in foods (except milk powder and modified milk powder, fats and oils as well as their products, condiments and foods for special dietary uses).
Part II of this standard specifies the determination method of abio-arsenic in foods.
Part II of this standard is applicable to the determination of abio-arsenic in cereals and their products, aquatic livestock and their products, edible mushrooms and their products, fats and oils as well as their products, condiments, complementary foods for infants and young children as well as algae and their products.
Part I Determination of total arsenic in foods
Method I Hydride generation atomic fluorescence spectrometry
2 Principle
After the specimen is digested with acid, thiourea is added to pre-reduce pentavalent arsenic to trivalent arsenic, and then sodium borohydride or potassium borohydride is added to reduce trivalent arsenic and to generate hydrogen arsenide, which is introduced by argon into the quartz atomizer and decomposed into atomic arsenic which, under the excitation of the emission light of arsenic hollow cathode lamp, generates atomic fluorescence with the fluorescence intensity directly proportional to the arsenic concentration in the solution under measurement under fixed conditions, which shall be quantified as per external standard method.
3 Reagents and materials
Unless otherwise specified, guaranteed reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
3.2.1 Potassium hydroxide solution (5g/L): weigh 5.0g potassium hydroxide, dissolve it in water and dilute to 1,000mL, and mix well.
3.2.2 Potassium borohydride solution (20g/L): weigh 20.0g potassium borohydride, dissolve it with 1,000mL potassium hydroxide solution (5g/L), and mix well. Freshly prepare before use.
3.2.3 Thiourea + ascorbic acid solution: weigh 10.0g thiourea, add about 80mL water, heat and dissolve it, add 10.0g ascorbic acid after cooling, dilute it to 100mL, and mix well. Freshly prepare before use.
3.2.4 Sodium hydroxide solution (100g/L): weigh 10.0g sodium hydroxide, dissolve it in water and dilute to 100mL, and mix well.
3.2.5 Magnesium nitrate solution (150g/L): weigh 15.0g magnesium nitrate, dissolve it in water and dilute to 100mL, and mix well.
3.2.6 Hydrochloric acid solution (1+1): take 100mL hydrochloric acid, pour it slowly into 100mL water, and mix well.
3.2.7 Sulfuric acid solution (1+9): take 100mL sulfuric acid, pour it slowly into 900mL water, and mix well.
3.2.8 Nitric acid solution (2+98): take 20mL nitric acid, pour it slowly into 980mL water, and mix well.
Note: Sodium borohydride (20g/L) may also be used as the reducing agent in this method: weigh 20g sodium borohydride, dissolve it in 1,000mL sodium hydroxide solution (5g/L), and mix well. The concentration of potassium borohydride or sodium borohydride solution may be adjusted according to the instrument sensitivity. Freshly prepare before use.
3.3 Standard substance
Arsenic trioxide (As2O3, CAS No.: 1327-53-3) standard substance: with a purity of greater than or equal to 99.5%.
3.4 Preparation of standard solutions
3.4.1 Arsenic standard stock solution (100mg/L, calculated by As): accurately weigh 0.0132g arsenic trioxide which has been dried at 100℃ for 2h, dissolve it with 1mL sodium hydroxide solution (100g/L) and a small amount of water, then transfer it into a 100mL volumetric flask, add proper amount of hydrochloric acid to adjust its acidity to be nearly neutral, and dilute it with water to the scale. Store it in a 2℃ to 8℃ refrigerator free of light, with a validity period of one year. Or the nationally recognized and certified arsenic standard solution.
3.4.2 Arsenic standard working solution (1.00mg/L, calculated by As): accurately pipette 1.00mL arsenic standard stock solution (100mg/L) into a 100mL volumetric flask, dilute it with nitric acid solution (2+98) to the scale. Store it in a 2℃ to 8℃ refrigerator free of light, with a validity period of 3 months.
3.4.3 Arsenic standard solution series: take a 25mL volumetric flask or seven colorimetric tubes, and accurately add 0.00mL, 0.05mL, 0.10mL, 0.25mL, 0.50mL, 1.50mL and 3.00mL arsenic standard solution (1.00mg/L) (equivalent to arsenic concentration of 0.0μg/L, 2.0μg/L, 4.0μg/L, 10.0μg/L, 20.0μg/L, 60.0μg/L and 120.0μg/L respectively), add 12.5mL sulfuric acid solution (1+9) and 2mL thiourea+ ascorbic acid solution, add water to the scale, mix well, and place for 30min before determination. Freshly prepare before use.
Note: The mass concentration range of arsenic in the standard solution series may be fine-tuned according to the instrument sensitivity and the actual content of arsenic in the sample.
4 Instruments and apparatus
4.1 Atomic fluorescence spectrometer.
4.2 Electronic balance: with a sensitivity of 0.01mg, 0.1mg and 1mg.
4.3 Homogenizer.
4.4 High speed disintegrator.
4.5 Electrothermal digestion device: temperature-controlled electric heating plate or graphite digester, with a maximum temperature of not lower than 350℃ and a temperature control precision of ±5℃.
4.6 Muffle furnace.
4.7 Thermostatic drying oven: with a temperature control precision of ±2℃.
4.8 Microwave digestion system: with a polytetrafluoroethylene digestion inner tank.
4.9 Pressure digestion tank.
Note: The glassware and polytetrafluoroethylene digestion inner tanks shall be soaked in nitric acid solution (1+4) for 24h, flushed with water repeatedly, and finally washed clean with water.
5 Analytical steps
5.1 Specimen preparation
5.1.1 Solid sample
5.1.1.1 Dry sample
Foreword i 1 Scope Part I Determination of total arsenic in foods Method I Hydride generation atomic fluorescence spectrometry 2 Principle 3 Reagents and materials 4 Instruments and apparatus 5 Analytical steps 6 Expression of analysis results 7 Precision 8 Others Method II Inductively coupled plasma/mass spectrometry Method III Graphite furnace atomic absorption spectrometry 9 Principle 10 Reagents and materials 11 Instruments and apparatus 12 Analytical steps 13 Expression of analysis results 14 Precision 15 Others Part II Determination of abio-arsenic in foods Method I Liquid chromatography-atomic fluorescence spectrometry 16 Principle 17 Reagents and materials 18 Instruments and apparatus 19 Analytical steps 20 Expression of analysis results 21 Precision 22 Others Method II Liquid chromatography - inductively coupled plasma mass spectrometry 23 Principle 24 Reagents and materials 25 Instruments and apparatus 26 Analytical steps 27 Expression of analysis results 28 Precision 29 Others Annex A Reference conditions for microwave digestion Annex B Reference conditions for instruments Annex C Reference conditions for instruments Annex D LC-AFS chromatogram Annex E LC-ICP/MS chromatogram
National food safety standard- Determination of total arsenic and abio-arsenic in foods
1 Scope
Part I of this standard specifies the determination method of total arsenic in foods.
Method I and Method II in Part I of this standard are applicable to the determination of total arsenic in foods, while Method III is applicable to the determination of total arsenic in foods (except milk powder and modified milk powder, fats and oils as well as their products, condiments and foods for special dietary uses).
Part II of this standard specifies the determination method of abio-arsenic in foods.
Part II of this standard is applicable to the determination of abio-arsenic in cereals and their products, aquatic livestock and their products, edible mushrooms and their products, fats and oils as well as their products, condiments, complementary foods for infants and young children as well as algae and their products.
Part I Determination of total arsenic in foods
Method I Hydride generation atomic fluorescence spectrometry
2 Principle
After the specimen is digested with acid, thiourea is added to pre-reduce pentavalent arsenic to trivalent arsenic, and then sodium borohydride or potassium borohydride is added to reduce trivalent arsenic and to generate hydrogen arsenide, which is introduced by argon into the quartz atomizer and decomposed into atomic arsenic which, under the excitation of the emission light of arsenic hollow cathode lamp, generates atomic fluorescence with the fluorescence intensity directly proportional to the arsenic concentration in the solution under measurement under fixed conditions, which shall be quantified as per external standard method.
3 Reagents and materials
Unless otherwise specified, guaranteed reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Sodium hydroxide (NaOH).
3.1.2 Potassium hydroxide (KOH).
3.1.3 Potassium borohydride (KBH4): analytical grade.
3.1.4 Thiourea (CH4N2S): analytical grade.
3.1.5 Hydrochloric acid (HCl).
3.1.6 Nitric acid (HNO3).
3.1.7 Sulfuric acid (H2SO4).
3.1.8 Perchloric acid (HClO4).
3.1.9 Hydrogen peroxide (H2O2): 30%.
3.1.10 Magnesium nitrate [Mg(NO3)2·6H2O]: analytical grade.
3.1.11 Magnesium oxide (MgO): analytical grade.
3.1.12 Ascorbic acid (C6H8O6): analytical grade.
3.2 Preparation of reagents
3.2.1 Potassium hydroxide solution (5g/L): weigh 5.0g potassium hydroxide, dissolve it in water and dilute to 1,000mL, and mix well.
3.2.2 Potassium borohydride solution (20g/L): weigh 20.0g potassium borohydride, dissolve it with 1,000mL potassium hydroxide solution (5g/L), and mix well. Freshly prepare before use.
3.2.3 Thiourea + ascorbic acid solution: weigh 10.0g thiourea, add about 80mL water, heat and dissolve it, add 10.0g ascorbic acid after cooling, dilute it to 100mL, and mix well. Freshly prepare before use.
3.2.4 Sodium hydroxide solution (100g/L): weigh 10.0g sodium hydroxide, dissolve it in water and dilute to 100mL, and mix well.
3.2.5 Magnesium nitrate solution (150g/L): weigh 15.0g magnesium nitrate, dissolve it in water and dilute to 100mL, and mix well.
3.2.6 Hydrochloric acid solution (1+1): take 100mL hydrochloric acid, pour it slowly into 100mL water, and mix well.
3.2.7 Sulfuric acid solution (1+9): take 100mL sulfuric acid, pour it slowly into 900mL water, and mix well.
3.2.8 Nitric acid solution (2+98): take 20mL nitric acid, pour it slowly into 980mL water, and mix well.
Note: Sodium borohydride (20g/L) may also be used as the reducing agent in this method: weigh 20g sodium borohydride, dissolve it in 1,000mL sodium hydroxide solution (5g/L), and mix well. The concentration of potassium borohydride or sodium borohydride solution may be adjusted according to the instrument sensitivity. Freshly prepare before use.
3.3 Standard substance
Arsenic trioxide (As2O3, CAS No.: 1327-53-3) standard substance: with a purity of greater than or equal to 99.5%.
3.4 Preparation of standard solutions
3.4.1 Arsenic standard stock solution (100mg/L, calculated by As): accurately weigh 0.0132g arsenic trioxide which has been dried at 100℃ for 2h, dissolve it with 1mL sodium hydroxide solution (100g/L) and a small amount of water, then transfer it into a 100mL volumetric flask, add proper amount of hydrochloric acid to adjust its acidity to be nearly neutral, and dilute it with water to the scale. Store it in a 2℃ to 8℃ refrigerator free of light, with a validity period of one year. Or the nationally recognized and certified arsenic standard solution.
3.4.2 Arsenic standard working solution (1.00mg/L, calculated by As): accurately pipette 1.00mL arsenic standard stock solution (100mg/L) into a 100mL volumetric flask, dilute it with nitric acid solution (2+98) to the scale. Store it in a 2℃ to 8℃ refrigerator free of light, with a validity period of 3 months.
3.4.3 Arsenic standard solution series: take a 25mL volumetric flask or seven colorimetric tubes, and accurately add 0.00mL, 0.05mL, 0.10mL, 0.25mL, 0.50mL, 1.50mL and 3.00mL arsenic standard solution (1.00mg/L) (equivalent to arsenic concentration of 0.0μg/L, 2.0μg/L, 4.0μg/L, 10.0μg/L, 20.0μg/L, 60.0μg/L and 120.0μg/L respectively), add 12.5mL sulfuric acid solution (1+9) and 2mL thiourea+ ascorbic acid solution, add water to the scale, mix well, and place for 30min before determination. Freshly prepare before use.
Note: The mass concentration range of arsenic in the standard solution series may be fine-tuned according to the instrument sensitivity and the actual content of arsenic in the sample.
4 Instruments and apparatus
4.1 Atomic fluorescence spectrometer.
4.2 Electronic balance: with a sensitivity of 0.01mg, 0.1mg and 1mg.
4.3 Homogenizer.
4.4 High speed disintegrator.
4.5 Electrothermal digestion device: temperature-controlled electric heating plate or graphite digester, with a maximum temperature of not lower than 350℃ and a temperature control precision of ±5℃.
4.6 Muffle furnace.
4.7 Thermostatic drying oven: with a temperature control precision of ±2℃.
4.8 Microwave digestion system: with a polytetrafluoroethylene digestion inner tank.
4.9 Pressure digestion tank.
Note: The glassware and polytetrafluoroethylene digestion inner tanks shall be soaked in nitric acid solution (1+4) for 24h, flushed with water repeatedly, and finally washed clean with water.
5 Analytical steps
5.1 Specimen preparation
5.1.1 Solid sample
5.1.1.1 Dry sample
Contents of GB 5009.11-2024
Foreword i
1 Scope
Part I Determination of total arsenic in foods
Method I Hydride generation atomic fluorescence spectrometry
2 Principle
3 Reagents and materials
4 Instruments and apparatus
5 Analytical steps
6 Expression of analysis results
7 Precision
8 Others
Method II Inductively coupled plasma/mass spectrometry
Method III Graphite furnace atomic absorption spectrometry
9 Principle
10 Reagents and materials
11 Instruments and apparatus
12 Analytical steps
13 Expression of analysis results
14 Precision
15 Others
Part II Determination of abio-arsenic in foods
Method I Liquid chromatography-atomic fluorescence spectrometry
16 Principle
17 Reagents and materials
18 Instruments and apparatus
19 Analytical steps
20 Expression of analysis results
21 Precision
22 Others
Method II Liquid chromatography - inductively coupled plasma mass spectrometry
23 Principle
24 Reagents and materials
25 Instruments and apparatus
26 Analytical steps
27 Expression of analysis results
28 Precision
29 Others
Annex A Reference conditions for microwave digestion
Annex B Reference conditions for instruments
Annex C Reference conditions for instruments
Annex D LC-AFS chromatogram
Annex E LC-ICP/MS chromatogram
