This standard replaces GB 5009.34-2016 National food safety standard—Determination of sulfur dioxide in foods.
The following main changes have been made with respect to GB 5009.34-2016:
——The original titrimetric method is modified to acid-alkali titrimetric method.
——The spectrophotometric method and the ion chromatography method are added.
National food safety standard——
Determination of sulfur dioxide in foods
1 Scope
This standard specifies the determination method of sulfur dioxide in foods.
The first acid-alkali titrimetric method is applicable to the determination of sulfur dioxide in foods; the second one is the spectrophotometric method, and its direct extraction method is applicable to the determination of sulfur dioxide in white sugar and white sugar products, starch and starch products, and wet flour products, and its nitrogen-filled distillation extraction method is applicable to the determination of sulfur dioxide in wine and brown sugar; the third ion chromatography method is applicable to the determination of sulfur dioxide in foods.
Method 1 Acid-alkali titrimetric method
2 Principle
The specimen is treated by nitrogen-filled distillation method. After acidification, sulfite and other series of substances release sulfur dioxide under heating conditions. The distillate is absorbed by hydrogen peroxide solution. The sulfur dioxide is dissolved in the absorption solution and oxidized into sulfuric acid. The sodium hydroxide standard solution is used for titration. The content of sulfur dioxide in the specimen is calculated according to the consumption of sodium hydroxide standard solution.
3 Reagents and materials
Unless otherwise specified, analytically-pure reagents and Class-III water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Hydrogen peroxide (H2O2): 30%.
3.1.2 Anhydrous ethanol (C2H5OH).
3.1.3 Sodium hydroxide (NaOH).
3.1.4 Methyl red (C15H15N3O2).
3.1.5 Hydrochloric acid (HCl) (ρ20=1.19 g/mL).
3.1.6 Nitrogen (purity>99.9%).
3.2 Preparation of reagents
3.2.1 Hydrogen peroxide solution (3%): measure 100 mL of hydrogen peroxide with a mass fraction of 30% and dilute it to 1,000 mL with water. Freshly prepare before use.
3.2.2 Hydrochloric acid solution (6 mol/L): measure 50 mL hydrochloric acid (ρ20=1.19 g/mL), slowly pour it into 50 mL water, and stir while adding.
3.2.3 Methyl red alcohol solution indicator (2.5 g/L): weigh 0.25g of methyl red indicator and dissolve it in 100 mL of anhydrous ethanol.
3.3 Preparation of standard solutions
3.3.1 Sodium hydroxide standard solution (0.1 mol/L): standard titration solution prepared and calibrated in accordance with GB/T 601, or certified by the country and awarded with a standard substance certificate.
3.3.2 Sodium hydroxide standard solution (0.01 mol/L): pipette 10.0 mL of sodium hydroxide standard solution (0.1 mol/L) into a 100 mL volumetric flask, and dilute it to the scale with water free of carbon dioxide.
4 Apparatus
4.1 Glass nitrogen-filled distiller: 500mL or 1,000 mL, additionally equipped with electric heating jacket, nitrogen source and gas flow meter, or equivalent distillation equipment. See Annex A for the schematic diagram of the device.
4.2 Electronic balance: with a sensitivity of 0.01g.
4.3 10 mL semimicro buret and 25 mL buret.
4.4 Pulverizer.
4.5 Tissue masher.
Foreword i
1 Scope
Method 1 Acid-alkali titrimetric method
2 Principle
3 Reagents and materials
4 Apparatus
5 Analysis procedure
6 Expression of analysis results
7 Precision
8 Limit of detection and limit of quantification
Method II Spectrophotometric method
9 Principle
10 Reagents and materials
11 Apparatus
12 Analysis procedure
13 Expression of analysis results
14 Precision
15 Limit of detection and limit of quantification
Method III Ion chromatography method
16 Principle
17 Reagents and materials
18 Apparatus
19 Analysis procedure
20 Expression of analysis results
21 Precision
22 Limit of detection and limit of quantification
Annex A Schematic diagram of acid-alkali titrimetric method distillation apparatus
Annex B Schematic diagram of steam distillation device
Annex C Typical spectrogram of sulfur dioxide standard working solution
