Foreword
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This standard replaces GB 31604.46-2016 National food safety standard - Food contact materials and articles - Determination of free phenol and its migration.
The following main changes have been made with respect to GB 31604.46-2016:
——The clause "Scope" has been modified;
——The limit of detection (LOD) and limit of quantification (LOQ) in Part I have been modified;
——The analytical procedures and result expression in Part II have been modified;
——"Part III Determination of phenol migration" has been added.
National food safety standard -
Food contact materials and articles -
Determination of free phenol and its migration
1 Scope
This standard specifies the determination method of free phenol and its migration of food contact materials and articles.
In this standard, Part I is applicable to the determination of free phenol in epoxy phenolic resin coatings for food contact; Part II is applicable to the determination of free phenol migration in food contact materials and articles; Part III is applicable to the determination of the migration of phenol in food contact materials and articles.
Part I Determination of free phenol
2 Principle
In the specimen, free phenol reacts with bromine to produce brominated phenol, and the remaining bromine reacts with potassium iodide. The precipitated iodine is titrated with sodium thiosulfate. The content of free phenol is calculated according to the consumption of sodium thiosulfate solution.
3 Reagents and materials
Unless otherwise stated, reagents used in this method are analytical reagents, and the water is Class-I water as specified in GB/T 6682.
3.1 Reagents
3.1.1 Hydrochloric acid (HCl): with a mass fraction of 36% to 38%.
3.1.2 Trichloromethane (CHCl3).
3.1.3 Ethyl alcohol (C2H6O).
3.1.4 Potassium iodide (KI).
3.1.5 Soluble starch [(C6H10O5)n].
3.1.6 Bromide water (Br2): with a content ≥ 3%.
3.1.7 Anhydrous sodium carbonate (Na2CO3).
3.1.8 Potassium bromide (KBr).
3.2 Preparation of reagents
3.2.1 Potassium iodide solution (100 g/L): Weigh 1.00 g of potassium iodide, dissolve it in water and dilute it to 10 mL.
3.2.2 Starch indicator solution (10 g/L): weigh 1.0 g of soluble starch, add 5 mL of water into it to make it a paste, and then put the paste to 90 mL of boiling water while stirring, boil it for 1 min to 2 min, and then cool it and dilute it to 100 mL. The shelf life of this solution is two weeks.
3.3 Standard
3.3.1 Sodium thiosulfate pentahydrate (Na2S2O3·5H2O, CAS No.: 10102-17-7): working chemical, or its reference material certified by the state and issued with the reference material certificate.
3.3.2 Potassium bromate (KBrO3, CAS No.: 7758-01-2): working chemical, or its reference material certified by the state and issued with the reference material certificate.
3.3.3 Bromine standard solution for volumetric analysis: reference material certified by the state and issued with the reference material certificate.
3.4 Preparation of standard solutions
3.4.1 Sodium thiosulfate standard volumetric solution [c(Na2S2O3) = 0.1 mol/L]
Weigh 26 g of sodium thiosulfate (Na2S2O3·5H2O), add 0.2 g of anhydrous sodium carbonate, dissolve in 1,000 mL water, slowly boil for 10 min and cool. Place it in a brown reagent bottle, keep away from light for 2 weeks and then filter, and calibrate according to GB/T 5009.1 before use. Sodium thiosulfate standard volumetric solution for volumetric analysis with the same concentration may also be used.
3.4.2 Bromine standard solution
Weigh 3.0 g of potassium bromate and 25.0 g potassium bromide, dissolve in 1,000 mL of water, shake well, and calibrate according to GB/T 5009.1 before use. Bromine standard solution for volumetric analysis with the same concentration may also be used.
4 Apparatuses
4.1 Balance: with sensitivity of 0.01 g and 0.1 mg.
4.2 Steam distillation device: See Annex A for schematic diagram, or automatic steam distiller.
Foreword i
1 Scope
2 Principle
3 Reagents and materials
4 Apparatuses
5 Analytical procedures
6 Expression of analysis results
7 Precision
8 Others
9 Principle
10 Reagents and materials
11 Apparatuses
12 Analytical procedures
13 Expression of analysis results
14 Precision
15 Others
16 Principle
17 Reagents and materials
18 Apparatuses
19 Analytical procedures
20 Expression of analysis results
21 Precision
22 Others
Annex A Schematic diagram of steam distillation device
Annex B Chromatogram of phenol standard working solution
