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This standard replaces 5009.69-2008 Method for Analysis of Hygienic Standard of Epoxy Phenolic Coatings for Inner Wall of Food Cans and GB/T 5009.99-2003 Method for Analysis of Hygienic Standard of Polycarbonate Resin Used as Food Containers and Packaging.
The following main changes have been made with respect to GB/T 5009.69-2008 (the previous edition):
——the standard is renamed as National Food Safety Standard - Food Contact Materials and Articles - Determination of The Content and Migration of Free Phenol;
——the application scope of the standard is modified;
——the detection limit of this method is added;
——the polarography is deleted.
National Food Safety Standard
Food Contact Materials and Articles - Determination of Free Phenols and Determination of Migration
1 Scope
This Standard specifies determination methods of free phenols in food contact materials and articles (modified water-based epoxy paint, epoxy-phenol resin paint, polycarbonate) and determination of migration.
This Standard is applicable to determination of free phenols in food contact materials and articles (modified water-based epoxy paint, epoxy-phenol resin paint, polycarbonate) and determination of migration.
Determination of Free Phenol
2 Principle
Combine bromine and phenol to form tribromo phenol, and the remaining bromine acts with potassiumiodide, separate out quantitative iodine; titrate separated iodine with sodium hyposulfite; based on the consumption of sodium hyposulfite solution, work out the content of phenol.
3 Reagents and Materials
Unless otherwise specified, analytically-pure reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1 Reagents
3.1.1 Chlorhydric acid (HCl).
3.1.2 Ethyl alcohol (CH3OH).
3.1.3 Methenyl choloride (CHCl3).
3.1.4 Potassiumiodide (KI).
3.1.5 Soluble starch [(C6H10O5)n].
3.1.6 Bromide water (Br2).
3.1.7 Anhydrous sodium carbonate (Na2CO3).
3.2 Preparation of reagents
3.2.1 Potassium iodide solution (100 g/L): weigh 1.0 g potassium iodide, dissolve with water and dilute to 10mL.
3.2.2 Starch indicating liquid (10 g/L): weigh 1.0 g soluble starch, add a small amount of water to make it pasty, pour it to 100 mL boiling water, boil it a short while, prepare immediately before use.
3.3 Standard products
3.3.1 Sodium hyposulfite (Na2S2O3·5H2O): guaranteed reagent.
3.3.2 Potassium bromate (KBrO3): guaranteed reagent.
3.3.3 Potassium bromide (KBr): guaranteed reagent.
3.4 Preparation of standard solutions
3.4.1 Sodium hyposulfite standard titrant [c(Na2S2O3)=0.1 mol/L]
Weigh 26 g (accurate to 0.001 g) sodium hyposulfite (Na2S2O3·5H2O), add 0.2 g anhydrous sodium carbonate, dissolve it in 1000 mL water, slowly boil for 10 min; filter it after being placed for two weeks; before use, calibrate it as specified in GB/T 601.
3.4.2 Bromine standard solution [c( Br2)=0.1 mol/L]
Weigh 3.0 g potassium bromate and 25.0 g potassium bromide, dissolve them in 1000 mL water, shake it well; before use, calibrate it as specified in GB/T 601.
4 Instruments and Apparatus
Balance: with sensibility of 0.1mg and 0.01g.
5 Analysis Steps
5.1 Distillation of specimen
Weigh 1 g (accurate to 0.001 g) specimen, put into a distilling flask, dissolve with 20 mL ethyl alcohol (for water-soluble resin, dissolve with 20 mL water), add 50mL water; heat it with water vapor, distill out free phenol, collect the distill-out solution into a 500 mL volumetric flask (control the distill-out distillate 300 mL ~ 400 mL within 40 min ~ 50 min); finally take a small amount of fresh distill-out solution, add 1~ 2 drops of bromide water; no white precipitation means that phenol has been distilled out, therefore the distillation may end; dilute the distillate to the scale with water, shake well and preserve it for standby.
5.2 Titration determination
Pipet 100 mL distillate into a 500 mL conical beaker with a stopper; add 25 mL bromine standard solution and 5 mL chlorhydric acid; place at a dark place under the ambient temperature for 15min; add 10 mL potassium iodide solution, place in the dark for 10min; add 1 mL methenyl choloride; titrate it with sodium hyposulfite standard titrant until it appears yellow, add 1 mL starch indicating liquid, titrate it until blue fades.
5.3 Blank test
Simultaneously measure 20 mL ethyl alcohol, dilute with water to 500 mL, pipet 100 mL the diluted solution (for water-soluble resin, pipet 100 mL water), and carry out the determination as specified in 5.2 herein.
Foreword i
1 Scope
2 Principle
3 Reagents and Materials
4 Instruments and Apparatus
5 Analysis Steps
6 Expression of Analysis Results
7 Accuracy
8 Other
Annex A Gas Chromatogram of Standard Solutions
