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This standard replaces GB/T 23296.22-2009 Food Contact Materials - Determination of Isocyanates in Plastics - High Performance Liquid Chromatography and SN/T 2741-2010 Imported and Exported Food Contact Materials - Determination of Polymers Isocyanate - High Performance Liquid Chromatography.
The following main changes have been made with respect to GB/T 23296.22-2009 and SN/T 2741-2010:
——the standard is renamed as National Food Safety Standard - Food Contact Materials and Articles - Determination of Isocyanate;
——the analytes are added to 7 items;
——the preparation of blank specimen is deleted;
——the matrix standard curve is revised as standard solution standard curve;
——the expression of analysis results is modified.
National Food Safety Standard
Food Contact Materials and Articles - Determination of Isocyanate
1 Scope
This Standard specifies determination methods of respective contents and total content of the seven isocyanates including toluene-2,6-diisocyanate, diphenyl methane-4,4′- diisocyanate, toluene-2,4-diisocyanate, naphthalene-1,5-diisocyanate, benzyl isocyanate, hexamethylene diisocyanate and cyclohexyl isocyanate in plastics and their products for food contact materials and articles.
This Standard is applicable to determination methods of repective contents and total content of the seven isocyanates including toluene-2,6-diisocyanate, diphenyl methane-4,4′-diisocyanate, toluene-2,4-diisocyanate, naphthalene-1,5-diisocyanate, benzyl isocyanate, hexamethylene diisocyanate and cyclohexyl isocyanate in urethane plastics and their products.
2 Principle
Perform vibrating extraction on the isocyanate (in specimen) with dichloromethane, then carry out derivation reaction with 9-N-methylaminomethyl anthracene; separate the derivative with C18 liquid chromatogram columns, determine with fluorescence detector, and carry out the quantitative determination by external standard method.
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 standard.
3.1 Reagents
3.1.1 Dichloromethane (CH2Cl2): dry it with 5A molecular sieve overnight for standby.
3.1.2 Sulfuric ether (C2H6O).
3.1.3 Phosphoric acid (HPO3).
3.1.4 Acetonitrile (C2H3N): chromatographically pure.
3.1.5 N, N-dimethylformamide (C3H7NO): with purity >99%.
3.1.6 Triethylamine(C6H15N).
3.1.7 9- N- Methylaminomethyl Anthracene (C16H15N): with purity > 99%.
3.2 Preparation of reagents
3.2.1 Derivatization reagent (260 mg/L): weigh 0.013 g 9-N-Methylaminomethyl Anthracene, dissolve it with dichloromethane, transfer to a 50 mL volumetric flask, scale the volume with dichloromethane; keep in a dark place. Prepare it before use.
3.2.2 Derivative dissolvent: measure 50 mL N, N-dimethylformamide and put into a 100 mL volumetric flask, add 40 mL acetonitrile, scale the volume with water.
3.2.3 Triethylamine solution (3%, volume fraction): add 30 mL triethylamine in a 1 L volumetric flask, and scale the volume with water.
3.2.4 Buffer solution: add 950 mL 3% triethylamine solution (3%, volume fraction) in a 1L volumetric flask, adjust pH value 3 with phosphoric acid, and scale the volume with water.
3.3 Standard product
3.3.1 Toluene-2,6-diisocyanate (C9H6N2O2, CAS No.: 91-08-7): with purity > 98%.
3.3.2 Diphenyl methane-4,4'-diisocyanate (C15H10N2O2, CAS No.: 101-68-8): with purity > 98%.
3.3.3 Toluene-2, 4-diisocyanate (C9H6N2O2, CAS No.: 584-84-9): with purity > 98%.
3.3.4 Naphthalene-1,5-diisocyanate (C12H6N2O2, CAS No.: 3173-72-6): with purity > 98%.
3.3.5 Benzyl isocyanate (C7H5ON, CAS No.: 103-71-9): with purity > 98%.
3.3.6 Cyclohexyl isocyanate (C7H11ON, CAS No.:3173-53-3): with purity > 98%.
3.3.7 Hexamethylene diisocyanate (C8H12O2N2, CAS No.: 822-06-0) with purity > 98%.
3.4 Preparation of standard solutions
3.4.1 Isocyanate stock solution (1000 mg/L): weigh 0.01 g (accurate to 0.1 mg) isocyanate standard substances, dissolve with dichloromethane, transfer to 10 mL volumetric flasks, and scale the volume with dichloromethane. Keep the stock solution at -20℃ in a dark place, which will be valid for 1 month.
3.4.2 Isocyanate standard intermediate solution (100mg/L): respectively measure 5 mL dichloromethane and put into six 10 mL volumetric flasks, add 1.0 mL isocyanate stock solutions respectively, and scale the volume with dichloromethane. Keep the standard intermediate solution at -20℃ in a dark place, which will be valid for 1 month.
3.4.3 Isocyanate standard working solution (1mg/L): respectively measure 5 mL dichloromethane and put into six 10 mL volumetric flasks, add 100μg isocyanate standard intermediate solutions respectively, scale the volume with dichloromethane, and mix them uniformly. Keep the standard working solution at -20℃ in a dark place, which will be valid for two weeks.
3.4.4 Mixed isocyanate standard working solution: respectively measure 5 mL dichloromethane and put into six 10 mL volumetric flasks, add 0.00 mL, 0.01 mL, 0.05 mL, 0.10 mL, 0.25 mL and 0.50 mL isocyanate standard intermediate solutions in sequence, scale the volume with dichloromethane, mix them uniformly, obtain mixed standard working solutions with isocyanate concentrations of 0.0 mg/L, 0.10 mg/L, 0.50 mg/L, 1.0mg/L, 2.5mg/L and 5.0mg/L respectively. Keep the mixed standard working solution at -20℃ in a dark place, which will be valid for two weeks.
4 Instruments and Apparatus
4.1 Liquid chromatograph: with fluorescence detector.
4.2 Glass container: 20mL, with polytetrafluorethylene cap; keep dry before use.
4.3 Water phase filter membrane: 0.45μm.
4.4 PH meter.
4.5 Analytic balance: with sensibility of 0.0001g and 0.01g.
5 Analysis Steps
5.1 Pretreatment of specimen
Weigh 1g (accurate to 0.01 g) specimen (cut into pieces with an area not larger than 1 cm × 1cm), put into a 20 mL glass container, add 10 mL dichloromethane and 1 mL derivatization reagent, seal it, keep it from light, shake 12h; transfer the extract to another 20mL glass container, seal it and keep it at - 20℃. Re-extract the remaining sample residual for 12h, and merge the extracts, concentrate it with nitrogen gas until dry, add 10 mL derivative dissolvent, dissolve it by ultrasound method, filter with 0.45 μm filter membrane, and put on machine for determination.
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 Chromatograph of Derivatives in Isocyanate Standard Solution
