Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.
This standard replaces GB/T 23296.15-2009 Food Contact Materials - Polymer - Determination of 2,4,6-triamino-1,3,5-triazine (Melamine) in Food Simulants - High Performance Liquid Chromatography.
The following changes have been made with respect to GB/T 23296.15-2009 (the previous edition):
——This standard is renamed as "Food Contact Materials and Articles - Determination of Migration of 2,4,6-triamino-1,3,5-triazine (Melamine)".
National Standard for Food Safety
Food Contact Materials and Articles
Determination of Migration of
2,4,6-triamino-1,3,5-triazine (Melamine)
1 Scope
This standard specifies the determination method of migration of melamine in food contact materials and articles (melamine formaldehyde resin and finished products).
This standard is applicable to the high performance liquid chromatography determination method for migration of melamine in food contact materials and articles (melamine formaldehyde resin and finished products).
2 Principle
Contact the food contact materials and articles (melamine formaldehyde resin and finished products) with the food simulants and carry out the migration test under specific soaking conditions. Test the solution obtained after soak solution treatment with high performance liquid chromatography, and convert the result to special migration of melamine. Select corresponding food simulant and migration test conditions (duration and temperature) respecting the food category in accordance with GB 31604.1. If the food simulant is composed of water, acetic acid of 4% (volume fraction) and ethyl alcohol of 10%, 20% or 50%~95% (volume fraction), the soak solution shall be taken as directly injected as test solution; if the food simulant is vegetable oil, the test solution obtained after extraction treatment to the soak solution shall be directly injected. Then determine the melamine content in the test solution with high performance liquid chromatography, determine the soak solution volume and specimen contact area in accordance with GB 5009.156 and convert them to special migration (settling out amount of the migrating substance) of melamine according to the formula.
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. As for the containers and transferring tools in the test, those made of plastic material shall not be used.
3.1 Reagents
3.1.1 Water-based, acidic, alcoholic and oil-based food simulants: the reagents used shall comply with the requirements of GB 31604.1.
3.1.2 Sodium hydroxide (NaOH).
3.1.3 Sodium phosphate monobasic dihydrate (NaH2PO4·2H2O).
3.1.4 Isopropyl alcohol [(CH3)2CHOH].
3.1.5 Methanol (CH3OH): chromatographically pure.
3.1.6 Isooctane [(CH3)2CHCH2C(CH3)3].
3.1.7 Acetonitrile (CH3CN): chromatographically pure.
3.2 Reagent preparation
3.2.1 Water-based, acidic, alcoholic and oil-based food simulant: prepare according to the requirements of GB 5009.156.
3.2.2 Sodium hydroxide solution (100g /L): weigh 10g of sodium hydroxide and dissolve it in 100 mL of water.
3.2.3 Buffer solution of sodium phosphate monobasic (0.005 mol/ L, pH = 6.5): weigh 0.780 g of sodium phosphate monobasic dihydrate and dissolve it with 900 mL of water; adjust its pH to 6.5 with sodium hydroxide solution (100g/L, refer to 3.2.2) and scale the volume with water to 1,000mL.
3.2.4 Isopropanol solution (100mL/L): measure 10mL of isopropyl alcohol and dissolve it in 100 mL of water.
3.2.5 Methanol-water mixed solution (1+1): measure 100mL of methanol and add it into 100mL of water.
3.3 Standard product
3.3.1 Melamine (C3H6N6) (CAS No.: 108-78-1): with purity ≥99%.
3.4 Preparation of standard solutions
3.4.1 Standard stock solution of melamine (1,000 mg/L): accurately weigh 50 mg of melamine standard product (accurate to 0.1 mg), put it into a volumetric flask (50mL) and add in 40 ml of water, then keep it in the water bath (temperature: 70℃) for ultrasonic treatment which lasts for 15 min~30 min so that the melamine can be fully dissolved; cool it to ambient temperature and scale the volume with water, then keep it away from light at 4℃ ~ 20℃ so that its concentration remains stable within 6 months.
3.4.2 Standard intermediate solution of melamine (100 mg/L): pipet 5.00 ml standard stock solution of melamine and inject it into a volumetric flask (50mL), then scale the volume with water.
3.4.3 Preparation of food simulant standard working solution
3.4.3.1 Standard working solutions of water-based, acidic and alcoholic food simulants
Accurately pipet 0mL, 0.125 mL, 0.250 mL, 1.25 mL and 2.50 mL of standard intermediate solution of melamine (3.4.2) respectively, inject them into volumetric flasks (25mL) and scale the volume with water-based food simulant, in which the concentrations of melamine are 0 mg/L, 0.500 mg/L, 1.00 mg/L, 5.00 mg/L and 10.0 mg/L respectively. Prepare the melamine standard working solution with the same concentration series in the same way with acidic and alcoholic food simulants respectively.
3.4.3.2 Standard working solution of oil-based food simulant
Accurately weigh 5 g (accurate to 0.01 g) oil-based food simulant (refined corn oil or olive oil) respectively and put them into five glass test tubes with stopper (25mL); transfer 0 μL, 25.0 μL, 50.0 μL, 250 μL and 500 μL of standard intermediate solution of melamine (3.4.2) into the test tubes respectively with a pipette and obtain the standard working solution of oil-based food simulant, in which the concentrations of melamine are 0 mg/kg, 0.500 mg/kg, 1.00 mg/kg, 5.00 mg/kg and 10.00 mg/kg respectively. Add in 5.0 mL of isooctane (3.1.6) to each test tube and mix uniformly, then add in 5.0 mL of isopropanol solution (3.2.4); put the test tube in a thermostatic waterbath (70℃) for ultrasonic extraction which lasts for 30 min, and then subject it to centrifugal stratification. Pipet 1mL~2mL of the water solution in the underlayer and filter it with organic-phase microfiltration membrane (0.22 μm), leaving the test solution thus obtained for sample injection and determination of the high performance liquid chromatograph.
3.5 Materials
Organic-phase microfiltration membrane: 0.22 μm.
4 Instruments and Apparatus
4.1 High-performance liquid chromatograph: with ultraviolet absorption detector or light emitting diode array detector.
4.2 Vortex oscillator.
4.3 Ultrasonic bath with heater.
4.4 Centrifuge: with rotation speed greater than 4,000 r/min.
4.5 Analytical balance: with sensibility of 0.0001g and 0.01g.
5 Analysis Steps
5.1 Preparation of food simulant test solutions
5.1.1 Preparation of food simulant soak solution
Select corresponding food simulant and migration test conditions respecting the intended use and service conditions of melamine formaldehyde resin and finished products in accordance with the requirements of GB 5009.156 and GB 31604.1, carry out the migration test and obtain the food simulant soak solution. If the food simulant soak solution fails to be used for the next test immediately, it shall be kept in the refrigerator at 0℃~4℃ and away from light.
Carry out the preparation of test solutions for next step after the food simulant soak solution temperature is the same as the ambient temperature.
5.1.2 Preparation of food simulant test solutions
5.1.2.1 Test solution for water-based, acidic and alcoholic food simulants
Accurately measure 1 mL of soak solution for water-based, acidic or alcoholic food simulant obtained after the migration test and then filter it with organic-phase microfiltration membrane (0.22 μm), leaving the test solution thus obtained for sample injection and determination of the high performance liquid chromatograph.
5.1.2.2 Test solution for oil-based food simulant
Accurately weigh 5 g (accurate to 0.01 g) soak solution for oil-based food simulant obtained after the migration test and put it into the glass test tube with stopper (25 mL). Add in 5.0 mL of isooctane and mix uniformly, then add in 5.0 mL of isopropanol solution; put the test tube in a thermostatic waterbath (70℃) for ultrasonic extraction which lasts for 30 min, and then subject it to centrifugal stratification. Pipet 1mL~2mL of the water solution in the underlayer and filter it with organic-phase microfiltration membrane (0.22 μm) ,leaving the test solution thus obtained for sample injection and determination of the high performance liquid chromatograph.
5.1.3 Preparation of blank test solution
As for water-based, acidic and alcoholic food simulants having not contacted with specimens of food contact materials or articles, operate in accordance with 5.1.2.1; as for oil-based food simulant, operate in accordance with 5.1.2.2; the solution obtained after filtering is the blank test solution.
5.2 Reference conditions of apparatus
a) Chromatographic column: with amino column (length: 250mm; inner diameter: 4.6 mm; particle size: 5 μm); or with chromatographic column with equivalent performance.
b) Mobile phase: buffer solution of acetonitrile-sodium phosphate monobasic (75+25, volume ratio).
c) Flow rate: 1.0 mL/min.
d) Column temperature: ambient temperature.
e) Injection volume: 20μL.
f) Detection wavelength: 230 nm.
g) Duration: 20min.
5.3 Plotting of standard work curve
Test the standard working solution according to the reference conditions of apparatus as specified in 5.2 and determine the corresponding peak area. Take the melamine concentration as x-coordinate, and corresponding peak area as y-coordinate, draw the standard work curve of the food simulant and obtain the linear equation.
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 Others
Annex A Chromatogram of Melamine in Food Simulant Test Solutions
