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GB 31604.56-2023: National food safety standard - Food contact materials and products - Determination of laurolactam migration
GB 31604.56-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National Food Safety Standards -- Food Contact Materials
and Products -- Determination of Migration Amount of
Laurolactam
ISSUED ON: SEPTEMBER 06, 2023
IMPLEMENTED ON: MARCH 06, 2024
Issued by: National Health Commission of the People's Republic of China;
State Administration for Market Regulation.
Table of Contents
1 Scope ... 3
2 Principle ... 3
3 Reagents and materials ... 3
4 Instruments and equipment ... 5
5 Analysis steps ... 5
6 Expression of analysis results ... 7
7 Precision ... 9
8 Other ... 9
9 Principle ... 10
10 Reagents and materials ... 10
11 Instruments and equipment ... 11
12 Analysis steps ... 12
13 Expression of analysis results ... 14
14 Precision ... 14
15 Other ... 14
Annex A Chromatogram of laurolactam standard solution ... 16
National Food Safety Standards -- Food Contact Materials
and Products -- Determination of Migration Amount of
Laurolactam
1 Scope
This Standard specifies the method for determining the migration amount of
laurolactam in food contact materials and products.
This Standard is applicable to the determination of the migration amount of laurolactam
in polyamide food contact materials and products.
Method one -- Liquid chromatography
2 Principle
After the migration test of food contact materials and products, liquid chromatography
is used for testing. Among them, water-based, acidic, ethanol-containing food simulants
and chemical alternative solvents of 95% (volume fraction) ethanol are directly injected
after filtration. Oil-containing food simulants are filtered and injected after liquid-liquid
extraction and solid-phase extraction. The chemical alternative solvent isooctane is
injected by filtration after solvent removal and reconstitution with acetonitrile. Use
retention time to qualitative determination. Use external standard method for
quantification.
3 Reagents and materials
Unless otherwise stated, the reagents used in this method are analytically pure, and the
water is grade one water specified in GB/T 6682.
3.1 Reagents
3.1.1 Acidic, ethanol-containing, grease-containing food simulants and chemical
alternative solvents: The reagents used are in accordance with the regulations of GB
5009.156.
3.1.2 Acetonitrile (C2H3N): chromatographically pure.
3.1.3 Formic acid (CH2O2): chromatographically pure.
3.1.4 Ammonia water: the mass fraction of ammonia is 25%~28%.
3.1.5 Absolute ethanol (C2H6O).
3.2 Reagent preparation
3.2.1 Formic acid-water solution: measure 5.0 mL of formic acid and 95 mL of water,
and mix well.
3.2.2 Ammonia-acetonitrile solution: measure 2.0 mL of ammonia, 8.0 mL of water and
90 mL of acetonitrile, and mix well.
3.2.3 Formic acid-acetonitrile-water solution: measure 20 mL of acetonitrile and 80 mL
of water; pipette 100 μL of formic acid; mix well.
3.3 Standard product
Laurolactam standard product (C12H23NO, CAS: 947-04-6, also known as laurolactam
or azacyclotridecane-2-one): purity ≥98%, or certified by the country and awarded as a
standard material certificate of reference material.
3.4 Standard solution preparation
3.4.1 Laurolactam standard stock solution (1000 mg/L): Weigh 100 mg (accurate to 0.1
mg) of laurolactam standard product. Dissolve in absolute ethanol and adjust the
volume to 100 mL. Shake well. Transfer the solution to a brown glass container. Store
at 4°C away from light. Validity period is 3 months.
3.4.2 Laurolactam standard intermediate solution (200 mg/L): Pipette 5.0 mL of
laurolactam standard stock solution into a 25 mL volumetric flask. Dilute to volume
with absolute ethanol. Shake well. Transfer the solution to a brown glass container.
Store at 4°C away from light. Validity period is 3 months.
3.4.3 Aqueous, acidic, ethanol-containing food simulants or 95% (volume fraction)
ethanol standard working solution: Pipette 0.50 mL, 1.0 mL, 2.5 mL, 5.0 mL, and 10
mL of laurolactam standard intermediate solution into 100 mL volumetric flasks. Dilute
to volume with corresponding aqueous, acidic, ethanol-containing food simulant or 95%
(volume fraction) ethanol. Prepare standard working solutions with concentrations of
1.0 mg/L, 2.0 mg/L, 5.0 mg/L, 10 mg/L and 20 mg/L, respectively. Prepare when
needed.
3.4.4 Standard working solution of oil-containing food simulants: Weigh 2 g (accurate
to 0.01 g) of olive oil. Add 20 μL, 30 μL, and 50 μL of laurolactam standard
intermediate solution and 20 μL and 40 μL of laurolactam standard stock solution,
respectively. Mix well. Prepare standard working solutions with concentrations of 2.0
mg/kg, 3.0 mg/kg, 5.0 mg/kg, 10 mg/kg and 20 mg/kg. Prepare when needed. Before
putting on the machine, follow 5.1.3 to process it simultaneously with the soaking
solution of oil-containing food simulants.
5.1.3 Fat-containing food simulants test solution
Weigh 2 g (accurate to 0.01 g) of the oil-containing food simulant soaking solution into
a 15 mL centrifuge tube. Add 4.0 mL of acetonitrile. Vortex and extract for 10 min.
Centrifuge at 8500r/min for 2 min. Take the supernatant. Repeat extraction of soaking
liquid once. Combine the two extracts. Concentrate to approximately 0.5 mL with
nitrogen blowing at 45°C. After reconstitution with 4.0 mL of formic acid-aqueous
solution, transfer to a mixed cation solid-phase extraction cartridge activated with 3.0
mL of acetonitrile, pure water, and formic acid-aqueous solution. Elute with 3.0 mL of
formic acid-water solution and acetonitrile in sequence. Elute with 3.0 mL of ammonia-
acetonitrile solution. The eluate is blown dry with nitrogen at 45°C. Add 1.0 mL of
formic acid-acetonitrile-water solution. Vortex for 1 min to reconstitute. Filter with
microporous membrane for measurement.
5.1.4 Isooctane test solution
Pipette 1.0 mL of the isooctane soaking solution obtained from the migration test. Blow
dry with nitrogen at 45°C. Add 1.0 mL of acetonitrile to dissolve the residue. Filter with
microporous membrane for measurement.
5.1.5 Preparation of blank test solution
Food simulants and chemical alternative solvents that are not in contact with food
contact materials and products are processed according to 5.1.2, 5.1.3 and 5.1.4 to
obtain a blank test solution.
5.2 Instrument reference conditions
The instrument reference conditions are as follows:
a) Chromatographic column: C18 column; column length is 250 mm; column inner
diameter is 4.6 mm; particle size is 5 μm, or a chromatographic column with
equivalent performance;
b) Mobile phase: acetonitrile and water (50+50, volume ratio);
c) Flow rate: 1.0 mL/min;
d) Injection volume: 20 μL;
e) Column temperature: 25℃;
f) Detection wavelength: 210 nm.
5.3 Preparation of standard curve
Determine the standard working solution according to the instrument reference
conditions listed in 5.2. Draw a standard curve with the concentration of laurolactam in
the standard working solution as the abscissa and the corresponding peak area as the
ordinate. The reference chromatogram of laurolactam standard solution is shown in
Figure A.1 of Annex A.
5.4 Determination of test solution
Measure the food simulant test solution and blank test solution according to the
instrument reference conditions listed in 5.2. Use the retention time to determine the
peak area of the target substance. Obtain the concentration of laurolactam in the test
solution according to the s...