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This standard replaces GB/T 20499-2006 Method for the Determination of Di(2-ethylhexyl)adipate Migrating from Polyvinyl Chloride Film in Contact with Foodstuffs, "Determination of Di(2-ethylhexyl)adipate" in GB/T 20500-2006 Method for the Determination of Di(2-ethylhexyl)adipate and Di-n-octyl Adipate in Polyvinyl Chloride Film and "Method for the Determination of Di(2-ethylhexyl)adipate Migration" in SN/T 2826-2011 Food Contact Materials for Export - Polymers - Determination of Adipate Plasticizers in Food Stimulants - Gas Chromatography-Mass Spectrometry.
The following changes have been made with respect to GB/T 20499-2006 and GB/T 20500-2006 (the previous editions):
——This standard is renamed as "National Standard for Food Safety Food Contact Materials and Articles Determination of Di(2-ethylhexyl)adipate and Determination of Migration";
——The "Gas Chromatography Determination Method for Di(2-ethylhexyl)adipate " is deleted.
National Standard for Food Safety
Food Contact Materials and Articles
Determination of Di(2-ethylhexyl)adipate and Determination of Migration
1 Scope
This standard specifies determination method of di(2-ethylhexyl)adipate (DEHA) in food contact materials and articles and its migration.
This standard is applicable to determination of di(2-ethylhexyl)adipate in polyvinyl chloride products and its migration.
Determination of Di(2-ethylhexyl)adipate
2 Principle
Dissolve the specimen with tetrahydrofuran, add in methanol to precipitate the polymers in it, with DEHA left in the filtrate. Determine with the gas chromatography-mass spectrometer and carry out the quantative determination by external standard method.
3 Reagents and Materials
3.1 Reagents
Unless otherwise specified, analytically-pure reagents and Class-I water (defined in GB/T 6682) are adopted for the purpose of this method.
3.1.1 Tetrahydrofuran (C4H8O, CAS No.: 109-99-9).
3.1.2 Methanol (CH4O, CAS No.: 67-56-1).
3.1.3 N-hexane (C6H12, CAS No.: 110-54-3): chromatographically pure.
3.2 Standard products
Di(2-ethylhexyl) adipate (C22H42O4, CAS No.: 103-23-1): with purity ≥99.8%, or standard substances approved and awarded with reference material certificate by the State.
3.3 Preparation of standard solutions
3.3.1 DEHA standard stock solution
Weigh 100 mg of DEHA (accurate to 0.0001g), dissolve it with n-hexane and scale the volume to 50mL to get the stock solution with the concentration of 2mg/mL. Store the solution in a refrigerator, with validity period of one month.
3.3.2 DEHA standard intermediate solution
Pipet 2.5 mL of DEHA standard stock solution (3.3.1) with the graduated pipette and put it into the volumetric flask (50 mL), dilute it with n-hexane to the scale to get the DEHA standard intermediate solution with concentration of 100.0 mg/L. The storage mode of the solution is the same as that in 3.3.1.
3.3.3 DEHA standard working solution
Pipet 50 μL, 0.2 mL, 0.5 mL, 1.0 mL, 2.0 mL and 5.0 mL of DEHA standard intermediate solutions (3.3.2) respectively with the graduated pipette and microinjector, put them into six volumetric flasks (10 mL), dilute with n-hexane and scale to the volume, then shake uniformly and sufficiently to get the DEHA standard working solutions with corresponding concentration of 0.5 mg/L, 2.0 mg/L, 5.0 mg/L, 10.0 mg/L, 20.0 mg/L and 50.0 mg/L. The storage mode of the solution is the same as that in 3.3.1.
4 Instruments and Apparatus
4.1 Gas chromatograph-mass spectrometer: equipped with electron bombardment ion source (EI source).
4.2 Analytical balance (with the precision of 0.1mg).
4.3 Ultrasonic cleaner.
4.4 Nitrogen blowing instrument.
4.5 Microinjector: 100μL.
4.6 Test tube: 50mL.
Note: all the glassware used in the test are rinsed with methanol and dried in the air for subsequent use.
5 Analysis Steps
5.1 Specimen treatment
Take the sample and cut it into sample pieces (0.5 cm×0.5cm) with the scissor and mix uniformly.
5.2 Preparation of specimen solution
Weigh 0.1 g (accurate to 0.0001 g) of sample and put it into a test tube (50 mL), add in 5mL of tetrahydrofuran and leave it for ultrasonic extraction for 30 min. After the sample is fully dissolved, add in 25mL of methanol slowly to precipitate the polyvinyl chloride high polymer, then filter, after which flush the precipitate for three times with 5mL of methanol respectively. Combine the filtrate in a volumetric flask (50mL), scale the volume with methanol and mix uniformly. Take 100 μL of the filtrate and blow it dry with nitrogen at ambient temperature, scale the volume to 1.0 mL with n-hexane and leave it for testing. If the sample concentration goes beyond the linear range of standard working solution, it may be diluted properly with n-hexane before determination.
5.3 Preparation of blank solution
The analysis steps, reagents and dosages identical with those in 5.2 are adopted except that the specimen is not added.
5.4 Reference conditions of apparatus
5.4.1 Chromatographic conditions
Chromatographic conditions are listed as follows:
a) Chromatographic column: the stationary phase is copolymer of (5 %) diphenyl (95%) dimethyl arylene siloxane (column length: 30m; inside diameter: 0.32mm; film thickness: 0.25μm);
b) Column temperature procedure: with initial temperature of 90℃ rising to 280℃ at the speed of 15℃/min; keep it at 280℃ for 10 min.
c) Injection port temperature: 280℃;
d) Carrier gas: helium gas, 1.5 mL/min;
e) Injection mode: split injection, with splitting ratio of 50: 1;
f) Injection volume: 0.2μL.
5.4.2 Mass spectrometry conditions
Mass spectrometry conditions are listed as follows:
a) Mass spectrum interface temperature: 250℃;
b) Temperature of ion source: 250℃;
c) Ionization method: EI;
d) Ionization energy: 70 eV;
e) Determination mode: select the ion monitoring mode; ion monitoring range for DEHA: 40~370 (m/z); characteristic ions of DEHA: 129, 147, 112 and 71, among which 129 is the quantification ion;
f) Solvent delay: 5 min.
5.5 Plotting of standard work curve
Inject the standard working solutions (3.3.3) into the gas chromatography-mass spectrometer respectively according to the determination conditions listed in 5.4. Plot the standard curve with the concentration of standard working solution as x-axis, in the unit of mg/L, and the corresponding peak area of DEHA as y-axis. See Figure A.1 for the standard chromatogram.
5.6 Determination of specimen solution
5.6.1 Qualitative determination
Inject the specimen solution (5.2) and blank solution (5.3) into the gas chromatography-mass spectrometer for determination according to the determination conditions listed in 5.4. Carry out sample determination under the same experiment conditions, and it can be determined that such to-be-determined substance exists in the sample if the chromatographic peak retention time of the to-be-determined substance in specimen solution deviates from the corresponding standard time by a value within ± 2.5 %, all the ions selected appear in the sample mass spectrum after background deduction, and compared with the relative abundance corresponding to the qualitative ion in the spectrogram of standard solution with the concentration approximate to the sample, the deviation of that in the spectrogram of the sample does not exceed the range specified in Table 1. See Table 2 for the characteristic ions of DEHA and the abundance ratio and Figure A.2 for the DEHA mass spectrogram.
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
9 Principle
10 Reagents and Materials
11 Instruments and Apparatus
12 Analysis Steps
13 Expression of Analysis Results
14 Accuracy
15 Others
Annex A Total Ions Chromatogram and Mass Spectrogram of the Standard Solution
