GB/T 5009.152-2003Determination of residual acrylonitrile monomer in styrene-acrylonitrile copolymers and rubber-modified acrylonitrile-butadiene-styrene resins and their products used for food packaging (English PDF)

3.1 Reagent purity. it shall use analytical reagent. If other grades of reagents

are used, they must have a sufficiently high purity so as not to reduce the

accuracy of determination.

3.2 Solvents. N,N-dimethylformamide or N,N-Dimethylacetamide (DMA). When

conducting chromatography of solvent headspace, there must be no interfering

peaks at retention time of acrylonitrile (AN) and propionitrile (PN).

3.3 Propionitrile. chromatographic grade.

3.4 Acrylonitrile. chromatographic grade.

4.1 Gas chromatograph

It shall be equipped with nitrogen-phosphorus detector.

It is better to use the device that can automatically collect and analyze the

headspace, for example, manual collection and analysis of headspace shall be

attached with the following equipment.

4.1.1 Thermostatic bath that can be maintained at 90°C±1°C.

4.1.2 Gas tight syringe used for headspace collection and injection.

4.2 Headspace bottle sealer.

4.3 5.0 mL headspace sampling bottle.

4.4 Aluminum sealing bottle cap.

4.5 Silicone rubber or butyl rubber with good gas tightness of which inner

surface is covered with polytetrafluoroethylene membrane.

5.1 Internal standard calibration

5.1.1 Prepare polymer solvent that contains the known amount of internal

standard substance (PN).

5.1.2 Fill certain amount of the solvent (3.2) in advance into a 100 mL flask.

gasket and aluminum cap, fully shake it to make the polymer in the bottle

completely dissolved or dispersed.

5.3 Gas chromatographic conditions

5.3.1 Chromatographic column. Phi 3mm×4m stainless steel column.

Fill in 101 white test acidic carrier body (60~80 mesh) painted with 15% of

polyethylene glycol-20M.

5.3.2 Temperature

Column temperature. 130°C;

Vaporization temperature. 180°C;

Detector temperature. 200°C.

5.3.3 Gas speed

Carrier gas nitrogen (N2) flow rate. 25 mL/min ~ 30 mL/min.

5.3.4 Other conditions

Nitrogen of 99.95% or greater purity.

Hydrogen shall be dried and purified.

Air shall be dried and purified.

5.4 Determination

Place headspace bottle in a 90°C bath for thermal equilibrium for 50 min. Use

a heated gas syringe to extract 2.0 mL of headspace that has reached to vapor-

liquid equilibrium from the bottle. Immediately inject gas chromatograph to

determine. Operation conditions of gas chromatograph shall be set according

to 5.3. If it uses commodity instrument of automated headspace analysis, it shall

adjust according to the instructions for use of this instrument.

5.5 Result calculation

Calculate the content of residual acrylonitrile in sample (c, mg/kg) according to

equation (5).

7.1 N,N-dimethylformamide (DMF). analytical reagent. There must be no

interfering peaks at retention time of acrylonitrile.

7.2 Acrylonitrile (AN). analytical reagent.

7.3 GDX-102 (60~80 mesh).

7.4 Acrylonitrile standard stock solution. weigh 0.0500 g of acrylonitrile; add

N,N-dimethylformamide to dilute constant volume to 50 mL. Per milliliter of this

storage solution equals to 1.0 mg of acrylonitrile. Store it in the refrigerator.

7.5 Acrylonitrile standard solution. draw 0.2 mL, 0.4 mL, 0.6 mL, 0.8 mL and 1.6

mL of stock solution. Respectively move them to 10 mL flasks. Separately add

N,N-dimethylformamide to dilute constant volume to scale. Well mix it (each

milliliter equals 20 µg, 40 µg, 60 µg, 80 µg and 160 µg of acrylonitrile

respectively).

8.1 Gas chromatograph (with flame ionization detector).

8.2 1 mL centered type glass syringe.

8.3 12 mL headspace determination bottle with rubber cover that is coated with

polyvinyl fluoride silicon and aluminum cap.

8.4 Electric heated water bath.

9.1 Sample processing

Weigh 0.5g~1g (accurate to 0.001 g) of homogeneous sample in headspace

determination bottle. Add 3 mL of N,N-dimethylformamide. Immediately seal it

with cover. Sample shall be determined after it is dissolved.

9.2 Gas chromatographic conditions

9.2.1 Chromatographic column. Phi 4mm×2m glass column. Fill GDX-102

(60~80 mesh).

9.2.2 Temperature

Column temperature. 170°C;

Vaporization temperature. 180°C;

Detector temperature. 220°C.

9.2.3 Gas speed

Carrier gas nitrogen (N2) flow rate. 40 mL/min;

Hydrogen flow rate. 44 mL/min;

Air flow rate. 500 mL/min.

9.2.4 Other conditions

Instrument sensitivity. 101;

Attenuation. 1;

Paper speed. 0.7 cm/min.

9.3 Determination

9.3.1 Adjust gas chromatography to the best working condition (referring to 9.2).

Put the test sample in the 90°C±1°C water bath for accurate heating for 40 min.

Take 1.0 mL of liquid gas into chromatogram. When necessary, adjust the

amount of headspace to suit sample determinations of different amounts.

9.3.2 Standard curve making. separately add 3.0 mL of N,N-dimethylformamide

into 5 empty headspace bottles. Then respectively take 0.2 mL of standard

solution (7.5) and put into determination bottles. The content of acrylonitrile of

each determination bottle shall equal to 4 µg, 8 µg, 12 µg, 16 µg, and 32 µg

respectively. Immediately seal the bottle cover. Well mix it. Place in 90°C water

bath. Use same sample for the following determination, i.e., respect...

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