GB 31604.31-2016National food safety standard - Food contact materials and products - Determination of sulfur dioxide in wood materials (English PDF)

3.1 Reagents

N,N-Dimethylacetamide. purity is greater than 99%.

3.2 Standard substance

Vinyl chloride reference solution. 5000mg/L; take acetone or methanol as solvent.

3.3 Preparation of standard solution

b) Equilibrium temperature. 70°C;

c) Quantitative loop temperature. 90°C;

d) Transmission line temperature. 120°C;

e) Balance time. 30min;

f) Pressurization time. 0.20min;

g) Filling time of quantitative loop. 0.10min;

h) Equilibration time of quantitative loop. 0.10min;

i) Sample injection time. 1.50min.

NOTE. if the manual headspace sampling injection is performed, the reference method can refer to Appendix A.

5.2.1.2 Chromatographic conditions

a) Chromatographic column. polyethylene glycol capillary chromatographic column with length of 30m, inner diameter of 0.32mm, film thickness of 1µm, or equivalent column;

b) Column temperature program. maintain the initial temperature of 40°C for 1min;

raise the temperature to 60°C at the speed rate of 2°C/min, maintain for 1min;

raise the temperature to 200°C at the speed rate of 20°C [Translator note. here it should be 20°C/min], maintain for 1min;

c) Carrier gas. nitrogen, flow rate of 1mL/min;

d) Sample injecting mode. split, split ratio of 1.1;

e) Sample injecting temperature.200°C;

f) Detector temperature.200°C.

5.2.2 Drawing of standard working curve

The standard working solution prepared in 3.3.2 was tested under the instrumental parameters listed in 5.2; take the mass concentration of vinyl chloride standard working solution as abscissa; take the corresponding peak area as the ordinate; then draw the standard working curve; obtain t he linear equation. Standard solution chromatogram is shown in Appendix B.

5.2.3 Quantitative determination

10.1 Reagents

10.1.1 Water-based, acidic, alcoholic, oil-fat food simulants. as per the provisions of

GB 31604.1.

10.1.2 N,N-Dimethylacetamide. purity greater than 99%.

10.2 Preparation of reagents

Water-based, acidic, alcoholic, oil-fat food simulants. prepare as per GB 5009.156.

10.3 Standard substance

Vinyl chloride reference solution. 5000mg/L; take acetone or methanol as solvents.

10.4 Preparation of standard solution

10.4.1 Vinyl chloride stock solution. separately add 10mL of N,N-Dimethylacetamide

into 6 pieces of 10mL glass bottles; successively add 5µL, 10µL, 20µL, 30µL, 40µL,

50µL of vinyl chloride into each bottle; mix evenly; then the concentrations of the obtained vinyl chloride are 2.5mg/L, 5.0mg/L, 10.0mg/L, 15.0mg/L, 20.0mg/L,

25.0mg/L. Store into 4°C refrigerator.

10.4.2 Water-based food simulant standard working solution. separately add 10mL

of water into 6 headspace bottles; successively add 20mL of vinyl chloride stock solution with different concentrations into each headspace bottles; immediately use cap to seal; mix evenly; then the concentrations of the obtained vinyl chloride in water are 0.0050mg/L, 0.010mg/L, 0.020mg/L, 0.030mg/L, 0.040mg/L and 0.050mg/L.

Adopting the same modes, separately use acidic, alcoholic food simulants to prepare the vinyl chloride serial standard working solution with the same concentration.

10.4.3 Oil-fat food simulant standard working solution. respectively take 10g

(accurate to 0.1g) of oil-fat food simulants into 6 headspace bottles; successively add

20µ of vinyl chloride stock solution with different concentrations into each headspace bottle; immediately use the cap to seal; mix evenly; the concentrations of the obtained vinyl chloride in oil-fat food simulants are sequentially 0.0050mg/kg, 0.010mg/kg,

0.020mg/kg, 0.030mg/kg, 0.040mg/kg and 0.050mg/kg.

NOTE. before preparing the standard solution, food simulant needs to be fully cooled in the 4°C refrigerator; the standard solution shall be prepared quickly.

12.3 Determination

12.3.1 Instrument reference condition

The same as 5.2.

12.3.2 Drawing of standard working curve

The standard working solution is tested as per the measurement conditions listed in

12.3.1.Take the concentration of vinyl chloride in the food simulant standard working solution as the abscissa; while take the corresponding peak area as the ordinate; then draw the standard working curve.

12.3.3 Quantitative determination

Sequentially inject the samples of food simulant test solution and blank test solution;

obtain the peak area of vinyl chloride chromatogram; deduct the blank value during the calculating process. According to the peak area of vinyl chloride chromatogram, calculate the concentration of vinyl chloride in sample solution by standard curve.