Detail of GB 31604.31-2016

Introduction of GB 31604.31-2016

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This standard replaces the determination of vinyl chloride monomer of GB/T 5009.122-2003 Determination of Residual Ethylidene Dichloride in Polyvinyl Chloride Resin and Product for Food Container and Packaging Material, GB/T 5009.67-2003 Method for Analysis of Hygienic Standard of Product of Polyvinyl Chloride for Food Packaging and GB/T 5009.68-2003 Method for Analysis of Hygienic Standard of Perchlorovinyl-coating for Inner Wall of Food Container, as well as such standards as GB/T 23296.14-2009 Food Contact Materials - Polymer - Determination of Vinyl Chloride in Food Simulants - Gas Chromatography, GB/T 23296.13-2009 Food Contact Materials - Determination of Vinyl Chloride Monomer in Plastics - Gas Chromatography and SN/T 2898-2011 Food Contact Materials for Export - Metal Materials - Determination of Migration of Vinyl Chloride in Surface Coating - Gas Chromatography-Mass Spectrometry. The following main changes have been made with respect to GB/T 5009.122-2003, GB/T 5009.67-2003, GB/T 5009.68-2003, GB/T 23296.14-2009, GB/T 23296.13-2009 and SN/T 2898-2011: ——This standard is renamed as "National Food Safety Standard - Food Contact Materials and Articles - Determination of Vinyl Chloride and Determination of Migration"; ——The application scope is modified; ——The examination methods are unified into gas chromatography. National Food Safety Standard Food Contact Materials and Articles Determination of Vinyl Chloride and Determination of Migration 1 Scope This standard specifies determination method of vinyl chloride and its migration in plastics and its products used as food contact materials. This standard is applicable to the determination of vinyl chloride and its migration in polyvinyl choride or vinyl chloride copolymer. This standard is also applicable to the determination of 1,1-dichloroethane in polyvinyl choride or polyvinyl choride copolymer. Determination of Vinyl Chloride 2 Principle Place the specimen in a sealed equilibration flask and dissolve it with N,N-dimethyl acetamide. Vinyl chloride diffuses at certain temperature，and when it reaches gas-liquid equilibrium, inject the head space gases into the gas chromatograph, determine with hydrogen flame ionization detector and carry out the quantitative determination by external standard method. 3 Reagents and Materials Unless otherwise specified, all the reagents are analytically pure. 3.1 Reagents N,N-dimethyl acetamide: with purity greater than 99%. 3.2 Standard products Vinyl chloride standard reference solution: 5,000mg/L, with acetone or methanol as solvent. 3.3 Preparation of standard solutions 3.3.1 Preparation of vinyl chloride stock solution (10mg/L): add 10mL of N,N-dimethyl acetamide into a 10mL brown glass bottle, pipet 20μL of vinyl chloride standard reference solution into the bottle and immediately seal the bottle with its cap; carry out equilibrium for 2h and preserve the solution in a 4℃ refrigerator. 3.3.2 Preparation of vinyl chloride standard working solution: respectively add 10mL of N,N-dimethyl acetamide into seven headspace bottles, pipet 0μL, 50μL, 75μL, 100μL, 125μL, 150μL and 200μL of vinyl chloride stock solution respectively with the microinjector, inject them slowly into the headspace bottles, cover the bottles immediately and mix uniformly so that the vinyl chloride concentrations in N,N-dimethyl acetamide are 0mg/L, 0.050mg/L, 0.075mg/L, 0.100mg/L, 0.125mg/L, 0.150mg/L and 0.200mg/L respectively. 4 Instruments and Apparatus 4.1 Gas chromatograph: equipped with automatic head space sampler and hydrogen flame ionization detector. 4.2 Glass bottle: 10mL, the cap of which is equipped with silicone rubber or butyl rubber sealing gasket. 4.3 Headspace bottle: 20mL, the cap of which is equipped with silicone rubber or butyl rubber sealing gasket. 4.4 Microinjector: 25μL, 100μL and 200μL. 4.5 Analytical balance: with sensibility of 0.0001g and 0.01g. 5 Analysis Steps 5.1 Preparation of test solution Weigh 1g (accurate to 0.01g) of fragmented specimen (of which the area is not greater than 1cm×1cm), place it into the headspace bottle, add into 10mL of N,N-dimethyl acetamide and seal the bottle with the cap; oscillate to dissolve the specimen (it may be properly heated if it is difficult to dissolve the specimen) and after full dissolution, place it in the automatic head space sampler for determination. 5.2 Determination 5.2.1 Reference conditions of instruments 5.2.1.1 Conditions of the automatic head space sampler a) Quantitative loop: 1mL or 3mL; b) Equilibrium temperature: 70℃; c) Quantitative loop temperature: 90℃; d) Transfer line temperature: 120℃; e) Equilibrium time: 30min; f) Pressuring time: 0.2min; g) Filling time of quantitative loop: 0.10min; h) Equilibrium time of quantitative loop: 0.10min; i) Injection duration: 1.50min. Note: if manual headspace sampling is adopted, see Annex A for the reference method. 5.2.1.2 Chromatographic conditions a) Chromatographic column: polyethylene glycol capillary chromatographic column with length of 30m, inside diameter of 0.32mm and film thickness of 1μm; or equivalent column; b) Column temperature programming: maintain the initial temperature 40℃ for 1 min, then raise to 60℃ at a rate of 2℃/min, maintain for 1min, then raise to 200℃ at a rate of 20℃/min, maintain for 1min; c) Carrier gas: nitrogen at a flow rate of 1mL/min; d) Injection mode: split injection, with splitting ratio of 1: 1; e) Temperature of injection port: 200℃; f) Detector temperature: 200℃. 5.2.2 Plotting of standard work curve Test the standard working solutions prepared in 3.3.2 with the instrument parameters listed in 5.2, then plot the standard work curve with the mass concentration of vinyl chloride standard working solution as x-axis and corresponding peak area as y-axis so as to obtain linear equation. See Annex B for the standard solution chromatogram. 5.2.3 Quantitative determination Test the samples prepared in 5.1 with the instrument parameters listed in 5.2, then calculate the content of vinyl chloride monomer in the sample solution through the standard curve according to the chromatographic peak area of vinyl chloride.

Contents of GB 31604.31-2016

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 Manual Injection Method Annex B Gas Chromatogram of Vinyl Chloride Standard Solution