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This standard is drafted in accordance with the rules given in the GB/T 1.1-2009.
This standard was proposed by China Petrochemical Corporation.
This standard is under the jurisdiction of Subcommittee 1 on Petrochemical Plastic Resin Product of National Technical Committee 15 on Plastic of Standardization Administration of China (SAC/TC15/SC1).
Plastics — Determination of Residual Acetaldehyde in Polyethylene Terephthalate (PET) Resin for Bottles — Headspace Gas Chromatography
1 Scope
This standard specifies the headspace gas chromatography for determination of residual acetaldehyde in polyethylene terephthalate (PET) resin for bottles.
This standard is applicable to the determination of residual acetaldehyde in polyethylene terephthalate (PET) resin for bottles.
The detection range of residual acetaldehyde in polyethylene terephthalate (PET) resin is 0.1 μg/g to 4 μg/g.
2 Principle
The sample is crushed and powders of a specified size are weighed into a sealed container. The sample will release residual acetaldehyde at a certain temperature. After the equilibrium is reached, the gas above the sealed container is injected onto a gas chromatographic column. The acetaldehyde is separated from other components, and detected by hydrogen flame ionization detector. The acetaldehyde released from the sample is quantitatively calculated by the external standard method.
3 Normative References
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 601 Chemical Reagent — Preparations of Reference Titration Solutions
GB/T 6682 Water for Analytical Laboratory Use — Specifications and Test Methods
GB/T 8170 Rules of Rounding of for Numerical Values & Expression and Judgement of Limiting Values
4 Reagents and Materials
Unless otherwise specified, only the analytical reagents and Grade 3 water or water with equivalent purity conforming to the requirements of GB/T 6682 are used in analysis.
4.1 Acetaldehyde: chromatographically pure, or acetaldehyde aqueous solution with a concentration of 1 mg/mL and other known concentrations.
4.2 Nitrogen, with purity not less than 99.99%; Prior to use, it shall be purified with dehydration device, silica gel, molecular sieve or activated carbon.
4.3 Hydrogen: with purity not less than 99.8%. Prior to use, it shall be purified with dehydration device, silica gel, molecular sieve or activated carbon.
4.4 Air: it shall be free from corrosive impurities. Prior to use, it shall be dehydrated and degreased.
5 Apparatus
5.1 Gas chromatograph: equipped with hydrogen flame ionization detector and packed column injection inlet.
5.2 Chromatographic working station or integrator.
5.3 Headspace sampler
5.4 Chromatographic column: glass packed column or stainless steel packed column,2.2 m in length, 6.35 mm in inner diameter, using polystyrene porous polymer microsphere stationary phase (such as Porapak-Q), or other columns with the same separation effect can be used.
5.5 Refrigerator.
5.6 Headspace bottle: 20 mL, equipped with aluminum cap and silicone rubber gasket covered with PTFE film.
5.7 Crimper.
5.8 Decapper.
5.9 Sample crusher.
5.10 Liquid nitrogen container.
5.11 Analytical balance: with an accuracy of 0.1 mg.
5.12 Microinjector: 10 μL;
5.13 Glass bottle with fluoropolymer lined diaphragm gasket.
6 Preparation and storage of acetaldehyde standard solution
6.1 Preparation and calibration of acetaldehyde standard solution
Prepare the acetaldehyde standard solution according to Annex A, and calibrate the concentration of prepared solution.
6.2 Storage of acetaldehyde standard solution
After preparation and calibration of the acetaldehyde standard solution, the solution shall be immediately transferred into the glass bottle with fluoropolymer lined diaphragm gasket (5.13), until the solution is overflowed so as to eliminate the air and guarantee that there is no air in the container; then seal it, stick mark on it and put it into the refrigerator (5.5) for standby.
Note: It is recommended to use certified acetaldehyde standard solution or prepare with pure acetaldehyde reagent. The recommended storage life of unopened acetaldehyde standard solution is 3 to 6 months.
Foreword II
1 Scope
2 Principle
3 Normative References
4 Reagents and Materials
5 Apparatus
6 Preparation and storage of acetaldehyde standard solution
7 Test Procedure
8 Calculation of Results
9 Expression of Results
10 Precision
Annex A (Normative) Preparation and Ccalibration of 1 mg/mL Acetaldehyde Standard Solution
Annex B (Informative) Recommended Operating Conditions for Gas Chromatograph and Headspace Sampler
Annex C (Informative) Chromatogram of typical sample of acetaldehyde
