GB/T 29614-2021 Vulcanized rubber—Determination the content of polycyclic aromatic hydrocarbons
WARNING—Persons using this document shall be familiar with normal laboratory practice. This standard does not purport to address all the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulatory conditions.
IMPORTANT: The adoption of the procedures specified herein may involve the use or generation of some substances, which may generate some waste. This may cause local environmental hazards and shall be handled and disposed of safely after use as specified in the appropriate documents.
1 Scope
This document provides two methods for the determination of polycyclic aromatic hydrocarbons (PAHs) content in vulcanized rubber compounds. Method A is based on proton nuclear magnetic resonance (NMR) spectrometry; Method B is based on gas chromatography-mass spectrometry (GC-MS).
This document applies to the determination of the PAHs content in vulcanized rubber compounds, and also applies to the determination of the PAHs content in tires.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions 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 3516 Rubber - Determination of solvent extract (GB/T 3516-2006, ISO 1407:1992, MOD)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
polycyclic aromatic hydrocarbon (PAH)
hydrocarbon consisting of two or more benzene rings in its molecule
Note: By the way the benzene rings are connected, PAHs may be divided into three categories: polyphenyl-substituted aliphatic hydrocarbons, biphenyl and fused polycyclic aromatic hydrocarbons.
4 Method A: Proton nuclear magnetic resonance spectrometry (1H NMR)
4.1 Principle
The molecular structure of non-linear PAH with three or more fused rings contains a characteristic three-sided concave area, located at the periphery of the aromatic hydrocarbon molecule: these specific hydrogen atoms in this area are called bay region hydrogens (see Figure 1). 1H-NMR spectroscopy can identify and quantify selectively the hydrogen atoms in the bay region, which are characteristic for PAHs.
This method describes the procedure to determine the content of bay region hydrogens (m/m) in a sample solution by 1H-NMR, thus concluding on the aromatic character of the oil in vulcanized rubber compounds. The higher the amount of bay region hydrogens, the higher is the aromaticity.
a) Benzopyrene b) 7,12-Dimethylbenzanthracene c) 3,5-Methylchrysene
Key:
1—bay region.
Figure 1 Common bay region hydrogens
4.2 Reagents and materials
Unless otherwise specified, all reagents shall be of analytical grade.
4.2.1 Extraction solvent
Acetone, analytical grade or higher.
4.2.2 Reagents for sample preparation
4.2.2.1 n-Heptane, analytical grade or higher.
4.2.2.2 Nitrogen, purity required >99.9%, for protecting the extract from oxidation during the drying step.
4.2.2.3 Hexamethyldisiloxane (HMDS), 99.5 %, NMR grade, or tetramethylsilane (TMS), 99.5 %, NMR grade.
4.2.2.4 Deuterated chloroform (CDCl3), > 99.95 % deuteration degree, NMR grade containing 0.05 % TMS or 0.03 % HMDS. The resonance peak of either TMS or HMDS is used for the calibration of the chemical shifts. Alternatively, a commercially available deuterated chloroform containing TMS or HMDS may be used.
4.2.2.5 Acetaldehyde, purity ≥ 99.5 %, may optionally be added at a concentration of 0.6 % (v/v) to the deuterated chloroform containing the TMS or HMDS. The added acetaldehyde provides a resonance peak at around 9.8 ppm which is useful for a good phasing of the spectrum. The solution has to be prepared freshly in order to avoid interference from acetaldehyde decomposition products formed upon aging.
4.3 Apparatus
4.3.1 Analytical balance, accurate to 0.1 mg.
4.3.2 Extraction apparatus, as specified in GB/T 3516.
4.3.3 Steam bath.
4.3.4 Extract purification apparatus, consisting of the items specified as follows:
a)For single sample purification at one time (manually operated filtration):
1)2mL, 5mL, 25mL or 30mL syringes with conical end fitting compatible with solid phase extraction (SPE) columns for manually operated purification.
2)SPE cartridge, containing 500 mg or 1,000 mg of silica gel.
b)For simultaneous purification of multiple samples (optional):
1)2mL, 5mL, 25mL or 30mL syringes with conical end fitting compatible with solid phase extraction (SPE) columns for manually operated purification.
2)SPE cartridge, containing 500 mg or 1,000 mg of silica gel.
3)Solid phase filtration equipment connected to a vacuum pump, for simultaneous purification of many extracts;
4)Glass test tubes, to collect the extract.
c)Laboratory glassware.
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Method A: Proton nuclear magnetic resonance spectrometry (1H NMR)
5 Method B: Gas chromatography-mass spectrometry (GC-MS)
6 Test report
Annex A (Informative) Structural changes between this document and ISO 21461:2012
Annex B (Informative) Preparation of clean samples of rubber compounds from tires
Annex C (Informative) 1H NMR spectra of extracts from compounds containing aromatic oil and MES oil
Annex D (Informative) Precision
Annex E (Informative) Retention times, molecular formulae, relative molecular weights, qualitative ions and quantitative selective ions for the 18 polycyclic aromatic hydrocarbons and 3 internal standards
Annex F (Informative) Typical GC-MS chromatograms of the 18 polycyclic aromatic hydrocarbons and 3 internal standards
Bibliography
