ISO 2561:2023
(Main)Plastics — Determination of residual styrene monomer in polystyrene (PS) and impact-resistant polystyrene (PS-I) by gas chromatography
Plastics — Determination of residual styrene monomer in polystyrene (PS) and impact-resistant polystyrene (PS-I) by gas chromatography
This document specifies a method for the determination of the residual styrene monomer in polystyrene (PS) and impact-resistant polystyrene (PS-I) by gas chromatography. It can also be used for the simultaneous determination of other volatile aromatic hydrocarbons in PS and PS-I.
Plastiques — Détermination du styrène monomère résiduel dans le polystyrène (PS) et le polystyrène résistant au choc (PS-I) par chromatographie en phase gazeuse
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INTERNATIONAL ISO
STANDARD 2561
Fourth edition
2023-11
Plastics — Determination of residual
styrene monomer in polystyrene (PS)
and impact-resistant polystyrene (PS-
I) by gas chromatography
Plastiques — Détermination du styrène monomère résiduel dans
le polystyrène (PS) et le polystyrène résistant au choc (PS-I) par
chromatographie en phase gazeuse
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and materials . 1
5.1 Internal standard . 2
5.2 Solvent . 2
5.3 Precipitator . . 2
5.4 Aromatic hydrocarbons. 2
5.5 Carrier gases and fuel gases for gas chromatograph . 2
6 Apparatus . 2
6.1 General . 2
6.2 Gas chromatograph . 2
6.3 Data processor . 3
6.4 Sample injection syringe . 3
6.5 Analytical balance . 3
6.6 Volumetric flasks . 3
6.7 Headspace Vials . 3
7 Preparation of sample . 3
8 Procedure .3
8.1 General . 3
8.2 Preparation of internal-standard solution . 3
8.3 Preparation of sample solution for sample introducing option A . 3
8.4 Preparation of sample solution for sample introducing option B . 3
8.5 Preparation of sample solution for sample introducing option C . 4
8.6 Preparation of calibration solutions . 4
8.6.1 General . 4
8.6.2 Calibration solutions for sample introducing option A . 4
8.6.3 Calibration solutions for sample introducing option B . 4
8.6.4 Calibration solution for sample introducing option C . 4
8.7 Gas-chromatographic procedure . 5
8.7.1 Gas-chromatograph operating conditions . 5
8.7.2 Recording the gas chromatograms of sample solutions and calibration
solutions . 6
8.7.3 Evaluation of the gas-chromatographic peaks . 6
9 Expression of results . 7
9.1 Calculation of results from a calibration graph . 7
9.2 Acceptability of results and measurement sensitivity . 8
10 Test report . 8
Annex A (informative) Examples of typical test conditions . 9
Annex B (informative) Correlation between mass of aromatic hydrocarbon in calibration
solution and concentration of aromatic hydrocarbon in sample solution for typical
calibration solutions .13
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
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Any trade name used in this document is information given for the convenience of users and does not
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 9,
Thermoplastic materials.
This fourth edition cancels and replaces the third edition (ISO 2561:2012), which has been technically
revised.
The main changes-are as follows:
— adding headspace injection as another sample introducing option for gas chromatography.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
INTERNATIONAL STANDARD ISO 2561:2023(E)
Plastics — Determination of residual styrene monomer in
polystyrene (PS) and impact-resistant polystyrene (PS-I)
by gas chromatography
1 Scope
This document specifies a method for the determination of the residual styrene monomer in
polystyrene (PS) and impact-resistant polystyrene (PS-I) by gas chromatography. It can also be used
for the simultaneous determination of other volatile aromatic hydrocarbons in PS and PS-I.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 472, Plastics — Vocabulary
ISO 1042, Laboratory glassware — One-mark volumetric flasks
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
PS or PS-I sample is dissolved in solvent containing an internal standard. To obtain separation of
styrene and other volatile materials, gas chromatography method is employed, in which three sample
introducing options are available:
— Option A: a small volume of the polymer solution is injected directly into a gas chromatograph.
— Option B: a small volume of the supernatant solution remaining after precipitation of polymer by
addition of a precipitator is injected into a gas chromatograph.
— Option C: a small volume of vapor of the polymer solution under thermal equilibrium is injected into
a gas chromatograph.
5 Reagents and materials
Use only reagents of recognized analytical grade, unless otherwise specified.
5.1 Internal standard
The internal standard shall be selected based on consideration of the retention times of the materials
contained in the polymer sample and solvent. Recommended candidates are n-butylbenzene,
cyclopentanol, 1,2,4-trimetylbenzene and 1,4-diethylbenzene of sufficient purity for analytical use.
5.2 Solvent
Use dimethylformamide, butanone, dichloromethane, or tetrahydrofuran. Tetrahydrofuran is used only
for method A. Only dimethylformamide is used in method C.
5.3 Precipitator
Use 2,2,4-trimethylpentane or ethanol.
5.4 Aromatic hydrocarbons
Use styrene and other aromatic hydrocarbons such as ethylbenzene, cumene or α-methylstyrene, if
required. Styrene shall be checked for self-polymerizaiton before use. The criterion for acceptance is
that the mixture of styrene and ethanol of the same volume shall be clear. When determining the content
of other aromatic hydrocarbons in the sample, other aromatic hydrocarbons such as ethylbenzene,
cumene or α-methylstyrene shall be used.
5.5 Carrier gases and fuel gases for gas chromatograph
Hydrogen, helium or nitrogen, according to the type of detector used, shall be used as carrier gas. Use
hydrogen and air as fuel gases. If detectors are used which require carrier gases and fuel gases other
than those mentioned, the carrier gases and fuel gases shall be specified.
WARNING — Strict observance of safety regulations is essential when using hydrogen.
6 Apparatus
6.1 General
Normal laboratory equipment and the following apparatus are required. Typical operating conditions
are described in Annex A.
6.2 Gas chromatograph
6.2.1 Injection port. Use an injection port for liquid samples or gas samples. When using a capillary
column, an injection port with splitter may be applicable.
6.2.2 Headspace sampler. only used in method C, including backflush capability, thermostated
sample tray, and associated accessories fulfil these requirements while providing for automatic
sequential sampling of headspace vapors.
6.2.3 Column. The column diameter and length, as well as the packing material and stationary phase
shall be selected based on consideration of column resolution and calibration curve linearity. Both
packed columns and capillary columns are acceptable. Capillary columns are recommended in the light
of accuracy.
6.2.4 Detector. Use a suitable detector.
NOTE The most commonly used detector is a hydrogen flame ionization detector (FID).
6.3 Data processor
Use a recorder or microcomputer to record the signals from the detector.
6.4 Sample injection syringe
Use a micro-syringe of the 1 μl to 50 μl type. A micro-syringe integrated with the auto-injector may
also be used.
6.5 Analytical balance
Shall be accurate to the nearest 0,1 mg.
6.6 Volumetric flasks
Volumetric flasks as standardized in ISO 1042 shall be used.
6.7 Headspace Vials
Vials matching the headspace sampler shall be used, including a lid with a sealing gasket and vial sealer.
NOTE The volume of headspace sample bottle is usually 10 ml, 20 ml or 22 ml.
7 Preparation of sample
The sample may be taken from material in the form of powder, pellets or moulded parts. In order to
ensure the desired accuracy of the sample mass, large pieces of sample shall be reduced to smaller
fragments.
8 Procedure
8.1 General
During the dilution processes described below, the temperature of each solution shall remain under
25 °C.
8.2 Preparation of internal-standard solution
Weigh 200 mg of internal standard (5.1), to the nearest 1 mg, into a 1 000 ml volumetric flask (6.6).
Then add solvent (5.2) to make exactly 1 000 ml, stopper tightly and mix well.
8.3 Preparation of sample solution for sample introducing option A
Weigh 0,5 g of sample, to the nearest 1 mg, into a volumetric flask (6.6) having a volume between 25 ml
and 100 ml. Using a syringe or a pipette, add 20 ml of the internal standard solution pre
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