ISO 24538:2008

Plastics - Homopolymer and copolymer resins of vinyl chloride - Determination of residual vinyl chloride monomer by gas-chromatographic analysis of dry powder

ISO 24538:2008 specifies a method for the determination of residual vinyl chloride monomer in homopolymer and copolymer resins of vinyl chloride. The method is based on a static headspace gas-chromatographic technique (i.e. the analysis of the vapour phase in equilibrium with the solid phase at constant temperature) and is suitable for all kinds of homopolymer and copolymer resin. It is done directly on the resin in powder form.

Plastiques — Résines d'homopolymères et de copolymères de chlorure de vinyle — Dosage du chlorure de vinyle résiduel par chromatographie en phase gazeuse sur poudre sèche

General Information

• Status: Published
• Publication Date: 21-Oct-2008
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: ISO/TC 61/SC 5 - Physical-chemical properties
• Drafting Committee: ISO/TC 61/SC 5/WG 11 - Analytical methods
• Current Stage: 9093 - International Standard confirmed
• Start Date: 09-Jun-2021
• Completion Date: 13-Dec-2025

Overview

ISO 24538:2008 specifies a laboratory method for the determination of residual vinyl chloride monomer (VCM) in homopolymer and copolymer resins of vinyl chloride (PVC). The standard is based on a static headspace gas‑chromatographic technique with flame‑ionization detection (GC‑FID) and is performed directly on PVC in dry powder form. It is intended for routine quality control, regulatory testing and safety verification of unfilled PVC resins.

Key topics and technical requirements

• Measurement principle: static headspace analysis - vapour in equilibrium with the solid powder at a fixed temperature is injected into a GC and analyzed by FID.
• Apparatus: gas chromatograph with automatic static headspace sampler (or manual injection), suitable GC column(s), FID, 10 ml and 22 ml glass vials with PTFE‑faced septa, gastight syringes, analytical balance (0.1 mg readability), and high‑purity carrier and FID gases.
• Thermal conditioning: vials are equilibrated at 120 °C for 15 minutes before injection to reach headspace equilibrium.
• Procedures: two validated procedures are described:
  • Procedure A: uses 2–4 g test samples and calibration by spiking VCM into VCM‑free PVC; suitable down to about 0.01 mg/kg.
  • Procedure B: uses ~0.20 g test samples in 10 ml vials and external gas standards for calibration.
• Calibration and calculation: methods to prepare calibration standards (diluted or pure VCM), to correct for headspace volume and added gas, and to compute response factors and final VCM content (mg/kg).
• Safety: warns that vinyl chloride is flammable and calibration preparation should be done under a well‑ventilated hood.
• Supporting content: sections on sampling, precision, and test reporting; Annex A lists example GC columns.

Applications and who uses it

ISO 24538:2008 is used by:

• PVC resin manufacturers for quality control and release testing.
• Independent analytical and polymer testing laboratories performing residual monomer analysis.
• Regulatory and compliance labs verifying product safety and ensuring residual VCM levels meet workplace and product regulations.
• R&D groups developing new vinyl chloride homopolymers or copolymers requiring validated quantification of residual monomer.

Practical benefits include reproducible, sensitive measurement of residual VCM in powder resins, enabling process control, product safety checks and documentation for compliance.

Related standards

• ISO 6401 - referenced for compounded materials, granulates and films (dissolution required for headspace equilibrium).
• ISO 472 - vocabulary for plastics terminology used in the document.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 24538
First edition
2008-11-01
Plastics — Homopolymer and copolymer
resins of vinyl chloride — Determination
of residual vinyl chloride monomer by
gas-chromatographic analysis of dry
powder
Plastiques — Résines d'homopolymères et de copolymères de chlorure
de vinyle — Dosage du chlorure de vinyle résiduel par chromatographie
en phase gazeuse sur poudre sèche

Reference number
©
ISO 2008
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©  ISO 2008
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ii © ISO 2008 – All rights reserved

Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Principle. 1
5 Apparatus and materials. 2
6 Sampling. 2
7 Procedure . 2
8 Procedure A. 3
8.1 Preparation of test sample and analysis. 3
8.2 Calibration . 3
8.3 Calculation. 3
9 Procedure B. 5
9.1 Preparation of test sample and analysis. 5
9.2 Calibration . 5
9.3 Calculation. 6
10 Precision. 7
11 Test report . 7
Annex A (informative) Examples of suitable columns . 8
Bibliography . 9

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 through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 24538 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
iv © ISO 2008 – All rights reserved

INTERNATIONAL STANDARD ISO 24538:2008(E)

Plastics — Homopolymer and copolymer resins of vinyl
chloride — Determination of residual vinyl chloride monomer
by gas-chromatographic analysis of dry powder
SAFETY STATEMENT — Persons using this document should be familiar with normal laboratory
practice, if applicable. This document does not purport to address all of the safety concerns, 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 regulatory requirements.
1 Scope
This International Standard specifies a method for the determination of residual vinyl chloride monomer in
homopolymer and copolymer resins of vinyl chloride.
The method is based on a static headspace gas-chromatographic technique (i.e. the analysis of the vapour
phase in equilibrium with the solid phase at constant temperature) and is suitable for all kinds of homopolymer
and copolymer resin. It is done directly on the resin in powder form.
For compounded material, granulate, extrudate, films, etc., use ISO 6401.
NOTE In the case of compounded material, it is necessary to dissolve the sample in a suitable solvent in order to
reach complete headspace equilibrium.
2 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.
ISO 472, Plastics — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 apply.
4 Principle
A weighed amount of the sample is sealed into a glass vial. After thermal conditioning for a certain period of
time to permit the vinyl chloride monomer (VCM) to equilibrate between the powder and the vapour phase, a
gas sample is taken from the headspace, e.g. by automatic injection, into the gas chromatograph. The
components are separated on a column and detected using a flame-ionization detector.
5 Apparatus and materials
5.1 Gas chromatograph, fitted either with an automatic static headspace sampler or with facilities for
manual sample injection. Chromatographic columns and conditions shall be chosen in such a way that VCM
and impurities are separated reliably.
NOTE Examples of suitable columns are described in Annex A.
5.2 Flame-ionization detector (FID).
5.3 Glass vials, for most purposes of capacity 22 ml and 10 ml, with PTFE-faced silicone or butyl rubber
septa and aluminium caps. No peaks which could interfere with the VCM determination shall come from the
septa.
5.4 Crimping and decapping tools, for sealing and reopening the vials.
5.5 Gastight syringes, of capacity up to 5 ml, depending on the VCM concentration. Syringes are chosen
in accordance with the volume analysed.
5.6 Analytical balance, capable of reading to 0,1 mg.
5.7 Data system, or equivalent system (recording potentiometer or integrator), for the acquisition and
evaluation of gas-chromatographic data.
5.8 Vinyl chloride gas standards, prepared by consecutive dilution of pure VCM (purity greater than
99,5 % by volume), for calibration purposes.
The use of a commercially available standard in helium, nitrogen or air in a gas cylinder fitted with a capillary
outlet or a syringe adapter is recommended.
SAFETY PRECAUTIONS — Vinyl chloride is a flammable gas at ambient temperature. The preparation
of calibration samples must therefore be carried out under a well-ventilated hood.
5.9 FID gases and carrier gas.
For low limits of quantification, so-called “zero air” (dry, contaminant-free air) shall be used for the FID and the
other gases used shall be of similarly high purity.
6 Sampling
During storage, a concentration gradient may have formed in the PVC being sampled, since the upper layers
release residual VCM faster. Cooling of the sample is advisable, but condensation of humidity shall be
avoided. To minimize losses of residual monomer, carry out sample preparation as quickly as possible. When
exchanging samples between laboratories or when storage is necessary, seal samples in completely filled
glass vials.
7 Procedure
Two different procedures are described.
Procedure A is suitable for determining the residual VCM content of homopolymers and copolymers of vinyl
chloride down to a level of 0,01 mg/kg. Calibration is performed by adding known amounts of VCM to samples
of completely VCM-free PVC.
Procedure B is similar to procedure A except that a smaller amount of test sample is used and calibration is
performed using external VCM standards rather than VCM added to PVC.
2 © ISO 2008 – All rights reserved

In procedure A, it is important to perform the calibration using the same type of PVC as that being analysed
and using the same mass of PVC as that taken as the test sample. It is also important that equilibrium
between the solid and gaseous phases be established under the same conditions during calibration and
during actual analysis and that the reduction in the headspace volume caused by the presence of the PVC in
the vial be allowed for.
8 Procedure A
8.1 Preparation of test sample and analysis
Before taking the test sample, it is recommended that the vial into which the test sample will be placed be
purged with nitrogen in order to remove any possible traces of VCM.
Weigh between 2 g and 4 g of the PVC resin to be analysed (the same amount as used for calibration), to the
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