Overview
ISO 21257:2024 specifies an analytical method by gas chromatography (GC) for determining residual acrylonitrile and styrene monomers in polymer polyols used to produce polyurethanes. The second edition updates sample preparation precision and clarifies the title. The method uses internal standardization and established calibration curves to quantify low levels of residual monomers, supporting product safety and regulatory compliance for polyurethane applications.
Key topics and technical requirements
- Scope and principle: Measurement of residual acrylonitrile and styrene in polymer polyols by GC with internal standardization; amounts are calculated from peak areas against a calibration curve.
- Suitable solvents: Analytical-grade methanol, N,N‑dimethylformamide (DMF), tetrahydrofuran (THF), dipropylene glycol monomethyl ether (DPGME), or toluene; other solvents allowed if separation and stability are adequate.
- Internal standards and pairings: Selection based on retention times; recommended combinations include methanol + 2‑methyl‑1‑propanol, DMF + ethylbenzene, DPGME + bromobenzene.
- GC configuration: Flame ionization detector (FID) required; both open tubular (OT / capillary) and packed columns are acceptable using split or splitless injectors. Typical operating conditions are provided in Annex A.
- Calibration and sample prep: Four-level calibrations with internal standard. Two preparation methods are given - Method A for OT columns and Method B for packed columns - with example sample dilutions (e.g., 4.0 g sample to 50 ml for Method A).
- Quality controls and limits: Guidance on calibration curve preparation, single-point and multi-point calculations, measurement sensitivity and acceptability criteria. Typical chromatograms and precision data are included in Annexes B and C.
- Instrumentation care: Notes on injector contamination risk from high‑molecular‑weight polyol components and recommendations for monitoring/cleaning injector liners (glass wool liners suggested).
Applications and users
ISO 21257:2024 is intended for:
- Quality control and analytical laboratories in polymer polyol and polyurethane manufacturing.
- Safety and compliance teams assessing residual acrylonitrile and residual styrene for product safety (skin or food contact applications).
- Third‑party testing labs, regulatory bodies, and R&D groups developing polymer polyols or formulating polyurethane foams and molded parts.
Benefits include reproducible quantification of volatile monomers, improved product safety evaluation, and a standardized approach for inter‑laboratory comparability.
Related standards
- ISO 472 - Plastics - Vocabulary
- ISO 648 - Laboratory glassware - Single‑volume pipettes
- ISO 1042 - Laboratory glassware - One‑mark volumetric flasks
Annexes in ISO 21257:2024 provide typical GC conditions, example chromatograms and precision data to assist implementation.