Overview
ISO 20536:2017 specifies a laboratory method for the determination of phenol in footwear and footwear components (except metal parts). The standard defines sample preparation, extraction, calibration and GC‑MS analysis steps to quantify phenol in materials used in uppers, linings and insocks. It includes requirements for reagents (toluene/acetone extraction mixture), surrogates and internal standards (Phenol‑D6 and Anthracene‑D10) and sets performance expectations such as a typical quantification limit of 0.5 mg/kg (for 1 g sample, 10 ml extraction).
Key topics and technical requirements
- Scope and applicability: All non‑metal parts of footwear; see ISO/TR 16178:2012 for material classification.
- Sampling and sample prep: Test pieces must be homogeneous single‑material samples cut to pieces (edge length ≤ 5 mm); do not grind (volatile loss).
- Extraction method: Ultrasonic extraction at 60 °C ±5 °C for 60 min ±2 min using toluene/acetone (80/20, vol/vol). Typical ratio: 1 g sample in 9.8 ml extraction mixture.
- Standards and reagents: Phenol (target), Phenol‑D6 as extraction surrogate, Anthracene‑D10 as internal standard; solvents analytical grade; stock and working solutions specified.
- Analysis: Gas chromatography–mass spectrometry (GC‑MS) monitoring specified ions for phenol, Phenol‑D6 and Anthracene‑D10; calibration uses at least five levels and a regression of area ratios.
- Quality control: Recovery rate of the extraction surrogate must be between 75 % and 125 %; reanalysis required outside this range.
- Limits and concentration: Quantification limit given as 0.5 mg/kg for standard sample/extraction; concentration can be improved by reducing extract volume (e.g., evaporative concentration).
- Ancillary steps: Precipitation with methanol and 0.45 µm PTFE filtration if polymer dissolution occurs; use of calibrated volumetric glassware per ISO 4787.
Applications and users
ISO 20536:2017 is intended for:
- Laboratories performing chemical safety testing of footwear materials;
- Footwear manufacturers and component suppliers conducting internal quality control and supplier verification for phenol content;
- Regulatory bodies and compliance teams assessing products against chemical safety limits;
- Third‑party testing and certification organizations verifying product safety and material declarations.
Practical benefits include standardized phenol measurement, reproducible GC‑MS procedures, validated calibration and recovery checks, and traceable test reporting.
Related standards
- ISO/TR 16178:2012 - material classification for footwear testing (referenced in scope).
- ISO 4787 - laboratory glassware and volumetric methods (referenced for apparatus).
Note: Users should have laboratory experience and follow appropriate safety practices when handling solvents and phenol.