Overview
ISO 21135:2024 specifies a solvent-extractable analytical method for the determination of the total content of selected bisphenols in chemicals used in the leather tanning industry. The method covers bisphenol A, AF, B, F and S and employs liquid chromatography (LC) coupled with a range of detectors - LC-MS/MS, LC-MS, LC‑UV, LC‑DAD or LC‑FLD - to identify and quantify target compounds. The procedure includes methanol extraction, optional centrifugation/filtration and calibrated instrumental analysis. Note: bisphenol S cannot be detected with FLD.
Key technical topics and requirements
- Scope: Total (solvent-extractable) content of bisphenol A, AF, B, F, S in leather-tanning chemicals. Method may be validated for other bisphenols by the laboratory.
- Sample extraction: Ultrasonic methanol extraction (sample example: 0.20 g ± 0.050 g with 20 mL methanol at 60 ± 5 °C for 60 ± 5 min), followed by centrifugation/filtration if needed.
- Instrumentation options:
- LC‑MS/MS (preferred for sensitivity and selectivity)
- LC‑MS
- LC‑UV, LC‑DAD or LC‑FLD (note FLD cannot detect bisphenol S)
- Calibration and quantification:
- Calibration ranges suggested for MS methods: 0.05–1 µg/mL.
- For UV/DAD/FLD: 0.5–20 µg/mL.
- Calculations provided with and without internal standards; use of mass-labelled internal standards (e.g., bisphenol A‑D8, B‑D8, AF‑13C12, F‑D10, S‑D8) is recommended to correct matrix effects.
- Reporting: Results expressed as mass fraction (mg/kg); procedures for dilution, detection limits and precision are included in the standard and annexes.
Practical applications and users
- Quality control laboratories testing raw chemicals, tanning agents and intermediates for bisphenol residues.
- Leather chemical manufacturers implementing supplier control and product safety checks.
- Independent testing labs offering compliance testing for customers in the leather and footwear supply chain.
- Regulatory and compliance bodies monitoring potentially hazardous bisphenols given their classification concerns (e.g., reproductive toxicity, endocrine disruption).
- Use cases include supplier qualification, incoming material inspection, product release testing and regulatory compliance testing for bisphenol contamination in tanning agents.
Related Standards and context
- This document was developed by the IULTCS Chemical Test Commission in collaboration with CEN/TC 289 (Leather) under ISO procedures.
- Normative references: none listed in the standard.
- Annexes provide example chromatographic parameters for LC‑MS/MS, LC‑MS and LC‑UV/DAD/FLD plus precision (reliability) information.
Keywords: ISO 21135:2024, bisphenol, leather tanning chemicals, LC‑MS/MS, LC‑UV, LC‑DAD, LC‑FLD, bisphenol A, bisphenol S, analytical method, extraction, quality control.
Open preview (PDF)Chemicals for the leather tanning industry — Determination of the total content of certain bisphenols
