Overview - ISO 17234-1:2020 (Leather chemical test for certain azo colourants)
ISO 17234-1:2020 specifies a laboratory method for detecting the use of certain azo colourants in dyed leathers by measuring aromatic amines released by reductive cleavage. The method targets aromatic amines listed in regulatory lists (for example EU Regulation 1907/2006 Annex XVII, Appendix 8 and GB 20400‑2006) and defines sample preparation, extraction and chromatographic analysis routes to identify and quantify these potentially hazardous substances.
Key technical topics and requirements
- Scope: Determines whether leather contains azo colourants capable of releasing specific aromatic amines.
- Principle: After degreasing, leather is subjected to reductive cleavage using sodium dithionite in citrate buffer (pH 6) at 70 °C in a closed vessel; released amines are recovered by liquid–liquid extraction into t‑butyl methyl ether using diatomaceous earth columns.
- Analytical methods: Identification requires at least two different chromatographic separation methods to avoid false positives (examples given in Annex A). Accepted techniques include:
- HPLC with DAD or MS (quantification by HPLC‑DAD)
- GC‑MS (quantification)
- Capillary electrophoresis with DAD (CE‑DAD)
- TLC / HPTLC (qualitative)
- Quantification: Performed by HPLC‑DAD or GC‑MS; internal standards and calibration procedures are specified.
- Apparatus & reagents: Lists reaction vessels, heating systems (70 ± 2 °C), diatomaceous earth columns (20 g), vacuum rotary evaporator, sodium dithionite (200 mg/ml), solvents (t‑butyl methyl ether, acetonitrile, methanol), and analytical-grade reagents.
- Sampling & preparation: Sampling follows ISO 2418 and sample prep follows ISO 4044; adhesive residues must be removed.
- Safety: Aromatic amines covered are classified as known or suspected carcinogens. The standard mandates good laboratory practice and PPE; local regulations apply.
- Annexes: Provide expanded guidance on chromatographic analyses (Annex A), method reliability (Annex B), interpretation and reporting (Annex C), and a screening extraction without diatomaceous earth (Annex D).
Practical applications and users
- Who uses it: Leather testing laboratories, tanneries and leather manufacturers, regulatory compliance teams, importers/retailers, product safety assessors, and accreditation bodies.
- Why it matters: Ensures compliance with chemical safety regulations, supports product safety declarations, prevents distribution of leather articles that could release carcinogenic aromatic amines, and helps in supply‑chain control and consumer safety verification.
Related standards
- ISO 17234-2 (Part 2: determination of 4‑aminoazobenzene)
- ISO 2418 (sampling location for leather)
- ISO 4044 (preparation of chemical test samples)
- ISO 3696 (water for analytical laboratory use)
Keywords: ISO 17234-1:2020, azo colourants, aromatic amines, leather testing, HPLC, GC‑MS, reductive cleavage, diatomaceous earth, sodium dithionite, compliance.