Overview
EN ISO 17226-1:2021 - Leather - Chemical determination of formaldehyde content - Part 1: Method using high-performance liquid chromatography (ISO 17226-1:2021) - is a CEN-endorsed ISO method for the selective, precise quantification of free and released formaldehyde in leather. The method measures the quantity of free formaldehyde plus formaldehyde released by hydrolysis from a standardized water extract. It is HPLC-based, robust against coloured extracts and intended for analytical laboratories and quality control use.
Key topics and technical requirements
- Scope and principle
- Determines free and released formaldehyde from leather extracted under standard conditions.
- Formaldehyde in the extract is derivatized and separated by reversed-phase HPLC and detected by UV or diode array detectors (UV/DAD).
- Sampling and sample prep
- References ISO sampling and preparation standards (e.g., ISO 2418, ISO 4044).
- Extraction uses a detergent solution at elevated temperature (document specifies elution at 40 °C).
- Derivatization and analysis
- Aldehydes and ketones are converted to hydrazones using 2,4-dinitrophenylhydrazine (DNPH) prior to HPLC separation.
- DNPH solution composition was revised in this edition (no concentrated o‑phosphoric acid) to avoid artefactual formaldehyde release from some tanning agents.
- Reaction conditions updated (reaction time and temperature increased-document specifies new limits) to ensure complete derivatization.
- Calibration, quantification and quality checks
- Calibration using formaldehyde standards or commercial formaldehyde‑DNPH solutions is described.
- Procedures for spiking and recovery determination, expression of results and required reporting are included.
- Precision and method details
- Annex A provides interlaboratory precision data; Annex B lists recommended HPLC conditions.
- Conformity
- When results differ from ISO 17226‑2 (colorimetric), this HPLC method is the reference in disputes.
Practical applications and users
- Who uses it:
- Leather testing laboratories and instrumented QC labs
- Leather manufacturers and tanneries performing product control
- Third‑party conformity testing bodies and regulators verifying chemical safety
- R&D teams validating tanning processes and emissions
- Why it’s used:
- Provides accurate, selective formaldehyde quantification even in coloured or complex leather extracts
- Supports product safety assessments and regulatory/compliance testing
- Helps evaluate processing steps that may release bound formaldehyde
Related standards and references
- ISO 2418 - sampling location
- ISO 3696 - laboratory water quality
- ISO 4044 - preparation of chemical test samples
- ISO 4684 - determination of volatile matter
- Companion method: ISO 17226‑2 (colorimetric method) - trends comparable but HPLC is preferred for disputes
Keywords: EN ISO 17226-1:2021, formaldehyde content, leather testing, HPLC, DNPH, released formaldehyde, leather chemical analysis, formaldehyde determination.
