Overview
ISO 17226-1:2021 - Leather - Chemical determination of formaldehyde content - Part 1: Method using high-performance liquid chromatography (HPLC) specifies a selective, quantitative laboratory method to determine free and released formaldehyde in leather. The method uses derivatization with 2,4‑dinitrophenylhydrazine (DNPH) and separation by reversed‑phase HPLC with UV or diode array detection (DAD). It is designed to give precise quantification that is not sensitive to coloured extracts and is intended for use under standard conditions of leather extraction.
Key topics and technical requirements
- Analyte and scope: Measures free formaldehyde and formaldehyde released by hydrolysis in a water extract from leather.
- Extraction: Leather is extracted with a preheated detergent solution (0.1% sodium dodecylsulfonate) at (40 ± 2) °C with shaking for (60 ± 2) minutes; warm filtrate is cooled before further processing.
- Derivatization: Filtered extract is reacted with DNPH in acetonitrile; reaction conditions are (50 ± 2) °C for (180 ± 5) minutes to form hydrazone derivatives suitable for HPLC.
- HPLC analysis: Reversed‑phase separation with UV or DAD detection; Annex B gives example HPLC conditions. Membrane filtration (0.45 µm) is used prior to injection.
- Calibration and quantification: Calibration uses a formaldehyde stock solution whose concentration can be verified by iodine/thiosulfate titration; spiking and recovery procedures are included to assess method performance.
- Reagents and apparatus: Lists analytical‑grade reagents (formaldehyde solution, DNPH in acetonitrile, acetonitrile LC grade, detergent) and required equipment (thermostatted water baths, HPLC system, analytical balance).
- Method robustness: The 2021 edition updated the DNPH composition (removal of concentrated phosphoric acid) to avoid artefactual formaldehyde release from some tanning resins; precision data and interlaboratory results are provided in Annex A.
Applications and users
ISO 17226-1:2021 is used for:
- Quality control and incoming inspection in tanneries and leather product manufacturers.
- Regulatory compliance and product safety testing where formaldehyde content must be quantified for consumer protection or trade requirements.
- Laboratory accreditation and method validation in independent test laboratories performing leather chemical analysis.
- R&D and raw material evaluation to assess tanning agents, resins, finishes and their contribution to formaldehyde release.
Typical users: analytical chemists, leather technologists, quality assurance teams, notified bodies, and regulatory laboratories.
Related standards
- ISO 17226-2 (alternative/colorimetric method) - trends similar but not always identical results; HPLC method preferred in disputes.
- ISO 2418 (sampling location), ISO 4044 (sample preparation), ISO 4684 (moisture/volatile matter), ISO 3696 (water for analytical use).
Keywords: ISO 17226-1:2021, formaldehyde in leather, HPLC method, DNPH derivatization, leather testing, formaldehyde determination.
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