Overview
EN ISO 17226-2:2019 - "Leather - Chemical determination of formaldehyde content - Part 2: Method using colorimetric analysis" (adopted by CEN) specifies a screening colorimetric method for determining free and released formaldehyde in leather. The method reports the formaldehyde content present in a water extract obtained under standard conditions. It is intended for routine screening rather than for highly precise quantification.
Key topics and requirements
- Scope: Measurement of free-formaldehyde plus formaldehyde released by hydrolysis in a water extract from leather. Not fully selective for formaldehyde; other extracted compounds (e.g., dyes) can interfere at the analytical wavelength.
- Principle: Leather is eluted with a detergent solution at 40 °C. Formaldehyde in the eluate reacts with acetylacetone to form a yellow derivative (3,5-diacetyl-1,4-dihydrolutidine) whose absorbance is measured at 412 nm. Results are obtained from a calibration curve prepared under identical conditions.
- Reagents and apparatus: Uses common analytical-grade reagents (e.g., detergent solution, ammonium acetate/acetylacetone mix, dimedone for checks) and standard lab equipment, including a spectrophotometer capable of readings at 412 nm and a thermostatically controlled water bath at (40 ± 1) °C.
- Limitations: The method is not absolutely selective for formaldehyde; co-extracted substances can produce a colour at 412 nm. For disputes or when precise quantification is required, ISO 17226-1 (HPLC method) is the preferred reference.
- Quality control: The standard includes calibration, blank checks for reagents, spiking and recovery checks, and guidance on sampling and sample preparation.
Applications and users
- Practical use: Fast screening of leather batches for formaldehyde content during production, incoming material inspection, or routine quality control.
- Who uses it:
- Leather manufacturers and tanneries performing in-house QC
- Independent testing laboratories offering formaldehyde screening
- Regulatory bodies and compliance officers checking product safety limits
- Product designers and procurement teams verifying supplier claims
- Why choose this method: Colorimetric analysis is relatively simple, cost-effective and faster than chromatographic techniques, making it suitable for routine screening where approximate trends are acceptable.
Related standards
- ISO 17226-1 - Leather - Chemical determination of formaldehyde content - Part 1: Method using high performance liquid chromatography (HPLC) (for precise quantification)
- Normative references incorporated in EN ISO 17226-2: ISO 2418, ISO 3696, ISO 4044, ISO 4684 (sampling, water quality, sample prep and volatile matter)
Keywords: EN ISO 17226-2:2019, formaldehyde determination, leather testing, colorimetric analysis, acetylacetone, 412 nm, screening method, ISO 17226 series.
