ISO 17226-2:2018

Overview

ISO 17226-2:2018 - "Leather - Chemical determination of formaldehyde content - Part 2: Method using colorimetric analysis" defines a laboratory screening method to determine free and released formaldehyde in leather using a colorimetric reaction. The standard describes extraction of leather with a detergent solution, derivatization with acetylacetone to form a yellow chromophore (3,5-diacetyl-1,4-dihydrolutidine) and photometric measurement at 412 nm. ISO 17226-2:2018 is intended as a practical, routine screening technique rather than a high-precision quantification method.

Key topics and technical requirements

• Scope & limitations
  • Measures free and hydrolysis-released formaldehyde in a water extract under standard conditions.
  • Not absolutely selective for formaldehyde; other compounds (e.g., extracted dyes) can interfere at 412 nm.
  • For disputes or precise quantification, ISO 17226-1 (HPLC method) takes precedence.
• Principle
  • Extraction with 0.1% sodium dodecylsulfate (detergent) at (40 ± 1) °C.
  • Reaction of formaldehyde with acetylacetone/ammonium acetate to yield a measurable chromophore; absorbance read at 412 nm.
• Reagents & controls
  • Formaldehyde stock preparation and titrimetric verification (iodine/thiosulfate) or use of certified formaldehyde solutions.
  • Solution 1: ammonium acetate + glacial acetic acid + acetylacetone.
  • Dimedone test to detect other compounds that react with acetylacetone.
  • Reagent blank absorbance limits (e.g., ≤0.025 in 20 mm cell at 412 nm) to verify reagent purity.
• Apparatus & procedure
  • Thermostatted water bath with shaker at 40 °C, spectrophotometer (recommended 20 mm cell; longer path lengths allowed), glass-fibre filtration.
  • Sampling/preparation per ISO 2418 and ISO 4044; moisture per ISO 4684 if dry-basis reporting is required.
• Calibration & calculation
  • Use of calibration curves prepared under identical conditions and procedures for spiking/recovery checks.

Applications and who uses it

• Routine quality control in tanneries and leather finishing plants for screening formaldehyde levels.
• Independent testing laboratories performing compliance checks or batch screening.
• Product safety and regulatory pre-screening where a fast, cost-effective method is needed (e.g., textiles/leather goods supply chain checks).
• R&D and process monitoring to track trends in formaldehyde release after tanning/finishing changes.

Related standards

• ISO 17226-1 - Leather - Chemical determination of formaldehyde content - Part 1: Method using high performance liquid chromatography (preferred for disputes or precise quantification).
• ISO 2418, ISO 4044, ISO 4684, ISO 3696 - referenced for sampling, sample preparation, moisture determination, and water quality.

Keywords: ISO 17226-2:2018, leather formaldehyde testing, colorimetric analysis, acetylacetone, formaldehyde screening, leather testing standards.