ISO 27587:2021

Overview

ISO 27587:2021 - Leather - Chemical tests - Determination of free formaldehyde in process auxiliaries specifies a quantitative analytical method to measure free formaldehyde released from leather process auxiliaries when heated under dynamic, inert conditions. The procedure captures released formaldehyde on 2,4‑dinitrophenylhydrazine (DNPH) cartridges, elutes the derivative with acetonitrile, and quantifies it by HPLC with UV or DAD detection. Results are reported in milligrams per kilogram (mg/kg) of sample.

Key topics and technical requirements

• Principle: Thermal release of formaldehyde in an inert, dry atmosphere; trapping with DNPH; HPLC analysis of DNPH‑derivative.
• Sample preparation: Typical sample mass 0.1–2.0 g (adjust for liquids); heat in a U‑tube immersed to a defined level in an oil bath at (90 ± 3) °C for 30 min.
• Inert atmosphere: Nitrogen purge; initial purge recommended at 500 ml/min (15 min), analysis flow adjusted between 150–350 ml/min.
• Trapping media: DNPH cartridges sized for carbonyl capacity (example capacity 6 400 µg); recommended cartridge excess capacity ≥20% of predicted formaldehyde.
• Elution and analysis: Elute cartridges with HPLC‑grade acetonitrile, filter (e.g., 0.45 µm), and analyse by RP‑C18 HPLC using UV/DAD. Annex B provides suggested HPLC conditions.
• Calibration and quantitation: External standard calibration using derivatized formaldehyde‑DNPH in the range 0.5 µg/10 ml to 100 µg/10 ml. Calculation converts calibration result to mg/kg sample.
• Quality control: Blank checks for reagent and system background (blank must be