Overview
ISO 18218-2:2019 specifies an indirect analytical method for determining alkylphenols and their ethoxylates in leather and leather process auxiliaries. The standard covers the determination of nonylphenol (NP) and octylphenol (OP) and the indirect quantification of nonylphenol ethoxylate (NPEO) and octylphenol ethoxylate (OPEO) by cleaving the ethoxylates to release NP/OP, then measuring the released phenols by HPLC or GC‑MS. This method is intended for laboratory analysis supporting environmental compliance, product safety and quality control in the leather industry.
Key topics and technical requirements
- Scope: Analysis of NP, OP, NPEO and OPEO in leather and process auxiliaries using chromatographic methods.
- Analytical principle: Ethoxylated alkylphenols are cleaved (using aluminium triiodide) to alkylphenols; NP/OP are quantified by HPLC (DAD or FLD) or GC‑MS and used to infer NPEO/OPEO content.
- Sample preparation: Typical leather extraction uses ~2.5 g sample mixed with Na2SO4 and extracted with 50 ml acetonitrile in an ultrasonic bath at (50 ± 5) °C for (60 ± 5) min; extracts are filtered prior to analysis.
- Reagents and standards: Acetonitrile, n‑hexane, aluminium triiodide, sulfuric acid, sodium thiosulfate, drying agents (MgSO4, Na2SO4); calibration solutions for NP/OP and representative ethoxylates are specified. A 4‑n‑nonylphenol internal standard is recommended for GC‑MS.
- Instrumentation: HPLC with diode‑array or fluorescence detector, or GC with mass selective detector (MSD). Calibration, blank determinations, and calculation procedures are defined.
- Method relationship: ISO 18218‑2 is an indirect cleavage method; ISO 18218‑1 provides a direct determination of ethoxylates. Different extraction solvents are used between parts, so results are expected to show similar trends but may differ in absolute values.
Applications and users
- Who uses it: Leather testing laboratories, quality control teams in tanneries and leather product manufacturers, environmental testing labs, regulatory agencies and certification bodies.
- Practical uses:
- Verify compliance with regulatory limits (e.g., REACH and Directive 2003/53/EC concerns on NPEOs/NP).
- Screen incoming process auxiliaries and finished leather for unwanted alkylphenol residues.
- Support supplier qualification, product safety declarations and environmental monitoring programs.
- Benefits: Provides a validated laboratory procedure that links chromatographic analysis to regulatory and environmental concerns about persistent, endocrine‑active alkylphenol residues.
Related standards
- ISO 18218‑1 (direct method for ethoxylated alkylphenols)
- Normative references cited in the method: ISO 2418 (sampling locations), ISO 3696 (laboratory water), ISO 4044 (sample preparation)
Keywords: ISO 18218-2, leather testing, nonylphenol (NP), octylphenol (OP), nonylphenol ethoxylate (NPEO), octylphenol ethoxylate (OPEO), indirect method, HPLC, GC‑MS, aluminium triiodide, REACH.