Overview
EN ISO 5398-4:2019 - Leather - Chemical determination of chromic oxide content - Part 4: Quantification by inductively coupled plasma (ICP) - specifies a laboratory method for measuring total chromium in leather extracts using inductively coupled plasma techniques (ICP-OES or ICP-MS). The method reports results as chromic oxide (Cr2O3) in mg/kg (dry matter) and is applicable to leathers expected to contain chromic oxide in excess of 1 mg/kg. This standard is the CEN adoption of ISO 5398-4:2018 and supersedes the 2007 edition.
Key topics and technical requirements
- Scope: Determination of total chromium in aqueous solutions obtained from leather. Not compound- or oxidation-state-specific.
- Preparation techniques: Two preparation methods are included:
- Wet oxidation (recommended in case of dispute). Warning: add nitric acid first to avoid hazardous reactions with perchloric acid. Typical analytical sample mass guidance: 2 g of prepared leather (perform duplicate determinations if possible).
- Microwave digestion (or other validated digestion methods) using ultrapure acids.
- Analytical techniques: Measurement by ICP-OES (per ISO 11885) or ICP-MS (per ISO 17294-2). Annex B provides guidance on suitable ICP equipment.
- Reagents & quality: Analytical-grade reagents (nitric, sulfuric/perchloric mix), ultrapure acids for microwave digestion, and grade 3 water per ISO 3696. Commercial chromium standards (e.g., 1 000 mg/L) are used for calibration.
- Apparatus: ICP instrument, filtration (glass-fibre or membrane), anti-bumping granules (for wet oxidation), volumetric flasks, etc.
- Reporting: Chromium content is expressed as chromic oxide (mg/kg) based on dry matter; follow sample preparation and sampling rules (ISO 2418, ISO 4044).
Practical applications and users
- Who uses it: Leather testing laboratories, tanneries, quality control departments, material compliance teams, research institutes and forensic labs analyzing leather contaminants.
- Why it’s used: Provides a precise, reproducible method for quantifying chromium levels in leather for product quality control, process monitoring, comparative testing, and laboratory accreditation.
- Benefits: ICP methods deliver higher precision and sensitivity than simpler colorimetric or titrimetric techniques, and are suitable where accurate total chromium measurement above ~1 mg/kg is required.
Related standards
- ISO 2418 - Sampling location for leather testing
- ISO 4044 - Preparation of chemical test samples (leather)
- ISO 3696 - Water for analytical laboratory use
- ISO 11885 - ICP-OES for selected elements
- ISO 17294-2 - ICP-MS application for selected elements
- ISO 4684 - Determination of volatile matter (informative for dry-mass reporting)
Keywords: EN ISO 5398-4:2019, leather chromic oxide, chromium determination, ICP-OES, ICP-MS, wet oxidation, microwave digestion, leather testing.
