Overview
EN ISO 5398-3:2018 - "Leather - Chemical determination of chromic oxide content - Part 3: Quantification by atomic absorption spectrometry" is a CEN-endorsed ISO test method for measuring total chromium in leather. The standard specifies how to solubilize chromium from leather into an aqueous solution and quantify it using atomic absorption spectrometry (AAS). Results are reported as chromic oxide (Cr2O3) content in mg/kg (based on dry matter). This method applies to leathers expected to contain more than 5 mg/kg chromic oxide.
Key topics and requirements
- Scope: Determination of total chromium in leather; not compound- or oxidation-state-specific.
- Sample handling: Sampling in accordance with ISO 2418 and sample preparation per ISO 4044. Typical test portion: 2 g of prepared leather (weighed to 0.001 g); at least two determinations per sample.
- Preparation techniques: Two procedures for producing the analytical solution:
- Wet oxidation (specified as the reference method in disputes)
- Microwave digestion
- Reagents: Analytical-grade reagents such as nitric acid (70 %), a sulfuric/perchloric acid mix (1:3 v/v), potassium dichromate standard (traceable), and potassium chloride solution for matrix modification.
- Instrumentation: Atomic absorption spectrophotometer with appropriate hollow cathode lamp and nitrous oxide burner (or high-solids N2O burner). Filtration using glass-fiber or membrane filters is specified.
- Quality and reporting: Use grade 3 water per ISO 3696; calculation and expression of results are defined, and the test report must include sampling and method details. Annexes include guidance on volatile matter determination and suitable AAS equipment.
Practical applications
- Routine laboratory testing of finished leather and leather components for chromium content.
- Compliance testing for regulatory, environmental or product-safety requirements where chromium levels must be known.
- Quality control in tanneries and material suppliers to monitor chromium tanning residues.
- Dispute resolution assays (wet oxidation is mandated if results are contested).
Who should use this standard
- Analytical laboratories performing leather chemistry tests.
- Tannery quality-control teams and product compliance departments.
- Certification bodies, regulators and testing services assessing chromium content in leather goods.
- Research organizations studying chromium in leather processing.
Related standards
- ISO 2418 - Sampling locations for leather
- ISO 4044 - Preparation of chemical test samples
- ISO 3696 - Water for laboratory use
- ISO 4684 - Determination of volatile matter
- EN 14602 - Footwear ecological test methods
This standard is part of the ISO 5398 series and is intended for laboratories that require accurate, AAS-based quantification of chromic oxide in leather products.