ISO 5398-4:2018 PDF

Overview

ISO 5398-4:2018 - Leather - Chemical determination of chromic oxide content - Part 4: Quantification by inductively coupled plasma (ICP) describes a standardized laboratory method to determine total chromium in leather samples by inductively coupled plasma (ICP). The method reports chromium as chromic oxide (Cr2O3) and is applicable to leathers expected to contain more than 1 mg/kg chromic oxide. It is Part 4 of the ISO 5398 series and was updated to include both ICP-OES and ICP-MS techniques.

Key topics and requirements

• Scope: Determination of total chromium in aqueous extracts from leather; not compound- or oxidation-state-specific.
• Sample preparation:
  • Prepare samples following ISO 2418 (sampling location) and ISO 4044 (preparation of chemical test samples).
  • Two digestion techniques:
    • Wet oxidation (preferred in disputes): weigh ~2 g prepared leather; add nitric acid first, then a sulfuric/perchloric acid mix; heat and dilute. Warning: add nitric acid first to avoid hazardous reactions.
    • Microwave-assisted digestion (MAD) or other validated digestion: typically use 0.1–1 g sample with ultrapure acids.
• Measurement:
  • Analysis by ICP-OES or ICP-MS following manufacturer guidance and relevant ISO methods (ISO 11885 for ICP-OES; ISO 17294-2 for ICP‑MS).
  • Prepare at least four calibration standards plus a blank; match acid matrix between standards and samples.
  • For wet oxidation, ICP-OES is preferred due to possible interferences with ICP‑MS.
• Calculation:
  • Convert measured chromium concentration (ρ, μg/ml) to chromic oxide using the factor 1.462 (Cr → Cr2O3).
  • Correct results for volatile matter (ISO 4684) using F = 100 / (100 − w), where w is volatile matter %.
• Reporting: Include method reference (ISO 5398-4), sample description, digestion type, volatile matter, results in mg/kg and any deviations.

Applications and users

• Practical for laboratory quality control, regulatory compliance, and forensic testing of leather from tannery process control to finished goods.
• Typical users: chemical testing laboratories, leather technologists, tanneries, suppliers, regulatory bodies and auditors assessing chromium levels in leather products.
• Useful where precise quantification of chromium (as chromic oxide) is required for safety, environmental reporting, or material specification.

Related standards

• ISO 2398 series (other parts for chromic oxide)
• ISO 2418 - sampling location
• ISO 4044 - test sample preparation
• ISO 4684 - volatile matter determination
• ISO 11885 - ICP-OES analysis
• ISO 17294-2 - ICP‑MS analysis

Keywords: ISO 5398-4, chromic oxide, leather testing, chromium determination, ICP, ICP-OES, ICP-MS, wet oxidation, microwave digestion, leather quality control.