ASTM D7967-21 PDF

Overview

ASTM D7967-21 is the internationally recognized standard test method for determining chrome content, specifically as chromium(III) oxide (Cr₂O₃), in Wet Blue and leather materials using Atomic Absorption (AA) or Inductively Coupled Plasma (ICP) techniques. This standard, published by ASTM International, outlines procedures that provide reliable data for both manufacturers and buyers in the leather industry, supporting quality control, material specification, and trade requirements.

Wet Blue refers to semi-processed leather that has been tanned with chromium salts and retains moisture. Accurate analysis of chromium content in Wet Blue is essential for evaluating the degree of tannage, assessing compliance with purchase specifications, and ensuring product safety.

Key Topics

• Chromium Content Analysis: Testing is performed on a moisture-free basis, ensuring standardized results for chrome quantification.
• Analytical Methods:
  • Atomic Absorption (AA): Utilizes nitrous oxide-acetylene or air-acetylene flame for analysis; applies suitable wavelengths and slit widths for accurate Cr₂O₃ measurement.
  • Inductively Coupled Plasma (ICP): Provides an alternate, sensitive technique for chrome determination.
• Sample Preparation: Wet Blue samples are digested using specific acid mixtures, depending on the analytical approach.
• Calibration and Standardization: Requires preparation and validation of reference solutions to ensure precision in results.
• Precision and Interference Control: The method addresses potential interferences (notably from iron) and includes guidance on matrix matching and use of modifiers.
• Safety and Compliance: The standard highlights necessary laboratory safety, health, and environmental practices due to the use of hazardous chemicals and equipment.

Applications

• Quality Assurance in the Leather Industry: This test method is critical for verifying chrome content in Wet Blue, directly impacting product quality, durability, and buyer-supplier agreements.
• Specification and Purchase Contracts: Chrome content is often a required parameter in sourcing Wet Blue, making this standard essential for contractual compliance.
• Regulatory Compliance: Many regulations restrict chromium levels in leather products for environmental and health reasons. This standardized method ensures reliable data for compliance documentation.
• Research and Development: Laboratories conducting R&D on tanning processes or substitute materials utilize ASTM D7967-21 for comparative analysis of chrome levels across materials and processing methods.
• Alternative to Perchloric Acid Methods: This standard serves as an alternative to ASTM D6656, offering flexibility in testing method selection.

Related Standards

• ASTM D1517: Terminology relating to leather.
• ASTM D2813: Practice for sampling leather for physical and chemical tests.
• ASTM D6656: Test method for determination of chromic oxide in Wet Blue using perchloric acid oxidation.
• ASTM D6659: Practice for sampling and preparation of Wet Blue and Wet White for tests.
• ASTM D6658: Test method for volatile matter (moisture) of Wet Blue by oven drying.
• ASTM E177: Practice for use of terms precision and bias in ASTM test methods.
• ASTM E691: Practice for conducting interlaboratory studies to determine test method precision.

Practical Value

Adoption of ASTM D7967-21 enhances consistency, comparability, and credibility in the leather supply chain. Using well-established analytical methods for chrome analysis helps manufacturers, laboratories, and buyers:

• Ensure product quality by accurately verifying chromium content.
• Meet regulatory requirements and avoid compliance risks.
• Simplify trade and specification checks between suppliers and buyers.
• Streamline internal quality processes with a repeatable, reliable test.
• Support sustainable practices by monitoring and controlling chromium usage in leather tanning.

Careful adherence to this test method ensures accurate analysis of Wet Blue and leather, supporting industry best practices and global trade standards.