Overview
ISO 6101-1:2019 specifies an atomic absorption spectrometric (AAS) method for the determination of zinc content in rubber. It applies to raw rubber and rubber products with zinc contents of at least 0.05% (mass fraction); lower concentrations can be measured by adjusting sample mass, solution concentrations or by using the standard additions method to improve detection limits. The method replaces the 1991 edition and clarifies organic-matter destruction, result expression and precision data.
Key topics and technical requirements
- Principle: Ash the test portion at 550 °C ± 25 °C, dissolve the ash in hydrochloric or nitric acid, and measure zinc absorption at 213.8 nm using a zinc hollow‑cathode lamp. Silicates can be volatilized using sulfuric and hydrofluoric acids.
- Sample sizes: Typical test portions recommended (from the standard) are about 1–5 g for rubber products and 5–10 g for raw rubber; halogenated rubbers use smaller portions (e.g., 0.1 g).
- Reagents and standards: Uses analytical-grade acids (HCl, HNO3, H2SO4, HF) and zinc standard solutions (stock 1 mg/ml and working 10 µg/ml preparations described).
- Instrumentation: Flame AAS with acetylene/air burner is specified; graphite furnace (electrothermal atomization) is an acceptable alternative when operated by qualified personnel.
- Procedure elements: sampling, ashing (ISO 247‑1), destruction of organic matter, dissolution of inorganic residue, calibration graph preparation, spectrometric measurement, blanks, dilution and calculation of results (expressed in mg/kg).
- Quality aspects: Use of standard additions to lower detection limits, blank determinations, and precision data provided (updated in Annex B).
Practical applications and users
- Applications:
- Quality control in rubber manufacturing (vulcanizates, compounds)
- Raw material inspection (natural and synthetic rubber)
- Compliance testing for product specifications and supplier acceptance
- R&D and formulation development where zinc levels (e.g., zinc oxide activator residues) are important
- Who uses this standard:
- Industrial and third‑party testing laboratories
- QC chemists and analysts in rubber and polymer plants
- Standards bodies, regulatory laboratories and academic researchers
Related standards
Safety note: follow normal laboratory safety, acid handling and waste‑disposal practices as the standard includes warnings about hazardous reagents and waste.