ISO 6101-6:2018

Overview

ISO 6101-6:2018 - Rubber - Determination of metal content by atomic absorption spectrometry - Part 6: Determination of magnesium content specifies an atomic absorption spectrometric (AAS) method for measuring magnesium in natural rubber latex concentrate, raw natural rubber, and rubber products. The standard covers sample preparation (ashing and dissolution), calibration, spectrometric measurement and result expression to ensure reliable, comparable magnesium determinations.

Key Topics and Requirements

• Scope: Method for magnesium content in natural rubber materials (latex concentrate, raw rubber, products).
• Sample preparation:
  • Test portion sizes: typically 1–5 g for rubber products, 5–10 g for raw rubber; ~10 g total solids for latex concentrate (dried).
  • Ashing (destruction of organic matter) in a muffle furnace: 550 °C ± 25 °C for raw natural rubber or 950 °C ± 25 °C for products with high carbon black content (per ISO 247-1).
  • If ash is black (carbon black residues), re-treat with concentrated nitric acid and re-ash.
• Dissolution: Ash dissolved in dilute nitric acid (1.6% by mass) and made up to a volumetric flask for analysis.
• Reagents and standards:
  • Use analytical-grade reagents and distilled water.
  • Standard magnesium stock (1 g·dm−3) and working standard (10 µg·cm−3) preparation described.
• Instrumentation:
  • Flame AAS with magnesium hollow-cathode lamp at 285.2 nm (acetylene/air flame) is specified; graphite furnace (electrothermal atomization) is permitted as an alternative.
• Calibration & measurement:
  • Prepare a five-point calibration series, measure absorbance in duplicate, and plot a calibration graph (least-squares or visual fit).
  • Perform duplicate measurements on test solutions, include blanks, and dilute if readings exceed calibration range.
• Quality aspects:
  • Duplicate determinations, blank corrections, and expression of results in mg·kg−1.
  • Precision data and method of standard additions are provided in informative annexes.

Applications and Who Uses It

• Quality control labs in rubber manufacturing to monitor magnesium levels affecting vulcanization and product properties.
• Contract testing laboratories performing compositional analysis of natural rubber and rubber products.
• Research and development groups studying trace metals in rubber formulations.
• Regulatory bodies and product specifiers requiring standardized metal-content reporting.
• Useful when precise, comparable magnesium measurement by AAS is required for product compliance, failure analysis, or process optimization.

Related Standards

• ISO 6101 series (other parts)
• ISO 247-1 (ash - dry combustion technique)
• ISO 123 (rubber latex sampling)
• ISO 124 (latex total solids)
• ISO 1795 (raw rubber sampling/preparative procedures)
• Laboratory glassware & crucible standards referenced: ISO 1042, ISO 648, ISO 835, ISO 1772

Keywords: ISO 6101-6:2018, magnesium determination, atomic absorption spectrometry, AAS, natural rubber, rubber testing, sample ashing, calibration, magnesium in rubber.