ISO 3856-2:1984

Overview

ISO 3856-2:1984 is an international standard published by the International Organization for Standardization (ISO) that specifies two precise analytical methods for determining the "soluble" antimony content in paints, varnishes, and related coating materials. This standard covers the application of the flame atomic absorption spectrometric (AAS) method and the Rhodamine B spectrophotometric method for quantifying antimony concentrations ranging from approximately 0.05% to 5% by mass.

The AAS method is considered the referee method and is preferred in cases of disputes regarding antimony content results. The spectrophotometric method provides an alternative for routine analyses based on the formation of a coloured complex with Rhodamine B dye.

Key Topics

• Scope and Applicability
  The standard applies to paints, varnishes, printing inks, pigments, and related coating materials with "soluble" antimony in the range of about 0.05% to 5% by mass. It also addresses sample preparation and acid extraction techniques for accurate testing.

• Flame Atomic Absorption Spectrometric Method (AAS)

  • Involves aspirating the test solution into an acetylene/air flame.
  • Measures antimony absorption lines emitted by antimony hollow-cathode or discharge lamps, typically at a wavelength around 217.6 nm.
  • Utilizes calibration with standard antimony solutions for quantification.
  • Includes spectral interference corrections for elements like lead, calcium, and copper.
  • Requires analytical-grade reagents and purified water according to ISO 3696 standards.

• Rhodamine B Spectrophotometric Method

  • Extracts antimony from acidified solutions using di-isopropyl ether after oxidation with cerium(IV) sulfate.
  • Forms a red complex with Rhodamine B, measurable at approximately 553 nm wavelength.
  • Requires careful preparation, including acid concentration control and phase separation with separating funnels.
  • Calibration graphs are prepared using standard calorimetric antimony solutions.
  • Appropriate for samples where AAS equipment is unavailable or as an agreed alternative.

• Sample Preparation and Test Solutions

  • Based on ISO 6713 guidelines for acid extraction from liquid or powder paints.
  • Provides detailed procedures for pigment and liquid portions of paint.
  • Highlights dilution factors, correction for blank solutions, and stability of reagents during analyses.

• Calculation and Results Expression

  • Detailed formulae are included for converting absorbance readings into percentage content by mass.
  • Addresses the summation of soluble antimony from both pigment and liquid paint portions for total content.
  • Notes that precision data for the methods were not available at the time of publication.

Applications

• Quality Control in Paints and Coatings Industry
  Ensures compliance with regulatory and product specifications relating to the metal content of paints and varnishes.

• Regulatory Compliance and Environmental Monitoring
  Enables manufacturers to monitor soluble antimony levels, critical due to antimony's toxicity and environmental impact.

• Material Safety and Consumer Protection
  Helps verify antimony content to prevent excessive amounts in consumer products, thus ensuring safer usage.

• Research and Development
  Laboratories can use these standardized methods for formulating new coatings and tracking changes in metal content during product development.

Related Standards

• ISO 3856-1: Paints and varnishes – Determination of soluble metal content – Part 1: General principles
  Provides foundational concepts and common procedures linked to metal content determination.

• ISO 6713: Paints and varnishes – Preparation of acid extracts from paints in liquid or powder form
  Defines the extraction procedures used in preparing samples for antimony analysis as referenced by ISO 3856-2.

• ISO 3696: Water for laboratory use – Specifications
  Specifies the quality of water required for reagent preparation and analysis to ensure accuracy.

• ISO 4800: Laboratory glassware – Separating funnels and dropping funnels
  Covers requirements for glassware critical for solvent extraction steps in the Rhodamine B method.

• ISO 385/1: Laboratory glassware – Burettes – Part 7: General requirements
  Important for accurate volume measurements during preparation of standard solutions.

By adhering to ISO 3856-2:1984, laboratories and manufacturers can reliably determine the soluble antimony content in coatings using validated flame atomic absorption spectrometry and spectrophotometric techniques. These methods contribute to maintaining high-quality standards in the coatings industry while supporting health, safety, and environmental regulations.