ISO 9277:2022

Overview

ISO 9277:2022 - "Determination of the specific surface area of solids by gas adsorption - BET method" defines a standardized procedure to measure the specific surface area (external + accessible internal surface) of disperse (e.g., nano‑powders) and porous solids by gas adsorption using the Brunauer–Emmett–Teller (BET) method. The standard aligns with the 2015 IUPAC recommendations and replaces the 2010 edition. It describes the principle of monolayer capacity determination from an adsorption isotherm and specifies procedures, instrumentation alternatives and reporting requirements.

Key topics and requirements

• Scope & applicability
  • Measurement of overall specific surface area for disperse and porous solids; not reliable for solids that chemically absorb the measuring gas.
  • BET is applicable mainly to IUPAC isotherm Type II (nonporous/disperse) and Type IV (mesoporous) - caution with Type IVb and microporous materials.
• Principle
  • Determination of monolayer capacity from adsorption isotherms and conversion to surface area using molecular cross‑section of the adsorptive.
• Sample preparation
  • Sampling per ISO 8213 and ISO 14488.
  • Careful degassing to remove physisorbed species without altering the surface; vacuum to ~1 Pa typically sufficient.
• Measurement methods
  • Static manometric (volumetric)
  • Flow manometric (volumetric)
  • Gravimetric
  • Carrier‑gas methods
  • Dynamic Vapour Sorption (DVS) - newly described in this edition
• Choice of adsorptive
  • Common adsorptives: nitrogen (77 K), argon (87 K), krypton (77 K) for very low surface areas.
  • Note: nitrogen’s quadrupole can introduce ~20% uncertainty on some surfaces; argon is less surface‑chemistry sensitive.
• Data evaluation
  • Multipoint and single‑point BET evaluation approaches are specified (monolayer capacity calculated from the BET plot).
• Reporting & reference materials
  • Required test report elements and guidance on using BET reference materials. Annexes provide cross‑sectional areas of common adsorptives and guidance for microporous materials.

Applications and users

• Who uses ISO 9277:2022
  • Materials scientists, catalysis researchers, adsorbent manufacturers, pharmaceutical formulators, carbon/activated charcoal producers, nanomaterials labs, quality control and certification bodies, and instrument manufacturers.
• Practical applications
  • Characterizing surface area of catalysts, powders, activated carbons, nanotubes, silica, cementitious materials and porous adsorbents.
  • Supporting product development, quality control, performance benchmarking, and regulatory/compliance documentation.

Related standards

• ISO 8213 - Sampling techniques for solid chemical products
• ISO 14488 - Sampling and sample splitting for particulate materials
• IUPAC recommendations on physisorption (2015) - referenced classification of adsorption isotherms

Keywords: ISO 9277:2022, BET method, specific surface area, gas adsorption, adsorption isotherm, nitrogen adsorption, argon adsorption, krypton adsorption, degassing, microporous, mesoporous, surface area analysis.