Overview
ISO/TR 33402:2025 - Good practice in reference material preparation is an ISO Technical Report (first edition, 2025) that provides practical guidance on the preparation of candidate matrix reference materials (RMs). The document focuses on the front-end production steps - material specification, sourcing and selection of bulk material, and material processing - that are essential to produce homogeneous and stable candidate RMs suitable for laboratory use and quality control. It is intended for laboratory staff who prepare or use matrix materials and as an information source for reference material producers (RMPs).
Key technical topics and requirements
ISO/TR 33402:2025 highlights key considerations (not a full production manual) and covers technical topics including:
- Material specification
- Intended use and acceptable measurement uncertainty
- Matrix type and matrix matching to routine samples
- Properties/property values, unit size, and total bulk amount
- Sourcing and selection of bulk material
- Criteria for choosing material representative of routine samples
- Considerations for commercial sourcing or third-party processing
- Material processing steps
- Prevention and avoidance of contamination
- Drying, milling/grinding, sieving
- Mixing/blending, filtration
- Stabilization and sterilization when applicable
- Subdivision and packaging, including container selection and subdivision procedures
- Case studies (Annexes A–F) illustrating preparation of QCMs and RMs in different fields (e.g., coal, geological/metallurgical, fortified food, bauxite, pharmaceutical reference standards, bromate in water)
Important boundaries: this Technical Report focuses on preparation steps and explicitly does not replace guidance on characterization, homogeneity and stability assessment, or value assignment - those topics are covered in ISO 33405 and ISO 17034.
Practical applications and who uses this standard
ISO/TR 33402:2025 is useful for:
- Laboratory analysts preparing candidate RMs or in-house quality control materials (QCMs)
- Reference material producers (RMPs) seeking practical preparation guidance
- QA/QC managers and method developers needing matched matrix reference materials
- Organizations producing test materials for regulatory, forensic, environmental, food, pharmaceutical, and metallurgical testing
Use cases:
- Preparing matched matrix materials when commercial RMs are unavailable
- Designing processing workflows (milling, blending, packaging) to achieve sufficient homogeneity and stability prior to characterization
- Informing decisions on container choice, unit size and bulk material sourcing
Related standards
- ISO 17034 - General requirements for the competence of reference material producers
- ISO 33405 - Guidance for homogeneity, stability and characterization of reference materials
- ISO Guide 30, ISO/IEC Guide 99, ISO 3534-1 - Terminology and statistical vocabulary referenced by this report
Keywords: ISO/TR 33402:2025, reference material preparation, matrix RMs, reference material producers, quality control material, RM processing, material specification.