AS/NZS ISO 33405:2024
Reference materials – Approaches for characterization and assessment of homogeneity and stability
Standard identically adopts ISO 33405:2024, which explains concepts and provides approaches to the following aspects of production of reference materials (RMs): assessment of homogeneity; assessment of stability and management of risks associated with possible stability issues related to properties of interest; characterization and value assignment of properties of RM; evaluation of uncertainty for certified values; and establishment of metrological traceability of certified values.
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AS/NZS ISO 33405:2024 Approaches for characterization and assessment of homogeneity and stability
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Conventions
6 Overview of reference material production
6.1 General
6.2 Summary of project design
6.3 Acquisition of starting material
6.4 Feasibility studies
6.5 Reference material processing
6.6 Homogeneity assessment
6.7 Stability assessment
6.8 Choice of measurement procedures
6.9 Metrological traceability
6.10 Characterization and uncertainty evaluation
6.11 Commutability assessment
6.12 Transport issues
6.13 Value assignment
6.14 Stability monitoring
6.15 Reference materials produced in repeated batches
7 Assessment of homogeneity
7.1 Preamble
7.2 Need for an experimental homogeneity study
7.3 Properties to be studied
7.4 Statistically valid sampling schemes
7.4.1 Minimum number of units for a homogeneity study
7.4.2 Use of statistical power analysis
7.4.3 Sampling strategies for a homogeneity study
7.5 Choice and conduct of the measurement procedure for a homogeneity study
7.5.1 Choice of measurement procedure
7.5.2 Conduct of measurements for homogeneity studies
7.6 Homogeneity study designs
7.6.1 Objective of a homogeneity study
7.6.2 The basic homogeneity study design – measurement in a single run
7.6.3 Randomized block design
7.6.4 Balanced nested design
7.6.5 Alternative strategies
7.7 Evaluating a homogeneity study
7.7.1 Initial inspection for measurement trends and outliers
7.7.2 Inspection for processing trends
7.7.3 Evaluation of the between-unit term – basic design
7.7.4 Evaluation of the between-unit term – randomized block design
7.7.5 Evaluation of the between-unit term – balanced nested design
7.7.6 Other homogeneity designs and alternative estimation methods
7.8 Insufficient repeatability of the measurement procedure
7.9 Within-unit homogeneity
7.9.1 Assessing the need for within-unit homogeneity study
7.9.2 Testing for significant within-unit heterogeneity
7.9.3 Assessing minimum sample size
7.10 Check for sufficient homogeneity
7.11 Uncertainty evaluation from homogeneity studies
8 Assessment and monitoring of stability
8.1 Preamble
8.2 Assessment of stability
8.2.1 Requirement for stability assessment
8.2.2 Types of (in)stability
8.2.3 General methods for assessment of stability
8.2.4 Need for experimental study of stability
8.3 Classification of stability studies
8.3.1 General
8.3.2 Classification according to conditions of measurement
8.3.3 Classification according to stability study duration and conditions
8.3.4 Classification by study objective
8.3.5 Designs for different storage and treatment conditions
8.4 General requirements for effective stability studies
8.4.1 Overview of requirements
8.4.2 Selection of RM units
8.4.3 Suitable measurement procedure(s) for stability studies
8.4.4 Appropriate experimental design
8.5 Evaluation of stability study results
8.5.1 General considerations for stability study data treatment
8.5.2 The basic stability study: multiple points in time at a single storage condition
8.5.3 Isochronous designs
8.5.4 Accelerated stability studies with multiple exposure conditions
8.5.5 Additional sources of random variation in stability studies
8.6 Action on finding a significant trend in a stability study
8.7 Uncertainty evaluation from stability studies
8.7.1 General considerations for uncertainty evaluation from stability studies
8.7.2 Sources of uncertainty in predicted change over time
8.7.3 Estimation of stability uncertainties in the absence of significant trends
8.7.4 Evaluation of stability uncertainties in the case of a known significant trend
8.8 Estimation of storage lifetime (“shelf life”) from a stability study
8.9 Instructions for use related to management of stability
8.10 Stability monitoring
8.10.1 Requirements for monitoring
8.10.2 Choice of initial monitoring point and monitoring interval(s)
8.10.3 Experimental approaches and evaluation for stability monitoring
9 Characterization of the material
9.1 Preamble
9.2 Establishing metrological traceability
9.2.1 Principle
9.2.2 Metrological references
9.2.3 Types of measurands
9.2.4 Effect of sample preparation or pre-treatment
9.2.5 Verification of traceability
9.3 Characterization using a single reference measurement procedure (as defined in ISO/IEC Guide 99) in a single laboratory
9.3.1 Characterization by a reference measurement procedure without direct comparison with a CRM of the same kind
9.3.2 Characterization by value transfer from a reference material to a closely matched candidate reference material using a single measurement procedure performed by one laboratory
9.3.3 Selection of RM units for single-laboratory characterization
9.3.4 Formulation methods
9.4 Characterization of a non-operationally defined measurand using two or more methods of demonstrable accuracy in one or more competent laboratories
9.4.1 Concept
9.4.2 Study design
9.4.3 Evaluation
9.4.4 Single-laboratory multi-method studies
9.5 Characterization of an operationally defined measurand using a network of competent laboratories
9.5.1 Concept
9.5.2 Study setup
9.5.3 Evaluation
9.6 Purity
9.6.1 General
9.6.2 Direct determination of purity
9.6.3 Indirect determination of purity
9.7 Ordinal scales
9.8 Nominal properties including identity
9.9 Characterization of non-certified values
10 Evaluating measurement uncertainty
10.1 Basis for evaluating the uncertainty of a property value of a CRM
10.2 Basic model for a batch characterization
10.3 Uncertainty sources
10.4 Coverage intervals and factors
Annex A (informative) Design and evaluation of studies for the characterization of a method-independent measurand using two or more methods of demonstrable accuracy in one or more competent laboratories
Annex B (informative) Statistical approaches
Annex C (informative) Examples
Annex D (informative) Measurement uncertainty evaluation
Bibliography
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AS/NZS ISO 33405:2024 Approaches for characterization and assessment of homogeneity and stability
Preface
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Conventions
6 Overview of reference material production
6.1 General
6.2 Summary of project design
6.3 Acquisition of starting material
6.4 Feasibility studies
6.5 Reference material processing
6.6 Homogeneity assessment
6.7 Stability assessment
6.8 Choice of measurement procedures
6.9 Metrological traceability
6.10 Characterization and uncertainty evaluation
6.11 Commutability assessment
6.12 Transport issues
6.13 Value assignment
6.14 Stability monitoring
6.15 Reference materials produced in repeated batches
7 Assessment of homogeneity
7.1 Preamble
7.2 Need for an experimental homogeneity study
7.3 Properties to be studied
7.4 Statistically valid sampling schemes
7.4.1 Minimum number of units for a homogeneity study
7.4.2 Use of statistical power analysis
7.4.3 Sampling strategies for a homogeneity study
7.5 Choice and conduct of the measurement procedure for a homogeneity study
7.5.1 Choice of measurement procedure
7.5.2 Conduct of measurements for homogeneity studies
7.6 Homogeneity study designs
7.6.1 Objective of a homogeneity study
7.6.2 The basic homogeneity study design – measurement in a single run
7.6.3 Randomized block design
7.6.4 Balanced nested design
7.6.5 Alternative strategies
7.7 Evaluating a homogeneity study
7.7.1 Initial inspection for measurement trends and outliers
7.7.2 Inspection for processing trends
7.7.3 Evaluation of the between-unit term – basic design
7.7.4 Evaluation of the between-unit term – randomized block design
7.7.5 Evaluation of the between-unit term – balanced nested design
7.7.6 Other homogeneity designs and alternative estimation methods
7.8 Insufficient repeatability of the measurement procedure
7.9 Within-unit homogeneity
7.9.1 Assessing the need for within-unit homogeneity study
7.9.2 Testing for significant within-unit heterogeneity
7.9.3 Assessing minimum sample size
7.10 Check for sufficient homogeneity
7.11 Uncertainty evaluation from homogeneity studies
8 Assessment and monitoring of stability
8.1 Preamble
8.2 Assessment of stability
8.2.1 Requirement for stability assessment
8.2.2 Types of (in)stability
8.2.3 General methods for assessment of stability
8.2.4 Need for experimental study of stability
8.3 Classification of stability studies
8.3.1 General
8.3.2 Classification according to conditions of measurement
8.3.3 Classification according to stability study duration and conditions
8.3.4 Classification by study objective
8.3.5 Designs for different storage and treatment conditions
8.4 General requirements for effective stability studies
8.4.1 Overview of requirements
8.4.2 Selection of RM units
8.4.3 Suitable measurement procedure(s) for stability studies
8.4.4 Appropriate experimental design
8.5 Evaluation of stability study results
8.5.1 General considerations for stability study data treatment
8.5.2 The basic stability study: multiple points in time at a single storage condition
8.5.3 Isochronous designs
8.5.4 Accelerated stability studies with multiple exposure conditions
8.5.5 Additional sources of random variation in stability studies
8.6 Action on finding a significant trend in a stability study
8.7 Uncertainty evaluation from stability studies
8.7.1 General considerations for uncertainty evaluation from stability studies
8.7.2 Sources of uncertainty in predicted change over time
8.7.3 Estimation of stability uncertainties in the absence of significant trends
8.7.4 Evaluation of stability uncertainties in the case of a known significant trend
8.8 Estimation of storage lifetime (“shelf life”) from a stability study
8.9 Instructions for use related to management of stability
8.10 Stability monitoring
8.10.1 Requirements for monitoring
8.10.2 Choice of initial monitoring point and monitoring interval(s)
8.10.3 Experimental approaches and evaluation for stability monitoring
9 Characterization of the material
9.1 Preamble
9.2 Establishing metrological traceability
9.2.1 Principle
9.2.2 Metrological references
9.2.3 Types of measurands
9.2.4 Effect of sample preparation or pre-treatment
9.2.5 Verification of traceability
9.3 Characterization using a single reference measurement procedure (as defined in ISO/IEC Guide 99) in a single laboratory
9.3.1 Characterization by a reference measurement procedure without direct comparison with a CRM of the same kind
9.3.2 Characterization by value transfer from a reference material to a closely matched candidate reference material using a single measurement procedure performed by one laboratory
9.3.3 Selection of RM units for single-laboratory characterization
9.3.4 Formulation methods
9.4 Characterization of a non-operationally defined measurand using two or more methods of demonstrable accuracy in one or more competent laboratories
9.4.1 Concept
9.4.2 Study design
9.4.3 Evaluation
9.4.4 Single-laboratory multi-method studies
9.5 Characterization of an operationally defined measurand using a network of competent laboratories
9.5.1 Concept
9.5.2 Study setup
9.5.3 Evaluation
9.6 Purity
9.6.1 General
9.6.2 Direct determination of purity
9.6.3 Indirect determination of purity
9.7 Ordinal scales
9.8 Nominal properties including identity
9.9 Characterization of non-certified values
10 Evaluating measurement uncertainty
10.1 Basis for evaluating the uncertainty of a property value of a CRM
10.2 Basic model for a batch characterization
10.3 Uncertainty sources
10.4 Coverage intervals and factors
Annex A (informative) Design and evaluation of studies for the characterization of a method-independent measurand using two or more methods of demonstrable accuracy in one or more competent laboratories
Annex B (informative) Statistical approaches
Annex C (informative) Examples
Annex D (informative) Measurement uncertainty evaluation
Bibliography
AS/NZS ISO 33405:2024
Online Library subscription information
Online library subscriptions provide a cost-effective solution for organisations of any size to access the latest standards, offering 24/7 access to a personalised catalogue. The service ensures subscribers have have the most up-to-date version of selected standards, incluing automatic updates for any amendments or versions. Pricing is dependent on the chosen standards and the number of concurrent users, with discounts applied from the standards PDF price. For customised subscriptions or further inquiries, contact the Online Library team.