Meeting the ISO/IEC 17025 Requirements for Traceability and Measurement Uncertainty APLAC Approaches

1. Meeting the ISO/IEC 17025 Requirements for Traceability and Measurement Uncertainty APLAC Approaches Dr Bernard King NARL, Australia

2. Interpretation of ISO/IEC 17025 Requirements • Extensive consultation leading to common interpretation and new Guides • APLAC held 3 day Workshop in May 01 to develop a common interpretation, across five fields. • Draft guide produced • Final guide expected by end of 2002 • Will supplement an ILAC guide

3. Some of the Difficulties • Anxiety in labs and accreditation bodies • Need for training of lab staff and assessors • Time / cost of additional work • Lack of customer demand • Some countries / fields are moving faster than others Need to interpret requirements in a pragmatic, progressive and common sense way ILAC MRA will help ensure level playing field

4. Interrelated Requirements in ISO/IEC 17025 • Specification of measurement requirement • Method validation • Traceability • Measurement Uncertainty

5. ISO/IEC 17025 Method Validation Requirements • Specifically required for in-house methods • Implicitely required for all methods • Long standing requirement, but often inadequately addressed • Needs to be subject to closer scrutiny If method validation data is available, then evaluating MU is not difficult

6. ISO/IEC 17025 Traceability Requirements • Measurements must be traceable to SI, where feasible • Where above is not feasible, traceability to other measurement standards must be established • This can be achieved by use of transfer standards, that are themselves traceable to higher level standards

7. Example 1- Cd in soil • Measurand &Units - Total Cd in soil, measured in mg/kg • Equation C = I . dC . V mg/kg dI m . R • I . dC is traceable to SI through PSRM dI • R is traceable to SI through matrix RM or ... • m and V are traceable to SI through calibrated standards If the model is valid then C is also traceable to SI

8. Traceability of RMs

9. ISO/IEC 17025 MU Requirements • An uncertainty evaluation is required for all measurements • Labs shall at least attempt to: • identify all significant components • make a reasonable estimation of U • ensure that reported results do not give a false impression of U.

10. Sampling Effects Reproducibility MU Bias Effects Reproducibility Based MUCombine other significant effects with reproducibility

11. Summary of International MU Policy • Target implementation date - Dec 2002 • ISO GUM and Eurachem / CITAC strategies are recommended but not compulsory • Strategies based on reproducibility need to also consider other significant effects • MU estimates can be based on available or readily obtainable data, including professional judgement • The degree of rigour required in evaluating uncertainty depends on the end use of the measurement

12. cont... • The evaluation of uncertainties associated with qualitative tests is not required, but the probability of false identification does need to be considered. • Any limitations associated with traceability and MU claims need to be reported with results • It is expected that reporting MU, where relevant and necessary, will become the norm with time

13. Conclusions • Measurements need to facilitate sound decisions • Effort required depends on the level of acceptable MU • A matter for professional judgment • Not as difficult as it first seems • Eg- If validation data available MU takes 0.5 to 2 days • Reasonable progress is being made in implementing the new requirements in a pragmatic and harmonized way.

14. Sources of Help • Literature - policy papers, guides, journals, web • Training courses, seminars, workshops, • eg. On RMs, MU and validation • Web- based training on MU at www.mutraining.com