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

APLAC Approaches

Dr Bernard King NARL, Australia

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

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

Interrelated Requirements in ISO/IEC 17025

Specification of measurement requirement

Method validation

Traceability

Measurement Uncertainty

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 scrutinyIf method validation data is available, then evaluating

MU is not difficult

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

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

Traceability of RMs Reference Comments / Traceability

CRM Can be accepted

RM Can be accepted after assessment

CommercialChemicals

Lab are responsible, however: Often ‘best available’ Often entirely adequate

For physical measurements there are accreditationrequirements for calibration, but for chemical measurements

there is little yet in place!

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.

Reproducibility Based MUCombine other significant effects with

reproducibility

Reproducibility

MU

Bias Effects

Sampling Effects

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

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

Conclusions Measurements need to facilitate sound

decisions

Effort required depends on the level of

acceptable MUA 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.

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