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 | Technical guidelines for the production and acceptance of a European Reference Material |  |
- General principles
- European Reference Materials samples
- Homogeneity testing
- Stability testing
- Batch characterisation
- Establishment of a certificate
- Transfer of samples to final storage place
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Every European Reference Material project must be executed in accordance with
internationally accepted guidelines such as ISO-Guides 30-35 (and more
particularly ISO Guide 34, specifying the general requirements for the
competence of reference material producers), WHO Guidelines (for clinical
reference materials), the ISO-Guide to the Expression of Uncertainty in
Measurement (GUM), etc.
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Details of the European Reference Material project planning related to
selection of base material, technical aspects of the production process of the
candidate material and its subsequent storage, homogeneity control, short- and
long-term stability testing, characterisation of the batch, long-term storage
and monitoring are described in a project planning form, to be submitted to
and approved by the European Reference Materials panel within 6 weeks after
receiving the complete documentation.
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| | European Reference Materials samples | |
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European Reference Materials samples (bottles, vials, ampoules, etc.) must be
tight and contain not less than the stated amount of material
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Samples must have appropriate homogeneity and stability.
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Whenever relevant (e.g., in case of clinical ERM-CRMs), the commutability of
the European Reference Material has to be assured.
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Packaging must be appropriate for the purpose.
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Labelling must be clear and of good quality.
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Usually, between bottle homogeneity must be examined. Exceptions can be made,
when previous experience has shown that CRMs are prepared with negligible
heterogeneity, such as for some solutions. However, even in such cases
homogeneity testing is advisable to check for possible heterogeneity due to
contamination.
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Any possible between-bottle heterogeneity must be accounted for in the overall
estimated CRM uncertainty. This requirement applies even when no statistically
significant between-bottle variation is present. In this case the method
variation or the actual calculated between-bottle variation (whichever is
larger) should be included in the overall uncertainty.
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Whenever relevant, long-term stability must be positively demonstrated by
appropriate statistical extrapolation for the certified European Reference
Material's shelf-life to be within the certified uncertainty; the uncertainty
related to this demonstration is normally part of the estimated CRM
uncertainty.
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Exceptions can be made, when previous experience has shown that the
uncertainty of stability is negligible. In such cases the uncertainty
contribution of long-term stability is set zero. In all other cases this
parameter is determined from regression analysis of the results of the
long-term stability study.
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Whenever possible, stability studies should be carried out using isochronous
measurements.
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When a quantity that is not method dependant is certified, batch
characterisation can be carried out
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on hand of a primary method of measurement by a primary/definitive method of
measurement
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or by laboratory intercomparison, using, whenever possible, two or more
independent analytical methods.
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When a method dependant quantity is certified by laboratory intercomparison,
all laboratories must strictly comply with the imposed standard operating
procedure.
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be applied under metrologically valid conditions,
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have been properly validated before use (see ISO/IEC 17025: 5.4.5)
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have precision and accuracy compatible with the target uncertainty.
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Each set of measurements must:
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be traceable to the stated references, and
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be accompanied by a GUM-compatible uncertainty statement whenever possible.
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Participant laboratories must:
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have the required competence for the execution of the task in the European
Reference Material project,
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be able to achieve traceability to the required stated references,
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be able to estimate its measurement uncertainty in accordance with GUM,
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have in place a sufficient and appropriate quality assurance system.
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Estimation of uncertainty of batch-characterisation:
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Whenever possible, standard uncertainties of bacth-characterisation (uchar) by
both primary methods of measurement or laboratory intercomparisons should be
based on the combination of detailed uncertainty budgets of the contributing
values.
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If insufficient information is available for values based on laboratory
intercomparisons, uchar can, in the absence of uncertainties common to all
participants (e.g., common standard), also be approximated by the standard
deviation of the mean of laboratory means.
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be able to estimate its measurement uncertainty in accordance with GUM,
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If such common uncertainties are present, they have to be added to the
uncertainty of the mean of laboratory means.
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| | Establishment of a certificate | |
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The European Reference Material-Project Manager establishes a draft
certificate (possibly complemented by a certification report) in accordance
with ISO Guide 30, containing all information relevant to and needed by the
user.
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Certified values must be traceable to stated references and be accompanied by
a GUM-compatible expanded uncertainty statement valid for the entire
shelf-life of the European Reference Material.
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After approval by the European Reference Materials panel, the certificate and
report are made available, both on the European Reference Materials-web site
and in printed form, and the European Reference Material is put on sale.
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| | Transfer of samples to final storage place | |
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To avoid degradation after certification, all samples are best transported to
the location which offers the conditions designated for the final storage of
the European Reference Material before measurements are started.
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Otherwise, they must be transported from door to door keeping them at all
times under such storage conditions for which it has been demonstrated that
there is no influence on the certified values.
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2004-2007 by ERM All rights reserved.
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