134
3 Traceability: Reference Materials
word "trackability" has lately been used to designate an unequivocal relationship
between a result and a sample aliquot in terms of a property of the result rather
than one of the sample.
I 3.6.3 Traceability of an Instrument
As shown in Box 3.2, the generic concept of traceability encompasses calibration,
whereby measuring equipment is related to national or international standards.
Consequently, in the metrological domain, traceability can be considered a
property of a measuring instrument. Calibration with an appropriate physical,
physico-chemical or chemical standard, and the ensuing correction, ensure that
the instrument will operate as required to assure traceability in its results.
This essential operation should be supplemented with a detailed "history" of
the instrument's operation in the form of a comprehensive, customized record
including detailed, timed descriptions of installation, malfunctioning, repair,
servicing, calibration and correction operations, hours of use, number of
samples processed, etc.
These activities are considered and organized in the quality systems of analyticallaboratories. They constitute an essential chapter in the Quality Manual
mentioned in the standards of the EN-4S000 family and are the subjects of
Standard Operating Procedures (SOPs) in Good Laboratory Practices (GLPs).
The traceability of each instrument and apparatus should be visually and
documentarily inspected in pertinent audits.
Any apparatus (oven, extractor, reactor) should also be the subject of continual inspection in order to ensure proper functioning as scheduled. Thus, a
refrigerator set to maintain a temperature of 4°C should be periodically checked
to ensure that it keeps the desired temperature. Malfunctioning in an apparatus
used in a CMP can lead to alterations affecting the traceability of the final results.
I 3.6.4 Traceability of a Sample Standard
The more relevant properties of certified reference materials (CRMs) can also be
traceable. Thus, the certified value and its uncertainty should be traced to base
standards through the results produced by the laboratories participating in the
certifying campaign and through the standards used for calibration in each case.
It is essential for the user to know why given results, if any, were discarded, what
the most significant sources of error (e.g. sample treatment) were, which
methods provided the highest accuracy and precision, etc. Also, the reference
material should be documented with technical details about its preparation,
homogeneity and stability. For example, the user should be able to know whether
the analyte was added (spiked) to the sample or initially present in the bulk
material since some techniques (e.g. supercritical fluid extraction for PCBs in
sediment) can lead to rather disparate results in these two situations. Assuring
traceability in a CRM entails documenting it in all these respects and also pro-
3 Traceability: Reference Materials
word "trackability" has lately been used to designate an unequivocal relationship
between a result and a sample aliquot in terms of a property of the result rather
than one of the sample.
I 3.6.3 Traceability of an Instrument
As shown in Box 3.2, the generic concept of traceability encompasses calibration,
whereby measuring equipment is related to national or international standards.
Consequently, in the metrological domain, traceability can be considered a
property of a measuring instrument. Calibration with an appropriate physical,
physico-chemical or chemical standard, and the ensuing correction, ensure that
the instrument will operate as required to assure traceability in its results.
This essential operation should be supplemented with a detailed "history" of
the instrument's operation in the form of a comprehensive, customized record
including detailed, timed descriptions of installation, malfunctioning, repair,
servicing, calibration and correction operations, hours of use, number of
samples processed, etc.
These activities are considered and organized in the quality systems of analyticallaboratories. They constitute an essential chapter in the Quality Manual
mentioned in the standards of the EN-4S000 family and are the subjects of
Standard Operating Procedures (SOPs) in Good Laboratory Practices (GLPs).
The traceability of each instrument and apparatus should be visually and
documentarily inspected in pertinent audits.
Any apparatus (oven, extractor, reactor) should also be the subject of continual inspection in order to ensure proper functioning as scheduled. Thus, a
refrigerator set to maintain a temperature of 4°C should be periodically checked
to ensure that it keeps the desired temperature. Malfunctioning in an apparatus
used in a CMP can lead to alterations affecting the traceability of the final results.
I 3.6.4 Traceability of a Sample Standard
The more relevant properties of certified reference materials (CRMs) can also be
traceable. Thus, the certified value and its uncertainty should be traced to base
standards through the results produced by the laboratories participating in the
certifying campaign and through the standards used for calibration in each case.
It is essential for the user to know why given results, if any, were discarded, what
the most significant sources of error (e.g. sample treatment) were, which
methods provided the highest accuracy and precision, etc. Also, the reference
material should be documented with technical details about its preparation,
homogeneity and stability. For example, the user should be able to know whether
the analyte was added (spiked) to the sample or initially present in the bulk
material since some techniques (e.g. supercritical fluid extraction for PCBs in
sediment) can lead to rather disparate results in these two situations. Assuring
traceability in a CRM entails documenting it in all these respects and also pro-