3.6 Specific Meanings of Traceability
135
viding basic information about its certified value. Only if such comprehensive
documentation is made available can a standard be properly used. In fact, a
standard with no traceability is like a building without foundations. This should
never be ignored, particularly by RM and CRM issuing bodies, but also by their
clients (analysts), who should demand such information as a matter of course.
I 3.6.5 Traceability of a Method
An analytical method is the description of a chemical measurement process, the
product of which is a result. Obviously, if a result is traceable to base standards,
the CMP that produces it can also be traceable and hence a quality process.
Until fairly recently, the use of the words "official", "standard" and "reference"
to qualify recommended methods was a source of widespread confusion
regarding the quality of their results. At present, analytical methods are
evaluated in every single technical respect in interlaboratory exercises; if the
final results are acceptable, then the method in question is technically validated.
However, the mere use of a good method does not ensure excellence, which must
be demonstrated.
As a result, the quality methods of today are not official or systematically
revised methods reported by renown institutions, but methods that can be
traced to base standards. The traceability of a method should be assured in experimental and documental terms, not only on issuance, but also when first
implemented by a laboratory. Traceability is unequivocally realized when the
results and associated uncertainties obtained by subjecting aliquots of a CRM to
the CMP concerned are statistically consistent with the values of the certified
quantities (and their uncertainties). A less unequivocal realization can be
accomplished by comparing the results of the potentially traceable method with
those provided by aliquots of the same sample subjected to a primary or absolute
method (e.g. gravimetry, coulometry, isotope dilution mass spectrometry).
I 3.6.6 Relationships among Traceability Meanings
The primary metrological meaning of traceability is that which relates it to a
result. As can be seen from Fig. 3.16, traceability of a result rests on other,specific
traceability notions.
The definition of traceability of a result places special emphasis on its
relationship to standards. The linear or branched chains leading to base
standards (the kilogram, the mole) implicitly include the mutual traceability of
the standards (Fig. 3.7), without which no result can be traceable.
For a result to be traceable, the equipment (instruments and apparatuses)
used in the CMP whereby it is obtained must also unavoidably be made traceable
through appropriate standards. One should bear in mind that equipment and
method calibration require different types of standards. Similarly, the traceability of the analytical method that produces the result rests on a CRM.
135
viding basic information about its certified value. Only if such comprehensive
documentation is made available can a standard be properly used. In fact, a
standard with no traceability is like a building without foundations. This should
never be ignored, particularly by RM and CRM issuing bodies, but also by their
clients (analysts), who should demand such information as a matter of course.
I 3.6.5 Traceability of a Method
An analytical method is the description of a chemical measurement process, the
product of which is a result. Obviously, if a result is traceable to base standards,
the CMP that produces it can also be traceable and hence a quality process.
Until fairly recently, the use of the words "official", "standard" and "reference"
to qualify recommended methods was a source of widespread confusion
regarding the quality of their results. At present, analytical methods are
evaluated in every single technical respect in interlaboratory exercises; if the
final results are acceptable, then the method in question is technically validated.
However, the mere use of a good method does not ensure excellence, which must
be demonstrated.
As a result, the quality methods of today are not official or systematically
revised methods reported by renown institutions, but methods that can be
traced to base standards. The traceability of a method should be assured in experimental and documental terms, not only on issuance, but also when first
implemented by a laboratory. Traceability is unequivocally realized when the
results and associated uncertainties obtained by subjecting aliquots of a CRM to
the CMP concerned are statistically consistent with the values of the certified
quantities (and their uncertainties). A less unequivocal realization can be
accomplished by comparing the results of the potentially traceable method with
those provided by aliquots of the same sample subjected to a primary or absolute
method (e.g. gravimetry, coulometry, isotope dilution mass spectrometry).
I 3.6.6 Relationships among Traceability Meanings
The primary metrological meaning of traceability is that which relates it to a
result. As can be seen from Fig. 3.16, traceability of a result rests on other,specific
traceability notions.
The definition of traceability of a result places special emphasis on its
relationship to standards. The linear or branched chains leading to base
standards (the kilogram, the mole) implicitly include the mutual traceability of
the standards (Fig. 3.7), without which no result can be traceable.
For a result to be traceable, the equipment (instruments and apparatuses)
used in the CMP whereby it is obtained must also unavoidably be made traceable
through appropriate standards. One should bear in mind that equipment and
method calibration require different types of standards. Similarly, the traceability of the analytical method that produces the result rests on a CRM.