6.14 The Use of Certified Reference Materials …
83
a and the laboratory LAB B obtained a result b. Both laboratories used the RMs
(measurement standards) purchased from local producers A or B.
Consider two scenarios:
(1) Measurement standards A and B do not have a reference to a common standard,
which causes a lack of measurement traceability in relation to a standard measurement
reference.
Working measurement standard A → LAB A → result a
Working measurement standard B → LAB B → result b
In this case, it is NOT relevant to compare (meaning metrological comparison)
the results obtained in both laboratories, due to the lack of a common reference.
(2) Measurement standards A and B have a reference to a common standard
CRM, which ensures measurement traceability by reference to a common standard
working measurement standard A LAB A result a
CRM
working measurement standard B
LAB B
result b
In this case, it is relevant to compare (meaning metrological comparison) the
results obtained in both laboratories, as both working standards are traceable to a
common CRM.
The example discussed above shows the necessary condition for ensuring the
metrological comparison of results from various laboratories. The generic meaning of
the verb ‘compare’ differs to its use in the metrological sense. Thus, the metrological
comparability means that results are expressed with the same unit of measurement
and/or were obtained with the use of the same analytical procedure.
The metrological comparability of measurement results: comparability of measurement results, for quantities of a given kind, which are metrologically traceable to the same reference.
Clause 2.46, ISO/IEC Guide 99
The metrological comparability does not mean that the measured quantity values
are of the same order of magnitude, but rather that they should be expressed in the
same units.
The results that can be compared metrologically:
The results of the determination of zinc in two samples:
Sample A: 20 mg/L
Sample B: 120 mg/L
Conclusion: The content of zinc in sample B is six-fold higher compared with the
contents of the zinc in sample A. The results can be compared.
Sample A: 20 mg/L
Sample B: 20 g/kg
Conclusion: Although the values are the same, the results are expressed in different
units, so it is not possible to directly assess, in which sample the content of zinc is
higher. The results cannot be compared.
83
a and the laboratory LAB B obtained a result b. Both laboratories used the RMs
(measurement standards) purchased from local producers A or B.
Consider two scenarios:
(1) Measurement standards A and B do not have a reference to a common standard,
which causes a lack of measurement traceability in relation to a standard measurement
reference.
Working measurement standard A → LAB A → result a
Working measurement standard B → LAB B → result b
In this case, it is NOT relevant to compare (meaning metrological comparison)
the results obtained in both laboratories, due to the lack of a common reference.
(2) Measurement standards A and B have a reference to a common standard
CRM, which ensures measurement traceability by reference to a common standard
working measurement standard A LAB A result a
CRM
working measurement standard B
LAB B
result b
In this case, it is relevant to compare (meaning metrological comparison) the
results obtained in both laboratories, as both working standards are traceable to a
common CRM.
The example discussed above shows the necessary condition for ensuring the
metrological comparison of results from various laboratories. The generic meaning of
the verb ‘compare’ differs to its use in the metrological sense. Thus, the metrological
comparability means that results are expressed with the same unit of measurement
and/or were obtained with the use of the same analytical procedure.
The metrological comparability of measurement results: comparability of measurement results, for quantities of a given kind, which are metrologically traceable to the same reference.
Clause 2.46, ISO/IEC Guide 99
The metrological comparability does not mean that the measured quantity values
are of the same order of magnitude, but rather that they should be expressed in the
same units.
The results that can be compared metrologically:
The results of the determination of zinc in two samples:
Sample A: 20 mg/L
Sample B: 120 mg/L
Conclusion: The content of zinc in sample B is six-fold higher compared with the
contents of the zinc in sample A. The results can be compared.
Sample A: 20 mg/L
Sample B: 20 g/kg
Conclusion: Although the values are the same, the results are expressed in different
units, so it is not possible to directly assess, in which sample the content of zinc is
higher. The results cannot be compared.