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6 Reference Materials in Chemical Measurements
Recommendations of manufacturers of
reference materials include:
– The temperature of storage;
– The minimum amount of sample to be used;
– The hygroscopic feature of the material (the
reference value may relate to the material
dried at a predetermined temperature for a
predetermined time);
– The use of the certified value
6.14 The Use of Certified Reference Materials for Ensuring
the Traceability of the Result
The CRM ensures, the reference value with the assigned uncertainty held by this
material. In many cases, the reference value is obtained from a statistical evaluation
of results obtained in different laboratories. Unfortunately, obtaining very similar
result by participating laboratories is no guarantee that the result is close to the true
value, as the systematic effect cannot be detected.
It is worth remembering the meaning of the accuracy and precision of measurements; a precise result is not always an accurate result.
In chemical measurements, CRMs play a role similar to the standard units of
the International System (SI) in a physical measurement, which means that they
allow the transfer of properties (e.g., iron content in blood serum) between different laboratories and independent reproduction by the various entities. As a result,
they constitute one of the most important tools to ensure measurement traceability,
especially in those situations where it is not possible to establish direct reference
to SI units. In this case, the principle is that the reference material of the highest
possible metrological value is recognized by all interested parties. Thus, the periodic
use of CRMs, together with the set of the test sample measurements, should provide
measurement traceability.
The use of laboratory measurement standards and the comparison of these standards to a common standard of higher order (standard measurement reference)
provides the traceability.
Suppose that two laboratories LAB A and LAB B conduct measurements of a
given component in a given type of objects. Laboratory LAB A obtained a result
6 Reference Materials in Chemical Measurements
Recommendations of manufacturers of
reference materials include:
– The temperature of storage;
– The minimum amount of sample to be used;
– The hygroscopic feature of the material (the
reference value may relate to the material
dried at a predetermined temperature for a
predetermined time);
– The use of the certified value
6.14 The Use of Certified Reference Materials for Ensuring
the Traceability of the Result
The CRM ensures, the reference value with the assigned uncertainty held by this
material. In many cases, the reference value is obtained from a statistical evaluation
of results obtained in different laboratories. Unfortunately, obtaining very similar
result by participating laboratories is no guarantee that the result is close to the true
value, as the systematic effect cannot be detected.
It is worth remembering the meaning of the accuracy and precision of measurements; a precise result is not always an accurate result.
In chemical measurements, CRMs play a role similar to the standard units of
the International System (SI) in a physical measurement, which means that they
allow the transfer of properties (e.g., iron content in blood serum) between different laboratories and independent reproduction by the various entities. As a result,
they constitute one of the most important tools to ensure measurement traceability,
especially in those situations where it is not possible to establish direct reference
to SI units. In this case, the principle is that the reference material of the highest
possible metrological value is recognized by all interested parties. Thus, the periodic
use of CRMs, together with the set of the test sample measurements, should provide
measurement traceability.
The use of laboratory measurement standards and the comparison of these standards to a common standard of higher order (standard measurement reference)
provides the traceability.
Suppose that two laboratories LAB A and LAB B conduct measurements of a
given component in a given type of objects. Laboratory LAB A obtained a result