8.9 Requirements Concerning the Uncertainty
129
“the calculation of uncertainty is not either a routine task or a strictly mathematical task. It depends on the detailed knowledge of the nature of the measured
quantity and the measurement procedure…”
In chemical measurements, a significant source of the uncertainty can be the way
that samples are prepared or the matrix effects influence the result of the determination
(interferences).
When does a need arise to determine the uncertainty again? It is obvious that it
does not concern every determination, but uncertainty should be established in the
following scenarios:
– When the laboratory introduces a new measuring procedure;
– When the measurement conditions change (new device, new employee);
– During the validation of the measuring procedure.
The resulting uncertainty value, determined for a given measuring procedure,
can then be used when the results are provided to the clients. Hence, it is worth
emphasizing once more that it is not necessary to determine the uncertainty of every
single measurement; once determined, uncertainty can be used for all results obtained
with the use of a specific measuring procedure in specific conditions.
8.10 Determination of the Measurement Uncertainty
In many fields, not only in science, many decisions are made on the basis of analytical results. It is thus obvious that more and more attention is paid to their quality.
The uncertainty is the property of each measurement results, is associated always
with measurements and is coming out on each steps of measuring procedure. It is,
therefore, not a property that is supposed to add additional difficulty to the measuring
process. The measurement uncertainty results from the uncertainties of all activities
performed during the analytical procedure. By evaluating the combined uncertainty,
it is therefore necessary to examine the sources and types of uncertainties for individual steps of the analytical procedure.
The uncertainty of the measurement result demonstrates its reliability and is used
for the comparison of results provided by different laboratories and/or carried out at
different times. It is thus important to conduct the determination of the uncertainty
in the same way. That is why the aforementioned ISO GUM guide was issued, as
it describes the guidelines regarding the definition, assessment and recording of the
uncertainty of the measurement result. The requirements of the ISO standards in the
scope of determination and expression of the resulting uncertainty are obligatory
for accredited laboratories. The unified—on the international forum—convention
regarding the theory of uncertainty (ISO GUM) has been commonly accepted, not
because it is an imposed law, but most of all, because of the advantages of the solutions
129
“the calculation of uncertainty is not either a routine task or a strictly mathematical task. It depends on the detailed knowledge of the nature of the measured
quantity and the measurement procedure…”
In chemical measurements, a significant source of the uncertainty can be the way
that samples are prepared or the matrix effects influence the result of the determination
(interferences).
When does a need arise to determine the uncertainty again? It is obvious that it
does not concern every determination, but uncertainty should be established in the
following scenarios:
– When the laboratory introduces a new measuring procedure;
– When the measurement conditions change (new device, new employee);
– During the validation of the measuring procedure.
The resulting uncertainty value, determined for a given measuring procedure,
can then be used when the results are provided to the clients. Hence, it is worth
emphasizing once more that it is not necessary to determine the uncertainty of every
single measurement; once determined, uncertainty can be used for all results obtained
with the use of a specific measuring procedure in specific conditions.
8.10 Determination of the Measurement Uncertainty
In many fields, not only in science, many decisions are made on the basis of analytical results. It is thus obvious that more and more attention is paid to their quality.
The uncertainty is the property of each measurement results, is associated always
with measurements and is coming out on each steps of measuring procedure. It is,
therefore, not a property that is supposed to add additional difficulty to the measuring
process. The measurement uncertainty results from the uncertainties of all activities
performed during the analytical procedure. By evaluating the combined uncertainty,
it is therefore necessary to examine the sources and types of uncertainties for individual steps of the analytical procedure.
The uncertainty of the measurement result demonstrates its reliability and is used
for the comparison of results provided by different laboratories and/or carried out at
different times. It is thus important to conduct the determination of the uncertainty
in the same way. That is why the aforementioned ISO GUM guide was issued, as
it describes the guidelines regarding the definition, assessment and recording of the
uncertainty of the measurement result. The requirements of the ISO standards in the
scope of determination and expression of the resulting uncertainty are obligatory
for accredited laboratories. The unified—on the international forum—convention
regarding the theory of uncertainty (ISO GUM) has been commonly accepted, not
because it is an imposed law, but most of all, because of the advantages of the solutions