9.4 Quality Measures
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results stays within the acceptable range. For this purpose, it is worthwhile to use the
statistical methodology, in order to use distributions and probability functions.
Internal QC encompasses the evaluation of results obtained in the laboratory,
involving the entire analytical process. The commonly accepted approach is the use
of control charts, where the reported values are plotted on the chart so as to evaluate
whether the measurements are performed within the given limits. All control samples
(e.g., blanks, control samples, standards), should run as routine test samples in exactly
the same conditions, using the same analytical practice. It is convenient to record the
results of measurements directly on the control charts, since it allows for the visual
evaluation of any trends and/or immediate confirmation if the value of the given
property is with previously established limits.
Control charts are therefore a valuable source of information on the quality of the
measurement; they allow the stability and trends to be tracked.
9.5 Routine and Blind Samples
In the case of internal and external quality control, samples may enter the analytical
process as known control samples, which means that the analyst is aware it is a
control; or as a blind samples mixed with other routine test samples, which means
that the analyst cannot identify the control sample before performing measurements.
Both approaches have their advantages and limitations; however, the main aim is to
process the control samples under the everyday conditions.
9.6 Internal Quality Control
A laboratory should design a program of internal quality management for every
type of test (method, sample type) and such a program should be carefully planned
and documented. The selection of control samples is also important; they should
allow information on the behaviour relating to the measuring system to be obtained.
Control samples should be stable and available in such a quantity that they could
be used for QC purposes for a long time. Various samples can be used as a control
items; they should be selected so as to be fit for purpose. The most commonly used in
laboratory practice are matrix CRM, reference material (RM), blank samples, routine
test samples or spiked routine test samples.
When the result obtained for the control sample is within the previously set
limits, it is assumed that analytical system is stable and under control.
161
results stays within the acceptable range. For this purpose, it is worthwhile to use the
statistical methodology, in order to use distributions and probability functions.
Internal QC encompasses the evaluation of results obtained in the laboratory,
involving the entire analytical process. The commonly accepted approach is the use
of control charts, where the reported values are plotted on the chart so as to evaluate
whether the measurements are performed within the given limits. All control samples
(e.g., blanks, control samples, standards), should run as routine test samples in exactly
the same conditions, using the same analytical practice. It is convenient to record the
results of measurements directly on the control charts, since it allows for the visual
evaluation of any trends and/or immediate confirmation if the value of the given
property is with previously established limits.
Control charts are therefore a valuable source of information on the quality of the
measurement; they allow the stability and trends to be tracked.
9.5 Routine and Blind Samples
In the case of internal and external quality control, samples may enter the analytical
process as known control samples, which means that the analyst is aware it is a
control; or as a blind samples mixed with other routine test samples, which means
that the analyst cannot identify the control sample before performing measurements.
Both approaches have their advantages and limitations; however, the main aim is to
process the control samples under the everyday conditions.
9.6 Internal Quality Control
A laboratory should design a program of internal quality management for every
type of test (method, sample type) and such a program should be carefully planned
and documented. The selection of control samples is also important; they should
allow information on the behaviour relating to the measuring system to be obtained.
Control samples should be stable and available in such a quantity that they could
be used for QC purposes for a long time. Various samples can be used as a control
items; they should be selected so as to be fit for purpose. The most commonly used in
laboratory practice are matrix CRM, reference material (RM), blank samples, routine
test samples or spiked routine test samples.
When the result obtained for the control sample is within the previously set
limits, it is assumed that analytical system is stable and under control.