164
9 Managing the Quality Systems
they could be a test sample where the content of substance of interest is below the
detection limit.
Blanks can be used for the evaluation of the purity of reagents used in sample
preparation (reagent blank), for the determination of the limit of detection and limit
of determination.
9.9 Principle of Quality Control
Quality control is used to monitor the stability of the analytical system; thus, various
tools can be used accordingly. Several measurements can be used to give the relevant
information:
– Measurement of blank samples;
– Measurement of chemical standard or CRM;
– Measurement of test sample—as it is or spiked with standard;
When selecting the type of control sample, various approaches can be used, including:
– Measurement of repeat samples;
– Measurement of blind samples;
– Measurement of test samples.
NOTE! The number of replicate measurements for control samples should be the
same as used for the routine test samples. It is important for the samples used in the
quality management (i.e., standards, CRMs, RMs, laboratory samples, blanks) to be
analyzed in the same way and in the same conditions as the laboratory samples.
9.10 Control Charts
Control charts are the graphical presentation of data obtained for the measurements
performed for the control samples, representing the flow of the analytical process over
time. It is essential that current measurement results are recorded on the chart in order
to visually evaluate it with regards to previously established limits or, when they are
considered as provisionary, to allows those limits to be established. Control charts are
graphs that plot data in time-ordered sequence. Most control charts include a center
line, an upper control limit, and a lower control limit. The center line represents the
mean value, and the control limits represent the process variation. By default, the
control limits are drawn at distances of 3σ above and below the center line.
When processing the large set of data, their statistical distribution should be considered. In most cases, results of subsequent measurements display a certain distribution around the mean value, and if they are subject to regular distribution, then they
will arrange themselves symmetrically in relation to the mean value (the measure of
9 Managing the Quality Systems
they could be a test sample where the content of substance of interest is below the
detection limit.
Blanks can be used for the evaluation of the purity of reagents used in sample
preparation (reagent blank), for the determination of the limit of detection and limit
of determination.
9.9 Principle of Quality Control
Quality control is used to monitor the stability of the analytical system; thus, various
tools can be used accordingly. Several measurements can be used to give the relevant
information:
– Measurement of blank samples;
– Measurement of chemical standard or CRM;
– Measurement of test sample—as it is or spiked with standard;
When selecting the type of control sample, various approaches can be used, including:
– Measurement of repeat samples;
– Measurement of blind samples;
– Measurement of test samples.
NOTE! The number of replicate measurements for control samples should be the
same as used for the routine test samples. It is important for the samples used in the
quality management (i.e., standards, CRMs, RMs, laboratory samples, blanks) to be
analyzed in the same way and in the same conditions as the laboratory samples.
9.10 Control Charts
Control charts are the graphical presentation of data obtained for the measurements
performed for the control samples, representing the flow of the analytical process over
time. It is essential that current measurement results are recorded on the chart in order
to visually evaluate it with regards to previously established limits or, when they are
considered as provisionary, to allows those limits to be established. Control charts are
graphs that plot data in time-ordered sequence. Most control charts include a center
line, an upper control limit, and a lower control limit. The center line represents the
mean value, and the control limits represent the process variation. By default, the
control limits are drawn at distances of 3σ above and below the center line.
When processing the large set of data, their statistical distribution should be considered. In most cases, results of subsequent measurements display a certain distribution around the mean value, and if they are subject to regular distribution, then they
will arrange themselves symmetrically in relation to the mean value (the measure of