Page 39 - Quality control of pharmaceuticals (07-PA 704)
P. 39
The first step in making a control chart is to obtain a control material
with the analyte in the proper matrix and at appropriate
concentrations.
Next, this control material is analyzed many times (typically, 20-30) by
the method to be evaluated, using identical conditions to those that
will be utilized for testing samples.
You then calculate the mean and standard deviation of the results for
this control material, which are then used to construct a control
chart for the analytical technique.
A control chart is a graphical presentation of data over time and shows
upper and lower limits of the process we want to control.
Samples of process output are examined.
If they fall outside certain specific ranges, the process is stopped and the
assignable cause is located and removed.
We say that a process is out of control when a plot of data reveals that
one or more samples fall outside the control limits.
Principle of a Control Chart
The principle of a control chart is a visual representation of “quality”
based on the quality limits (see Figure 2-2).
For the latter, one distinguishes between
Warning limits, a single transgression of which can be tolerated, and
