Metrohm 746 VA Trace Analyzer - Manual (Page 558)

7.7 Standard operating procedure in the context of GLP/ISO 9001 guidelines
746 VA Trace Analyzer / 747 VA Stand
7-59
5 Testing the stirrer
• Press the softkey several times and check the on/off switch-
ing of the stirrer motor.
6 Copying the TEST747.mth method to the working storage
• Press the yellow key.
• Use the cursor keys to select the TEST747.mth method.
• Press the softkey and then .
7 Entry of the sample volume
• Press the yellow key.
• Use the cursor keys to select the parameter Sample size/S0 .
• Press the key.
• Enter < * > and press .
8 Start program
• Press the key.
• Attach the electrode cable as described in the instructions on the screen
to the clamping screws of the dummy cell.
9 Assessment of the linearity
• The first of the printed curves should satisfy the following conditions:
− In principle, the plotted diagonal must be straight. Small deviations
are partly due to the resolution of the printer.
− Current at voltage – 200 mV: – 1.6 µ A ... – 2.4 µ A*
− Current at voltage +200 mV: +1.6 µ A ... +2.4 µ A*
* These tolerance values refer to illustrative scatters, that is to the differences
between individual instruments. The value determined for a specific instrument
shows less scatter. The deviation depends mainly on the temperature and should
be around 10%.
10 Assessment of peak measurement
• The second curve plot should satisfy the following conditions:
− A symmetrical, gaussian-shaped peak should be plotted. The
evaluation must provide a result for the peak voltage U and the peak
current I, which are printed out at the end of the curve.
− Peak voltage U : – 450 mV ... – 550 mV