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5061-049 REV 1.4
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9.1. Pathlength calibration over-range
Under exceptional circumstances an error message may be given when
undertaking a pathlength calibration because one or both of the pathlengths are
too far from 0.2 or 0.5 mm for the instrument to compensate. This means that the
pathlengths will need manually adjusting. This can be done within the Pathlength
Calibration function as described in section 7.7.
Step 1
Enter the certificate ID on the certificate/bottle of the calibration solution using the
keypad.
Press the down arrow.
Step 2
Enter the calibration value of the calibration solution found on the side of the
bottle (Figure X). This value is the Absorbance of the solution at a 1 mm pathlength
Note this value down & work out the target Absorbance values at 0.5 mm &
0.2 mm pathlengths:-
i.e. if the calibration fluid has a value of 0.952. Then this would give 0.952/2 =
0.476 A as the target value at the 0.5 mm pathlength & 0.952/5 = 0.190 A at the
0.2 mm Pathlength. Acceptable values are +/- 10% of the target value.
Press OK
to carry on with the Calibration (or Cancel
Esc
to return to the
Utilities Screen).
Step 3
Clear previous measurements by using the cursor and the ‘C’ clear key.
As with the calibration check in section 7.7, the first step is to measure two
reference samples.
Open the NanoVue Plus sampling head and pipette 5 µl of distilled water onto the
correct position on the sample plate. Close the sampling head, clear all previous
readings using the cursors and “C” key. Press the 0A/100%T key as in section 7.7.
This will need to be done twice to complete reference QA.
Step 4
Open the sampling head, clean off the water from both the top and bottom
sample plates. Apply a drop of the calibration fluid (Figure X) by gently squeezing
the bottle. Press
to measure the Absorbance of the calibration fluid. Observe
the 0.5 mm value and compare to the calculated value for the 0.5 mm pathlength
found in Step 2. – this should be +/- 10% of the target value.
The left hand screw controls the 0.5mm pathlength and the right hand screw the
0.2 mm pathlength & they work in opposite directions. (Figure 22). So:
Turning the screws outwards (red arrows) increases the pathlength
Turning the screws inwards (blue arrows) decreases the pathlength.
If the value for the 0.5 mm pathlength is higher than the required value from Step
2, the left hand screw must be turned inwards about half a turn.
Similarly, for the 0.2 mm Pathlength (Figure 23) if the measured value is higher
than it should be from the calculation in Step 2, the right hand screw must be
turned inwards about half a turn.
Once the adjustment is made, open the head and replace the calibration droplet.
Press
to see the effects of the adjustments. Repeat this process until the value
is within 0.02 A of the target value for the 0.5 mm pathlength and 0.015 A for the
0.2 mm pathlength.
9.0. TROUBLESHOOTING
Figure: 22
Figure: 23
Figure X
Calibration Fluid
