10
10.3. Sterilization of The Pipette
The entire Proline
®
Plus pipette can be sterilized by steam autoclaving at
121°C, (252°F), 1 bar overpressure for 20 minutes. Remove the tip cone
filter (if fitted, Chapter 7.3). The single channel pipettes can be autoclaved
without special preparations. Unscrew the lower part of the multichannel
pipettes by holding the connecting collar and turning the lower part 360°
counterclockwise. Put the pipette into the sterilization bag and place it into
the autoclave. After autoclaving, the pipette must be cooled down and
left to dry overnight before use. Screw the lower part of the multichannel
pipettes by holding the connecting collar and turning the lower part
360° clockwise. Make sure that the lower part is properly tightened. It
is recommended to check the performance of the pipette after every
autoclaving. It is also recommended to grease the piston|seal of the pipette
after every 10 autoclaving.
11. Testing the Performance and
Recalibration
It is recommended to check the performance of your Proline
®
Plus pipettes
regularly (e.g. every 3 months) and always after in-house maintenance.
However, the user should establish a regular testing routine for their pipettes
with regard to accuracy requirements of the application, frequency of use,
number of operators using the pipette, nature of the liquid dispensed and the
acceptable maximum permissible errors established by the user. (ISO 8655-1.)
11.1. Testing the Performance
Performance testing should take place in a draught-free room at 15 - 30°C,
constant to +/- 0.5°C and humidity above 50%. The pipette, tips and the
test water should have stood in the test room a sufficient time (at least
2 hours) to reach equilibrium with the room conditions. Use distilled or
deionised water (grade 3, ISO 3696). Use an analytical balance with a
readability of 0.01 mgs. (ISO 8655-6.)
Weighing
1. Adjust the desired test volume V
s
.
2. Carefully fit the tip onto the tip cone.
3. Fill the tip with test water and expel to waste five times to reach a
humidity equilibrium in the dead air volume.
4. Replace the tip. Pre-wet the tip by filling it once with test water and
expel to waste.
5. Aspirate the test water, immersing the tip only 2-3 mm below the
surface of the water. Keep the pipette vertical.
6. Withdraw the pipette vertically and touch the tip against the inside wall
of the test water container.
7. Pipette the water into the weighing vessel, touching the tip against the
inside wall of the vessel just above the liquid surface at an angle of 30°
to 45°. Withdraw the pipette by drawing the tip 8-10 mm along the inner
wall of the weighing vessel.
8. Read the weight in mgs (m
i
).
9. Repeat the test cycle until 10 measurements have been recorded.
10. Convert the recorded masses (m
i
) to volumes (V
i
)
V
i
= m
i
Z Z = correction factor (Table 1)
11. Calculate the mean volume (V) delivered: V=(V
i
)/10
12. For conformity evaluation, calculate the systematic error (e
s
) of the
measurement:
in μl: e
S
= V- V
S
V
S
= selected test volume
Connecting collar
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