be cooled down and left to dry overnight before use. Screw the lower
part of the multichannel pipettors 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
pipettor after every autoclaving. It is also recommended to grease the
piston/seal of the pipettor after every 10 autoclaving.
11. Testing the performance and recalibration
It is recommended to check the performance of your Biohit
m
LINE
pipettors regularly (e.g. every 3 months) and always after in-house
maintenance. However, the user should establish a regular testing
routine for their pipettors with regard to accuracy requirements of the
application, frequency of use, number of operators using the pipettor,
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
O
C, constant to +/- 0.5
O
C and humidity above 50%. The pipettor, 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 pipettor vertical.
6.
Withdraw the pipettor 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 pipettor 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
µ
l:
e
s
= V – V
s
V
s
= selected test volume
or in %: e
s
= 100 (V – V
s
)/V
s
12
