Gilson guide to pipetting - Emidio Albertini

Step 3-
Leak test
n For Pipetman
pipettes
P1000 to P10ml
- Select the
maximum volume
setting and fill the
tip with water.
- Stabilize for 20
seconds.
If a drop appears at
the end of the tip, there is a leak.
n For Pipetman pipettes
P2 to P200
- Select the maximum volume
setting and fill the tip.
- Stabilize for 20 seconds.
If a drop appears at the end of the
tip, there is a leak.
If no drop appears, re-immerse the
tip in the test liquid.
- While immersed, the level of the
liquid in the tip should remain
constant.
If the level in the tip goes down,
there is a leak.
Q
AWhat are the main causes
of leaks?
• Tip holder scratched or damaged
• Use of non-Gilson tips
• Use of non-Gilson seals
• Vapor pressure from organic
solvents.
Q
AHow do organic solvents
cause leaks?
When an organic solvent is used
with an air-displacement pipette,
leaks may occur. These leaks are
caused by the difference between
the vapor pressure of the solvent
and pressure of the air cushion
between the piston and the sample
(see page 9).
Solution
1 Use a positive-displacement pipette because
it has no air cushion. (See page 6.)
2 If you are using an air-displacement pipette,
saturate the air cushion of your pipette with
solvent vapor by aspirating and distributing
solvent repeatedly. The leak will stop when
pressure equilibrium is reached.
Learning more
Chapter 5
41