Page 129 - The Veterinary Laboratory and Field Manual 3rd Edition

98 Willy Schauwers

Pipettes calibrated ‘to contain’ (‘TC, In’). instructions of the manufacturer. For how to
use mechanical pipettes see section ‘Automatic
• Filling: mechanical pipettes and dispensers’.

• aspirate the liquid to the mark WorkInG WItH PIPEttE aIdS
• hold the pipette horizontally and carefully Pipetting by mouth is not allowed. The use of
wipe off with a tissue. pipetting aids is mandatory. Pipetting aids can
be manual or motorized.
• Delivering: Manual pipetting aids (pipette fillers) use a
valve system to create pressure (Figure 2.68).
• to empty capillaries blow out the liquid
with a pipetting aid, and rinse two to three • The pipetting aid (pipette filler) is attached to
times with the diluting medium (required the top of the pipette.
due to calibration ‘to contain’). • Press ‘A’ to squeeze the ball and to create
negative pressure.
Mechanical, air-displacement or positive dis- • Press ‘S’ to fill the pipette just above the
placement pipettes with disposable tips are mark.
frequently used to measure small volumes. • Press ‘E’ to drain the pipette.
They are available in a variety of volumes, rang-
ing from 1 to 5000 µl. Used tips are disposed of Motorized pipettors (Figure 2.69) are useful
directly into disinfectant using the ejector mech- for longer pipetting series. The pipette aid is
anism of the pipette. The micropipettes usually
have two positions of the plunger operated by
thumb. The first position is used to pick up the
sample and the second to expel the sample from
the tip into a tube or well. Micropipettes must
be calibrated and maintained according to the

Figure 2.68 Pipette filler. Photo: Willy Schauwers, Figure 2.69 Pipette filler electric. Photo:
Provincial Institute for Hygiene, Antwerp, Belgium. Willy Schauwers, Provincial Institute for Hygiene,
Antwerp, Belgium.

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