Pre-Rinsing; Dense And Viscous Liquids - PCE Instruments PIP 2 Manual Del Usuario

Eject the tip by pressing the tip ejector
button. Fig. 2F. It is necessary to change the
tip if a different liquid is being sampled or if
the volumeter setting is changed.

4 PRE-RINSING

Whenpipetting liquids of higher viscosity oe
lower surface tension than water (e.g. sera
or organic solvents), a film of liquid is formed
on the inside wall of the pipette tip. This film
can create an error. Since the film remains
relatively constant in successive pipetting
operationswith the same tip, this error can
be avoided by forming the film before
transferring the first sample. This is done by
aspirating a sample and dispensing it back
into the same vessel. Since the film is
already formed, all of the following samples
will have better accuracy and repeatability.
This pre-rinsing operation should be
repeated when the volume to be aspirated is
changed or when a new tip is used.
5 DENSE AND VISCOUS
LIQUIDS
The pipette specifications of accuracy and
precision are based on pipetting distilled
water. The handling of liquids with physical
qualities of density, viscosity and surface
tension differing extremely from water may
need a gravimetrically checked
compensation of the volume setting.
Normally the degree of error resulting from
heavy or viscous liquids is negligible if the
pipetting is done slowly and carefully. It is
most important to give the liquids some time
to follow the change of pressure by holding
the pipette tip in its position for at least 2
20