4 - PRE-RINSING
When pipetting liquids of higher viscosity or 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. As the film remains relatively
constant in successive pipetting operations with the same
tip, this error can be eliminated by forming the film before
transferring the first sample. This is done by aspi
ra
ting
a sample and dispensing it back into the same vessel.
Now, as 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
AXYPET specifications of accuracy and precision are
based on pipetting distilled water. Handling of liquids
with physical qualities of density, viscosity and surface
tension which differ substantially from water may need
gra
vimetrically checked compensation of the volume
setting.
Normally the degree of error resulting from heavy
or viscous liquids is negligible if pipetting is done slowly
and carefully. It is most important to give the liquids
some time to react to the change of pressure by holding
the pipette tip in its position for at least 2 sec. after the
aspiration and the blow out stroke.
If in extreme cases, this method of operation does not
result in accurate values, a compensation may be
achieved as follows:
Weigh the liquid pipetted when the AXYPET is set to the
nominal value. Then calculate the set-off from the nominal
value:
Corr: val. = 2 x nom. val. -
- weight of the sample
- density of liquid
Check this operation once again and correct if necessary
.
Note the corrected value for further pipetting of the same
kind of liquid.
6 - AXYGEN PIPETTE TIPS
AXYGEN tips are made from high performance
polypropylene and their quality guarantees the precision
m
-
γ
m
γ
ENGLISH
7
and accuracy associated with the AXYPET. Strict control
is maintained throughout the manufacturing process to
ensure the highest quality.
The accuracy and precision figures for the AXYPET are
only guaranteed when AXYGEN tips are used. The use of
inferior quality tips will seriously degrade the performance
of the AXYPET.
Tips 10
These tips are used for volumes between 0.1 μl and 10 μl.
They are used with the AP-2 and the AP-10 models
.
Tips 200
These tips are used for volumes between 2 μl and 200 μl.
They are used with the AP-20, AP-50, AP-100 and the
AP-200 models.
Tips 250
These tips are used for volumes between 50 μl and 250 μl.
They are used with the AP-250 model.
Tips 1,000
These tips are used for volumes between 100 μl and
1,000 μl. They are used with the AP-1000 model.
Tips 5,000
These tips are used for volumes between 1,000 μl and
5,000 μl. They are used with the AP-5000 model.
Tips 10ML
These tips are used for volumes between 1,000 and
10,000 μl. They are used with the AP-10ML model.
7 - RECOMMENDATIONS
Observing the following recommendations will ensure
maximum possible accuracy and precision of liquid
sampling.
•
Make sure to operate the AXYPET slowly and smoothly.
•The depth of immersion in the sample liquid should be
the minimum necessary and should remain constant
during aspiration.
•The AXYPET should be held in a vertical position.
•Change the tip when volume setting is changed or
when a different liquid is to be aspirated.
•Change the tip if a droplet remains on the end of the tip
from the previous pipetting operation.
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