Pre-Rinsing; Aspirating High Density Liquids; Recalibration - VWR Ultra High-Performance VE2 Handbuch

• After about one second press the pipetting pushbutton
to the final stop, blowing out the remaining liquid from
the tip (fig. 4D).
• Holding the pushbutton depressed remove the pipettor,
drawing it against the vessel inner wall.
• Release the pipetting pushbutton to its starting position
(fig. 4E) and eject the tip by pressing the tip ejector
button (fig. 4F).
CAUTION: Replace the tip with a new one whenever a
different liquid is to be pipetted.

4.3 PRE-RINSING

When pipetting liquids of viscosity higher or surface
tension lower than those of water (e.g. serum or organic
solvents) a film of liquid is formed on the inside wall
of the pipetting tip. The film can create an error. Since
the film remains relatively constant in successive pipetting
operations with the same tip, this error can be avoided
by forming the film before the first pipetting. This is done
by performing a full pipetting cycle of a liquid into the
same vessel. After such a procedure, the film of liquid is
already formed in the tips and ensures better accuracy
and repeatability of successive pipetting operations.

4.4 ASPIRATING HIGH DENSITY LIQUIDS

The accuracy errors provided in Table 1 have been
determined using distilled water. When pipetting liquids
whose properties (density, viscosity, surface tension)
differ from the properties of water, it may be necessary to
compensate for volume settings.
CAUTION: Aspiration differences can be avoided if the
pipetting operation is conducted slowly, so that the liquid
can slowly adjust to the changing pressure. Wait for
about 2 seconds after each aspirating and dispensing,
without changing the position of the pipettor.
If the above procedure does not provide accurate
results, pipettor recalibration is required according to
section 5.
After calibration, it is recommended to record recalibration
and the adjustment value, which will facilitate return cali-
bration to the standard liquid.
9

5. RECALIBRATION

VWR UHP pipettors are calibrated by gravimetric
method, using VWR tips and distilled water, at the tem-
perature 20°±1°C, according to EN ISO 8655 standard.
It is recommended to conduct periodic inspection of the
pipettor operation, with the interval between inspections
being dependent on the type of load (aspirated liquids)
and other conditions (load intensity and autoclave sterili-
zation, replacement of subassemblies) in which the
pipettor is used.
The pipettor recalibration procedure should be carried
out if during the pipettor operation you find that the accu-
racy error (the difference between the real aspirated vol-
ume and the preset volume) exceeds the permissible
value given in Table 1.
Checking the pipettor parameters
To determine accuracy error of the pipettor, the following
requirements must be fulfilled:
• The ambient temperature of the pipettor, tip and the
test liquid (typically distilled water) should be within the
range of 20-25°C and stabilized during weighing within
the range ±0.5°C,
• The density of the liquid used should be close to that of
distilled water,
• The balance sensitivity should be appropriate to the
tested volume (Table 3),
• The mg/μl conversion factor, dependent on temperature
and pressure, should be taken into account (Table 4).
Volume [μl]
Balance sensitivity [mg]
Table 3
Temperature [°C]
20
21
22
23
24
25
Table 4
ENGLISH
0.1 - 10 10 - 100 > 100
≤ ≤ ≤
0.001 0.01 0.1
Pressure [kPa]
95 101.3 105
1.0028 1.0029 1.0029
1.0030 1.0031 1.0031
1.0032 1.0033 1.0033
1.0034 1.0035 1.0036
1.0037 1.0038 1.0038
1.0039 1.0040 1.0040
10