Checking The Volume - VITLAB micropipette Mode D'emploi

8. Checking the Volume

Depending on use, we recommend inspection of the instrument every 3 to 12 months. The cycle
can, however, be adjusted to individual requirements.
The gravimetric testing of the pipette volume is performed according to the following steps and is in
accordance with DIN EN ISO 8655, Part 6.
1. Set nominal volume
Set volume to the maximum volume indi-
cated on the instrument (see page 25 for
procedure).
2. Condition the pipette
Condition the pipette before testing by using
a pipette tip to aspirate and discharge the
test liquid (distilled H
this, discard the pipette tip.
3. Carry out the test
a) Attach new pipette tip and prerinse one time
with test liquid.
b) Aspirate liquid and pipette it into the weigh-
ing vessel.
Calculation for nominal volume V
x = Weighing results
i
n = Number of weighings
Z = Correction factor (e.g. 1,0029 µl/mg at 20 °C, 1013 hPa)
Mean value
x =
Mean volume
V = x · Z
Standard Deviation
s = Z ·
O) five times. After
2
0
Σ x
i
n
Σ (x
– x )
2
i
n – 1
c) Weigh the pipetted quantity with an
analytical balance. Please follow the operat-
ing manual instructions from the balance
manufacturer.
d) Calculate the volume, taking the tempera-
ture of test liquid into account.
e) At least 10 pipettings and weighings in three
volume ranges (100%, 50%, 10% of nomi-
nal volume) are recommended for statistical
analysis.
Accuracy*
V – V
A% =
Coefficient of Variation*
CV% =
*) = Calculation of accuracy (A%) and variation
coefficient (CV%): A% and CV% are calculated
according to the formulas for statistical control.
Note:
Testing instructions (SOPs) are available for
download at www.vitlab.com.
0 · 100
V
0
100 s
V
27