Checking The Volume - VITLAB micropipette Gebrauchsanweisung

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 indicated 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 O) five times.
2
3. Carry out the test
Note:
In accordance with DIN EN ISO 8655-2, a tip change is recommended after each individual
measurement. An exception to this rule can be made, according to DAkkS guideline DKD-R8-1.
a) Aspirate liquid and pipette it into the weighing vessel.
b) Weigh the pipetted quantity with an analytical balance. Please follow the operating manual
instructions from the balance manufacturer.
c) Calculate the volume, taking the temperature of test liquid into account.
d) At least 10 pipettings and weighings in three volume ranges (100%, 50%, 10% of nominal vol-
ume) are recommended for statistical analysis.
Calculation for nominal volume V
x = Weighing results
i
n = Number of weighings
Mean value
x =
Mean volume
V = x · Z
Standard Deviation
s = Z ·
0
Σ x
i
n
Σ (x
– x )
2
i
n – 1
Z = Correction factor (e.g. 1,0029 µl/mg at 20
°C, 1013 hPa)
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
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