BrandTech Scientific Transferpette electronic - Manual (Page 56)

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.
Checking the Volume
*) = Calculation of accuracy (A %) and variation coefficient (CV %):
A % and CV % are calculated according to the formulas for statistical control.
x
i
= Weighing results
n = Number of weighings
Z = Correction factor
(for example 1.0029 µl/mg at 20 °C, 1013 hPa)
V
0
= Nominal volume
1.
Set nominal volume
Set volume to the maximum volume indicated on the instrument.
See page 42 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
2
O) five times.
After this, discard the pipette tip.
3.
Carry out the test
a) Attach new pipette tip and pre-rinse one time with test
liquid.
b) Aspirate liquid and pipette it into the weighing vessel.
c) Weigh the pipetted quantity with an analytical balance.
Please follow the operating manual instructions from the
balance manufacturer.
d) Calculate the volume, taking the temperature into account.
e) At least 10 pipettings and weighings in three volume ranges
(100 %, 50 %, 10 %) are recommended for statistical
analysis.
Calculation (for nominal volume)
100 s
V
CV% =
Σ (x
i
– x) 2
n – 1
s = Z ·
V – V
0
V
0
A% = · 100
Mean value x =
Σ x
i
n
Mean volume V = x · Z
Accuracy* Standard Deviation Coefficient of Variation*
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