Checking The Volume - VITLAB continuous E Instrucciones De Manejo

12. 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 complete testing procedure (SOP) can be downloaded
at www.vitlab.com. In addition, a simple inspection can also be carried out over shorter time spans, for
example by titration against a standard.
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. Clean the burette (see 'Cleaning', chapter 9),
fill it with distilled water and then prime it
carefully.
2. To check the instrument, dispense distilled
water into a weighing vessel.
3. Weigh the dispensed amount on an analytical
balance. (Please follow the operating manual
from the balance manufacturer.)
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
*) = Calculation of accuracy (A%) and variation
coefficient (CV%): A% and CV% are calculated
according to the formulas for statistical control.
0
Σ x
i
n
4. Convert the indicated weight into volume
units, taking into account the temperature,
density and atmospheric pressure. (The
conversion factor Z is published in the
standard.)
5. 10 dispensed amounts in 3 volume ranges
(100%, 50%, 10%) are recommended.
6. From the 10 measured values, calculate the
mean measured volume. Then calculate
accuracy (%) and coefficient of variation (%).
Accuracy*
V – V
A% =
Coefficient of Variation*
CV% =
Standard Deviation
s = Z ·
Note:
Testing instructions (SOPs) are available for
download at www.vitlab.com.
0 · 100
V
0
100 s
V
Σ (x
– x )
2
i
n – 1
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