Gravimetric volume testing according to DIN EN ISO 8655-6 (for measurement conditions, see 'Error Limits',
page 38) is performed as follows:
1. Preparation of the instrument
Clean the instrument ('Cleaning', page 41), fill
it with distilled H
2
O and then prime it carefully.
2. Check the volume
a) 10 dispensing operations with distilled H
2
O
in
3 Volume ranges (100 %, 50 %, 10 %) are
recommended.
b) For filling pull up the piston gently until the
upper stop of the volume set.
c) For discharge depress piston slowly and
steadily without force until the lower stop.
Depending on use, we recommend that gravimetric testing of the instrument be carried out every 3-12
months. This time frame should be adjusted to correspond with individual requirements. The complete test-
ing procedure (SOP) can be downloaded at www.vitlab.com. In addition, you can also carry out function
checks at shorter intervals, e.g. dispensing the nominal volume into a volumetric test flask.
10. Checking the Volume (Calibration)
d) Wipe off the tip of discharge tube.
e) Weigh the dispensed quantity on an ana-
lytical balance. Please follow the operating
manual of the balance manufacturer.
f) Calculate the dispensed volume. The Z fac-
tor takes account of the temperature and
air buoyancy.
Calculations for nominal volume V
N
x
i
= results of weighings
n = number of weighings
Z = correction factor
(e. g., 1.0029 µl/mg at 20 °C, 1013 hPa)
Mean value
Mean volume
Accuracy
Coefficient of variation
Standard deviation
V = x · Z
100 s
V
CV% =
Σ
(x
i
– x)
2
n – 1
s = Z ·
V – V
N
V
N
A% = · 100
39
x =
Σ
x
i
n