Manual

13
– What is the temperature of the sample? (In open tubes, water at room
temperature evaporates)
– What is the temperature of the pipette?
– What is the temperature of the air?
– Has mg been converted into µL?
– Does the sample have a different density to that of water?
– Is the pipetting speed too high?
If the place where the pipette is used is at extremely high altitude, an adjustment
must be made in line with the ambient air pressure. At 1,000 m above sea level,
there is a volume error of approx. –0.4 %.
Assistance with these questions is contained in Eppendorf’s SOP (
S tandard
O perating P rocedure), which is available upon request. An SOP can be called up
from our home page
www.eppendorf.com .
If these checks prove to be unsuccessful, it is safe to assume that the
alignment of the pipette has altered (e.g. due to several components having
been replaced).
5.2.2 Follow-up alignment in the case of error
From a technical point of view, this is a zero-point shift. The value by which the
setting of the pipette is shifted remains constant across the entire measuring
range. If, for example, in the case of a 10–100 µL, follow-up alignment of
1 µL takes place at 100 µL (=1 %), the pipette is also adjusted by 1 µL at 10 µL
(=10 %!)
a The pipette, tip and water must all be the same temperature
(20–25 °C, constant to ± 0.5 °C).
b In the case of adjustable pipettes, the pipette is set to the nominal volume
required.
c With a pipette tip attached to the pipette, the desired volume is pipetted
and weighed 10 times (for multi-channel pipettes, this is carried out for each
channel). The mean of this weighing is converted into µL using the following
formula:
The value obtained is the actual setting
(density of water at 20 °C: 0.9982 mg/µL).
Volume =
Weight
Density of liquid
(at the temperature specified)
Research – Part A – Section 5
2_ResearchE.fm Seite 13 Donnerstag, 17. April 2008 12:31 12