Agilent Technologies 3100 OFFGEL Fractionator User Manual page 104

7 Troubleshooting
Troubleshooting the Application
Table 12
Symptom
After fractionation has
finished, the external wells of
the frame have reduced liquid
or are empty.
Sparking at the electrodes.
After fractionation has
finished, the cooling platform is
contaminated with mineral oil.
104
Troubleshooting the OFFGEL application (continued)
Possible Cause
3 the corresponding sample
has higher salt
concentration or higher
protein/peptide content
than the other samples.
1 During IEF, a water transport
is observed due to migrating
ions that drag the water in
their hydration shell to the
electrodes. Furthermore,
water is dragged from wells
at the basic strip end
(cathodic end of strips pH
3-10) to wells in the neutral
pH range due to the
ionization of DTT. Therefore,
after OFFGEL
electrophoresis the wells
close to the electrodes are
sometimes filled with less
liquid than the inner wells or
are even empty.
1 short circuits at the
electrodes.
1 Mineral oil tends to creep
across the electrodes and
tray wells once they are
moistened. However, if the
electrodes do not dry out
during fractionation this
does not impair the focusing
results.
Action
• Run only samples similar in
protein content and buffer
composition on the same
tray.
• If low recovery in the
extreme wells is a problem,
refill the corresponding
wells with diluted OFFGEL
Stock Solution without
ampholytes (4 parts OFFGEL
Stock Solution without
ampholytes plus one part
water) one hour prior to the
end of the focusing phase.
• make sure that the
electrodes and the electrode
connectors are completely
dry.
• carefully pipette the mineral
oil and avoid spillages.
• when inserting the tray into
the instrument, make sure
that no oil is spilled out of
tray.
• Insert the tray before adding
the mineral oil to the
instrument.
OFFGEL User Manual