Pharmacia Biotech Multiphor II User Manual page 64

8. Trouble shooting
Symptom
Drying out of the gel
near the electrodes
Sparking along edge
of gel onto cooling plate
Condensation over the
entire surface of the glass
electrode holder
Local condensation on
the glass electrode holder
Excessive amount of
condensation along
electrode strips
Skewed or wavy bands
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Cause
Incorrect electrode solutions
Excessive power setting
Excess moisture on gel or under
cooling plate
Electrode strips overhanging the
ends of the gel
Liquid expelled at sides of electrode
strips due to electroendosmotic flow
of water towards the cathode
Excessive power setting
Insufficient cooling
Local overheating due to a high salt
concentration in the sample
Incorrect electrode solutions in relation
to electrode polarity
Localized hot spots due to air
bubbles under the gel
Cathodic drift may cause an
electroendosmotic flow of water
towards the cathode. Thus, cathode
strip may become over saturated
Reversed polarity of electrode strips
(lower pH at cathode, higher
pH at anode)
Localized gradient disturbances
due to excessive salt
Remedy
Use the recommended electrode
solution at the specified
concentration.
Check the power setting
Remove the excess moisture
Cut the electrode strips short
of the ends of the gel
Occasionally remove the excess
fluid by blotting
Check the power setting.
When only a portion of the gel is
used, reduce the power setting
proportionally
Check the temperature and flow
of the cooling fluid
Reduce the salt content of the
sample by gel filtration using
PD-10 columns pre-packed with
Sephadex G-25
Check the electrode polarity.
Check the pH of the applied
electrode strips
Use insulating fluid under the gel
and check for air bubbles
Cut the electrode strips shorter
than the edge of the gel. If
necessary, blot the pooled liquid.
Check pH of the strips and
polarity of the plugs in the power
supply. Reverse polarity if the
strips have been incorrectly
applied (should be acid at anode)
Reduce the salt content of the
sample by gel filtration using PD-
10 columns pre-packed with
Sephadex G-25. Salt content
should be <50 mmol/l.
Too much ammonium
persulphate may also cause wavy
bands