Hoefer IEF100 - Manual (Page 50)

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Problem Solution
Set voltage not reached Continue with the IEF.
IPG strip is being limited by μA or W.
Conductivity of the strip is too high.
One IPG strip will focus at its max μA or W, and limit the voltage to all
strips. This strip can be removed, and the remaining strips will focus at
higher voltages.
7 cm strips should not be focused at volts higher than 6000 V and watts
higher than 0.5 W per strip.
Browning, burning of strips Strips have high conductivity due to salts or other ionic compounds.
arcing, erratic μA readings
Reduce the ionic strength by limiting salt concentration to 10 mM or below.
Reduce Tris concentrations to 50 mM or below.
This indicates the power, volt or current delivered to the strip is too high.
Limit current in the IPG strips to 50 μA.
Too little oil and/or strips not completely covered in oil.
Level the instrument. Ensure mineral oil completely covers the strips, and
the empty channels. If strips are not completely covered urea will crystallize
out and cause local heating/burning.
Overheating of the tray. Check tray is securely slid and locked into place to
ensure the best contact between the tray base and the platform surface.
Rehydration/equilibration tray has residual Excess volume used. Do not exceed the IPG strip manufacturer’s
liquid after rehydration of IPG strips recommended volumes.
Strip accidentally rehydrated with the gel side up or strip cover sheet
not removed.
Extend rehydration time. 8 –10 hours minimum is required for the best
uptake of rehydration solution.
No proteins present in gel after Load of proteins is too little for the detection method. Load more protein
2nd dimension completed or try a more sensitive method of detection.
IPG strip was not properly hydrated.