Hoefer SE900 - Manual (Page 26)

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Troubleshooting
Problem Solution
Casting Issues:
Gel caster leaks
If the stack is too tall, the front plate may not seat firmly against the gasket.
Remove filler plates or cassettes until the gasket seals.
Apply a light film of gel seal to the foam gasket each time the unit is used.
Check the foam gasket for cracks or nicks and replace if necessary.
Caster face plate not properly aligned. Check that the faceplate is evenly
positioned on caster.
Poor or Incomplete gel polymerization Use only recent stock of the highest quality reagents.
APS reagents or solutions are old and lose their activity when exposed to
moisture. Make up fresh APS daily. If the dry ammonium persulfate does not
crackle when water is added to it, replace the product with fresh stock. Store
reagent tightly closed and in a dessicator to prevent absorption of moisture.
Remove oxygen from the gel environment. Degas the monomer solution
5 minutes before pouring and then overlay the gel surface with water
saturated n-butanol.
Allow gel solutions to come to room temperature before casting (a minimum
of 20 °C, especially for low % T gels).
Increase both APS and TEMED by 30–50%.
Solutions with extreme pH values (especially acidic) may not polymerize.
Check pH of gel buffers.
Poor polymerization at the spacers. Make sure to clean the plates well at
the spacer edges, that the sides are free of dirt or grease, and that the gel is
fully polymerized before removing from the caster.
Gel is too soft, too brittle or white Adjust crosslinker concentration. Crosslinker should be at 2.6% C for
Vertical protein streaks standard SDS gels where %C = (g bis × 100) ÷ (g monomer + g bis)
Gel contains swirls Indicates convection currents during polymerization, usually from
polymerizing too fast.
If gel polymerized in <10 min, too much catalyst. Reduce concentration of
ammonium persulfate and TEMED by 25%.
If gel polymerized in >50 min, not enough catalyst. Increase concentration
of ammonium persulfate and TEMED by 50%.
Make sure gel solutions are near room temperature when casting.
Gels cast simultaneously are different sizes Wait one minute before overlaying each gel so that the solution “settles.”
Use the same amount of overlay on each separation gel. Add the overlay
evenly across the gel surface.