TBE Acrylamide/Formamide gels running slowly - (Jan/19/2011 )

Recently our PAGE gels have been running slowly, needing about 40% more time to reach necessary separation.

We have swapped out Acrylamide and Urea brands, and tried fresh APS, TEMED and TBE, with no luck.

Any ideas?

Thanks.


We run large scale PAGE gels (BioRad SequiGen 38x50cm) for DNA SSR analysis.
Usually 1.75h @ 110watts (1800V-2800V)

7% (19:1 acrylamide:Bis)
1X TBE
We use both "regular" acrylamide gels, as well as acrylamide+formamide, with the same results.

have you tried a different power supply? apparatus?

maybe the limits are changed or not outputting what you expect or the electrodes damaged or dirty.

We have 3 different BioRad power packs, and have recently purchased a new base unit (base with electrodes)

Unfortunately, it happens with all 3 packs, as well as the new and old base units.

How's your water? High salt in the water could cause this.

We have a 4-cartridge E-Pure system with Culligan pre-filter (the water originates from our building's de-ionized water supply).

Our cartridges are due for a change (thanks for the reminder)... but I can't imagine they're that bad yet.