9.1 Equipment (continued)
Problem
Cause
Solution
Perpendicular gradient (DGGE only)
Glass plate cracked
Excessive force at
Apply only one turn
comb gasket
to thumb gasket screw
after it touches glass
Gel solution leaks during casting
Not sufficient pressure
Make sure pressure
on comb gasket
clamp screws are
turned two turns
Poor contact between
Reassemble glass
comb gasket and spacers plates as in Section
4.1. Visually confirm
contact at spacers and
comb gasket
Casting stand gasket
Position gray gasket
positioned incorrectly
so that it covers the entire
bottom section of the glass
plate
Wrong comb gasket
Make sure correct
comb gasket is used
Misaligned comb gasket
Insure that comb gasket
notches are against
spacer notches
Misaligned plates
Pressure clamp may
force plates to shift if
sandwich clamps are not
tight. Insure that sandwich
clamps are tightened
Misalignment of spacers
Check alignment at
and glass plates
bottom of glass plates,
using alignment slot on
casting stand
Damaged or dirty
Replace spacers or
spacers and/or combs
combs
Different thickness of
Use spacers and comb
spacers and comb
of same thickness
Dirty inlet fitting
Replace fitting
or missing O-ring
Loose stopcock
Tighten stopcock/inlet
port screw connection
No air vent plug
Plug vent after casting gel
Damaged or non-
Replace with Bio-Rad
Bio-Rad glass plates
glass plates only
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