User Manual

Troubleshooting
14
Problem Cause Solution
General Troubleshooting Tips
Current is zero or less than
expected, and samples do not
migrate into gel
Tape at bottom of cassette not removed Remove tape
Insufficient buffer in integral buffer
chamber
Fill buffer chamber with running buffer
Insufficient buffer in lower buffer
chamber
Fill both halves of lower buffer tank with
400 ml running buffer when running two
gels
Electrical disconnection Check electrodes and connections
Gels run faster than expected Running buffer too concentrated or
incorrect
Check buffer composition
Gel temperature too high Do not exceed recommended running
conditions
Bands “smile” across gel: band
pattern curves upward at both
sides of the gel
Excessive heating of gel Check buffer composition
Do not exceed recommended running
conditions
Insufficient buffer Fill both halves of lower buffer tank with
400 ml running buffer when running two
gels
Bands “smile” or “frown” within gel
lanes
Protein load too high Load less protein
Sample or buffer preparation issues Minimize salts, detergents, and solvents
in sample preparation and sample loading
buffers
Incorrect running conditions Set correct voltage
Bands are skewed or distorted;
lateral band spreading
Too much salt in samples Remove salt from samples (dialysis,
precipitation, or other method)
Insufficient or wrong sample buffer Check buffer composition and dilution
instructions
Sample precipitation Selectively remove predominant proteins in
sample
Dilute sample in sample buffer
Insoluble materials (for example, cell
membranes) in samples
Centrifuge samples to remove particulates
prior to sample loading
38 Technical Support: 1-800-4BIORAD • 1-800-424-6723 • www.bio-rad.com
Table 14.1. Troubleshooting electrophoresis and detection with Criterion
™
gels. For more troubleshooting tips, refer to the
Criterion cell, Criterion blotter, and Trans-Blot
®
SD cell instruction manuals, or contact Technical Support.