GE AxiChrom 50 Operating Instructions Manual page 147

Problem
HETP values
unrealistically low
(number of theoretical
plates too high).
Unstable base line.
High HETP value.
AxiChrom 50, 70 and 100 columns Operating instructions 28-9331-08 AG
Comment
Test molecule interacts with
the chromatography
medium under the
conditions used, e.g. acetone
interacts with SOURCE me-
dia.
The volume measurement
failed to reset at start of
sample elution, resulting in a
very high retention volume.
Leaking adapter bed
support.
Leaking bottom bed support.
Liquid velocity too high or
too low.
Too large sample volume
(gives a broad peak).
Too great a distance
between the sample injection
and column inlet, or between
the column outlet and
analyzing instrument.
Large liquid volume in tubing,
valves, connectors, etc.
Action
Use appropriate test molecule and con-
•
ditions, e.g. use salt for SOURCE media.
Adjust the chromatogram in UNICORN
•
to correct the retention volume. See
UNICORN manual for further informa-
tion.
Inspect the bed support for damage and
•
replace if necessary.
Inspect the bed support for damage and
•
replace if necessary.
Liquid velocity should be in the range
•
15-60 cm/h depending on particle size.
The smaller the particle, the higher the
velocity.
Use a sample volume that is maximum
•
2% of the column volume.
Shorten these distances (minimizes dilu-
•
tion).
Minimize dilution by reducing the liquid
•
volume. For example, if the inner diame-
ters of the tubing, valves, connectors,
etc. are wider than the column inlet and
outlet, change them to the same diame-
ter.
7 Troubleshooting
7.1 Performance
147