Wandering Detector Baseline - Agilent Technologies 1100 Series Service Manual

2 Troubleshooting and Test Functions

Wandering Detector Baseline

Critical Decision
Determine if the problem is in the DAD, or coming from the LC system:
Remove the flow cell from the DAD. Close the cell cover, and see if the baseline
performance improves.
1 If baseline performance has not improved:
2 If baseline performance has improved, focus attention on the possible
Table 12 Wandering Detector Baseline Possible Causes and Suggested Actions
Possible Causes
Dirty or defective flow cell
The analytical column
"Mixing Noise" when
pumping a binary mobile
phase from two channels.
Unstable flow and/or system
pressure.
100
a Replace the lamp(s).
b Evaluate the environment for excessive drafts, temperature changes, etc.
causes and suggested actions below.
Suggested Actions
• Clean or replace the flow cell
• Bypass the column. Pump directly into the flow
cell. If performance improves, try a new column.
• Try premixing the mobile phase in one bottle,
and pumping 100% from that one solvent
channel.
If baseline performance improves, a solution
must be found which is a compromise between
mixing volume and other chromatographic
requirements. For an isocratic analysis,
premixing and pumping 100% one channel is the
best solution.
• Refer to the problem Unstable flow and/or
system pressure above. If your system suffers
from this problem, go through the possible
causes and suggested actions described there.
Notes
This problem occurs when one (or
both) of the solvents has a high
background absorbance at the
detection wavelength. In this case,
the pump's mixing efficiency may
not be good enough to produce a
sufficiently homogeneous mobile
phase.
The detector reacts to gluts of the
more detectable parts of the solvent
mixture, and baseline disturbances
result.
Failure to maintain stable column
flow or system pressure can also
cause unwanted baseline activity.
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