34 Troubleshooting
3 Chromatographic Symptoms
• To Bakeout Contaminants from the PTV Inlet
• To Bakeout Contaminants from the VI Inlet
• Verify the purity of carrier and detector gases.
• Verify proper reassembly after recent maintenance.
• Inspect the detector for contamination.
If noise increases gradually to an unacceptable level, check the
following possible causes:
• Inspect the detector for contamination.
• Inspect the column and inlet for contamination.
• Inspect the FID or NPD jet for contamination.
• Verify that the FPD photomultiplier tube (PMT) is properly
installed. If it is not, light leaks and ultimately noise will
result.
Other factors that can contribute to noise:
• Column installed too high into detector.
• Oven temperature exceeds column maximum recommended
temperatures.
Baseline wander and drift
• Baseline wander or drift can occur when a flow or
temperature setting is changed. If the system has not
stabilized at the new conditions before it starts a run, some
baseline changes are to be expected. If experiencing baseline
wander, check for leaks, especially at the septum and at the
column. (See “Checking for Leaks” .) Baseline drift is most
often seen during temperature programming. To correct
baseline drift, do the following:Verify that column
compensation is used and the profile is current. (To
compensate for bleed.)
• Verify that the column is conditioned.
• Check column bleed while at operating temperature.
• Check the signal mode assigned to the column in the data
system.
Baseline spiking
There are two types of spiking on the baseline output: cyclic and
random.
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