24 Troubleshooting
3 Chromatographic Symptoms
Contamination or Carryover
If your output has contamination or unexpected peaks, do the
following:
Isolate the source
1 Perform a solvent blank run using a new, pure source of
solvent. If the contamination disappears, the problem may be
either in the sample or solvent-related.
2 Perform a blank run (remove the syringe from the injector
and start a run). If the contamination disappears, the
problem is in the syringe.
3 Remove the column from the detector and cap the detector
fitting. Perform another blank run. If the contamination
disappears, the problem is in the inlet or column. If the
contamination remains, the problem is in the detector.
Check possible causes—all inlet and detector combinations
• Check the septum type and installation.
• Perform complete inlet maintenance: Replace all consumable
parts and bake out the inlet.
• Perform column maintenance: Bake out contaminants,
remove the contaminated length of column near the inlet,
and reverse and bake out the column as needed.
• Check for sample carryover from previous runs. Make several
no-injection blank runs and see if the ghost peaks go away or
get smaller.
• Check the septum purge flow.
• Check all gas trap indicators and dates.
• Verify the gas purity. Check for supply tubing and fitting
contamination.
• If you suspect that there is contamination in the inlet,
column, or detector, perform the bakeout procedure.
• Verify that the oven program temperature and time are
sufficient for the samples being injected.
• Check the solvent level in the ALS wash bottles.
• Replace the ALS syringe if necessary.
• Check the sample injection volume.
• Install an Agilent column backflush system.
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