Chromatographic Troubleshooting
Peak symptoms
Peak symptoms
No peaks
This is usually due to operator error; possibilities include injection on the wrong column, incorrect signal assignment, attenuation too high (peaks are present but not visible), a bent syringe needle in an automatic sampler, etc. Check system parameters for the analysis.
Inverted peaks
This is likely an inappropriate signal assignment definition (e.g., B - A with sample injected on column A) or incorrect polarity with a TCD.
Extra peaks
These are divided into two classes: Additiona l peaks appear on the chart in addition to those expected from the sample. Ghost peaks appear even when no sample is injected (and also appear among the genuine peaks during a sample run).
1.Peaks appear during a blank run:
These are ghost peaks, usually found during temperature•programmedruns; the cause is contaminants trapped at the head of the column at the relatively cool starting temperature. These are released and chromatographed as column temperature rises.
Ghost peaks are often observed when a column has been at the starting temperature for some time. For example, the first few runs in the morning often contain ghost peaks.
C Ghost peaks may arise from septum bleed, carrier gas impurities, and contamination in plumbing by oils, grease, and other materials. Less commonly, they may be caused by reaction of
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