Chromatographic Troubleshooting

Peak symptoms

4. Top (apex) of the peak is split:

Figure 9-4.

FID/NPD Flameout, or TCD with H (in He Carrier)

CVerify that this is not a merged peak situation: Reduce oven temperature 30^C and repeat the run. If the split peak becomes better resolved, it is probably a merged pair.

CGross overload of an FID may cause the top of the peak to invert, giving appearance of a split peak. Check gas flows; overload is more likely when flows are too low.

Dilute the sample by a factor of at least 10 and repeat the run: If the split disappears, overload is the problem. It is advisable to dilute samples even more, by 100 or 1000, to ensure the detector is not close to its overload condition. Such dilution generally improves linearity as well.

CH1 peaks, analyzed with a TCD using He carrier, often shows a split top.

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