Recurring ghost peak

[chromatographer1]

Sometime there was a 'bleeding contamination' which fouled the pneumatics upstream from the injector. It may have come from the gas supply originally, or from the pneumatics hardware (grease, oil, lube of some sort) or from sample backflash from the injector. But when a spot in the gas flow is cool enough and there is a phase for the contamination to be trapped and focused into a plug, when the column is heated it proceeds through the column to the detector as a 'peak'. With more time it becomes larger. If the column is not allowed to cool, it elutes as a 'smear' or baseline increase hidden within the 'bleed' of the column.

best wishes,

Rod

[Peter Apps]

The old regulator has almost certaialy contaminated all the gas plumbing, so the blank peak is still bleeding onto the head of the column. There is very likely a small filter immediately upstream of the inlet - change that and then let the gas flow overnight (with a decent split flow at the inlet so that most of what bleeds off the last piece of tubing does not get oto the column). Then do a few runs.

Peter