Seeing peak towards the end of the run

Question

Hello Guys,

I am using Agilent 7890a GC with an FID detector. Last week I saw that there are few ghost peaks in my chromatogram, so I decided to bakeout the column. After baking the ghost peaks disappeared but now I see and increase in the peak towards the end of the run (please refer to the attached picture). I cleaned the liner, even put a new one and also trimmed the column a little bit. Problem still persists.

Do you have any idea why this is happening and what would be the solution?

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dmarchini · Answer

Hi Oishi It could be the column bleed; I've noticed this getting worst if I bake the column in presence of air. I usually change the liner, than run a solvent vial, then I bake for 2 hour, until the baseline get flat. I don't think it is necessary to bake out for longer than 2 hour. If you don't have peaks of interest on the bleed baseline you're doin good ; If you need good peaks on the bleed baseline I suggest to slow the gradient, I mean, it's seems you have like 50°C/5 min ramp or similar, it's too extreme. greetings Dario

abdur · Answer

Hi Oshin, You may want to consider adding backflush to your system. That way the late eluters never make it to your column.

Seeing peak towards the end of the run

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