GC-FID Mineral oil

[CrisTheChemist]

Hi Chromatographers,
I have a trouble with GC-FID analysis of mineral oils C10-C40 in water, soils, waste (ISO 16703). It is an instrumental problem not related to sample type or extraction.
I have been doing this analysis for many years, but now I have this problem that I have never seen before.

Sometimes the chromatogram of the blank or a std or a sample shows a negative band that goes below the starting level of chromatogram hence I can not integrate the classic large peak at the baseline.

I have just changed the column, the liner, the jet assy of the FID, but some days the problems doesn't appear, whereas other days the problem exist.
Do you have some similar experience?

I can share some chromatograms but I need your email address.

Really thank you

[Tdaniel25]

Hi Chromatographers,
I have a trouble with GC-FID analysis of mineral oils C10-C40 in water, soils, waste (ISO 16703). It is an instrumental problem not related to sample type or extraction.
I have been doing this analysis for many years, but now I have this problem that I have never seen before.

Sometimes the chromatogram of the blank or a std or a sample shows a negative band that goes below the starting level of chromatogram hence I can not integrate the classic large peak at the baseline.

I have just changed the column, the liner, the jet assy of the FID, but some days the problems doesn't appear, whereas other days the problem exist.
Do you have some similar experience?

I can share some chromatograms but I need your email address.

Really thank you

Hi!
The issue is related to the column length inserted into the FID. If the column is too short or too long inside the detector jet, it can cause negative bands and baseline instability.
Check and adjust the column insertion length according to the manufacturer’s specifications his usually solves the problem.

Tiago