Chromatography Forum

Hi,

Any comments how to convince a professor that a chromatogram with a drifting baseline is acceptable? I'm currently using a DB-225 column for FAME analysis. Said column is installed in an Agilent GC 7890 system connected to a 5975C MS detector. I tried convincing him by showing the chromatograms under the Agilent catalogue GC-MS Applications section.

Also how can we correct a chrom generated using the same GC system but with its baseline buried by the x-axis? I believe a chrom baseline has to float a little above the x-axis.

Many thanks for the help.

Point out to the learned academic that baseline drift is an inevitable consequence of temperature programming, and that if the separation is run isothermally it would take several times the age of the universe to elute the last peak.

You might find that you can export the raw data and then add a constant to all the y values to shift the whole chromatogram upwards.

Peter

Is your "drifting baseline" a repeatable rise at higher temperatures?

If yes, adding the detail that the baseline rise is due to the slow stripping of the stationary phase of the column might help him/her too. Column bleed is an unavoidable problem with high-temperature gas chromatography. As Peter Apps mentions, FAMES are too heavy to elute with temperatures close to ambient where bleed is not pronounced.

Point out to the learned academic that baseline drift is an inevitable consequence of temperature programming, and that if the separation is run isothermally it would take several times the age of the universe to elute the last peak.

You might find that you can export the raw data and then add a constant to all the y values to shift the whole chromatogram upwards.

Peter

Many thanks for the informative reply. I will try doing your suggestion on how to shift the chromatogram upwards.

Is your "drifting baseline" a repeatable rise at higher temperatures?

If yes, adding the detail that the baseline rise is due to the slow stripping of the stationary phase of the column might help him/her too. Column bleed is an unavoidable problem with high-temperature gas chromatography. As Peter Apps mentions, FAMES are too heavy to elute with temperatures close to ambient where bleed is not pronounced.

Thank you for the added information on the effect of high temperature to the GC method for FAME analysis. I'm using a DB-225 column. The Agilent Engineer mentioned to me that one possible solution would be to use a DB-225ms column instead. I've just recommended purchase of said column.