help! Big baseline shift with GC

[shaoheng86]

Hello everyone,

I am trying to test the phenolics in the wheat straw hydrolysate.

1. Using the activated carbon to adsorb the phenolics
2. Use the dichloromethane to desorb the activated carbon.
3. Test the elute solution with GC

Then I got this graph: a big baseline shift was shown.

There was no problem for the other samples for the other people test using the same GC.

Flickr 上 shaoheng86 的 GC
Thanks

[GasMan]

You should post the column that you are using and the conditions that you are running your analysis under, then somebody can probably help you. This to me is NOT a baseline shift, it is showing you what is in your sample. This chromatogram is very similar to a simulated distillation run, that you could find in a refinery. I do not think that there is any problem with the GC. If you only get this chromatogram with your sample, then I would say that you are using the wrong column.

Gasman

[AICMM]

shaoheng86,

2 comments. 1) What is the scale on the left? Volts, millivolts, microvolts. This could be baseline drift if you did not get a real injection and the scale is very small. More likely, as GasMan states, you have a "diesel" run from the looks of it.
2) Have you run a phenolics standard? Then you define if the problem is GC or extraction.

I will be very, very surprised if you have enough selectivity to do phenolics by themselves in that matrix with that detector. Perhaps better with dervitization but that's not really my expertise.


Best regards,

AICMM

[Don_Hilton]

Any chance the wheat straw or carbon was exposed to motor oil or diesel? I've seen such humps when troubleshooting manufacturing problems - there was a lubricant leak in the equipment...