Hello,
I'm doing an study about the chemical composition of birch tree at different temp and holdup-time with MS/GC, FID, TCD.
Unfortunately my background is not chemical engineering but closer to mechanical.
Now i have a problem with duplicates and even triplicates compounds found at different retention time in the same experiment when i analyze the resulting chromatogram.
What i do is to pyrolyse the sample with an pyrolysis unit (Pyrola 2000) and the pyrolysis gas is then fed to all three detectors simultaneously in the GC.
I use a capillary GC column Length= 30m I:D= 0.25mm Film thickness= 0,25µm
When I’m then transfer the peaks >2% from the Chromatogram to Excel i find duplicate and triplicate molecules in both MS and FID at different retention time with different area% and probability%. Sometimes this are just next to each other in the Chromatogram and sometimes there are other compounds in between them. At some extreme cases I will find one at 5.xx min and the duplicate At 20.xx min.
I use NIST MS search 2.0 library and Thermo Xcalibur qual browser.
I suspect that there might be some contamination in the the system that causes this problem.
From what i understand this should not be happening and I have no idea how to tackle this problem.
An example from an FID reading in the attachment.
i would really appreciate some help. Sorry for the bad spelling and language I'm from Sweden