can anyone give a reason if the gc-ms data I obtained for the C11 chain (octyl acrylate) came out first and had a retention time of 4.074, the second compound that came out was octane having a retention time of 4.209 while the third compound that came out was cyclopentanone with a retention time of 4.304 and the next compound that comes out is pentanoic acid?
in theory, the GC-MS principle is a compound that has a small molecular weight and comes out first, followed by a compound with a large molecular weight. whereas the GC-MS results that I have obtained are the opposite.
Hello Monica,
you've forgotten a crucial piece of information. Which stationary phase do you use? This determines the interaction with your individual compounds. Your assertion that low molecular weight compounds elute first is not correct. It depends on the substance class and the stationary phase. An example: If you have a very nonpolar phase, then nonpolar compounds such as alkanes have a much higher tendency to remain in the stationary phase than polar compounds (e.g. esters), i.e. the esters will elute earlier than your alkanes and that with a possibly higher molecular weight.
Regards
Markus
Hi.
It has been pointed out that you don't mention the exact column used (I'm assuming something appropriate for FAMEs). It would be nice to have a chromatogram, but I think that the compounds were just miss-identified and/or are ghost peaks with no actual significance other than noise. How was the identification made? Library match? It will often fail when you have linear long chain carbon based structures.....
Cheers!
the column that I use is PFlow-He with GC operational conditions in the following figure
Hi Monica,
I don't know the column type you described.
Which stationary phase is it?
Regards
Markus
Im unable to find the info about that column. Please send my a link to supplier web page.
If you are using the MS library to identify the compounds, then your identities may not be properly assigned. These compounds are going to have less than unique fragmentation patterns, which means the library will fit multiple options to each peak. I would run the compounds individually to get their RT and MS. Then, you can use that data to make the proper identifications in your mixture.
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