Presuming that your unspecified "general derivatization method" is something to derivatize alcohols and fatty acids, or transesterify glycerides, the reason that it does not work is that essential oils are mostly composed of terpenes and terpenoids, not the triglycerides that make up vegetabe oils.
What is the purpose of the derivatization ?
Peter
Thank you, Peter. I compared the list generated from ChromaTOF with the list of molecules from several papers, I could only get half overlapped with the papers (In paper, they used GC/MS, and I'm supposed the number of molecules I got from 2D GC-TOF/MS should be larger than the number from GC/MS and the molecules detected in GC/MS should included in the list from 2DGC/MS). So I applied derivatization to the sample because I hope the molecules got better chromatographic properties, and the results are even worse than those from non-derivatization runs.