It seems to be a right task for a metabolomics analysys, which proved to be quite effective for various complex biological liquids like juices, wines, urine etc. Though it requires quite a lot of preliminary work to setup a method for particular system, but the output is also gigantic.

See e.g. this paper: http://www.ncbi.nlm.nih.gov/pubmed/23682581. Though this setup for wines is much more complicated that might be needed for oils.

This method is also used now as a better alternative for a SNIF-NMR for a juice analysys, See e.g. this commercial product: http://www.bruker.com/products/mr/nmr/food-screener/juicescreener/applications.html

SNIF-NMR works well with alcholic beverages because the target molecule (ethanol) is simple to characterize by NMR. SNIF-NMR of fruit juices also targets ethanol; here the sugar in fruit juice is fermented to generate ethanol following a standarized protocol.

Proton NMR spectra (1H and 2H) of terpenoids are slightly more complex than ethanol. Which is probably why the "gold" standard for authentication of essential oils using stable isotope abundance of 2H and 13C is analysis by Isotope Ratio Mass Spectrometry (IRMS).

Dr. Augenstein Is GCIRMS way too expensive than ordinary GCMS?

Dear Prabodh, you are right, a good GC-IRMS system is more expensive than traditional bench-top GC/MS systems. However, this does not mean GC/MS is or can be the answer to this particular problem just because it is less expensive than GC-IRMS. By way of analogy I am sure you would agree there is no point trying to detect (take a picture) of a virus 20-100 nm in diameter with a light microscope (limited to 200 nm resolution for physical reasons: diffraction) just because an electron microscope is way too expensive. One's tool (= analytical instrument) must be fit-for-purpose. As I have explained to you already in a previous message, there are physical limitations to what level of stable isotope abundance can be reliably and accurately quantified with a scanning MS system.

Thank you Dr. W Meir-Augenstein for your valuable suggestion.

Dear Prabodh,

Synthetic and natural compound differs only from the isotopic ratio  so ratio of C12:C13 could be  mesured . In the mass spectra can find differant mass no for the same fragment based on the isotopic differance, The ratio of C12:C13 is unique for natural compound but not for the synthetic.

Dayananda