How to handle missing spectra

[perfumer]

JI2002, I will do that, thanks again.

The results are in. I now have a very simple spectrum - m/z 228 at 100%, basically no other m/z in the spectrum. That leads to the question what this could be... http://www.flavornet.org/mw.html shows only three substances with 228. (CAS:30673-36-0 butyl decanoate; CAS:106-33-2 ethyl laurate, ethyl dodecanoate; CAS:1117-55-1 hexyl octanoate)
None of this has an appropriate spectrum.

[Don_Hilton]

First question is where did the sample come from? Some information about the origin could help answer the question. If you have purchased this - call the vendor and tell them what you have found.

M+1 and M+2 can give you a hint about composition - but I work with quads, sectors and TOFs. I gather that traps can be a bit tricky about ratios for low abundance ions...

[ods-at-pacific]

I did a search for CASrn 39647-11-5 in the 4th Ed of the Adams library and the Wiley FFSC 1.3 libraries. The spectra are very similar.

This compound is a methyl ester and a cyclic ketone with a nominal mass of 226. The peak at m/z 156 is an odd-electron ion. These types of compounds are difficult at best when using a internal ionization QIT GC-MS. The peak at m/z 227 in you mass spectrum represents a protonated molecule formed by the ion/molecule reactions of ions with m/z 156 and the unionized molecules.

Dilute the sample. Even at very low concentrations you will still see an abnormally high intensity for m/z 227 given the low intensity of the peak at m/z 226 in the spectrum acquired using a transmission quadrupole instrument. The spectrum in the 2nd Ed. Of the Adams library is some what different than that shown in the 4th Ed. And has a peak at m/z 227 which is about twice the intensity of the peak at m/z 226. Both peaks in this mass spectrum are < 5%.

[perfumer]

David, thanks for your thoughts. I didn't know there is a Mass Spectral database from Adams? Do you refer to Robert P. Adams, who wrote "Identification of Essential Oil Components By Gas Chromatography/Mass Spectrometry"? Would you mind giving a link?

I'll do as you suggested. Thanks again!

Don, the supplier "swears an oath" the sample came directly from a Firmenich package. They are not very talkative, especially not about their captives

[ods-at-pacific]

Yes, I am talking about Robert P Adams and this is the 4th Ed. of his book/database from Allured Publishing

http://www.alluredbooks.com/Flavor-Chem ... n-p52.html

The book has structures; the electronic database does not. Each name in the electronic version of the database begins with the retention time making a name search in the NIST MS Search Program tricky. You have uses the setting that ignores numbers in the name.

[Consumer Products Guy]

We built our own GCMS fragrance library, injecting 20 pure compounds each night, then entering the spectra into our own GCMS library the next day. It was a several-month project, including retention indexes v. ethyl fatty acid esters, because that's what perfumers use. That was in early 1990s, on HP 5890/5971. Works good, and since it's ours, we can put on all our GCMS computers.

[Stryder08]

Yeah, I built my own LC-ToF ESI library with fragmentation using insource CID. Up to 1,200 compounds now.