A general question regarding LC/MS

[Tristan]

G'day all,
I am very new to the field of LC/MS and have a general question regarding the ionization modes. I heard someone say about LC/MS that it was not as useful as GC/MS (EI) in regards to unknown identification due to the soft ionization modes. Is this correct? Can LC/MS be used for compound identification?

Thank you all in advance!

Tristan

[Kostas Petritis]

Yes it can,

The problem is, that unlike GC/MS that is hi-energy fragmentation, the low energy fragmentation in LC/MS leads in not too reproducible MS/MS spectra (i.e. from model to model, different collision energies etc) which makes the development of compound spectrum libraries and automated searching tools difficult.

But there are tools developed, as for the proteomic (i.e. peptide identification for MS/MS). Tools like Sequest, Spectrum Mill, Mascot etc...

You can always do a manual interpretation of your spectra...

[james little]

There are a lot of EI reference spectra that can easily be searched for GC-MS. We search >800,000 spectra using the NIST search software.

There are some LC-MS tandem and in-source databases, but the spectra are not as reproducible and no standard spectra like EI. However, we have an in-house library of >2000 LC-MS (mainly in-source CID spectra) which we find very useful.