Reverse Matching?

[thohry]

Hi all,

I meet this term in searching the library (LC/MS) but I do not really understand it.
Could anyone explain the term " Reverse Matching"
Thanks in advance.

[Don_Hilton]

The reverse search score ignores all spectral peaks that are in the sample spectrum but not in the lilbrary spectrum. This allows for matches in spectra where there is a lot of background noise and even mixture of the spctrum from another compund.

Details for the NIST mass spec search routines are given in links shown in http://chemdata.nist.gov/mass-spc/ms-search/.

The "short" description of forward and reverse searching is: Forward searching looks to see if your unknown spectrum matches something in the library; reverse searching looks to see if a library spectrum matches something in your unknown spectrum.

[thohry]

Thank you Don_Hilton
In fact I can not see the difference of the two matching types. I will try !
Thanks again

[Peter Apps]

If you have some GC-MS data with a selection of clean and overlapping peaks of compounds that you know for sure are in the sample you can play around by taking spectra at different points, ans seeing how the fit and reverse fit numbers change.

Peter