MS/MS Precursor Mass accuracy and Smart Confirmation MS/MS Match Warning


Smart Confirmation MS/MS matches occur when the name of a compound in the components list does not match the name of the compound in the MS/MS library. This is very uuseful due to spelling differences, and it can be useful when a peak is not a postivie mach, but a similar compound in the library IS a postive match. However, this tool can be very misleading, becuse a good "Smart Confirmation" library match will still give an excellent purity or fit score, even though it is a fit for the WRONG compound.  For this reason, "Smart Confirmation" matches should be screened against the "Found at Mass" of the precursor compound using the formulat in the library and the correct adduct/charge listed in the components table (if present). Sometimes, the "Precursor Mass Tolerance" feature in the Library Search parameters will cause only results meeting these requirements to be shown as smart confimation matches. However, numerous tests have shown that this tool is inconsistent and causes false positives and false negatives. The reason may be incorrect formula or adduct assumptions in the MS/MS library.  To solve this, there should be a "Library Mass Error" column similar to "Mass Error" and "Fragment Mass Error". This would greatly improve the library searching by comparing the formula and mass of potential library hits to the formula/mass in the components table. This would also allow these matches to be viewed to identify the alternate matches and improve the scope of the screening method, but removed if the user only wants to see "real" hits. 
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    0 Comments Feb 19, 2019 29 Views