Mzmed - mz of fragment or compound? December 20, 2017, 07:05:43 AM Hello everyone, I'm a tad confused as to the mz XCMS spits out after pre-processing. Are these definitely compound masses or could they be fragments (not adducts) of a compound? I'm asking because that obviously makes a huge difference for identification and I find that my spectra for select retention times don't match the mass, i.e. they often contain base peaks that may be higher than the mzmed given by XCMS. So are the mzmed values both compounds and fragments thereof and if it's the latter how would you account for that (if it's not an adduct)? Many thanks!