I'm trying to expand the repertoire of DMPK analyses I can offer and am starting to think about how I might best perform the sample analysis for metabolite identification studies.  Putting aside the interpretation of the data I am trying to think ways of optimising the identification of emergent metabolite peaks from the noise of solvent peaks, solvent contaminants and microsome  contaminants.  An ideal way perhaps to identify new peaks amongst the noise might be to perform whole spectra subtraction.  By this I mean normalising two spectra to the intensity of an internal standard and performing a subtraction.  Is this possoble within Masslynx (v4.0)?  I know you can subtract background but this is not what I mean.  If not masslynx is there any freesource software that might be capable of this.  Thank you.