Figure 7.

EIC (alignment before and after retention time (Rt) alignment and mass-to-charge ratio (m/z)) correction with MetMatch. (a) A phenylalanine-derived chromatographic peak was annotated at position 3 in the reference file (black) and thus included in the reference feature list. The target peak (blue) at position 2 would probably be matched to it by means of manual matching or any other alignment approach that does not account for Rt shift; (b) Extracted ion chromatograms (EICs) after Rt and m/z shift correction using MetMatch. When the two corrected EICs are viewed simultaneously, it is apparent that each target peak should be matched to the reference peak denoted by the same ID number and that a systematic m/z shift is present between the two chromatograms.