Peak matching involves the process of comparing spectral data from a parent or starting material to an unknown compound. (The unknown compound can be referred more specifically as the product, impurity, degradant, metabolite, etc.). The similarities between the data indicate regions that have not changed while the differences indicate regions of change.
The ESI+ product ion spectra (MS/MS) for both the Parent (m/z 226) and Metabolite (m/z 228) are shown below. The spectra share a common fragment at m/z 121 and differ in the fragments at m/z 134/136 and 149/151.
Based on the fragments shown below, the suspected site of hydrogenation is on the carbonyl for metabolite A.