Results and Discussion The proline sample was measured using positive ion mode which produced an [M+H] + ion at m/z 116. This ion was monoisotopically selected as the precursor ion for TOF-TOF analysis. The resulting high-energy CID product ion spectrum is shown in Fig. 2a. The overall MS/MS spectrum was very simple for this sample with the low mass ions m/z 43 and m/z 70 attributed to the fragments shown in Fig. 3.