Figure 4

Ionization and fragmentation of derivatized analytes during MS analyses. EI: electron impact ionization source. (A) Methyl-[² H₁]ILA is first ionized and fragmented by EI. The molecular ion m/z 220 is selected and further fragmented to produce the quinolinium ion. Atoms in the molecular ion to the right of the dashed line are lost in the quinolinium ion. (B) Methyl-IAA and (C) methyl-IBA are first ionized by EI. The molecular ions m/z 189 and m/z 217 are selected and further fragmented to produce the quinolinium ions. Atoms in the molecular ions to the right of the dashed line are lost in the quinolinium ions. (D) Derivatized Trp is ionized and fragmented by EI. The molecular ion m/z 276 and quinolinium ion m/z 130 are the major products and are monitored by MS. Atoms in the original molecule to the right of the dashed line are lost in the quinolinium ion.