1. Primary site fragmentation process and its major fragmentation
pathway.
2. Stability of the studied dyes as positively charged molecules in
solid state phase and molecular ions in gas phase.
3. Selection of the most probable decomposition pathways in vitro
system using MS technique.
4. Substituent effects on experimental and computational results.
Electron ionization (EI) mass spectra of the four dyes (I–IV)
at 70 eV were recorded and investigated (e.g. of dye I, Fig. 5).
The proposed of principal and important fragmentation pathways
following electron impact is shown in Schemes 1–4. The signal