Analysis of phenoxazine chemosensitizers: An electron ionization and keV‐ion beam bombardment mass spectrometry study

The mass spectral behavior of a set of eight 2‐ and 10‐disubstituted phenoxazines putatively possessing anticancer drug enhancer properties was investigated. Both electron ionization (EI) and keV‐ion beam bombardment (liquid secondary ion mass spectrometry, LSIMS) were used. As expected, EI led to extensive fragmentation to produce structurally characteristic ions. Except in one example, the molecular ions were reasonably abundant. Two different liquid matrices—sulfolane and 3‐nitrobenzyl alcohol—were used to obtain LSIMS data. The use of the latter produced more stable molecular ions. Ion beam bombardment also produced several structure‐specific fragments. A unique feature of the LSI spectra obtained using either of the above matrices is production of both M^+. and [M + H]⁺ ions, with the former being more abundant in most cases. Adduct formation with the liquid matrices was also observed for many compounds.