Yoshiyuki Mochida

Effects of Solvents and Additives on Liquid Ionization Mass Spectra of Dialkyl Peroxides.

Appropriate solvents and additives were investigated for liquid ionization (LPI) mass spectra of dialkylperoxides having one peroxy group, such as di-t-butyl peroxide (BB), t-butyl cumyl peroxide (BC), dicumyl peroxide (CC), and having two peroxy groups, such as 2,5-dimethyl-2,5-di(t-butyl peroxy)hexane (BAB), α,α′-bis-(t-butyl peroxy)diisopropyl benzene (BPB), 2,5-dimethyl-2,5-di(t-butyl peroxy)hexyne-3 (BYB). When each sample was dissolved only in a solvent (e.g., ethanol, hexane, octane, or toluene), abundant hydrated protonated molecules [M+H+H2O]+ were observed for all samples, but peaks corresponding to protonated molecules [M+H]+ were weak, except for BAB. Addition of butanol to alkane (solvent) increased the abundance of [M+H]+, with decrease of [M+H+H2O]+ for BAB, BPB, and BYB. For these compounds (having two peroxy groups), the addition of butanol (BuOH) to the suitable solvent, such as toluene, was effective for producing dominant adduct ions [M+H+BuOH]+ with few [M+H+H2O]+. The addition of ethylamine (EA) to any solvent examined was also effective for producing adduct ions [M+H+EA]+ for all dialkylperoxides. It is interesting that BB having a symmetric structure gave dominant molecular ions M+· even in the ionization condition like LPI. The addition of p-cresol (PC) to a suitable solvent was useful for BB and BAB (both symmetric structures) to produce dominant molecular adduct ions like [M+PC]+·. LPI-MS is useful not only for determining relative molecular mass of dialkylperoxides but also for investigating the effects of solvents and various kinds of additives.