Mass spectra of hydroperoxides, such as cumen hydroperoxide (CHP), diisopropylbenzene hydroperoxide (DBH),
p-mentane hydroperoxide (PMH) were investigated by liquid ionization (LPI) mass spectrometry. Hydrated molecular ions [M+H+
nH
2O]
+,
n=1-10, were dominant in LPI mass spectra of all samples when they were dissolved simply in a solvent, although ethanol was a good solvent. When ethanol was used with butanol (1-3%),
i.e., a mixed solvent, and/or with acetone, which was evaporated in the ionization chamber (as a vapor matrix), those hydrated ions were suppressed and [M+H]
+ of PMH became the base peak. Acetone is a useful vapor matrix for obtaining [M+H]
+. When pyridine (Py, 3-8%)-ethanol mixture was used as a solvent, molecular adduct ions [M+H+Py]
+ became dominant for CHP and DBH. LPI-MS is useful not only for determining molecular weights of hydroperoxides but also for investigating the solvation and effects of various kinds of additives.
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