Abstract
The method for observing molecular related ions of methyl hydroperoxyoleates (OMH) by atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) was investigated. Since thermally labile OMH is decomposed in the APCI nebulizer and/or desolvation chamber heated to a high temperature, it is difficult to observe significant peaks of their protonated molecules. The addition of ammonia water to the mobile phase (ethanol) was quite effective to suppress the thermal decomposition of OMH. As the result the mass spectra exhibited the intense peaks of ammonium adduct ions of OMH, [M+NH4]+, at m/z 346. The nebulizer temperature at 170°C and the drift voltage at 170 V were adequate for observing the molecular ion species of OMH.
