Kazutetsu Nojima

Further study of the matrix effect on the extent of fragmentation in molecular ions M+ produced under fast atom bombardment (FAB) conditions

Abstract The extents of fragmentation in the molecular ions M + of prenylated flavonoids produced under FAB conditions using various liquid matrices are evaluated by comparison with the corresponding electron ionization (EI) mass spectral patterns at electron impact energies of 15–70 eV. The extents of fragmentation in the M + ions produced with m -nitrobenzyl alcohol as a FAB matrix are always lower than those produced with glycerol and thioglycerol as the matrices. A few FAB spectral data obtained here indicate that the extends of FAB fragmentation in the M + ions correspond to those of the EI fragmentation in the M + ions produced at the electron impact energy of more than 70 eV. Consequently, it is concluded that FAB is an EI-like hard ionization process even when a liquid matrix is used.

Determination of 17-hydroxyprogesterone in plasma by gas chromatography—mass spectrometry with high-resolution selected-ion monitoring

A method for determining 17-hydroxyprogesterone in plasma by isotope dilution-mass spectrometry is described. For the internal standard 17-hydroxy [2H4]progesterone is used. Extraction of plasma is followed by conversion into the 3,20-dienol,17-tristrimethylsilyl ether derivative and analysis by capillary gas chromatography-mass spectrometry with selected-ion monitoring, at a resolution of 6000. The lower limit of quantitation was 1 pg, judged from a criterion of a signal-to-noise ratio of 10. The precision and accuracy of the method were satisfactory.