Negative ion chemical ionization and collisionally activated decomposition mass spectra ofO-2,3,4,5,6-pentafluorobenzyloxime derivatives of prostaglandins

Abstract

Prostaglandin E1, prostaglandin E2, prostaglandin E3, 6-oxo-prostaglandin F1α, 1-carboxy-rioprostil and rioprostil were derivatized to the pentafluorobenzyloxime/trimethylsilyl ether/methyl ester and pentafluorobenzyloxime/trimethylsilyl ether (rioprostil) respectively. In the high-mass region, except for the 6-oxo-PGF1α, derivative, negative ion chemical ionization (methane) mass spectra show an intense [M - HF]−. ion. Collisionally activated decomposition mass spectra (0.2 Pa argon collision gas pressure, 15 eV collision energy) of this parent ion ([P]−.) of the syn and anti oxime isomers are quite different. The syn isomers have intense [P  (C1–C7)]− and [C6F4CH2O]− daughter ions, while the most abundant peaks in the spectra of the anti isomers are [P  OH  TMSOH]−, [P  OH  2TMSOH]− and [(C9–C10)  HF]−. Negative ion chemical ionization mass spectra of 6-oxo-prostaglandin F1α derivatives have intense [M  HF  (CH3)2SiCH2]− ions. Most prominent daughter ions are [P  (C1-C5)]− and [P - 2HF  H  (C1–C5)]−.