NEGATIVE-ION CHEMICAL-IONIZATION AND COLLISIONALLY ACTIVATED DECOMPOSITION MASS-SPECTRA OF O-2,3,4,5,6-PENTAFLUOROBENZYLOXIME DERIVATIVES OF PROSTAGLANDINS

Prostaglandin E(1), prostaglandin E(2), prostaglandin E(3), 6-oxo-prostaglandin F-1 alpha, 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-PGF(1 alpha) 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 F-1 alpha derivatives have intense [M - HF - (CH3)(2)SI = CH2](-) ions. Most prominent daughter ions are [P - (C1-C5)](-) and [P - 2HF - H - (C1-C5)](-).