HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY THERMOSPRAY MASS-SPECTROMETRY OF SOME PROSTAGLANDINS OF THE F-SERIES

Thermospray (TSP) mass spectra and chromatographic characteristics of the prostanoids PGF(2 alpha), 6-keto-PGF(1 alpha), 2,3-dinor-6-keto-PG F(1 alpha) and their methyl esters and methoximes are reported. The sp ectra of these compounds are dominated by ions of the type [M + H + xN H(3) - nH(2)O](+) in the positive-ion mode and [M - H + xAcOH - nH(2)O ](-) in the negative-ion mode (n ranges from 0-4 and x is 0 or 1). The relative abundances of these ions depend on the particular structure, source and interface temperatures and eluent composition, In addition , these compounds show losses of 44 mass units, mainly due to the loss of the C-10-C-11 moiety, as demonstrated by deuterium labelling of PG F(2 alpha). Methoximated derivatives of 6-keto-PGF(1 alpha) also show low-abundance ions due to fragmentation in the position a to the metho xime group. The liquid-phase equilibria of tautomers of 2,3-dinor-6-ke to-PGF(1 alpha) or products thereof which direct its particular chroma tographic behavior, can be effectively blocked by methoximation of the keto group thus improving its detectability. Detection limits of 20 n g on-column may be obtained for this derivative. Adsorption and hydrol ysis in the interface are the principal factors responsible for this r elatively high detection limit.