AbstractElectron capturing pentafluorobenzyl ester derivatives of prostanoids provide intense negative ion chemical ionization mass spectra. Fragmentation is directed almost entirely away from the prostanoid molecule and this provides intense [M ‐ C6F5CH2]−ions. These ions are ideal for specific and sensitive quantitative selected ion monitoring analysis. The limits of sensitivity employing this technique are in the range 1–8 pg on column compared with 100–500 pg using the corresponding methyl ester derivative in the electron impact mode. The capillary column characteristics of the pentafluorobenzyl esters are suitable for the development of multiprostaglandin gas chromatographic mass spectrometric