An XIC generated from the product ion m/z 191.145 that is found in PGF3α isomers (A). MS/MS product ion spectrum of m/z 351.215 at RT 19.1 minutes in the extracted HFF sample (B). The product ions m/z 333, 315, 307, 289, 245, 193, and 191 are observed in authentic PGF3α [23, 27]. Standards also available online at http://www.lipidmaps.org/data/standards/index.html. Arrows indicate major product ions that are not observed in PGF3α, but are observed in a PGF3α analog from C. elegans [27]. Peaks at RT 20.35 minutes and 20.65 minutes have several product ions observed in PGF3α spectra, including m/z 333, 315, 289, 245, 193, and 191. Cps, counts per second.