5-trans-17-phenyltrinorProstaglandinF2α (5-trans-17-phenyltrinor PGF2α) represents the 5-trans isomer and the free acid variant of 17-phenyltrinor PGF2α, distinct from its ethyl amide and dimethylamide derivatives. This compound serves as a potential impurity in 17-phenyltrinor PGF2α formulations. It is utilized as an analytical standard for the detection and quantification of itself in 17-phenyltrinor PGF2α preparations.