This assay employs the competitive inhibition enzyme immunoassay technique. An antibody specific for Prostaglandin F2 Alpha (PGF2a) has  been  pre-coated  onto  a  microplate.  A  competitive  inhibition  reaction  is  launched  between Horseradish Peroxidase (HRP) labeled Prostaglandin F2 Alpha (PGF2a) and unlabeled Prostaglandin F2 Alpha (PGF2a) (Standards or samples) with the pre-coated antibody specific for Prostaglandin F2 Alpha (PGF2a). After incubation the unbound conjugate is washed off. The amount of bound HRP conjugate is reverse proportional to the concentration of  Prostaglandin F2 Alpha (PGF2a) in the sample. After addition of the substrate solution, the intensity of color developed is reverse proportional to the concentration of  Prostaglandin F2 Alpha (PGF2a) in the sample.