This ELISA kit uses the Competitive-ELISA principle. The micro ELISA plate provided in this kit has been pre-coated with Mouse E2. Samples (or Standards) and Horseradish Peroxidase (HRP) linked antibody specific for Mouse E2 are added to the micro ELISA plate wells. Mouse E2 in samples (or standards) competes with a fixed amount of E2 on the solid phase supporter for sites on the HRP linked detection antibody specific to E2. Excess conjugate and unbound sample or standard are washed from the plate. The substrate solution is added to each well. The enzyme-substrate reaction is terminated by the addition of stop solution and the color turns yellow. The optical density (OD) is measured spectrophotometrically at a wavelength of 450±2 nm. The concentration of Mouse E2 in the samples is then determined by comparing the OD of the samples to the standard curve.