IgA ELISA Kit: The microtiter plate provided in this kit has been pre-coated with an antigen. Standards or samples are then added to the appropriate microtiter plate wells with a Horseradish Peroxidase (HRP)-conjugated secondary antibody. After TMB substrate solution is added, those wells that contain Anti-IgA will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450 nm