This ELISA kit uses the Sandwich-ELISA principle. The micro ELISA plate provided in this kit has been pre-coated with an antibody specific to SARS-CoV-2 N protein. Samples (or Standards) and biotinylated detection antibody specific for SARS-CoV-2 N protein are added to the micro ELISA plate wells. SARS-CoV-2 N protein would combine with the specific antibody. Then Avidin-Horseradish Peroxidase (HRP) conjugate are added successively to each micro plate well and incubated. Free components are washed away. The substrate solution is added to each well. Only those wells that contain SARS-CoV-2 N protein, biotinylated detection antibody and Avidin-HRP conjugate will appear blue in color. 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 OD value is proportional to the concentration of SARSCoV-2 N protein. You can calculate the concentration of SARS-CoV-2 N protein in the samples by comparing the OD of the samples to the standard curve.