Vitamin D3 (Cholecalciferol) is found in human epidermis and dermis. BioVision’s human Vit. D3 ELISA Kit is based on the standard principle of a sandwich enzyme-linked immunosorbent assay. Human Vit. D3 antibody is coated on a 96-well plate. Standards and test samples are added to the wells and Vit. D3 present in a sample is bound by the immobilized antibody. An HRP-conjugate reagent is added subsequently. After washing away the unbound antibody/HRP conjugates, HRP substrate TMB is used to visualize the HRP enzymatic reaction. TMB is catalyzed by HRP to produce a blue product that changes into yellow after adding acidic stop solution. The density of yellow color is proportional to the human Vit. D3 captured onto the plate. This ELISA kit shows no species cross-reactivity. Detection Range: 20