The Eagle Biosciences Biotin (Vitamin H) quantitative test is based on the principle of the enzyme linked immu nosorbent assay. Avidin, which shows a high affinity to biotin, is bound on the surface of a microtiter plate. Biotin containing samples or standards and a biotin-alkaline phosphatase conjugate are given into the wells of the microtiter plate. Enzyme labelled and free biotin compete for the binding sites. After one hour incubation at room temperature, the wells are washed with diluted washing solution to remove un bound material. A substrate solution is added and incubated for 30 minutes, resulting in the develop ment of a yellow colour. The colour development is inhibited by the addition of a stop solution. The yellow colour is measured photometrically at 405 nm. The concentra tion of biotin is indirectly proportional to the colour inten sity of the Eagle Biosciences Biotin ELISA Assay test sample. Sample Types: food products. Range: 1.0 - 25 ng/ml. Sensitivity: 0.5 ng/mL. Time: 1.5 hours ? Biotin serves as the prosthetic group of enzymes, which catalyze carboxylations in the organism. For this purpose, biotin is bound via its carboxy group to lysin residues of carboxylases, and the transfer of carbon dioxide takes place after its attachment to a nitrogen atom of biotin, forming the so-called active carbon dioxide.