Determination of biotin in foodstuffs and pharmaceutical preparations using a biosensing system based on the streptavidin–biotin interaction Original Research Article

An affinity biosensor system for the determination of biotin and its derivatives based on the specific non-covalent interaction between biotin and streptavidin is described. The permanent immobilisation of streptavidin on controlled-pore-glass (CPG) provides an adequate active support in which the specific and competitive reaction between biotin derivatives and biotin labelled with peroxidase (POD) takes place. Biotin was used as a model. The development of this competitive assay was revealed by determining the amount of POD which is not retained in the active support by using a derivatising reaction with fluorimetric detection. The method exhibits a linear range from 0.1 to 8.0 μg l−1 of biotin (r2=0.9986, n=9) with a precision, expressed as R.S.D., lower than 3.8% and a sampling frequency of 10 h−1. The approach has been applied to the determination of biotin in natural juices and pharmaceutical preparations with recoveries ranging between 88.1 and 104.8%.