Biosensor with an interferant detecting electrode

摘要

A highly reliable biosensor is provided which is reduced in influences of any interfering substance or preexisting oxygen in a sample solution. The biosensor comprises an electrode system including a working electrode (2), a counter electrode (4) and a third electrode (7) also usable as an interfering substance detecting electrode, a reagent layer containing at least an oxidoreductase and an electron mediator, and an electrically insulating base plate (11) for supporting the electrode system and the reagent layer, wherein the third electrode (7) is arranged at an opposing position to that of at least one of the working electrode (2) and the counter electrode (4) and the reagent layer is arranged at a predetermined position apart from the third electrode (7).