The aim of the invention is to improve existing amperometric sensors used to measure the quantity of a component present in a solution. This aim is reached by using a sensor provided with a measuring electrode (20) having at least one current collector (37) electrically connected at one of the electric contacts (34) and coated with a mixture (38) comprising at least one oxido-reduction enzyme specific to said component and at least one mediator transfering the electrons between said enzyme et said current collector, characterized in that the mediator is selected amongst the complexes of a transition metal with at least one bipyridine, terpyridine or phenanthroline ligand substituted by at least one electron donor group. Said sensor is applicable more particularly to the detection of glucose.