Resumen
The invention relates to a composite amperometric biosensor to determine cholesterol in foodstuffs, comprising a rigid electrode matrix that is renewable by polishing and made of graphite and powder Teflon (70%) in which the cholesterol enzymes oxidase and peroxidase are immobilized along with the mediator potassium ferrocyanide by simple physical inclusion. The composite bienzymatic electrode is compatible in predominantly non-aqueous media such as inverse micelles consisting of an organic solvent (ethyl acetate) as continuous phase, a small amount of an aqueous solution of an appropriate electrolyte (4 % of a solution regulating a pH 7.4 phosphate) as dispersed phase and a surface active agent (sodium dioctylsulfosuccinate 0.1 M) as emulsifier. This makes it possible to directly determine cholesterol in said media once it has been extracted from the foodstuff using the same solvent used to form the inverse micelles (ethyl acetate) as extraction solvent.