Development of novel glucose and pyruvate biosensors at poly(neutral red) modified carbon film electrodes. Application to natural samples

Amperometric biosensors based on the corresponding oxidase enzyme with poly(neutral red) redox mediator have been developed for the determination of glucose and pyruvate. The enzymes have been immobilized on top of poly(neutral red) modified carbon film electrodes with glutaraldehyde as the cross-linking agent. The biosensors were characterized by cyclic voltammetry and by electrochemical impedance spectroscopy. The glucose biosensor exhibited a linear response in the range 90 mu M to 1.8 mM with a detection limit of 22 mu M and the pyruvate biosensor in the range 90 to 600 mu M with a detection limit of 34 mu M. The relative standard deviations were found to be 2.1% (n = 3) and 2.8% (n = 4) respectively. The interference effects of various compounds were also studied. The glucose content of several types of wine and the amount of pyruvate in onion and garlic were determined and the results were compared with those obtained by standard spectrophotometric methods.