Frequency domain selection of the peroxide signal for amperometric biosensors

The amperometric biosensor has become a convenient analytical device concep t since the biorecognition element can be highly specific to the analyte of interest when coupled to the appropriate transducer. However, a shortcomin g of this system is that the transducer alone is not necessarily specific t o the analyte, but only in conjunction with the recognition element. Since many applications require that the sensor be used in complex analytical med ia, other sample species may cause a direct response at the transducer, for example electroactive species may be directly oxidized or reduced at an el ectrode in an electrochemical sensor, yielding an erroneous signal. Filtrat ion/membrane barriers have been proposed to overcome this, but this also el iminates any information about the interferent. In this article the role of impedence spectroscopy is examined as a technique to probe overlapping ele ctrochemical signals by separation in the frequency domain. Hydrogen peroxi de is examined as a model to test the feasibility of extraction of quantita tive data in this control mode, and experimental conditions are determined where analytical data may be obtained to extract the peroxide signal from o ther electrochemical information in an enzyme biosensor based on peroxide d etermination.