Redox interferences devices

In general, low level detection is masked by the noise level inherent in any measuring device. Electrochemical methods are susceptible to electrical interference from external sources, variations in reference electrode parameters resulting from aging or contamination, and interference from redox... 

A remaining crucial technological milestone to pass for an implanted device remains the stability of the biocatalytic fuel cell, which should be expressed in months or years rather than days or weeks. Recent reports on the use of BOD biocatalytic electrodes in serum have, for example, highlighted instabilities associated with the presence of 02, urate or metal ions [99, 100], and enzyme deactivation in its oxidized state [101]. Strategies to be considered include the use of new biocatalysts with improved thermal properties, or stability towards interferences and inhibitors, the use of nanostructured electrode surfaces and chemical coupling of films to such surfaces, to improve film stability, and the design of redox mediator libraries tailored towards both mediation and immobilization. 

Table 13.2 summarises the different approaches used to construct enzyme electrochemical biosensors for application to food analysis based on the different types of enzymes available. Generally, the main problems of many of the proposed amperometric devices have been poor selectivity due to high potential values required to monitor the enzyme reaction, and poor sensitivity. Typical interferences in food samples are reducing compounds, such as ascorbic acid, uric acid, bilirubin and acetaminophen. Electrocatalysts, redox mediators or a second enzyme coupled reaction have been used to overcome these problems (see Table 13.2), in order to achieve the required specifications in terms of selectivity and sensitivity. 

Interference from water was eliminated by calibrating with a redox peak that was not proton related. Gas phase analysis showed strong redox signals for TNT and DNT and demonstrated that ILs serve as a preconcentrator to improve the sensitivity of very low vapor pressure analytes. These examples demonstrate that the combination of IL materials and electrochemical transducers overcomes many obstacles in forming an effective sensor system. IL-electrochemical sensors are also well suited for miniaturization and can be fabricated with very low cost. In contrast to nonspecific transducers such as a surface acoustic wave device, arrays of amperomertic and EIS transducers allow a secondary perturbation (e.g., potential) that enhances selee-tivity and increases analytical information content without increasing the number of physical sensor elements. 

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