In general, sensors can be dened as devices that perceive changes in physical properties of the environment and turn them into a measurable signal (Gründler, 2007; Bard et al., 2008). Electrochemical sensing, in general, is devoted to identifying and/ or quantifying selected analyte(s) and involves:

Monitoring any electrochemical process experienced by electroactive • analytes. Monitoring an auxiliary electrochemical process whose parameters are • modied by the presence of the analyte. This approach can correspond to two basic possibilities: The analyte participates in the electrochemical process via catalysis, com-• plexation, etc. The analyte competes with electroactive species blocking of modifying • their electrochemical response (competitive methods).