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From the basic researches of the electrochemistry parents, Volta, Galvani, Sir Humphry Davy, and Faraday, a long period of silence followed in this interdisciplinary field that ends only at the beginning of the twentieth century with the invention of the glass electrode by M. Cremer and the discovery of polarography by J. Heyrovsky. That was the moment when modern electrochemistry was born. The research boom, which leads to the elaboration of the most well-known electrochemical methods and main types of electrodes, continues even today. Electrochemical methods (potentiometry, voltamperometry, and conductimetry) experienced a huge development due to their multiple advantages that they offer, mainly the high sensitivity that allows detection of concentrations in the range of 10 -8 -10-10 M especially for differential pulse, square wave voltammetry, and stripping techniques.At the same time the major disadvantage of the electrochemical methods became obvious: lack of selectivity. Practically, all the electroactive species can be reduced or oxidized from a sample or from a matrix and the simultaneous detection in the same sample is possible only in the case when two species possess redox potentials sufficiently separated in the investigated domain of potential. The reduced selectivity was the main issue that pointed the researchers' attention towards the delicate area of the electrode surface, where essential phenomena take place and trigger the race that still continues today having the goal of increasing the selectivity (specificity) for certain analytes. A new domain has been born, the field of modified electrochemical sensors. There are several possibilities today to modify the electrode material or its surface; the general strategies of electrochemical sensor technology will be discussed later.

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