There are many historical reviews on electrochemistry as well as on analytical chemistry, where-as hardly any survey of the history of electroanalytical methods exists. This contribution is an approach to provide a short overview on the development of the electroanalytical methods, electrodes and electrochemical sensors. Electrogravimetry belongs to the oldest quantitative procedures introduced 1864 by Wolcott Gibbs. Roots are even older and are represented by "voltameters". Closely related to electrogravimetry is coulometry, which is also based on Faradays laws; early applications comprise determinations of atomic masses and of thin metal layers. Conductivity measurements are also a rather old analytical method, applied (with direct current) in the 18 th century already. The effective procedure was developed in the 1860s after the use of alternating current by Friedrich Kohlrausch. The Nernst equation (1889) was the base for direct potentiometry, e.g., determination of sparingly soluble electrolytes. Max Cremer is the inventor of the glass electrode (1906), which is the first electrochemical sensor. Potentiometric indication of titrations by Robert Behrend (1883) was the first instrumental indication in volumetric analysis. The invention of polarography by Jaroslav Heyrovský (1922) is the starting point of the electroanalysis with the dropping mercury electrode. The polarograph, developed in cooperation with Masuro Shikata, was the first automated analytical device. As a follow-up various methods (e.g., pulse and alternating current methods) as well as voltammetry including stripping analysis have gained importance. Further development of electroanalysis is characterized by new electrodes and electrode materials, e.g., stationary mercury electrodes, carbon-paste electrodes, chemically modified electrodes, and increased application of electrochemical sensors.

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The preconcentration of silver at carbon paste electrodes (CPE) modified with N-benzoyl-N',N'-di-i-butyl-thiourea and its subsequent voltammetric determination is studied with test solutions. The preconcentration of silver at the surface of the modified CPE succeeds as well with open circuits as with applied potentials. The amount preconcentrated depends on the electrode potential with a maximum at +0.1 V vs. Ag/AgCl, thus enabling the preconcentration of silver without cathodic treatment. The detection limit is in the order of 10(-4) mmol/l Ag(+). The surface reactions during the preconcentration are discussed. It is assumed that silver complexes of the modifier are formed in a fast reaction followed by a slow reaction with participation of silver and of carbon surface groups.