A carbon-paste electrode (CPE) is made from a mixture of conducting graphite

Graphite

The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

 powder and a pasting liquid. These electrode

Electrode

An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

s are simple to make and offer an easily renewable surface for electron exchange

Electron transfer

Electron transfer is the process by which an electron moves from an atom or a chemical species to another atom or chemical species...

. Carbon paste electrodes belong to a special group of heterogeneous carbon

Carbon

Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 electrodes. These electrodes are widely used mainly for voltammetric

Voltammetry

Voltammetry is a category of electroanalytical methods used in analytical chemistry and various industrial processes. In voltammetry, information about an analyte is obtained by measuring the current as the potential is varied.- Three electrode system :...

 measurements; however, carbon paste-based sensor

Sensor

A sensor is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. For example, a mercury-in-glass thermometer converts the measured temperature into expansion and contraction of a liquid which can be read on a calibrated...

s are also applicable in coulometry

Coulometry

Coulometry is the name given to a group of techniques in analytical chemistry that determine the amount of matter transformed during an electrolysis reaction by measuring the amount of electricity consumed or produced....

 (both amperometry

Amperometry

Amperometry in chemistry and biochemistry is detection of ions in a solution based on electric current or changes in electric current.Amperometry is used in electrophysiology to study vesicle release events using a carbon fiber electrode...

 and potentiometry).

Advantages

In general, CPEs are popular because carbon pastes are easily obtainable at minimal costs and are especially suitable for preparing an electrode material modified with admixtures of other compounds thus giving the electrode certain pre-determined properties. Electrodes made in this way are highly selective sensors for both inorganic and organic

Organic chemistry

Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...

 electrochemistry

Electrochemistry

Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...

.

Disadvantages

The biggest disadvantage of CPEs, which limits their applicability in practical analysis, is that success in working with carbon paste-based electrodes depends on the experience of the user. While this is true for any type of solid electrodes, CPEs are rather an exceptional case. In contrast to commercially available solid electrodes for which basic electrochemical characteristics are comparable for almost all products from each manufacturer, each carbon paste unit is an individual, where the physical, chemical and electrochemical properties may differ from one preparation to another. For this reason each probe must be calibrated individually. While this may not be an issue in a research environment, it would be a considerable burden in production service.