analytical chemistry Analytical skill, Analytical chemistry studies and uses instruments and methods to Separation process, separate, identify, and Quantification (science), quantify matter. In practice, separation, identification or quantification may constitute t ...

, hydrodynamic voltammetry is a form of

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. The analytical d ...

in which the

analyte An analyte, component (in clinical chemistry), titrand (in titrations), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The remainder of the sample is called the matrix. The procedure ...

solution flows relative to a

working electrode Working may refer to: * Work (human activity), intentional activity people perform to support themselves, others, or the community Arts and media * ''Working'' (musical), a 1978 musical * ''Working'' (TV series), an American sitcom * ''Workin ...

. In many voltammetry techniques, the solution is intentionally left still to allow

diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

-controlled

mass transfer Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction, or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtra ...

. When a solution is made to flow, through stirring or some other physical mechanism, it is very important to the technique to achieve a very controlled

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

or mass transfer in order to obtain predictable results. These methods are types of

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference and identifiable chemical change. These reactions involve electrons moving via an electronically conducting phase (typi ...

studies which use

potentiostat A potentiostat is the electronic hardware required to control a three electrode cell and run most electroanalytical experiments. A ''Bipotentiostat'' and ''polypotentiostat'' are potentiostats capable of controlling two working electrodes and ...

s to investigate

reaction mechanisms Reaction may refer to a process or to a response (disambiguation), response to an action, event, or exposure. Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law *Chain reaction (disa ...

related to

redox Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...

chemistry among other chemical phenomenon.Douglas A. Skoog, F. James Holler, Timothy A. Nieman Principles of Instrumental Analysis. Harcourt Brace College Publishers, 1998 .

Structure

Most experiments involve a

three electrode setup 3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious and cultural significance in many societies ...

but the setup configuration varies widely. All cell configurations create a

laminar flow Laminar flow () is the property of fluid particles in fluid dynamics to follow smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral m ...

of solution across the

(s) producing a steady-state current determined by solution flow rather than

. The resulting current can be mathematically predicted and modeled. Among the most common hydrodynamic setup involves the working electrodes rotating to create a laminar flow of solution across the electrode surface. Both

rotating disk electrode In analytical chemistry, a rotating disk electrode (RDE) is a working electrode used in three-electrode systems for hydrodynamic voltammetry.Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications. New York: John Wiley & ...

s (RDE) and

rotating ring-disk electrode In analytical chemistry, a rotating ring-disk electrode (RRDE) is a double working electrode used in hydrodynamic voltammetry, very similar to a rotating disk electrode (RDE). The electrode rotates during experiments inducing a flux of analyte ...

s (RRDE) are examples where the working electrode rotates. Other configurations, such as flow cells, use pumps to direct solution at or across the working electrode(s).

Distinction

Hydrodynamic techniques are distinct from still and unstirred experiments such as

cyclic voltammetry In electrochemistry, cyclic voltammetry (CV) is a type of voltammetric measurement where the potential of the working electrode is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is reached in a CV expe ...

where the steady-state current is limited by the diffusion of substrate. Experiments are not however limited to

linear sweep voltammetry In analytical chemistry, linear sweep voltammetry is a method of voltammetry where the current at a working electrode is measured while the potential between the working electrode and a reference electrode is swept linearly in time. Oxidation or ...

. The configuration of many cells takes the substrate from one working electrode across another, RRDE for example. The potential of one electrode can be varied as the other is held constant or varied. The flow rate can also be varied to adjust the temporal gap the substrates experiences between working electrodes.

References

{{Electroanalytical Electroanalytical methods

Structure

Distinction

See also

References