Alternating-current polarography

Virtually any electrochemical technique may be used for either analytical or mechanistic (our focus) studies. The merits and limitations of each technique and the information that can be gleaned are discussed for direct-current (d.c.) polarography, pulse polarography, alternating-current (a.c.) polarography and cyclic voltammetry. Con-trolled-potential coulometry is technically not a voltammetric technique (there is no variation of potential), and this technique is considered in 12.3.5. 

Cyclic voltammetry Square-wave voltammetry Staircase voltammetry Linear-sweep voltammetry Fast cyclic voltammetry Rotating disc voltammetry Stripping voltammetry Hydrodynamic voltammetry Direct current (d.c.) polarography Alternating current (a.c.) polarography Pulse polarography... 

Clearly, with the apparatus described above we are dealing with direct current, and the technique as thus carried out is termed conventional d.c. polarography to distinguish it from various modifications (see later) and from the use of alternating current (a.c. polarography). 

B. Breyer and H Bauer, Alternating Current Polarography and Tensammetry, Wiley-Interscience, New York, 1963. 

Metallic (Cd, Zn, Ba) stearates Polymers Alternating current polarography... 

B. Breyer and H. H. Bauer, Alternating Current Polarography and Tensammetry, Interscience, New York, 1963 see also Z. Galus, Fundamentals of Electrochemical Analysis, Ellis Horwood, Chichester, 1976, p. 503-504, and H. Jehring, J. Electroanal. Chem., 20 (1969) 33 and 21 (1969) 77. 

Nevertheless, the mid-peak potentials determined by cyclic voltammetry and other characteristic potentials obtained by different electroanalytical techniques (such as pulse, alternating current, or square wave voltammetries) supply valuable information on the behavior of the redox systems. In fact, for the majority of redox reactions, especially for the novel systems, we have only these values. (The cyclic voltammetry almost entirely replaced the polarography which has been used for six decades from 1920. However, the abundant data, especially the half-wave potentials, 1/2, are still very useful sources for providing information on the redox properties of different systems.)... 

Breyer, B., and H. Bauer Alternating Current Polarography and Tensammetry. New York Interscience Publ. 1963. 

The oxidation-reduction behavior, ascertained by direct current (conventional) polarography, and its dependence on pH in aqueous solution of the [P2Mo18062] 6, [As2Moi8062]-6, and [P2Wi8062]-6 anions may be found in Refs.1S9 161>. The polarographic behavior of the dimeric 9-molybdophosphate anion of (NH4)6 [P2Moi 8062] was examined by cyclic voltammetry and alternating current... 

ACP — Acronym for alternating current polarography. -> polarography, and subentry AC polarography. 

Kinetic parameters of dimerization can be determined by polarography, -> chronoamperometry, -> linear potential scan and -> convolution voltammetry, -> rotating disc voltammetry, and alternating current sinusoidal polarography. See also -> association. 

Faradaic rectification — When the electrode potential of the working - electrode is modulated with a sinusoidal -> alternating current the mean potential is shifted from the DC value by a small increment in many cases when the AC modulation is sufficiently large. This effect has been named faradaic rectification, it is caused by the nonlinearity of the electrode response, in particular the variation of current with electrode potential [i]. A theoretical treatment for an electrode in contact with a solution containing a redox system has been provided [ii]. It was extended to reactions where one reactant is present in its element form dissolved in the liquid metallic phase (e.g., Cd2+ + 2e -> Cd(Hg)) [iii]. An improved evaluation technique has been proposed [iv], and some inherent problems have been reviewed [v]. A variant of this method applied to -> polarography has been described [vi]. Second and higher harmonics in - AC voltammetry (polarography) [vii] also arise from this nonlinearity, and hence these techniques also have some characteristics that resemble those found in - faradaic rectification voltammetry. 

Peak height (in -> voltammetry) — It is the maximum current in - linear scan voltammetry, -> cyclic voltammetry, - staircase voltammetry, - differential staircase voltammetry, -> alternating current polarography... 

In alternating current polarography of diffusion-controlled, reversible -> electrode reaction, the peak current is given by the equation [ii] ... 

Refs. [i] Bond AM (1980) Modern polarographic methods in analyti-calchemistry. MarcelDekker, New York [ii] GalusZ(1994) Fundamentals of electrochemical analysis, 2nd edn. Ellis Horwood, New York, Polish Scientific Publisher PWN, Warsaw [Hi] BreyerB, Bauer HH (1963) Alternating current polarography and tensammetry. Interscience, New York [iv] Bard AJ, Faulkner LR (2001) Electrochemical methods, Wiley, New York, pp 388-396 [v] Smith DE (1966) Electroanalytical chemistry. In Bard AJ, ed, Marcel Dekker, New York, vol. 1, chap 1... 

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