Pulsed rotation voltammetry

A variant of SRV is pulsed rotation voltammetry (PRV) [48-50]. Here, the rotation rate of a RDE is switched between two well separated speeds... 

In hydrodynamic voltammetry the solution is stirred either by using a magnetic stir bar or by rotating the electrode. Because the solution is stirred, a dropping mercury electrode cannot be used and is replaced with a solid electrode. Both linear potential scans or potential pulses can be applied. 

Another type of polymeric structure is based macrocyclics or on stacks of macro-cyclic units. An exhaustive electrodynamic investigation of the polymer derived from yU.-oxo-(tetra-ferf-butylphthalocyaninato)germanium and of the monomer was carried out using CPE, CV, voltammetry by RDE, rotating ring-disk electrode and differential pulse... 

As the field of electrochemical kinetics may be relatively unfamiliar to some readers, it is important to realize that the rate of an electrochemical process is the current. In transient techniques such as cyclic and pulse voltammetry, the current typically consists of a nonfaradaic component derived from capacitive charging of the ionic medium near the electrode and a faradaic component that corresponds to electron transfer between the electrode and the reactant. In a steady-state technique such as rotating-disk voltammetry the current is purely faradaic. The faradaic current is often limited by the rate of diffusion of the reactant to the electrode, but it is also possible that electron transfer between the electrode and the molecules at the surface is the slow step. In this latter case one can define the rate constant as ... 

The absence of dimer radical cation formation by diphenyl selenide under the pulse radiolysis conditions is in contrast to bimolecular reactions believed to occur under electrochemical conditions/ In these experiments, a rotating disk electrode was used in combination with commutative voltammetry under anhydrous conditions. The results led to the conclusion that reversible one-electron oxidation is followed by disproportionation, then reaction of the resulting dication with diphenyl selenide or an external nucleophile, with the likely intermediacy of the dimer dication (Fig. 33). As expected, the dihydroxy selenane is formed when water is present. Based on the kinetics of the electrochemical reaction, the authors believe the diselenide dication, not the radical cation, to be the intermediate that reacts with the nucleophile. 

Takamura et al. have determined chlorpromazine by the use of differential pulse voltammetry incorporating rotating glassy-carbon disc electrodes [170]. The determination was carried out after pre-treatment of vitreous carbon by anodic oxidation for two minutes in 0.5 M phosphate buffer (pH 6.3) at 1.6 V vs. Ag/AgCl reference electrode. The determination was made with the use of 50 mV pulses at 2 seconds intervals, a rotation rate of 2500 rpm, and a scan rate of 5 mV/sec. 

Many of the electroanalytical techniques that are routinely employed in conventional solvents, such as, chronoamperometry, chronocoulometry, chronopotentiometry, coulometry, cyclic (stationary electrode) voltammetry, rotating electrode voltammetry, and pulse voltammetry, have also been applied to molten salts. Some of these techniques are discussed next with special attention to their employment in molten salts. References to noteworthy examples appearing in the literature are included. Background information about these techniques is available elsewhere in this book. 

Recent studies describe the use of cyclic voltammetry in conjunction with controlled-potential coulometry to study the oxidative reaction mechanisms of benzofuran derivatives [115] and bamipine hydrochloride [116]. The use of fast-scan cyclic voltammetry and linear sweep voltammetry to study the reduction kinetic and thermodynamic parameters of cefazolin and cefmetazole has also been described [117]. Determinations of vitamins have been studied with voltammetric techniques, such as differential pulse voltammetry for vitamin D3 with a rotating glassy carbon electrode [118,119], and cyclic voltammetry and square-wave adsorptive stripping voltammetry for vitamin K3 (menadione) [120]. 

Notes DP-ASV, differential-pulse anodic stripping voltammetry RDE-Au, rotating gold electrode HG-AAS, /tydride generation atomic absorption spectrometry FA AS, /lame atomic absorption spectrometry FI-CV-AAS, /low-injection cold-vapor atomic absorption spectrometry and HMDE, /tanging mercury drop electrode. 

Differential pulse voltammetry at rotated glassy carbon disk cathodes proved successful for the accurate determination of inor-... 

M. L. Landy, An evaluation of differential pulse anodic stripping voltammetry at a rotating glassy carbon electrode for the determination of cadmium, copper lead and zinc in Antarctic snow samples. Anal. Chim. Acta, 121 (1980), 39-49. 

Convective renewal. When normal pulse voltammetry is carried out in a convective system, as at a rotating disk, one can rely on stirring to renew the diffusion layer while the potential is held at E. This can be true even if the chemistry cannot be reversed electrolytically, as in the case where the species created in the pulse decays to an inactive product. The convection can also affect the current sampled in each pulse, so that the theoretical expectation based on diffusion theory is exceeded. However the error is often either irrelevant (as in analytical applications where calibration is possible) or fairly small (because a pulse of short... 

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