Chronopotentiometric method

The simplest of the methods employing controlled current density is electrolysis at constant current density, in which the E-t dependence is measured (the galvanostatic or chronopotentiometric method). The instrumentation for this method is much less involved than for controlled-potential methods. The basic experimental arrangement for galvanostatic measurements is shown in Fig. 5.15, where a recording voltmeter or oscilloscope replaces the potentiometer. The theory of the simplest applications of this method to electrode processes was described in Section 5.4.1 (see Eqs 5.4.16 and 5.4.17). 

The better accuracy of current vs. potential or current vs. time measurements at controlled potential makes these methods preferable to the chronopotentiometric method. However, at controlled potential, the mathematical evaluation of the requisite relationships is more complex due to the difficult inverse transformation of the terms s 1/2 jF(s) and (s + ki) in jF (s), or the solution of the corresponding convolution... 

In the chronopotentiometric method the transition time is measured for constant current and the electrode area is calculated from the relation [Chapter 4, Eq. (4.17)] ... 

Alternating current chronopotentiometry) l7)T.Kambara. I.Tachi, JPhysChem 61, 1405-07 (1957) (Chronopotentiometry-stepwise potential-time curves for. arbitrary number of reducible species) 18)R.H.Adams et al, AnalChem30, 471-75 (1958) (Chronopotentiometric studies with solid electrodes) 19)P.J.EIving A.F.Krivis, AnalChem 30, 1648-52 (1958) (Anodic chronopotentiometry with a graphite electrode analytical applications) 20)J-D.Voorhies N.H.Furman, AnalChem 30, 1656-59 (1958) (Quantitative anodic chronopotentiometry with Pt electrode) 21)D.E.Dieball, UnivMicrofilms (Ann Arbor, Mich), Publ No 24553, 118pp Dissertation Abstr 18, 50-1 (1958) CA 52, 6051 (1958) (Evaluation of chronopotentiometric method of analysis) 22)Y.Takemori et al, ZPhysChem (Leipzig), Sonderheft, July 1958, 89 96 CA 53, 5952 (1959) (Chronopotentiometry. A... 

In the chronopotentiometric method, the quarter wave potentials are used and the corresponding function may be written as... 

Evaluation of chronopotentiometric method of analysis) 22)Y.Takemori et al, ZPhysChem (Leipzig), Sonderheft, July 1958, 89-96 CA 53, 5952 (1959) (Chronopotentiometry. A... 

A chronopotentiometric method for determination of amino derivatives of PAH is based on the high affinity of DNA for such compounds. In a cell consisting of a DNA-modified CPE, a reference SSCE and a Pt wire auxiliary electrode, an aqueous solution of the PAA is submitted to an accumulation period, during which the analytes are transferred to the working electrode by an intercalation mechanism, after which the solution is changed... 

Solution of the E Ci Scheme in Current Step (Chronopotentiometric) Methods... 

Fundamentals of Theory for Voltammetric and Chronopotentiometric Methods 485 For the forward step at constant current,... 

This case for the chronopotentiometric method was treated in Section 12.2.2, and the zones for pure diffusion behavior (DP) and pure kinetic behavior (KP) were derived in terms of the dimensionless kinetic parameter A (Table 12.3.1) DP, A < O.T, KP, A > 5 (Figure 12.2.1). These zones generally apply with the other techniques as well. 

Large differences between the interfacial properties of ds and ssDNAs observed earlier by capacitance measurements [10, 37] suggested that a.c. impedance measurements could be used to detect DNA hybridization on electrodes [433, 434] (Sect. 12.8.). A three-component ODN system on a gold electrode (involving avidin-biotin interactions) was used to detect specific DNA sequences by means of faradaic impedance spectroscopy [435]. Impedance spectroscopy does not seem, however, to be the most convenient method for the DNA biosensor faster and simpler voltam-metric or chronopotentiometric methods will probably be more convenient. Gon-ductivity of the perfect DNA, contrasting with a loss of conductivity in duplexes with mismatched bases, may be of use in... 

Fig. 27. Working curves for mechanism (chronopotentiometric method with current...

Fig. 28. Working curves for ECjrrE mechanism (chronopotentiometric method). (1) dependence of n pp (right-hand scale) on log(kfTtr) (2) dependence of (left-hand scale) on...

Chronopotentiometric methods were used to investigate the interdiffiision of Ag ions in melts. The data for 823 to 915C could be described by ... 

All these techniques have some uncertainties and chronopotentiometric method can be used accurately when the double layer charging process is negligible, that is for long transition time and high concentration 1eve1s. 

In connection with the above statements a next step has been made in the investigations, namely studying the influence of the Ce and Ce + ions as components of the corrosion medium (O.IN H2SO4) on the anodic behavior of stainless steel. These investigations were provoked by the observed occurrence of cathodic depolarization reaction of Ce + (CeCb) reduction, as a result of which the surface concentration of cerium is decreasing and theoretically it should approach zero value (Stoyanova et al., 2010). For this purpose an inverse experiment was carried out at different concentrations of Ce + ions in the corrosion medium we monitored the changes in the stationary corrosion potential of the thermally treated steel by the chronopotentiometric method. The aim of this experiment was to prove the occurrence of a reversible reaction of reduction of Ce + Ce +- e <-> Ce , (instead of the reaction of hydrogen depolarization), which in its turn creates also the option to form a film (chemically insoluble) of cerium hydroxides/oxides on the active sections of the steel surface. 

Chronopotentiometric analytical methods have also found application in the field of food analysis. In this technique, the oxidation or reduction of species at a constant current is carried out, and the transition time is measured as the quantitative characteristic [29]. In this context, recent chronopotentiometric methods have been reported for histamine determination in foodstuffs. One of these methods was based on the oxidation of the amine at a planar gold disc electrode in the presence of electrogenerated chlorine which facilitates charge transfer between the analyte and the electrode surface. Well-defined signals were observed at +1.15 V in hydrochloric acid medium, giving rise to a linear calibration plot in the 2- 1(X) mg/1 concentration range with an LOD of 0.27 mg/1 histamine. The method was applied to the determination of histamine in fermented sausages [30]. The same authors used a mercury film electrode to develop a chronopotentiometric method for histamine in cheese [29]. 

In the beginning of the 1950s, the USSR government has decided to establish a number of so-called problem laboratories (here the less literal but better translation Special Research Laboratory will be used) to improve the scientific research. On suggestion of academician 1. P. Alimarin, three centers for the development of voltammetric and chronopotentiometric methods were founded at Moscow State University (MSU), at the Vernadsky Institute of Geochemistry and Analytical Chemistry, and in Tomsk at Polytechnic Institute. In Moscow this research was... 

By various electrochemical methods we investigated adsorption phenomena in the riboflavin—dihydroriboflavin system. The chronopotentiometric method gave relationships between the surface concentration of the redox-system components and the potential of the electrode, and these were then compared with the polarographic curves [27]. The capacity curves (chronopotentiograms) were recorded on a suspended mercury drop at such current densities that the contribution of diffusion was negligibly small. In order to determine differences in the adsorption behavior of the riboflavin — dihydroriboflavin systems under conditions with and without a... 

The dependence of the surface concentration of riboflavin and dihydroriboflavin on their volume concentrations was also investigated by the chronopotentiometric method. It was found that the experimental curves readily satisfied the equation of the Langmuir isotherm with B = 3.4 10 liter/mole for riboflavin (at +0.10 V, vs. s.c.e.) and B= 2.4 10 liter/molefor dihydroriboflavin (at—0.5 V). The values are 1.25 10" and 1.82 10 mole/cm, respectively, for the oxidized and reduced forms [27]. 

The calculations were made for the half-wave potential of the prewave and of the main wave. The values obtained for S(9ri/0ci)Ci were compared with the results from adsorption measurements made by the chronopotentiometric method, by which means it was possible to determine the validity of the approximation. Since the adsorption of riboflavin and dihydroriboflavin is described by the Langmuir isotherm, by differentiating the isotherm equation we obtain ... 

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