Polarography constant current

Fujinaga, T., Constant-Current Polarography and Chronopotentio-metry at the Dropping Mercury Electrode, in Progress in Polarography (P. Zuman, I. M. Kolthoff, editors), Vol. 1, p. 201, Interscience, New York (1962). 

Contrary to potentiometric methods that operate under null current conditions, other electrochemical methods impose an external energy source on the sample to induce chemical reactions that would not otherwise spontaneously occur. It is thus possible to measure all sorts of ions and organic compounds that can either be reduced or oxidised electrochemically. Polarography, the best known of voltammetric methods, is still a competitive technique for certain determinations, even though it is outclassed in its present form. It is sometimes an alternative to atomic absorption methods. A second group of methods, such as coulometry, is based on constant current. Electrochemical sensors and their use as chromatographic detectors open new areas of application for this arsenal of techniques. 

The electrochemical behavior itself 5(6)-nitrobenzimidazole is investigated depending on media pH by classical polarography [992-994], constantly current, and variable current [995, 996], The reduction 5(6)-nitro-2-arylbenzimidazoles is carried out in DMF and H20/DMF media [997], The polarography was utilized in a study of the influence of 5(6)-nitrobenzimidazole on corrosion-electrochemical behavior of chromos steel [998],... 

Ostatna, V., Uslu, B., Dogan, B., Ozkan, S., Palecek, E. (2006). Native and denatured bovine serum albumin d.c. polarography, stripping voltammetry and constant current chronopotentiometry. 7 ZecfraawaZ C/zem 593, 172-178. 

Reversibility is not an absolute property in electrochemistry. It depends on the mutual ratio of the electrochemical time constant and the charge-transfer reaction rate. In direct current polarography the method s time constant is given by the drop time, the time available for the establishment of equilibrium, which can be varied only over a limited interval. Electrode reactions with charge-transfer control... 

Stability constants for many olefin complexes are currently known/ A variety of experimental methods are used to determine these constants potentiometry, polarography, thermometric titration, and others/... 

As described above, useful information is available from electrochemical measurements of CD systems. Since CD is a large macrocyclic compound, incorporation of small guest molecule in the bulky CD makes the apparent diffusivity of guest lower. Taking adsvantage of this phenomenon the formation constant of inclusion complex can be easily determined by quantitative treatment of the variation of peak current (CV) or diffusion current (polarography) on the CD concentration in the electrolyte solution. 

Delahay, R and Vielstich, W. (1955) Kinetics of the dissociation of weak acids and bases - Application of polarography and voltammetry at constant current. /. Am. 

Normal-pulse voltammetry consists of a series of pulses of increasing amplitude applied to successive drops at a preselected time near the end of each drop lifetime (4). Such a normal-pulse train is shown in Figure 3-4. Between the pidses, the electrode is kept at a constant (base) potential at which no reaction of the analyte occurs. The amplitude of the pulse increases linearly with each drop. The current is measured about 40 ms after the pulse is applied, at which time the contribution of the charging current is nearly zero. In addition, because of the short pulse duration, the diffusion layer is thinner than that in DC polarography (i.e., there is larger flux of... 

However, in contrast to the condition of a constant potential and current sampling in pulse polarography, which yields36 the Cottrell equation ... 

Fig. 4.6. Method for determining the concentration of residual impurities, [Impjj jjj., in a reaction mixture if the impurity is a catalyst or co-catalyst. The observed variable x can be peak-height h for a GLC method, absorbance A for spectroscopy, conductivity k for conductimetry, current i for polarography, or rate constant k for kinetics, etc.

---