Anson plot

Fig. 4 Chronocoulometry (a) typical charge response (b) Anson plot for a double-step chronocoulometric experiment.

Such a charge measurement procedure, known as chronocoulometry, is particularly useful for measuring the quantity of adsorbed reactants (because of the ability to separate the charges produced by the adsorbed and solution species). A plot of the charge (0 versus /12, known as an Anson plot, yields an intercept at t = 0 that corresponds to the sum of 0 and Qt (Fig. 3.2). The former can be estimated by subtracting the intercept obtained in an identical experiment carried out in the blank solution. 

Figure 3.2 Chronocoulometric experiment Anson plot of Q versus t1 2.

Thus, a plot of Q vs. Vi for the first, and Q YS. Vi — Vt for the second part of the curve results in two straight lines ( Anson plot [26]). Adsorption of redox active species can simply be diagnosed... 

Chronoamperometry, Chronocoulometry, and Chronopotentiometry, Fig. 4 Chronocoulometric charge versus (time) plot in the absence (1) and in the presence (2) of adsorption. The dashed, horiztmtal line represents the charge response in the absence of reactant. This representation is sometimes referred to as Anson plot in the literature... 

Chronocoulometry is a technique related to chronoamperometry in which a potential step is applied to the deposited polymer film and the integrated current response i.e., the charge is monitored as a function of time. It is customary to plot charge q versus t, which defines an Anson plot. The chronocoulometric response for a layer of finite thickness L is given by the following expression ... 

FIGURE 1.51. Anson plot for chronocoulometry, plot calculated from Eqn. 273. Same date as in Fig. 1.47. 

FIGURE 1.52. (a) Normalized modified Anson plot for chronocoulometry in a finite-diffusion space. The curve is calculated from Eqn. 275. (b) Schematic of T versus t plot to obtain Dcr-... 

The Wilhelmy plate technique has also been modified to measure surface or interfacial tensions under special conditions. By way of illustration we mention the application to the measurement of electrocapillanj curves for the mercuiy-aqueous electrolyte solution interface by Montgomery and Anson ), extending earlier work by Smith ). Electrocapillary curves are plots of y as a function of the potential applied across the interface, which should be polarizable. In fig. II.3.48 we already gave a few such curves. Montgomery and Anson found that their curve in 10 2 M NaF agreed within 0.005 mN m- with data obtained using the maximum bubble pressure. 

Zagal, J.H., M.J. Aguirre, L. Basaez, J. Pavez, L. Padilla, and A. Toro-Labbe (1995). Possible explanations for the volcano-shaped plots for the electrocatalytic reduction of O2 on electrodes modified with N-4 macrocychcs. In RC. Anson, R.R. Adzic, and K. Kinoshita, Oxygen Electrochemistry. The Electrochemical Society Symposium Series 95-26, pp. 89-100. 

FIGURE 1.35. Plot of the modified Nemst equation y = iO (see Eqn. 183) for an electroactive polymer film when redox site interactions are taken into account. Data points are recorded for a poly(thionine) film. The dashed line is computed from Eqn. 197 (the Brown-Anson model) with given by Eqn. 199. The full line is obtained from the Albery-Colby model, with i given by Eqn. 218. A good agreement between experiment and theory is obtained using the Albery-Colby model for a = 4.67. 

Figure 7.3 Non-linear Arrhenius plots due to sequential reactions with change in rate limiting step as temperature is varied, (a) A simulated plot for a two step essentially irreversible reaction with activation energies of 50 and 150 kJ mole respectively, (b) Arrhenius plot of data from Anson (1992) of the average velocities of actin filaments moving on skeletal myosin (in vitro assays). A cubic curve is fitted through the data by linear least square.

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