Cyclic voltammetry ohmic drop compensation

C. Amatore and C. Lefrou, New Concept for a Potentiostat for On-Line Ohmic Drop Compensation in Cyclic Voltammetry Above 300 kV s 1, J. Electroanal. Chem. 324 33-58 (1992). 

Minimization of time scale measurements Ultrafast undistorted cyclic voltammetry may be performed at ultramicroelectrodes using an ultrafast potentiostat allowing on-line ohmic drop compensation. 

Figure 2. Cyclic voltammetry of anthracene, 10 mM, in acetonitrile, 0.6 M NEt4Bp4, at a gold disk (ro = 5 /im) ultramicroelectrode, with and without ohmic drop compensation, at different scan rates as indicated in kV.s on each set of curves. ...

The very exergonic proton transfers in eq.4 are extremely fast. However their rate constants could be determined experimentally if the standard oxidation potential of the arenes (eq.3) could be determined independently under the same experimental conditions (acetonitrile, 0.1 M ionic strength).2 26 jq achieve such measurements we resorted to fast scan cyclic voltammetry. Figure 3 illustrates the merit of on line ohmic drop compensation... 

Figure 4. On line ohmic drop compensated cyclic voltammetry of 2,5-di-(p-anisole)pyrylium perchlorate (3), 5 mM, in acetonitrile, 0.6 M NBU4BF4, at a 5 /xm radius gold disk ultramicroelectrode and a scan rate of 153 kV.s 20 C. (a) in the absence or (b) in the presence of 1. (c) Background subtracted voltammogram (b - a).

Amatore C, Maisonhaute E, Simoimeau G (2000) Ohmic drop compensation in cyclic voltammetry at scan rates in the megavolt per second range access to nanometric diffusion layers via transient electrochemistry. J Electroanal Chem 486 141-155. doi 10.1016/80022-0728(00)00131-5... 

Figure 6.1.4.2 Theoretical limitations on ultrafast cyclic voltammetry. The shaded area between the slanted lines represents the radius that a microdisk must have if the ohmic drop is to be less than 15 mV and distortions due to nonplanar diffusion account for less than 10% of the peak current, (a) Without iR drop compensation by positive feedback, and (b) with 90 and 99% ohmic drop compensation. The dotted area in (a) and (b) represent the regions where transport within the double layer affects the voltammetric response. Limits are indicative and correspond approximately to a 5-mM anthracene solution in acetonitrile, 0.3 M tetrafluoroborate as supporting electrolyte. [Reproduced by permission of Marcel Dekker from C. Amatore, Electrochemistry at Microelectrodes, I. Rubenstein, Ed., 1995, Chapter 4, p. 198.]...

Explain clearly why effective compensation of the ohmic drop is essential for diagnostic applications of cyclic voltammetry (e.g., estimating n from AEp). 

C. Amatore, C. Lefrou, and F. Pfltiger, On-Line Compensation of Ohmic Drop in Submicrosecond Time Resolved Cyclic Voltammetry at Ultramicroelectrodes, J. Electroanal. Chem. 270 43-59 (1989). 

Garreau, D. Hapiot, P. Saveant, J.M. (1990). Fast cyclic voltammetry at ultramicroelectrodes Current measurement and ohmic drop positive positive feedback compensation by means of current feedback operational amplifiers. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 281,73-83. 

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