F, Faraday constant

E0 Standard electrode potential, V R The gas constant F Faraday constant... 

CaMiytt. concentration of analyte n, number of electrons in electrode reaction Vf, flow rate F, Faraday constant D, diffusion coefficient A, area of electrode. 

R = gas constant T = temperature (K) n = charge of the ion being detected F = Faraday constant... 

The well-known equation i = 4nFDCr (i limiting current, n number of electrons implied in the electrochemical process, F Faraday constant, D diffusion coefficient, C electroactive specie concentration and r radius of the disk) describes the theoretical steady-state limiting currents of the disk UMEs. This equation is useful to determine the effective radius of a disk UME and to estimate diffusion coefficients. In this sense, the above-mentioned polished carbon disk UMEs have been characterised through the limiting currents obtained in solution with known parameters, i.e. ferrocyanide aqueous solutions (0.05 M and 2M KC1) [118]. The experimental limiting currents were fairly accurately described by this equation ( + 10%). When the effective radius is determined, this equation can be employed to obtain unknown diffusion coefficients. In this way, we have estimated the diffusion coefficients for /i-carotene in several aprotic solvents with different electrolytic concentrations [123]. 

Definition of terms a = diameter of inlet, A = electrode area, b = channel height, C = concentration (mM), F = Faraday constant, D = diffusion coefficient, v = kinematic viscosity, r = radius of tubular electrode, U = average volume flow rate, u = velocity (cm/s), n = number of electrons. Source Adapted from Ref. 84. 

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