Fourier analysis, electrochemical impedance

Garland JE, Pettit CM, Roy D (2004) Analysis of experimental constraints and variables for time resolved detection of Fourier transform electrochemical impedance... 

Recently, Darowicki [29, 30] has presented a new mode of electrochemical impedance measurements. This method employed a short time Fourier transformation to impedance evaluation. The digital harmonic analysis of cadmium-ion reduction on mercury electrode was presented [31]. A modern concept in nonstationary electrochemical impedance spectroscopy theory and experimental approach was described [32]. The new investigation method allows determination of the dependence of complex impedance versus potential [32] and time [33]. The reduction of cadmium on DM E was chosen to present the possibility of these techniques. Figure 2 illustrates the change of impedance for the Cd(II) reduction on the hanging drop mercury electrode obtained for the scan rate 10 mV s k... 

Electrochemical impedance spectroscopy provides a sensitive means for characterizing the structure and electrical properties of the surface-bound membranes. The results from impedance analysis are consistent with a single biomembrane-mimetic structure being assembled on metal and semiconductor electrode surfaces. The structures formed by detergent dialysis may consist of a hydrophobic alkyl layer as one leaflet of a bilayer and the lipid deposited by dialysis as the other. Proteins surrounded by a bound lipid layer may simultaneously incorporate into pores in the alkylsilane layer by hydrophobic interactions during deposition of the lipid layer. This model is further supported by the composition of the surface-bound membranes and by Fourier transform infrared analyses (9). 

In the present state-of-the-art equipment, it is possible to measure and plot the electrochemical impedance automatically. Electronic circuitry is designed to generate the frequency sweep of a desired resolution over the range of interest. The generator can be programmed to sweep from a maximum to a minimum frequency in a number of required frequency steps. The commonly used modem equipment AC impedance measurement techniques can be subdivided into two main groups - single sine (lock-in amplification and frequency response analysis) and multiple sine techniques such as fast Fourier transforms (FFT). 

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