Extension of the measurement model approach for deconvolution of underlying distributions for impedance measurements

Electrochemical impedance spectra frequently reveal the influence of distributions of activation or relaxation processes, but methods for extracting information concerning these distributions are not well developed, Complex non-linear weighted regression of Voigt elements was applied to synthetic impedance data to identify the influence of stochastic noise and incomplete frequency ranges on the ability to resolve the expected distribution. The method was also applied to analysis of impedance data for heat-separated human stratum corneum. Regression of a Voigt series was found to provide a convenient way to identify a distribution of relaxation time constants corresponding to a given experimental spectrum. While the presence of stochastic noise reduces the number of Voigt elements that can be resolved, the parameters trace the same profile for the distribution of time constants. The technique should be particularly useful for experimental systems for which no deterministic model is available. (C) 2002 Elsevier Science Ltd. All rights reserved.