Application of a new graphical fitting approach for data analysis in electrochemical impedance spectroscopy

A new grahical method for analyzing impedance data presented in the complex plane plot is introduced. The advantage of our approach is that it can be employed easily with commonly available spreadsheet calculation software li ke Microsoft Excel, beneficial when no CNLS software is available. A semicircle in the complex plane plot is defined by three points of the ci rcumference. Knowing the trigonometric function, the radius, e.g., represen ting the bulk resistance of ion-selective membranes, can be calculated easi ly. The error of the data fit is determined by considering the standard dev iation of the data points referred to the fitted semicircle. The capacitanc e of the system under investigation can be calculated by plotting the real part of the impedance against the angular frequency. If the equivalent circ uit is known it is possible to obtain the value of the capacitor by employi ng the nonlinear least square method. The applicability and efficency of ou r method has been verified by analyzing networks and impedance spectra of i on-selective polymer matrix membranes. The results of our method were compa red with those obtained by applying the CNLS method.