Critical analysis of the impedance method for the evaluation of permittivity and conductivity of the plasma membrane

We report a critical analysis of a typical method of dielectric spectroscop y consisting in impedance measurements as a function of frequency. Experime ntal data were obtained by measuring impedance on human erythrocyte suspens ions. Since these cells do not have a nucleus they represent an ideal mater ial for the application of the well established single shell model. This al lows the evaluation of permittivity and conductivity of the plasma membrane . We discuss the influence on the reliability of results of parameters such as fractional volume, average dimensions and membrane thickness of cells.