NUMERICAL-ANALYSIS OF THE INFLUENCE OF EXPERIMENTAL CONDITIONS ON THE ACCURACY OF DIELECTRIC PARAMETERS DERIVED FROM ELECTROROTATION MEASUREMENTS

Two approaches were used to analyze the accuracy with which the dielectric properties of a particle may be deduced from experimental electrorotation (ROT) data. Firstly, the dependence of ROT spectra on individual dielectric parameters was assessed by a sensitivity analysis. Secondly, simulated rotational spectra were used to investigate the effects of typical experimental errors on the confidence levels with which dielectric parameters can be derived from ROT data by parameter optimization procedures. The focus was on the single-shell, spherical dielectric model most widely applied for analyzing cellular dielectric properties, but the methods are applicable to any model. The following conclusions were drawn: (1) ROT spectra show different sensitivities to different parameters, resulting in different accuracy levels when these parameters are derived by optimization; (2) each rotation peak in a ROT spectrum can only be used to determine uniquely two parameters; (3) unless the experimental field strength and frictional forces are precisely known, the scaling factor in the ROT spectrum should not be fixed; instead, the ROT optimization should either be constrained by additional experimental information or determination of the membrane conductance should be sacrificed; (4) experimental conditions should be chosen carefully to maximize the sensitivity of the ROT spectrum to the parameters of interest; (5) ROT spectra should be taken to as high a frequency as possible to allow accurate determinations of interior parameters; (6) the analysis techniques used here can be applied to other models and experimental conditions in order to substantiate the accuracy level of parameters in other applications.