Poisoning effects on anode by three inorganic impurities on the performance of a solid oxide fuel cell were tested, analyzed and compared by applying electrochemical impedance spectroscopy (EIS) and equivalent circuit modeling (ECM). A series impedance subtraction method was applied on the tested cells to account for only the degradation occurring in the cell anode due to impurities. This approach provided an alternative way to understand changes occurring in one particular electrode in the cell and identify the effect caused by the corresponding change in fuel conditions, provided other conditions remained same. Due to the fact that the respective SOFC electrodes and electrolyte were connected in series in an electrochemical circuit, cell performance change can be attributed to the anode in this approach. Degradation of the cell performance caused by inorganic impurities was characterized by measuring EIS spectra at a constant current density of 0.3 A cm^-2 for a diesel fuel reformate blend. The concentrations of impurities were selected in accordance with the levels expected after commercial biogas or diesel fuel cleaning processes. Critical electrochemical processes and degradation mechanisms which affect cell performance were identified and quantified. The impurities tested were sulfur, chlorine and siloxane at various ppb/ppm levels over a time period of 200-300 h. Sulfur and siloxane caused the most prominent degradation and the associated best fit electrochemical cell parameters, Gerischer and Warburg elements, were applied respectively for better understanding of the degradation processes. Degradation due to chlorine mainly occurred at the high frequency region of the spectrum which dominated the charge transfer processes in the cell. We have demonstrated that such an approach can help in generating finger-print spectra for a cell poisoned by a specific impurity or a combination of various impurities under different operating conditions.