This work describes a microgravimetric study of the charge compensation process in different supporting electrolyte solutions of propylene carbonate or acetonitrile for a polyaniline derivative, poly (aniline-co-N-propane sulfonic acid aniline), PAPSAH. The viscoelastic properties of thin PAPSAH films were investigated using an electroacoustic impedance technique. These results demonstrate that the film behaves rigidly, validating the use of the Sauerbrey equation for mass measurements with the electrochemical quartz crystal microbalance (EQCM). Both cation and anion participation in the charge compensation process were studied using cyclic voltammetry and EQCM measurements. On a molar basis, the cation and anion contributions during the redox process for thin films of this material are roughly 50% each in Li+-containing supporting electrolytes. The cation and anion participation during the redox process increase in the following order: tetrabutylammonium < Na+ < Li+ and ClO4- = AsF6-, respectively. The significance of these results for applications of self-doped polyaniline derivatives in nonaqueous media is discussed.