The ion adsorption properties of muscovite mica were exploited to prepare higher resolution alpha-spectroscopy samples of 242Pu. The samples prepared by our method are compared to those prepared using electrodeposition methods in terms of their energy resolution. The mica adsorption method results in significant increases in energy resolution vs. that of electrodeposition. Muscovite surface adsorption properties of the mica allow for monolayer adsorption of plutonium thus minimizing energy attenuation and maximizing energy resolution of the resulting spectra. The mica adsorption method allows for simplified preparation of higher-resolution alpha-spectroscopy samples useful for the isotopic analysis of alpha-emitting radionuclides.