The non-uniformity of particle charges is an important problem in electrical methods for producing standard aerosols, imposing strict limitations on the usability of the obtained standard aerosols. This paper examines the quality of the electrically separated aerosols, that is, the percent of singly charged particles among all charged particles in the separated aerosol. A model for the electrical separation process was developed and the separated aerosol quality was calculated as a function of parameters of the aerosol generation process. Theoretical results show that with particle sizes d >> 40 nm, a high quality standard aerosol is difficult to obtain using the common methods. Also a non-monotonic decline in quality with increasing particle size was observed, with the separated aerosol quality having a distinct minimum around the particle diameter of 200 nm. In addition to the theoretical calculations, a small number of experiments were carried out giving results (described in the appendix), which, in general, support the theoretical findings.