The fast and high-sensitivity technique has been developed for determining the concentration of aerosol forming substances in the atmosphere. The technique makes it possible to determine the concentration of non-volatile admixtures starting from 1 ng/m3. It takes about 4 minutes to make single measurement. In combination with the measurement of microphysical properties of atmospheric aerosol the technique allows one to estimate the resultant rate of the processes of formation of the aerosol forming substances in the atmosphere and to determine their basic physicochemical properties, in particular, the coefficient of molecular diffusion. The new experimental setup was examined under laboratory and field conditions.