Application of a multistep condensation nuclei counter as a detector for particle surface composition

To obtain information on the chemical nature and physical properties of particle surface, a method has been developed, which is based on the influence of particle surface on the condensation process. An electrostatic classifier is used to generate a monodisperse aerosol of known electrical mobility diameter. The Kelvin-equivalent diameter of this aerosol is then determined using a simple Nolan-Pollak-type condensation nuclei counter which has been modified to run automatically through a series of different water vapour supersaturations. First applications on coated and uncoated particles (e.g. H₂SO₄ n-HD vs H₂SO₄ of the same electrical mobility diameter show that the water condensation process reacts rather sensitive to the changed surface composition.