Abstract: An electrospray nebulizer generates an aerosol comprised of submicrometer droplets substantially uniform in size. A liquid sample is supplied at a controlled rate to a capillary needle of the nebulizer, and droplets are formed due to an electrical field in the region about the needle discharge. The tendency of the droplets to disintegrate due to Coulomb forces is counteracted by sources of ionizing radiation within the nebulizer. The ions reduce the charge in each droplet while solvent evaporation reduces the diameter of the droplet. To further ensure against Coulomb disintegration, a controlled air sheath is introduced to the nebulizer for transporting droplets more rapidly downstream. Optionally, solvent vapor can be introduced into the air flow to reduce the rate of solvent evaporation within the nebulizer, and ions can be added to the air flow upstream of the needle discharge.

Abstract: An apparatus and method for determining the concentration of macromolecules and colloids in a liquid sample is disclosed. The apparatus preferably includes an electrospray apparatus 16 for forming droplets from the sample. Liquid is removed from the droplets by drying in the electrospray apparatus 16, thereby forming an aerosol. The aerosol of a size greater than a predetermined size is then counted by a condensation nucleus counter 52. In this manner, the target macromolecules and colloids are counted. This apparatus is capable of detecting very small macromolecules and colloids of a wide range of materials in a liquid, for example, individual molecules having molecular weight as small as 10,000.