Chloride analysis of single aerosol particles

A selective and quantitative method for the determination of water-soluble chloride in single aerosols has been developed for the μm and sub-μm range. The method, a so-called spot test, is based on the chemical reaction between chloride and silver nitrate. The chloride-containing particles are collected on a glass slide which is coated with silver nitrate dispersed in a gelatin film. In a closed thermostatic chamber the soluble chloride salts dissolve at a relative humidity of 100% and react with silver nitrate. The inslouble reaction product AgCl exhibits characteristic precipitation rings around the particles which can be observed by light or scanning electron microscopy. A correlation between the chloride mass of a single particle and its corresponding reaction ring, the so-called halo, has been established.