General Principles of Aerosol Formation

The solution to be nebulized can be a one-off sample, pumped or drawn into the nebulizer at a rate varying from a few microliters per minute to several milliliters per minute. Alternatively, the supply of solution can be continuous, as when the nebulizer is placed on the end of a liquid chromatographic column. 

Many designs of nebulizer are commonly used in ICP/MS, but their construction and mode of operation can be collated into a small number of groups pneumatic, ultrasonic, thermospray, APCI, and electrospray. These different types are discussed in the following sections, which are followed by further sections on spray and desolvation chambers. 

For use in ICP/MS, an aerosol of analyte solution is produced in a nebulizer by mechanically breaking the solution into a spray of droplets and solvent vapor. This spray is swept along to the plasma flame by a flow of argon gas. The droplets have a range of diameters, depending on the type of nebulizer used. Frequently, before entering the torch, the aerosol first passes through a spray 

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Aerosols, like foams, emulsions, and dispersions, may be either advantageous or detrimental, depending on the situation. The previous discussion introduced some of the fundamental aspects of aerosol formation. Of equal or perhaps greater practical importance is the question of the suppression of aerosol formation, the destruction of unavoidable aerosols, or the controlled deposition of aerosols onto surfaces. Perhaps the best approach to solving such problems is through an understanding of some of the general principles involved in their stabilization and destruction. In that context, some of the mechanisms of destruction involved will be essentially the same as those for other colloidal systems flocculation and coalescence. 

FALLOUT (Radioactive . The term fallout generally has been used to refer to particulate mutter that is thrown into the atmosphere by a nuclear process of short time duration. Primary examples are nuclear weapon debris and effluents from a nuclear reactor excursion. The name fallout is applied both to matter that is aloll and to matter that has been deposited on the surface of the earfh. Depending on the conditions of formation, this material ranges in texture from an aerosol to granules uf considerable size. The aerodynamic principles governing tls deposition are the same as for any Other material of comparable physical nature that is thrown into the air. such as volcanic ash or particles from chimneys. Therefore, many of the principles learned in. studies of fallout from nuclear weapons can be applied lo studies of other particulate pollution in the atmosphere. 

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