Dual-beam, light-scattering interferometry for simultaneous measurements of droplet-size and velocity distributions of aerosols from commonly used nebulizers

Dual-beam, light-scattering interferometry is introduced for simultaneous measurement of droplet-size and droplet-velocity distributions. The technique was tested in the characterization of tertiary aerosols produced by five nebulization systems (a pneumatic, an ultrasonic, and three frit-type nebulizers) used in inductively coupled plasma spectrometry. In general, the Sauter mean diameter (D{sub 3,2}) of tertiary aerosol produced by frit-type nebulizer was smaller than those of ultrasonic and pneumatic nebulizers. At higher injector gas flow, D{sub 3,2} was reduced for the pneumatic nebulizer but was increased for the ultrasonic nebulizer. At the same injector gas flow rate, droplets move slightly faster if helium is used as injector gas instead of argon. For all practical purposes, the D{sub 3,2} values measured for tertiary aerosol with dual-beam, light-scattering interferometry are comparable to the same data obtained by laser Fraunhofer diffraction. Compared to laser Fraunhofer diffraction, the proposed technique possesses two unique advantages. First, droplet velocity distribution can be measured. Second, spatially resolved information on droplet-size and velocity distributions may be obtained directly and rapidly.