O. Kievit et al., THE ONLINE CHEMICAL-ANALYSIS OF SINGLE PARTICLES USING AEROSOL BEAMS AND TIME-OF-FLIGHT MASS-SPECTROMETRY, Chemical engineering communications, 151, 1996, pp. 79-100
This paper describes an on-line instrument, capable of measuring the s
ize and chemical composition of single aerosol particles. Possible app
lications include monitoring aerosol reactors and studying atmospheric
chemistry. The main conclusion is that a working prototype has been b
uilt and tested. It uses a three stage vacuum system to generate an ae
rosol beam with a low divergence angle and a high transmittance. The p
ressure is reduced sufficiently to allow the application of a time-of-
flight mass analyzer. The aerosol beam is probed in the analysis secti
on by the focused beam of a low-power helium-neon laser. Every particl
e crossing the laser beam scatters light, which is detected by two pho
tomultiplier tubes, mounted at angles of 45 and 90 degrees. The signal
is stored when both detectors produce a pulse simultaneously, and thi
s event triggers the chemical analysis cycle. A pulsed Nd:YAG laser va
porizes the particle and generates ions, which are next analyzed by a
time-of-flight mass spectrometer. In this way combined information on
the size and the composition of the particle is obtained.