Instrumentation, laser Doppler scattering

Recent development of laser-based instrumentation for electrophoretic mobility determination has made it possible to determine zeta potential of particles suspended in liquid media for systems that were difficult or impossible to study by classical techniques. These instruments measure electrophoretic mobilities by making direct velocity measurements of particles moving in an applied electric field by analyzing the Doppler shift of laser light scattered from the moving particles. Electrophoretic mobilities can then be converted into zeta potentials by use of standard equations 48-50),... [Pg.188]

Electrophoretic instruments for analysis of colloidal suspensions can be divided into two basic classes optical instruments for which the operator observes the migration of particles in a field using a microscope and laser-based instruments that measure the Doppler shift in the frequency of the scattered light from particles... [Pg.286]

Aerosols can be analysed using techniques that are based on the interactions between particles and light The examination of a scattered beam of light by a detector after hitting a particle is the basis for many optical instruments. For example, the number of scattered light pulses is a measure of particle number. Furthermore, the intensity and spatial scattering pattern can also be used for determination of particle size and particle shape, respectively. Optical methods are sensitive and easy to use. These methods are classified into four categories (1) optical particle counter, (2) laser diffractometer, (3) phase Doppler system and (4) intensity deconvolution system. [Pg.172]