Single Particle Light Interaction Methods

Individual particles have been measured with light for many years. The measurement of the particle size is established by: (1) the determination of the scattered light of the particle, (2) the measurement of the amount of light extinction caused by the particle presence, (3) the measurement of the residence time during motion through a defined distance, or (4) by particle velocity.

Many commercial instruments are available, which vary in optical design, light source type, and means, how the particles are presented to the light.

Instruments using light scattering cover a size range of particles of 50nm to about 10µm (liquid-borne) or 20µm (gas-borne), while instruments using light extinction mainly address liquid borne particles from 1µm to the mm size range. The size range capability of any single instrument is typically 50:1. International standards are currently under development [ISO 13323-1:2000 Determination of particle size distribution - Single-particle light interaction methods - Part 1: Light interaction considerations; ISO/DIS 21501-2 Determination of particle size distribution - Single particle light-interaction methods - Part 2: Light-scattering liquid-borne particle counter, ISO/DIS 21501-3; Part 3: Light-extinction liquid-borne particle counter; ISO/DIS 21501-4 Part 4: Light-scattering airborne particle counter for clean spaces].

Instruments using the residence time, as e.g. the aerodynamic particle sizers, or the particle velocity as used by the phase Doppler particle analyzers, measure the particle size primarily basing on the aerodynamic diameter.

Small Angle X-Ray Scattering ...