Devices for detecting particle sizes and distributions using focused
light scattering techniques, by passing a sample through a focused beam of light, are disclosed. In one embodiment, the devices include one or more lasers, whose light is focused into a
narrow beam and into a
flow cell, and dispersions are passed through the
flow cell using hydrodynamic sample injection. In another embodiment, a plurality of lasers is used, optionally with hydrodynamic sample injection. Particles pass through and scatter the light. The
scattered light is then detected using scatter and
extinction detectors, and, optionally,
fluorescence detectors, and the number and size of the particles is determined. Particles in the size range of 0.1 to 10 μm can be measured. Using the device, significantly smaller particles can be detected than if techniques such as EQELS,
flow cytometry, and other conventional devices for measuring
biological particles.