Dynamic Light Scattering Measurements on Latex Standards with the Litesizer 500

Dynamic light scattering (DLS) is used to measure the sizeof small particles in suspension and of macromolecules insolution. When light is passed through such a sample, theparticles scatter the light. Because the particles areconstantly moving, the scattering intensity in any onedirection fluctuates according to the particles' velocity.Since a particle's velocity depends on its size, the particlesize in a given sample can be derived from DLSmeasurements.

Since DLS is an absolute technique, the measurements donot require calibration. However, it is still important to carryout measurements on well-characterized standardsamples in order to verify that the device is functioningproperly, and to validate the user's measurementprocedures. Polymer latex spheres are very useful formaking such checks because they are readily available asmono-sized dispersions of highly spherical particles, theirhydrodynamic size has been thoroughly characterized andwidely reported, and the dispersions are usually stable atroom temperature for several months.

In this Application Report, we use polymer latex spheresranging from 22 nm to 9200 nm in diameter to verify theDLS performance of the Litesizer™ 500, using bothside-scattering (90°) and back-scattering (175°) detection.

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