A technique known as Dynamic Light Scattering (DLS) is used for the measurement of particle sizes for a given sample. The Zetasizer Nano ZS uses a laser to illuminate the particles in a given sample to produce and observe the speckle patterns produced by the particles. A sensitive avalanche photodiode detector detects the scattering intensity at a specific angle which fluctuate with time. The changes in intensity as detected by the detector are analysed with a digital autocorrelator which generates a correlation function to generate a curve. By using this curve, the size and the size distribution for particles in a given sample can be analysed.
During the dispersion procedure for the particle size analysis, the samples are added to a closed circuit filled with an appropriate liquid. This mixture is then pumped continuously through a measuring cell which enables the measuring of particle size following illumination by the lasers.