marine science

Particle Size Analyser (PSA)

Laser Diffraction Particle Size Analyzer facility (CILAS-1180) has been installed in the division during 2006 to analyse the sediment samples for particle size distribution. Particle Size Analyzer is widely used method to characterize the sediment particles based on diffraction of a laser light source by the samples under analysis. The analyzer is used to determine the size distribution of a powder, a suspension or an emulsion, based on light diffraction. When a particle is lightened by a monochromatic source (laser source) a diffraction pattern, called Airy’s pattern, is obtained at the infinity. This diffraction pattern gives the light scattering intensity I, in function of the diffraction angle ?. It is composed of concentric rings. The distance between the different rings depends on the particle size. The analyzer can also be used to visualize the shape of the particle which is under suspension.

PSAThe instrument is capable of measuring dry and wet samples of particle size ranging from 0.04 ?m to 2500 µm. The facility is gaining importance from the conventional analysis of sieving and pippeting due to the cover of a wide range of grain sizes, small amount of samples, short time for analysis (5-10min. per sample), high repeatability and can analyze the non-dispersed samples. The facility has been opened to the public/academic institution on payment basis.

The preparation of the sample is the most important step when making a measurement. The accuracy for the measurement depends on sample preparation and extraction. One has to carefully define a method for extraction and sample preparation in order to obtain precise and reproducible results. For a measurement in dry mode, the sample should be first treated and then cone and quartered to represent an amount between 1 mg and 100 mg. In liquid mode representative of the powdered or liquid sample should be poured into the tanker.