The most important applications for DLS are characterization of proteins, polymers, micelles, and other submicron particles, which are suspended/dissolved in a medium. Particle size distribution, which is usually intensity-based but can be converted to a volume- and number-based distributionĭLS devices on the market usually comply to ISO 22412, which makes DLS a suitable technique for highly regulated industries.It’s defined via the Stokes-Einstein equation:.The hydrodynamic diameter (HDD) is the diameter of a sphere, which diffuses with the same speed (translational diffusion coefficient D) as the particle in the same fluid under the same conditions.The most important measurement results that can be obtained from a DLS measurement are: They’re then converted to particle size and particle size distribution via the Stokes-Einstein equation, which assumes spherical particles. The scattered light from different particles in the sample interferes and causes intensity fluctuations that are measured. With this technology, it’s possible to determine sizes from a few nanometers to the micrometer range). When the beam of a laser light hits the suspended particles, it’s scattered in all directions (Rayleigh scattering). Smaller particles move faster, while larger ones move more slowly. It’s based on the Brownian motion of particles, which describes the random motion of particles suspended in a liquid or gas resulting from collision with other molecules in the surroundings. Sampling errors are the largest source of variation in any particle sizing experiment, especially for samples of large particles.ĭynamic light scattering (DLS), also called photon correlation spectroscopy (PCS), is an established and precise measurement method for characterizing particle size in suspensions and emulsions. The user needs to analyze a representative sample of the bulk material. One of the main problems is proper sampling. But there are also limitations and disadvantages. In addition, this method has a high degree of accuracy and repeatability, making it a suitable particle sizing method for quality control. They’re easy to perform, for example, and a variety of different samples, whether liquid or dry, can be measured. Laser diffraction measurements have various advantages over other techniques. Usually, laser diffraction measurements also comply to ISO 13320 in order to ensure that they can be used in strictly regulated industries (e.g., the pharmaceutical or food industry). D, mean volume diameter (De Brouckere Mean Diameter)įor laser diffraction results, a recalculation of the volume-based distribution to a surface- and number-based one is possible in order to extract even more information about the particle size distribution and to compare it with other measurement techniques.Important measurement results that can be calculated from the particle size distribution are: The most common and default weighting model is volume based, which means the particle’s contribution relates to its volume equivalent to mass for constant density.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |