Nanotechnology gives us the ability to study and manipulate matter at the molecular, atomic and sub-atomic level. It has a number of practical applications in the environmental, pharmaceutical, food, health, and beauty industries, to name just a few. One such application is laser diffraction, which allows analytical development scientists to accurately measure the size of particles in powders and liquids. This can be used for important quality control, testing and operational functions in fields such as pharmaceuticals.
Particle size analysis methods
Over the past twenty years, laser diffraction analysis has become the most important method to measure particle size. It is widely used for particle size determination for active pharmaceuticals (APIs), excipients, flyash, wastewater, and environmental emission samples. It can be used to measure the size of particles in liquid and powder samples, and has a wide dynamic range, from submicron to millimeters.
Analytical development scientists now use laser diffraction in preference to older methods like sieving and sedimentation, especially for smaller particles. For particles of larger sizes, over 1mm, sieving is still used.
How laser diffraction works
Laser diffraction has the beauty of simplicity. It measures the degree to which a beam of light or laser is scattered by a group of particles. The smaller the particles, the larger the angle through which the beam of light is scattered. In other words, the size of the particles is inversely proportional to the angle of laser scattering.
An analytical development scientist will then use a mathematical model like the Mie or Fraunhoffer Theory to create a particle size distribution and to produce a final report on the basis of Equivalent Spherical Diameter Volume. Laser diffraction has a number of advantages besides its wide dynamic range. These include speed, reliability, repeatability and instant feedback.
Some practical applications of laser diffraction
As mentioned above, one of the reasons for the widespread use of laser diffraction that it can be applied to powder and liquid samples, and across a wide range of sizes. Some common uses in industry include QA/QC batch testing, general screening measurements and comparative studies.
Especially in the field of pharmaceuticals, particle size is used to test for quality and performance, in powders, suspensions, emulsions, and aerosols. Particle size is important to drug testing in a number of ways, affecting performance in terms of dissolution, solubility, bioavailability, content uniformity, and stability. For example, particles that are smaller in size, in the 2-5um range, aerosolize better and also penetrate deeper into the lungs.
Analytical development scientists use laser diffraction for quality control and testing in a number of industries and fields. It has some very important applications in the pharmaceuticals industry.