Particle Size Distribution

There are four intrinsic properties for each solid in a given drug formulation: composition, particle size, particle shape and particle surface area. Among them, particle size is usually the main interest in pharmaceutical technology. Particle size is a critical process parameter, and particle size distribution (PSD) is an important consideration for pharmaceutical manufacturers. The reason is that PSD has a significant impact on physicochemical and biopharmaceutical properties of drug substances and dosage forms, such as bioavailability, dissolution, stability, uniformity of content, etc. PSD also affects some manufacturing considerations like flowability, blend uniformity, compatibility, which finally affect safety, efficacy and quality of the drug. Generally speaking, the narrower the particle size distribution, the better the final product will perform. Therefore, particle size and PSD are two important process parameters and most frequently monitored during pharmaceutical development and manufacturing process.

A variety of methods of particle size distribution analysis are available for the pharmaceutical industry, including sieving method, coulter counter, optical microscopy, electron microscopy, laser light diffraction method. Alfa Chemistry is equipped with various advanced analysis equipment, we choose an appropriate method for particle size distribution analysis based on the nature of the materials.

Sieving Method

Sieve method is applicable for dosage form development of the tablets and capsules, whose particle size ranges from 50 to 150μm. It is low cost, simple operation, rapid and reproducible. However, when powder is not dry, sieve method is unavailable since aperture becomes clogged with particles leading to improper sieving.

Coulter Counter Method

Coulter counter method was originally developed for sizing blood cells and cell cultures. Actually, particle volume is measured using coulter counter method, and then converted into the particle diameter. Particles with size ranging from 0.5 to 500μm can be measured. Coulter counter analysis is fast and exhibits good reproducibility of measurement, but it is expensive.

Microscopy Method

Microscopy is most commonly used as an absolute particle sizing method in the pharmaceutical research and development, through this method the individual particles can be observed, measured and their shape determined. It includes optical microscopy, electron microscopy. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are the most essential electron microscopy techniques.

Laser Light Diffraction Method

Laser light diffraction is the most popular particle size analysis technique used in the pharmaceutical industry. It is fast, easy to use, high precision repeatable and has wide measurement range (0.02-2000μm/0.01-3500μm). Among them, dynamic light scattering (DLS) is considered as a preferred technique for sub-micron particle size analysis, can be used for a variety of samples/applications, like emulsions, micelles, polymers, liposomes, proteins, viruses and nanoparticles.

If you would like to learn about our particle size distribution testing services, please contact us.