Dynamic Light Scattering is one of the easiest methods of measuring very small particles in the process of particle size determination and particle size analysis. However, when it comes to measuring the specific surface area to predict dissolution rate, BET (Brunauer, Emmett, and Teller) is the best theory to use.
BET theory utilizes the adsorption of gaseous molecules such as Nitrogen on a solid surface as a means of measuring the surface area of materials. Adsorption is best defined, according to Merriam-Webster, as “the adhesion in an extremely thin layer of molecules (as of gasses, solutes, or liquids) to the surfaces of solid bodies or liquids with which they are in contact.” Determining the size of the surface area is necessary to predicting dissolution rate and thus bioavailability, the consistency of manufacturing, and the performance of a product.
The BET theory utilizes gaseous adsorbates that do not chemically react with material surfaces such as nitrogen, water, argon, and carbon dioxide which can all be used in BET theory when used at specific temperatures. Nitrogen is the most commonly used gaseous adsorbate and so it’s important to utilize BET theory at the boiling point of Nitrogen at -196C.
A BET analysis instrument is specifically used for determining the surface area of pharmaceuticals. Standard measurements for pharmaceutical samples while utilizing a BET analysis instrument include P/P0 of 0,1; 0,2; and 0,3. The process of using a BET analysis instrument to determine the surface area of pharmaceutical samples consists of drying the pharmaceutical samples with nitrogen purging and then measuring the volume of the gas adsorbed to the particle surfaces, which then determines the surface area of the particles in total. The pharmaceutical samples can also be dried with the use of a vacuum, which then applies temperatures of differing elevations. Interestingly, the BET analysis instrument not only measures the surface area of the particles in the particular pharmaceutical samples but also determines the specific volume and the specific size of the micropores distributed.
When it comes to analytical methods in research, BET theory is an extremely helpful theory when determining and predicting dissolution rate and thus bioavailability. The BET analysis instrument is especially important to the analysis and measurement of pharmaceutical samples when applied with particle analytics as a means of releasing the testing of active pharmaceutical ingredients.