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Techniques for Air Jet Sieve Particle Size Analysis

A sieve is a classic tool for sorting particles by size. A traditional sieve is metal or cloth with holes that filter the particles by size. Some particles fall through the holes and others do not. The size of the particles to be analyzed determines the choice of sieve. An air jet sieve is a newer version of an old idea. It uses air pressure, while incorporating the principles of the traditional sieve.

Single Sieve
- The dry sieve method, for example, involves the use of several sieves. It uses mechanical agitation to analyze particle size. This means the sieves shake to force the particles through the holes. The air jet sieve method requires the use of one sieve at a time. The entire test of any given particles may require more than one sieve to be used at different times, but always only one at a time. Testing requires using the finest, or smallest, sieve first to obtain the correct results.
Moving Air
- The technique that differentiates the air jet sieve from the dry sieve method is the use of a moving air current. The air jet sieve method uses the same type sieve as the dry method. Instead of shaking the sieve, it involves using forced moving air in a closed device. The air disturbs the particles and cleans the sieve. This cleaning allows for the easy passage of the particles which settle on the sieve following the use of the air. The method works quickly as sieve is continually being cleaned by the air. It is not necessary to use a second sieve, as there is no clogging in the holes. The air jet sieve operates in a closed environment that keeps the particles in place.
Negative Pressure
- The air jet sieve creates negative pressure to perform its task. This pressure comes from a rotating nozzle, which sends out a current of air. Negative pressure means the pressure in the area under the sieve is less than the pressure in the surrounding area. Substances like particles are attracted to negative pressure and move in that direction. The purpose is to bring the smaller particles through the sieve and into a receptacle. All of this occurs in a closed confined space of a machine.
Quality of Technique
- The Massachusetts College of Pharmacy conducted a study involving particle size analysis of pharmaceutical powder. This study used both the air jet sieve and the traditional mechanical method. The results, which were were published in 1979 in the journal "Drug Development and Industrial Pharmacy," indicate the air jet sieve is faster and the results are not affected by sample size. The study concluded that air jet sieve is a easy, reliable method of analysis.

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