Application of acoustic emission to the monitoring of pharmaceutical unit operations

Michelle K Papp, Purdue University


The novel application of acoustic emission as a real time, non-destructive and non-invasive technique for the monitoring of two pharmaceutical unit operations is described in this thesis. Acoustic emission was shown to be a very reproducible technique that is capable of determining granule particle size, particle size distribution, moisture content and density in a high-shear granulation process regardless of equipment or granulating conditions. Prior studies for monitoring a high-shear granulation had used narrow frequency transducers. This study utilized two sensors that had a combined sensitive over the frequency range of 20-1000 kHz. Additionally, factors impacting the acoustic signal in a granulator were explored. These included sensor location, type of sensor, mass, and the formulation. The acoustic process signature appears to be formulation dependant, and can be attributed to the combination of the individual acoustic response of the excipients in the formulation. In a second pharmaceutical application, acoustic emission from the compaction of powders was examined by the attachment of a small acoustic sensor to the outer wall of tablet die. The method was capable of providing the tensile strength of tablets from the sounds the powder admitted during compaction in a hydraulic press. The technique likewise served useful in elucidating the functionality of two different grades of HPMC that exhibited similar compaction properties, but differed in their physical properties.




Pinal, Purdue University.

Subject Area

Pharmacy sciences|Acoustics

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