A secondary drying process is disclosed for removing residual solvent from drug-containing particles that have been formed by solvent-based processes, the secondary drying process utilizing a combination of vacuum, agitation, and a stripping gas. The difference between the primary volume and the base volume is managed by using the difference bitmaps that are different for the respective sections. In this way, gamma radiation is detected emanating from the source and backscattered from the underlying material sample through a first path of travel when the source mount is at the first active position and through a second path of travel when the source mount is at the second active position. In a similar manners remaining thermoplastic particle components can be selectively removed and purified. A rod housing is fluidly connected to the displacer chamber and the piston cylinder.