Inorganic Material Detection and Classification
For particle counting testing, all the samples must be prepared under conditions limiting particulate matter contamination. Laminar flow hoods are recommended for this purpose while glassware and filter assembly must be washed and rinsed with particle free-water.
Automated detection of features is based on the contrast of the backscatter signals of the sample and the substrate material (filter membrane). For the detection of inorganic/metallic material, the solution containing the drug powder is passed through a polycarbonate filter sample. The filter membrane with the deposited particles is then analyzed as is
using the Variable Pressure setting of the ASPEX Rx.
Filter membranes with the suspended material are loaded directly in the chamber of the Aspex Rx for analysis. No sample preparation or coating is necessary. Filter holders are available for 5 (47mmsq) filter membranes (ADD left) or 10 (25 mmsq) filter membranes (right). Custom filter holders can be designed for other types of samples.
Organic materials consist of mainly carbon and oxygen atoms and consequently minimal backscatter electrons are generated from organic particles and make it difficult, if not impossible, to automate their detection using standard organic-based filters. It is possible, however, to detect organic particles that contain inorganic elements on organic-based filters, like Teflon®, without the need for any additional preparation steps. But, if the analyst wants to detect purely organic materials as well as inorganic materials, metallic coated filters can be used. By coating the filters, backscatter coefficient of the substrate is increased to a point that one effectively inverts the contrast mechanism. With sufficient coating, as has been observed with commercially available gold coated filters, both organic and inorganic particles can simultaneously be detected.
Material Characterization: Shape and Morphology
For high resolution imaging of materials, including APIs, excipients, drug powders and carrier molecules, the ASPEX Rx can be used in manual mode. The Secondary Electron Detector (SED) and Backscatter Electron Detector (BSED) allow the acquisition of high quality imaging to evaluate your product. Samples in solution or suspension can be analyzed directly after filtering trough the appropriate filter membrane. Solids including, drug powders and granules, can be dispersed directly on an adhesive material.