Morphological particle identification

Particle Morphology, Size, and Distribution. Many fillers have morphological and optical characteristics that allow these materials to be identified microscopically with great accuracy, even in a single particle. Photomicrographs, descriptions, and other aids to particle identification can be found (1). 

Microscopic identification models ate similar to the CMB methods except that additional information is used to distinguish the source of the aerosol. Such chemical or morphological data include particle size and individual particle composition and are often obtained by electron or optical microscopy. 

The first linkage between a microscope and an IR spectrophotometer was reported in 1949 [15]. Today, every manufacturer of IR spectrophotometers offers an optical/IR microscope sampling accessory. The use of optical and IR microscopy is a natural course of action for any solid state investigation. Optical microscopy provides significant information about a sample, such as its crystalline or amorphous nature, particle morphology, and size. Interfacing the microscope to an IR spectrophotometer ultimately provides unequivocal identification of one particular crystallite. Hence, we have the tremendous benefit of IR microscopy for the identification of particulate contamination in bulk or formulated drug products. 

The identification of a particle as FDR is based on a combination of morphological and elemental composition criteria and also on the association of the particle with other particles present in the sample. 

The exact size distribution/nnmber density of the Pd particles formed is not very reproducible as the spatial arrangement of the particles is dictated by nncleation and growth during deposition. Snbseqnent heating leads to ripening of the ensemble [21] with concomitant changes in the total exposed metal surface area and the morphology of the particles. These factors can mask the formation of the SMSI state. However, STM facilitates local inspection on a particle-by-particle basis and the reproducible identification of common structnral motifs. 

The optical microscope is a valuable tool in the laboratory and has numerous applications in most industries. Depending on the type of data that is required to solve a particular problem, optical microscopy can provide information on particle size, particle morphology, color, appearance, birefringence, etc. There are many accessories and techniques for optical microscopy that may be employed for the characterization of the physical properties of materials and the identification of unknowns, etc. Utilization of a hot-stage accessory on the microscope for the characterization of materials, including pharmaceutical solids (drug substances, excipients, formulations, etc.), can be extremely valuable. As with any instrument, there are many experimental conditions and techniques for the hot-stage microscope that may be used to collect different types of data. Often, various microscope objectives, optical filters, ramp rates, immersion media, sample preparation techniques, microchemical tests, fusion methods, etc., can be utilized. 

The third major class of analytical techniques may be called morphological methods. This identification consists of comparing the form of particles captured with the morphology of particles of known composition. It goes without saying that morphological similarity is a necessary but not always sufficient condition for compositional identity. In spite of this problem this procedure is widely employed mainly in clean atmosphere, since even Aitken size particles can be identified morphologically (A. Meszaros and Vissy, 1974 Butor, 1976). 

Cadle et ai, 1968) who showed by means of special microscopic techniques (e.g. morphological identification) that in Antarctic air the large particles are built from sulfates. 

The composition of background aerosol particles, including a part of Aitken range, was investigated by morphological identification by A. Meszaros and Vissy (1974) on the basis of membrane filter samples collected in remote oceanic air in the Southern Hemisphere. They found that 75-95 % of the particles was composed of the following four substances (Fig. 33) ... 

The development of catalysts based on carbon supports is related to the challenge that solid properties determining the catalytic properties are not easily accessible. Regardless of the fact that catalysts do not show obvious differences with respect to solid properties (e.g., morphological and smface properties of the carbon support, metal particle size, particle dispersion or solid phase and oxidation state of the active metal), they often reveal differences in their catalytic behavior. For industrial application of catalysts in fine chemistry, these circumstances are serious obstacles for a straightforward rational development and the identification of suitable catalysts for conversion of certain substrates. 

---