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Drug Substance and Excipient Characterization
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Parind M. Desai, Lai Wah Chan, Paul Wan Sia Heng
X-ray diffractometry may be carried out using a powder x-ray or a single crystal diffractometer. The latter is used to elucidate the crystal structure while the powder x-ray diffractometer is for general purpose. The polymorphs of material have different crystal packing arrangements and thus produce different x-ray diffractograms with characteristic peaks that are related to lattice distances (Figure 3.8a). The extent of conversion of a crystalline drug to the amorphous form during processing can be determined by comparing the magnitude of their characteristic peaks [47]. The sharp peaks (Figure 3.8a) indicate a crystalline component, whereas broad diffraction peak or features (also referred to as “halo”) indicate an amorphous component (Figure 3.8b). The powder x-ray diffractometry method is non-destructive and requires a very small sample of the material, which can be examined without further processing. For structural determination, good single crystals are used in a single crystal diffractometer. Synchrotron sources have been employed to obtain high-resolution electron diffraction patterns for very small crystals or crystals of complex compounds. Very sensitive charge-coupled detectors have enabled electron diffraction patterns to be recorded in a few seconds using very low electron currents. In addition, microdiffractometers with 2D area detectors have been developed for quick data acquisition [48].
Inorganic Particulates in Human Lung: Relationship to the Inflammatory Response
Published in William S. Lynn, Inflammatory Cells and Lung Disease, 2019
Victor L. Roggli, J. P. Mastin, John D. Shelburne, Michael Roe, Arnold R. Brody
For many inorganic particulates, elemental composition is not sufficient for complete, accurate mineralogical characterization. In these instances, information about the crystalline structure of the material is required. Two techniques have been used in the study of inorganic particulates to obtain crystallographic data: X-ray diffraction, which is a bulk technique, and selected area electron diffraction, a microanalytical technique which permits analysis of individual microscopic particles and which may be performed on most modern transmission electron microscopes.12, 14 The diffraction of X-rays or electrons as they pass through the sample produces a characteristic pattern which may be recorded on photographic film, and the geometric and dimensional information obtained can then be related to the crystal structure through Bragg’s law. The diffraction patterns for thousands of known standard materials have been catalogued in the A.S.T.M. (American Society for Testing Materials) index. X-ray diffraction and selected area electron diffraction have been used fairly extensively in the study of inorganic particulates extracted from lung tissues.6, 24–30 In addition, X-ray diffraction may be used in the quantitative determination of mineral species (e.g., quartz31 and asbestos32).
Unmasking the Illicit Trafficking of Nuclear and Other Radioactive Materials
Published in Michael Pöschl, Leo M. L. Nollet, Radionuclide Concentrations in Food and the Environment, 2006
Stuart Thomson, Mark Reinhard, Mike Colella, Claudio Tuniz
Transmission electron microscopy (TEM) is capable of higher magnification than SEM and typically has a spatial resolution on the order of 0.1 nm, which allows extremely small structural features to be examined [40,41]. The use of a thin sample cross section enables electrons to be passed through the sample. The resultant images enable the user to observe structural features of the material, such as particle size, porosity, crystal morphology, and the presence of individual grains, stacking faults, twin boundaries, and dislocations. Electron diffraction enables crystal structures to be determined from individual areas of a sample. Information obtained from both imaging and electron diffraction can be used to determine the processing history of materials. This information is highly valuable in providing clues for tracing the source of the material. Excellent examples highlighting the use of the technique to analyze plutonium-bearing samples are detailed in recent review articles [23,42].
Natural mineral fibers: conducting inhalation toxicology studies – part A: Libby Amphibole aerosol generation and characterization method development
Published in Inhalation Toxicology, 2023
Anbo Wang, Amit Gupta, Michael D. Grimm, David T. Pressburger, Barney R. Sparrow, Jamie S. Richey, John R. Shaw, Karen E. Elsass, Georgia K. Roberts, Pei-Li Yao, Matthew D. Stout, Benjamin J. Ellis, Robyn L. Ray
Selected area electron diffraction patterns presented by amphibole fibers are uniform rows of closely spaced spots with patterns that are influenced by the orientation of the fiber to the direction of the electron beam (Millette 1987). The presence of concise spots conveys the crystallinity of the fiber. Upon measurement, sets of zone-axis patterns of spots are used to describe types of amphiboles in conjunction with chemical composition measured by EDS (Meeker et al. 2003). The electron diffraction patterns for the aerosol sample and the bulk LA 2007 test material indicated the aerosol and bulk material were highly crystalline and were consistent with the standards of amphibole asbestos from the Libby amphibole, MT region (Meeker et al. 2003). Representative SAED images for aerosol sample and bulk LA 2007 test material are shown in Figure 9.
Toxicological and epidemiological approaches to carcinogenic potency modeling for mixed mineral fiber exposure: the case of fibrous balangeroite and chrysotile
Published in Inhalation Toxicology, 2023
Andrey A. Korchevskiy, Ann G. Wylie
A sample of balangeroite was obtained from Dr. Francesco Turci (University of Piedmont, Vercelli, Italy). It was examined by polarized light microscopy (PLM) at the University of Maryland to evaluate habit, color, and optical properties. It was also examined by transmission electron microscopy (TEM) at the Bureau Veritas North America, Inc. (Kennesaw, GA). The objective of the TEM analysis was to identify and size 200 structures that meet 3:1 length/width (aspect ratio) criterion, with a minimum length of 0.5 µm, and a width greater than 0.05 µm. Representative portions of the sample were examined under a stereomicroscope. Approximately, 100 mg of the material were suspended in 5 ml of acetone. The mixture was ultrasonicated for three minutes. It was then centrifuged for three minutes and the acetone supernatant decanted to a level of 0.5 m. The remaining material was re-suspended and a drop of the suspension was placed on each of the two carbon-coated copper grids (3 mm diameter, 200 mesh). The sample grids were dried and then examined with TEM at high magnification (×15 000 or higher). Materials were identified by morphology, selected-area electron diffraction, and energy-dispersive X-ray spectroscopy (EDS).
In vitro antiplasmodial activity, hemocompatibility and temporal stability of Azadirachta indica silver nanoparticles
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2022
Joseph Hawadak, Loick Pradel Kojom Foko, Veena Pande, Vineeta Singh
The morphology and size of AgNPs were analysed by TEM imaging. Contrary to the SEM results TEM imaging showed well dispersed NPs, predominantly spheroidal in shape (Figure 5(A,B)). It could be assumed that NPs aggregation occurred during the low vacuum drying in SEM analysis [41]. Figure 5(C,D) representing the selected area electron diffraction (SAED) pattern show multiple diffraction rings, indicating their polycrystalline nature which is consistent with the XRD results. The NPs size ranged from 4 to 28 nm with an average size of 13.01 ± 2.54 and 19.30 ± 3.13 nm for AIL-AgNPs and AIB-AgNPs, respectively (Figure 5(E,F)). These values were close to that calculated above with Debye–Scherrer formula from XRD results and conform to the shape of SPR band in the UV visible spectrum.