Bulk characterization Raman analysis

The future of Raman spectroscopy in the research and the development of catalysts appears to be extremely promising. The recent revolution in Raman instrumentation has dramatically increased the ability to detect weak Raman signals and to collect the data in very short times. Thus, it is now possible to perform real-time Raman analysis and to study many catal) c systems that give rise to unusually weak Raman signals. The enormous strides in Raman instrumentation now allow for the characterization of a wide range of catalytic materials bulk mixed oxides, supported metal oxides, zeolites, supported metal systems, metal foils, as well as single crystal surfaces. Few Raman studies have been reported for sulfides, nitrides, or carbides, but these catalytic materials also give rise... 

Developed a Raman analysis technique that can be used to characterize the purity and defects in SWNT materials. Raman analysis can also be used to determine the degree of cutting in bulk SWNT samples. 

For IR bulk characterization, the AIN powder was dispersed in KBr and pressed according to the conventional san ling technique. The powder was analyzed as received under the Raman microscope. The XRD test sanq>le is made adhering the AIN powder onto an adhesive tape and for the TEM analysis the grid is dpped in a suspension containing the AIN powder. 

In essence, the test battery should include XRPD to characterize crystallinity of excipients, moisture analysis to confirm crystallinity and hydration state of excipients, bulk density to ensure reproducibility in the blending process, and particle size distribution to ensure consistent mixing and compaction of powder blends. Often three-point PSD limits are needed for excipients. Also, morphic forms of excipients should be clearly specified and controlled as changes may impact powder flow and compactibility of blends. XRPD, DSC, SEM, and FTIR spectroscopy techniques may often be applied to characterize and control polymorphic and hydrate composition critical to the function of the excipients. Additionally, moisture sorption studies, Raman mapping, surface area analysis, particle size analysis, and KF analysis may show whether excipients possess the desired polymorphic state and whether significant amounts of amorphous components are present. Together, these studies will ensure lotto-lot consistency in the physical properties that assure flow, compaction, minimal segregation, and compunction ability of excipients used in low-dose formulations. 

Quantitative and qualitative analyses of inorganic and organic compounds can be performed by Raman spectroscopy. Raman spectroscopy is used for bulk material characterization, online process analysis, remote sensing, microscopic analysis, and chemical... 

Having seen the power (and limitation) of nexafs spectroscopy in the preceding sections, one can readily envision the enhanced utility of nexafs spectroscopy as a characterization tool that would result from the addition of high spatial resolution capabilities. Since the spectroscopic sensitivity to specific moieties and functional groups can in many or even most cases be exceeded by ir, nmr, and Raman spectroscopies, nexafs microscopy will have to exceed the spatial resolution of these other spectroscopy techniques in order to be truly useful. To date, nexafs microscopy has surpassed a spatial resolution of 50 nm both in transmission to measure bulk properties (75-77) and in a reflection geometry to study surfaces (78,79). This level of spatial resolution is at least an order of magnitude better than what can be accomplished with complementary compositional analysis techniques. Future developments in nexafs microscopy might achieve a spatial resolution of a few nanometers (80,81). In addition, nexafs microscopy has exceptional surface sensitivity of about 10 nm, a sensitivity that could be improved to about 1 nm with photoemission electron microscopes (peem s) that incorporate a bandpass filter (80-82). 

Infrared spectroscopy performed both in the mid-IR [70] and near-IR [71] provides the potential of rapid determination with little or no sample preparation. Raman spectroscopy also has demonstrated capability for pharmaceutical analysis [72], Vibrational spectroscopic techniques are effective for compositional and structural characterization, as well as quantitation. However, bulk spectrosocpy is ineffective for measuring the spatial distribution and architecture of actives, which are heterogeneously distributed within intact tablets. Raman chemical imaging equipped with multivariate image processing capabilities is a powerful approach to the analysis of pharmaceutical tablet architecture. 

Fourier transform infrared (FTIR) spectroscopy probes bulk properties [103, 104], while Raman scattering (RS) spectroscopy is the tool to perform surface analysis [105, 106] for instance, the amount of carbon on LiFeP04 is too small to be detected by FTIR, but it is well-characterized by RS experiments [23]. The vibrational modes of LiFeP04 are primarily due to motion associated with phosphate and iron the other modes show some lithium contribution [13, 107, 108]. 

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