Optical microscopy, analytical method

The computer age has brought about considerable innovation in the operation of laboratory instrumentation. One consequence of this is the wider acceptance and utilization of the optical microscope as a quantitative analytical instrument. A brief literature survey illustrates the diversity of disciplines and optical methods associated with the development of computer interfaced optical microscopy. This is followed by a description of how our methods of fluorescence, interferometry and stereology, nsed for characterizing polymeric foams, have incorporated computers. 

The most frequently applied analytical methods used for characterizing bulk and layered systems (wafers and layers for microelectronics see the example in the schematic on the right-hand side) are summarized in Figure 9.4. Besides mass spectrometric techniques there are a multitude of alternative powerful analytical techniques for characterizing such multi-layered systems. The analytical methods used for determining trace and ultratrace elements in, for example, high purity materials for microelectronic applications include AAS (atomic absorption spectrometry), XRF (X-ray fluorescence analysis), ICP-OES (optical emission spectroscopy with inductively coupled plasma), NAA (neutron activation analysis) and others. For the characterization of layered systems or for the determination of surface contamination, XPS (X-ray photon electron spectroscopy), SEM-EDX (secondary electron microscopy combined with energy disperse X-ray analysis) and... 

Asbestos can be determined by several analytical techniques, including optical microscopy, electron microscopy, X-ray diffraction (XRD), light scattering, laser microprobe mass analysis, and thermal analysis. It can also be characterized by chemical analysis of metals by atomic absorption, X-ray fluorescence, or neutron activation techniques. Electron microscopy methods are, however, commonly applied for the analysis of asbestos in environmental matrices. 

Decreasing the nanochannel width thus leads to qualitatively new and counterintuitive behavior that can be exploited for molecular separations. Because details of the flow profiles in individual nanochannels are below the resolution limit of optical microscopy, only the average velocities of dye fronts can be monitored. Significant improvements in the lateral resolution of analytical imaging methods are required to study the transport of molecules in an individual channel. 

Technical examination of objects coated with a protective covering derived from the sap of a shrubby tree produces information that can be used to determine the materials and methods of manufacture. This information sometimes indicates when and where the piece was made. This chapter is intended to present a brief review of the raw material urushi, and the history and study of its use. Analytical techniques have included atomic absorption spectroscopy, thin layer chromatography, differential thermal analysis, emission spectroscopy, x-ray radiography, and optical and scanning electron microscopy these methods and results are reviewed. In addition, new methods are reported, including the use of energy dispensive x-ray fluorescence, scanning photoacoustical microscopy, laser microprobe and nondestructive IR spectrophotometry. 

For chemical sensing apphcations, viruses represent a type of species that is of special interest because their size normally is in the range between 10 and some lOOnm. Therefore, they are too small to be visualised by optical microscopy, which means that currently there are no fast, easy-to-use techniques for their detection. Additionally, as viruses may be a substantial threat to humans, livestock or plants, a direct on-line method for their determination would be highly desirable. The imprinting approach promises to solve these problems, because, as already mentioned, it is inherently applicable to a very wide variety of analytes and not restricted to a certain size or to defined chemical properties of the material or the template. 

Polymorphic forms As already discussed in the previous paragraph, two crystalline solids are regarded as polymorphic forms (or polymorphic modifications) when the difference only concerns the supramolecular arrangement in the crystal but not their chemical composition. In other words, we can discriminate between these species only in the solid state but the solution or melt of two polymorphs is indistinguishable. The consequences of the stmctural differences are more or less marked differences in the physicochemical properties. One set of analytical methods aims specifically at these physicochemical properties, particularly thermodynamic quantities, others at structural (spectroscopy, diffraction methods), optical (microscopy), or mechanical properties. Table 7.2 summarizes most of the properties that may differ among various solid-state forms and may thus be the object for analytical assays. 

High quality, cost effective analytical services are essential for the characterization of research samples. Analytical methods include Optical Microscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Electron Probe X-Ray Microanalysis, Electron Spectroscopy for Chemical Analysis, X-Ray Eluorescence,... 

Optical microscopy (OM), polarized light microscopy (PLM), phase contrast microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) are the methods normally used for identification and quantification of the trace amounts of asbestos fibers that are encountered in the environment and lung tissue. Energy-dispersive X-ray spectrometry (EDXS) is used in both SEM and TEM for chemical analysis of individual particles, while selected-area electron diffraction (SAED) pattern analysis in TEM can provide details of the cell unit of individual particles of mass down to 10 g. It helps to differentiate between antigorite and chrysotile. Secondary ion mass spectrometry, laser microprobe mass spectrometry (EMMS), electron probe X-ray microanalysis (EPXMA), and X-ray photoelectron spectroscopy (XPS) are also analytical techniques used for asbestos chemical characterization. 

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