Laser microscopy, analytical method

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. 

Finally we wish to introduce four new analytical methods for lacquer problems three are now used in the Detroit Institute of Arts lacquer project and the remaining method is undergoing development for lacquer use. These methods are energy dispersive x-ray fluorescence, laser microprobe, scanning photoacoustical microscopy, and nondestructive IR spectrophotometry. 

Laser diffraction is the most commonly used instrumental method for determining the droplet size distribution of emulsions. The possibility of using laser diffraction for this purpose was realized many years ago (van der Hulst, 1957 Kerker, 1969 Bohren and Huffman, 1983). Nevertheless, it is only the rapid advances in electronic components and computers that have occurred during the past decade or so that has led to the development of commercial analytical instruments that are specifically designed for particle size characterization. These instruments are simple to use, generate precise data, and rapidly provide full particle size distributions. It is for this reason that they have largely replaced the more time-consuming and laborious optical and electron microscopy techniques. 

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. 

Label-free optical techniqnes for detecting bound proteins on microarrays have been recently reviewed. The advantage of these methods over labeling methods is that the native form of the analyte is preserved. These methods include SPR, surface-enhanced laser desorption/ionization mass spectrometry (SELDI-MS), atomic force microscopy " and fiber-optic methods. 

The results herein demonstrated the successful application of parallel combinatorial methods to generate libraries of sensing SAMs covalently immobilized in the wells of a glass microtiter-plate. The fluorescence pattern after exposure of the array to different metal ion solutions allows identification of Cu2+, Co2+, Ca2+, Zn2+ and Pb2+ at 10"4 M concentration by laser confocal microscopy and fluorescence laser scanner. The collection of the unselective response of the monolayers in the presence of the cations generates a characteristic fluorescent pattern, a fingerprint of each analyte in the array. 

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. 

---