Nondestructive analysis

The uniqueness and desirability of EELS is realized when it is combined with the power of a TEM or STEM to form an Analytical Electron Microscope (AEM). This combination allows the analyst to perform spatially resolved nondestructive analysis with high-resolution imaging (< 3 A). Thus, not oiJy can the analyst observe the microstructure of interest (see the TEM article) but, by virtue of the focusing ability of the incident beam in the electron microscope, he or she can simultaneously analyze a specific region of interest. Lateral spatial resolutions of regions as small as 10 A in diameter are achievable with appropriate specimens and probe-forming optics in the electron microscope. 

In summary, CL can provide contactless and nondestructive analysis of a wide range of electronic properties of a variety of luminescent materials. Spatial resolution of less than 1 pm in the CL-SEM mode and detection limits of impurity concentrations down to 10 at/cm can be attained. CL depth profiling can be performed by varying the range of electron penetration that depends on the electron-beam energy the excitation depth can be varied from about 10 nm to several pm for electron-beam energies ranging between about 1 keV and 40 keV. 

Some preliminary laboratory work is in order, if the information is not otherwise known. First, we ask what the time scale of the reaction is surely our approach will be different if the reaction reaches completion in 10 ms, 10 s, 10 min, or 10 h. Then, one must consider what quantitative analytical techniques can be used to monitor it progress. Sometimes individual samples, either withdrawn aliquots or individual ampoules, are taken. More often a nondestructive analysis is performed, the progress of the reaction being monitored continuously or intermittently by a technique such as ultraviolet-visible spectrophotometry or nuclear magnetic resonance. The fact that both reactants and products might contribute to the instrument reading will not prove to be a problem, as explained in the next chapter. 

A. L. Segre, C. Federici 2003, (Degradation of historical paper nondestructive analysis by the NMR-MOUSE), J. Magn. Reson. 161, 204-209. 

Guineau, B. (1989), Nondestructive analysis of organic pigments and dyes using raman microprobe, microfluorimeter and absorption microspectrophotometer, Stud. Conserv. 34, 38-AA. 

A number of the previously cited investigators3->2>5 9 have employed UV spectroscopy as an analytical tool for following PC degradation. We have found the measurement of UV spectra of weathered PC films by difference from an unexposed reference sample to be an extremely simple and useful analytical method. This nondestructive analysis allows the repetitive return of a sample to the exposure conditions and thus enables one to essentially perform continuous analyses on the same sample. This technique, of course, will not detect the formation of non-chromophoric products such as aliphatic oxidation products which may form during the degradation. 

Raman spectroscopy, because of its versatility and wide applicability, has been used for a wide range of art historical and conservation science (Edwards 2000) and archaeological applications (Smith and Clark 2004). Fourier transform Raman spectroscopy (FTRS) in particular has the advantage of being a reflective method which allows direct, nondestructive analysis. It can also be used through a microscope to allow the characterization of small samples. 

Silicon has strong optical emission lines at 251.6113 and 288.1579 nm that can easily be detected by emission spectrography and that give sensitivities in the 1—100-ppm range. For nondestructive analysis, either x-ray diffraction or x-ray fluorescence may be used (see Spectroscopy X-ray technology). 

Tatavarti AS et al. Assessment of NIR spectroscopy for nondestructive analysis of physical and chemical attributes of sulfamethazine bolus dosage forms. Pharm Sci Tech 2005. 

Neutron Howitzer Irradiation. Whole-coin irradiation, however, has the advantage that the internal portions of the coin are irradiated and activated, thus permitting nondestructive analysis of the entire coin. One method we have devised is based on such irradiation but in a neutron beam that is about 100,000,000th as intense as that in a reactor. Only the silver in the coin is activated sufficiently for detection. None of the 255-day half-life isotope is detected, and the analysis is based on silver isotopes with half-lives of 24 sec (110Ag) and 2.4 min (108Ag). This silver activity dissipates in 10-15 min, and the coin is unharmed. We have analyzed over 4000 coins by this method which is described in Refs. 2, 3, 4. 

Electron Beam Techniques. One of the most powerful tools in VLSI technology is the scanning electron microscope (sem) (see Microscopy). A sem is typically used in three modes secondary electron detection, back-scattered electron detection, and x-ray fluorescence (xrf). All three techniques can be used for nondestructive analysis of a VLSI wafer, where the sample does not have to be destroyed for sample preparation or by analysis, if the sem is equipped to accept laige wafer-sized samples and the electron beam is used at low (ca 1 keV) eneigy to preserve the functional integrity of the circuitry. Samples that do not diffuse the charge produced by the electron beam, such as insulators, require special sample preparation. 

Several new methods and instruments based on infrared spectroscopy are being developed for food applications. Advances in spectroscopic instruments and data analysis have enabled the rapid and nondestructive analysis of cheese parameters in just a few seconds (e.g., Nicolet Antaris FT-NIR by Thermo Electron Corp.). Another recent development is the miniaturization of FTIR instrumentation, which would enable onsite analysis, while the cheese is being produced. The TruDefender FT handheld FTIR by Ahura Scientific, Inc. (Fig. 5.7) is a portable handheld spectrometer that could be applied to food analysis. With numerous developments in FTIR spectroscopy and several potential food analysis applications still unexplored, there is great research potential in this technique that could benefit the industry and research institutions. 

Ekube, N.K. Thosar, S.S. Roberts, R.A. etal., Application of near-infrared spectroscopy for nondestructive analysis of Avicel powders and tablets Pharm. Dev. Tech. 1999, 4, 19-26. 

Infrared microspectroscopy is used in the pulp and paper industry73 for compositional analysis of pulp, wet end and size press chemical components in paper contaminants, additives and cellulose, and inks. Wilkinson et al.74 studied ink-paper interactions to discern changing ink properties when applied to paper. In this work, the authors employed synchrotron-based reflectance infrared microspectroscopy as a rapid, direct and nondestructive analysis approach for the study of inks on paper. The authors of this chapter expect infrared imaging to gain popularity as a technique for paper analysis. 

Edwards, El. G. M. (2004). Forensic applications of Raman spectroscopy to the nondestructive analysis of biomaterials and their degradation, in Forensic Geoscience Principles, Techniques and Applications (K. Pye and D. J. Croft, Eds.). London Geological Society Special Publication 232,159-170. 

Method. In the present study, XRF was used to identify major elements in the enamel and the substrate of the cross and reliquary described in a previous section. We used an XRF system with a 1-Ci 241 Am source in a New England Nuclear holder. The source was used in the secondary mode with, in this case, a molybdenum target. The output of the Si-Li detector was analyzed by a Nuclear Data 6620 computer-based multichannel analyzer. The downfacing detector-source-exciter system was positioned above the objects to permit nondestructive analysis while the objects remained horizontal. 

Rosasco, G. J., and E. Roedder (1979). Application of a new Raman microprobe spectrometer to nondestructive analysis of sulfate and other ions in individual phases in fluid inclusions in minerals. Geochim. Cosmochim. Acta 43, 1907-15. 

Nondestructive analysis of solid HTSC oxides is based on voltammetric [42,45,62, 534] and chronopotentiometric [62] investigations of specially designed electrodes which contain microquantities of HTSC (paraffined graphite with the oxide powder pressed on the top [43-45] and carbon paste electrodes [34-41]). Analytical details are thoroughly documented for such systems (including HTSCs and other multi-component materials) [535-537]. 

Results published by Kirsch and Drennen in 1995 [87] suggest that valuable information about the tablet core can be obtained through the film coat, permitting nondestructive analysis of coated dosage forms for potency, hardness, and other parameters. Likewise, the NIR method provided an accurate measure of coating levels. 

While IR transmission spectroscopy is a general analytical method for resin samples, internal reflection spectroscopy is especially suited for solid polymer substrates known as pins or crowns. Single-bead analysis is best done by IR microspectroscopy, whereas photoacoustic spectroscopy allows totally nondestructive analysis of resin samples. 

Fitzgerald AJ, Cole BE, Taday PF. Nondestructive analysis of tablet coating thicknesses usign terahertz pulsed imaging. J Pharm Sci 2005 94(1) 177-183. 

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