Special Use Analysis Techniques

Multiple regression, where a dependent y variable is a function of a number of independent V ariables or factors, is a widely used analysis technique for multivariable problems The use of a specialized simplified multiple regression analysis, where all the independent factors are orthogonal, is discu.ssed in the next section on experimental design. A detailed discussion of customary multiple regres.sion analy.sis, where orthogonality may or may not be present for all variables, is a topic that is beyond the scope of this chapter... 

As the practice of system safety moves into its seventh decade of existence, special use analysis methods and techniques have been developed as a result of the steady increase in system complexity and acceleration in technological advancements. These changes have brought with them new concerns over the adequacy of existing hazard reduction and control techniques. Automated systems that incorporate complicated data and energy flow transfer paths, as well as those whose correct operation... 

Most EDS systems are controlled by minicomputers or microcomputers and are easy to use for the basic operations of spectrum collection and peak identification, even for the computer illiterate. However, the use of advanced analysis techniques, including deconvolution of overlapped peaks, background subtraction, and quantitative analysis will require some extra training, which usually is provided at installation or available at special schools. 

The detection of impurities or surface layers (e.g., oxides) on thick specimens is a special situation. Although the X-ray production and absorption assumptions used for thin specimens apply, the X-ray spectra are complicated by the background and characteristic X rays generated in the thick specimen. Consequently, the absolute detection limits are not as good as those given above for thin specimens. However, the detection limits compare very favorably with other surface analysis techniques, and the results can be quantified easily. To date there has not been any systematic study of the detection limits for elements on surfaces however, representative studies have shown that detectable surface concentrations for carbon and... 

Approximately 70 different elements are routinely determined using ICP-OES. Detection limits are typically in the sub-part-per-billion (sub-ppb) to 0.1 part-per-million (ppm) range. ICP-OES is most commonly used for bulk analysis of liquid samples or solids dissolved in liquids. Special sample introduction techniques, such as spark discharge or laser ablation, allow the analysis of surfaces or thin films. Each element emits a characteristic spectrum in the ultraviolet and visible region. The light intensity at one of the characteristic wavelengths is proportional to the concentration of that element in the sample. 

The HAZOP analysis technique uses a systematic process to (1) identify possible deviations from normal operations and (2) ensure that safeguards are in place to help prevent accidents. The HAZOP uses special adjectives (such as speed, flow, pressure, etc. see table 5.5) combined with process conditions (such as more, less, no, etc. see table 5.6) to systematically consider all credible deviations from normal conditions. The adjectives, called guide words, are a unique feature of HAZOP analysis. 

A first approach to determining explosives on-site might include a combination of specialized sample-collection techniques and subsequent analysis using established IMS technologies or instruments. A second level of development could involve the fabrication of analyzers or analytical systems for an on-site operation and real-time analysis of samples. During the past several years, the first step of development has been demonstrated for explosives in water, in soils, and in a few unique uses. 

MALDI-MS was developed for the analysis of nonvolatile samples and was heralded as an exciting new MS technique for the identification of materials with special use in the identification of polymers. It has fulfilled this promise to only a limited extent. While it has become a well-used and essential tool for biochemists in exploring mainly nucleic acids and proteins, it has been only sparsely employed by synthetic polymer chemists. This is because of lack of congruency between the requirements of MALDI-MS and most synthetic polymers. 

In some applications like newborn screening and filter paper blood spots, the internal standard that is labeled cannot be mixed with blood. It can only be present in the extraction solvents. Therefore, only the extracted metabolites can be quantitatively measured. I have denoted a term called pseudo-isotope dilution to account for the differences between traditional isotope dilution and the technique commonly used in newborn screening by MS/MS. A special analysis is capable using this technique, however, in terms of an extraction efficiency experiment. With isotope-labeled standards you can perform an experiment whereby a traditional isotope-dilution technique (internal standard added to liquid blood and spotted) is compared to pseudo-isotope dilution techniques (internal standard is added to the extraction matrix). The ratio of the results of these two analysis (pseudo/traditional) is the extraction efficiency. 

Figure 2.9. Accelerator mass spectrometer used for bioanalytical analysis at Xceleron (formely CBAMS). Pharmaceutical companies have not adopted AMS as an in-house technique because of cost and size of instrumentation (compare the scale of the instrument to the kitchen in the lower left). Samples are outsourced to companies that specialize in the technique.

Surface Electrochemistry is an important field in Surface Science, which is undergoing a very important development. In spite of the complexity of the systems, the experimental measurements have acquired a very high degree of sophistication and atomic resolution has almost been reached. After the development of special techniques that allowed the preparation of well defined single crystal electrodes [1, 2], attempts have been made to use surface analysis techniques in an electrochemical environment. However, one must... 

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