Other Electron-detecting Techniques

Edited by H. Bubert and H. Jenett Copyright 2002 Wiley-VCH Verlag GmbH ISBNs 3-527-30458-4 (Hardback) 3-527-60016-7 (Electronic) 2.5 Other Electron-detecting Techniques 2.5 

Auger Electron Appearance Potential Spectroscopy (AEAPS) 

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The intracellular osmiophilic area of the flavonoid gland can be correlated to flavonoids because of their heavy staining after osmium tetroxide fixation. However, at some stages of the synthetic process, flavonoids are not osmiophilic. Hence, other electron microscopic techniques for polyphenol detection are also used. Ultra-chemical tests with silver salt reactions are the most interesting ones (Eef. 13) Such investigations have been successfully applied, but in many oases are limited by... 

Frequently, electrochemical information can be interpreted better in the presence of additional nonelectrochemical information. Typically, however, there is one significant restriction electrochemical and spectroscopic techniques often do not detect exactly the same mechanisms. With spectroscopic measurements (e.g., infrared spectroscopy), products that are formed by electrochemical processes may be detected. In other cases (luminescence techniques) mechanisms may be found by which charge carriers are trapped and recombine. Other techniques (electroreflection studies) allow the nature of electronic transitions to be determined and provide information on the presence or absence of an electric field in the surface of an electrode. With no traditional technique, however, is it... 

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

In this chapter, firstly, a very brief survey is given of recent advances in such studies as classified according to the detection technique of transient species in pulse radiolysis. Secondly, examples are chosen from our recent investigations, with special emphasis on the important contributions of pulse radiolysis methods to gas-phase collision dynamics one is electron attachment, the other is Penning ionization and related processes. The detection techniques and corresponding reaction processes, together with major references, are given below ... 

It is expected that the geometrical dimensions of IC devices will continue to decrease through the use of electron beam and x-ray lithography. Analysis of these small geometries presents additional challenges since a tradeoff exists between analysis area, and detection limits for the microbeam analysis techniques, AES and SIMS. The other surface analysis techniques of XPS and RBS already have very limited spatial resolution with respect to the current geometrical dimensions of IC s. The fabrication of denser and more complicated IC s also increases the value of each wafer which increases the need for additional process characterization and control. The increased application of surface analysis to semiconductor problems will provide a better understanding of these processes and will stimulate the further development of instrumental surface analysis techniques. 

PIXE is the analogue to EDX/WDX (energy/wave dispersive analysis of X-rays) done with electron microprobes. Elements in the sample are identified by the characteristic X-rays emitted during MeV particle bombardment. PIXE is not well suited for fluorine detection because of the low energy of the corresponding X-rays. However, it is often performed simultaneously with other ion beam techniques and gives very valuable information on the bulk composition and other trace element concentrations in the sample. 

ICP-MS is only one of several detection techniques used for species-selective analysis of Sn in food matrices other detectors in use include electron impact (El) MS, l.iamc photometric detection (FPD), pulsed FPD and MIP-AES. 

Other detection methods. Besides XPS, other chemically sensitive techniques are available to probe the reaction. Surface reflection absorption infrared spectroscopy [130] and electron-energy loss spectroscopy [131] give detailed information on the vibrational states and thus the bonds of surface species. Gas-phase mass spectroscopic techniques provide information about the desorbing species. 

Because there is an equal probability that a given unpaired electron will have a quantum number of or 35, radicals are observed as a single line in an esr spec-tmm unless they interact with other electronic or nuclear spins or possess magnetic anisotropy, in which case two or more lines may appear in the spectrum. Another magnetic technique for the detection of free radicals uses an ordinary NMR instrument. It was discovered that if an nmr spectrum is taken during the course of a reaction, certain signals may be enhanced, either in a positive or negative direction others may be reduced. When this type of behavior, called chemically... 

A significant amount of literature regarding the antioxidant properties of flavonoids and other plant polyphenols is available. As the essence of redox chemistry involves electron transfer, it seems natural that electrochemical detection rivals spectrophotometric detection techniques for the compounds that are supposed to be antioxidants. With the improvements in electrochemical detector geometries and electronics over the last decade, coupled with a requirement for increased sensitivity, the use of electrochemical detectors offers significant additional advantages when combined with the traditional UV-VIS detection in the analysis of flavonoids and other plant polyphenols. ... 

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