Indirect identification

The pyrolysis products of expls in tandem with GC/MS served as indirect identification of contaminant expls in the environment. The pyrolysis products generated, which are indicative of the parent molecule, are separated by GC and identified by MS (Ref 108). Red water produced by the sellite purification of crude TNT was analyzed by GC/MS for potentially useful organic compds, 2,4-DNT, 3- and 5-sulfonic acids (Ref 124). The enhanced detection of TNT vapors was achieved by pre-concn on a metal surface, and flash-desorbed onto a chromatograph interfaced with a quadrupole MS (Ref 76). Vapors of TNT, acetone, toluene, cyclohexanone, and an organosilicon were detected and identified by GC/MS (Ref 78). Various reports were surveyed to determine which methods, including GC/MS, aire potential candidates for the detection of traces of TNT emitted from military land-mines (Ref 80) The vapors collected from Comp B were analyzed by GC/MS besides the TNT and RDX, H20, N20, C02, plus several unidentified compds, were detected (Ref 79). By the use of GC, isomeric impurities in the vapor, as well as solid phase of TNT, were resolved and identified by MS (Refs 61,62 115)... 

All the above studies indicated clearly that reduction of solvent, salt, and additives (e.g., H20) by Li contribute together to the buildup of the surface films on lithium in solutions. It should be emphasized that XRD, XPS, and AES studies of Li electrodes, as well as the indirect identification of surface species from studies of reactions of lithiated graphite or Li/Hg amalgam with electrolyte solutions, could not provide specific enough information on the chemical composition of the surface films. Moreover, application of XPS for Li electrodes may induce secondary surface reactions. Visible changes appear on Li surfaces during XPS measurements. More specific information on the composition of the surface layers formed on Li could be obtained by surface-sensitive FTIR spectroscopy that was introduced into this field in the middle of 1985 by Yeager et al. [84,85,178], and which is a nondestructive technique. 

It is important to notice that, from both viewpoints, as well as in all working procedures, experimental data are required and that, at the same time, mathematical models are absolutely needed for data processing. Generally, when the mathematical model of a process is relatively complex, a good accuracy and an important volume of experimental data are simultaneously required. Therefore, in these cases the quality of the determination of parameters is the most important factor to ensure model relevance. The strategy adopted in these cases is very simple for all the parameters of the process that accept an indirect identification, the research procedure of identification is carried out separately from the real process whereas for the very specific process parameters that are difficult to identify indirectly, experiments are carried out with the actual process. 

In view of the methodological difficulties involved in the (direct or indirect) identification of relevant indicator... 

Reaction or exchange with stable isotopic tracers and quantitative identification of all products by mass spectrometry provides indications for molecular interactions on the surface. Reactions can be studied at steady state or by following the transient distribution of isotopic products. Langer and co-workers (25,26) presented the first steady-state mechanistic analysis for the electrocatalytic hydrogenation of ethylene on Pt in deuterated electrolytes. Proton abstraction in electroorganic synthesis has also been verified using deuterated solvents (374, 375). On-line mass spectrometry permitted indirect identification of adsorbed radicals in benzene and propylene fuel cell reactions (755,795,194). Isotopic radiotracers provided some notion on adsorption isotherms (376, 377) and surface species on electrocatalysts (208, 378, 379). 

Indirect identifications are commonplace, and basing them on comparisons of profusely detailed spectra makes them trustworthy. Coincidence, however, sets infamous traps for researchers making indirect chromatographic comparisons. To compare mere hplc retention times or tlc flow rates invites misidentiflcations because disparate compoimds sometimes have identical values. As a rule, credible chromatographic identifications are always direct and even the best ones are never exclusive. 

In this chapter wc address the question that faces anyone trying to identify the molecular structure of a substance, namely, What is it To put it another way, this chapter begins to answer the obvious question that you may already have been thinking after the first nine chapters of this book, namely, How does anyone really know that all those molecules are what we say they are In the olden days," tedious indirect identification methods had to be used, and some are described in the text. Nowadays these questions are answered through the use of spectroscopy, a technique that literally serves as the eyes of an organic chemist with respect to the structures of molecules. The most important and widely used type of spectroscopy, iwrlear magnetic resonance (NMR), is described in this chapter. 

Indirect identification Instead of using part numbers (referred to as direct identification), the identification of individual variants from a generic item (within a family) is based on variety parameters and their instances (a list if parameter values). Such identification is ctilled indirect identification (Hegge and Wortmann. 1991). In the above example, a variety parameter, color, and its value list,, can be used for an indirect identification of a particular variant, i.e.. If ... 

There are three different approaches in determining the model structure of a closed-loop system indirect identification, direction identification, and joint input-output identification. 

The first method for closed-loop identification is called indirect identification, where Eq. (6.56) is first fit as... 

Indirect identification of closed-loop processes requires that only the input and output signals be available. 

Computed tomographic angiography (Fig. 22.1) and magnetic resonance angiography (Fig. 22.2) both provide excellent images of the aorta and main renal arteries in children. Limitations of spatial resolution make it difficult to exclude stenosis of branch and accessory arteries, however, and further technical developments are required to overcome this problem. One possibility is that MR perfusion techniques may allow the indirect identification of RVD by identifying delayed perfusion of one kidney or a segment of kidney. 

An indirect identification of amines consists in catalytic denitrogena-tion and subsequent identification of the resulting hydrocarbon by gas chromatography (32). Aung et al. (33) recommend the preparation of Schiff s bases with picolinaldehyde and the measurement of the rate of dissociation by reaction with ferrous salt. The half-time of the reaction is characteristic of each amine. Differences in rates of acetylation were used for the identification of amines in petroleum fractions (34). 

A substantial amount of indirect evidence supports the contention that the induction of apoptosis in tumor cells is critical to successful therapy. Cancer therapy might therefore be viewed as an attempt to induce apoptosis in a population of cells that have undergone selection for apoptotic defects. If correct, this hypothesis would suggest why cancer therapy is in many cases unsuccessful. However, recent studies indicate that this fundamental problem can be circumvented. Progress in the identification of molecules key to the cell death pathways has led to a growing understanding of how apoptosis occurs [3]. It has become clear that pathways to apoptosis are numerous and often interconnected. A solution to the clinical problem of therapeutic resistance, then, may lie in the fact that there appears to be multiple ways that a cell death program can be implemented. 

Studies have now started to clarify the role of histamine Hi and H2 receptors in the cardiovascular manifestations of anaphylaxis. However, histamine can activate H3 and H4 receptors [56, 57]. Levi and coworkers [58-60] identified H3 receptors as inhibitory heteroreceptors in cardiac adrenergic nerve endings. This suggests a mechanism by which endogenous histamine can activate norepinephrine release in normal and ischemic conditions [61,62]. The functional identification ofH3 receptors in the human heart [59] means that these receptors might be directly and/or indirectly involved in the cardiovascular manifestations of anaphylactic reactions. 

These simulation data should be proved by experiment. However, it is still unknown that what microorganisms are PAOs or GAOs. Therefore the precision of model for EBPR process should be determined with indirect methods. Then with the concentration decrease of PAOs, the GAOs concentration was increased rapidly. However, this simulation result shoidd be supported by the experimental data with the identification of PAOs and GAOs. 

The identification of plant models has traditionally been done in the open-loop mode. The desire to minimize the production of the off-spec product during an open-loop identification test and to avoid the unstable open-loop dynamics of certain systems has increased the need to develop methodologies suitable for the system identification. Open-loop identification techniques are not directly applicable to closed-loop data due to correlation between process input (i.e., controller output) and unmeasured disturbances. Based on Prediction Error Method (PEM), several closed-loop identification methods have been presented Direct, Indirect, Joint Input-Output, and Two-Step Methods. 

Identification of dyes on dyed textiles is traditionally carried out by destructive techniques [493], TLC is an outstanding technique for identification of extracted dyestuffs and examination of inks. Figure 4.9 shows HPTLC/SERRS analysis of acridine orange [492], Wright et al. [494] have described a simple and rapid TLC-videodensitometric method for in situ quantification of lower halogenated subsidiary colours (LHSC) in multiple dye samples. The results obtained by this method were compared with those obtained by an indirect TLC-spectrophotometric method and those from HPLC. The total time for the TLC-videodensitometric assay of five standards and four samples applied to each plate was less than 45 min. The method is applicable for use in routine batch-certification analysis. Loger et al. [495,496] have chromatographed 19 basic dyes for PAN fibres on alumina on thin-layer with ethanol-water (5 2) and another 11 dyes on silica gel G with pyridine-water... 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

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