Identification and structures

Legon A 0, Millen D J and Mjdberg P J 1977 The hydrogen cyanide dimer identification and structure from microwave spectroscopy Chem. Phys. Lett. 47 589... 

Most treatments of polarised light in transmission are to be found in the mineralogical literature, but a fine book presenting the subject in relation to crystal identification and structure analysis is by Bunn (1945). 

Modern Methods of Separation, Identification, and Structure Determination... 

Liaaen-Jensen, S., Combined approach identification and structure elucidation of carotenoids, in Carotenoids Spectroscopy, IB, Britton, G., Liaaen-Jensen, S., and Pfander, H., Eds., Birkhauser, Basel, 1995, 343. 

Christie, W.W., Lipids their structure and occurrence, in Lipid Analysis, Isolation, Separation, Identification and Structural Analysis of Lipids, Vol. 5, Christie, W.W., Ed., The Oily Press, England, 2003, pp. 3-33. 

The identification and structural characterization of biological materials, obtained for example from plants, was traditionally carried out via the classical sequence involving extraction, separation, isolation and characterization, a sequence which requires large amounts of substance and a great deal of time. Industrial problems, for example the search for small amounts of contaminants in industrial products or in waste water, also require intensive analytical studies. 

Owing to rapid development in analytical techniques, metabolite identification and structure elucidation have become possible even with trace levels of metabolites generated with in vitro or in vivo mammalian systems. However, the microbial bioreactor is still a valuable system for metabolite structure determination, especially when the metabolite of interest presents at a low level in in vitro or in vivo mammalian systems and the isolation from these matrices is hindered by the interference of other metabolites, the parent drug or endogenous compounds, or the structure determination requires appreciable amounts of samples due to structure complexity. 

Various analyzers have been used to analyze phenolic compounds. The choice of the MS analyzer is influenced by the main objective of the study. The triple quadrupole (QqQ) has been used to quantify, applying multiple reaction monitoring experiments, whereas the ion trap has been used for both identification and structure elucidation of phenolic compounds. Moreover, time-of-flight (TOF) and Fourier-transform ion cyclotron resonance (FT-ICR) are mainly recommended for studies focused on obtaining accurate mass measurements with errors below 5 ppm and sub-ppm errors, respectively (Werner and others 2008). Nowadays, hybrid equipment also exists, including different ionization sources with different analyzers, for instance electrospray or atmospheric pressure chemical ionization with triple quadrupole and time-of-flight (Waridel and others 2001). 

Stobiecki M. 2000. Application of mass spectrometry for identification and structural studies of flavonoid glycosides. Phytochemistry 54(3) 237-256. 

In the last fifteen years most efforts aimed at identification and structure determination of dienes and of polyenes were related to studies of bio-originated compounds. The analysis of dienes and polyenes has not been reviewed, so far. The analysis of double bonds containing molecules utilizes the chemical reactivity of the bonds, and hence conjugated double bonds require different approaches than methods used for non-conjugated double bonds. One example is the use of the Diels-Alder reaction which yields derivatives of conjugated dienes whereas isolated double bonds are not affected. Some of the methods... 

The determination of the structure of synthetic dienes and polyenes is somewhat easier than the identification and structure determination of natural products. Obviously, this stems from the need to separate the latter compounds from very complex mixtures. 

Each of the major techniques of molecular spectrometry, including mass spectrometry, will now be examined in more detail. Exercises in the interpretation of spectral data in relation to the identification and structural analysis of organic compounds are given at the end of the chapter. 

A most widely used technique for quantitative trace analysis. Used as an adjunct to other spectrometric techniques in the identification and structural analysis of organic materials. Relative precision 0.5-5%. 

Visible and UV spectrometry are of secondary importance to other spectral methods for the identification and structural analysis of unknown compounds. This is a direct consequence of the broad bands and rather simple spectra which make differentiation between structurally related compounds difficult. As an adjunct to infrared, magnetic resonance and mass spectrometry, however, they can play a useful role. They can be particularly helpful in confirming the presence of acidic or basic groups in a molecule from the changes in band position and intensity associated with changes in pH (p. 369). 

Very widespread use, largely for the identification and structural analysis of organic materials useful for quantitative analysis but less widely used than UV and visible spectrometry. Near infrared region used increasingly for industrial quality control. 

Identification and structural analysis of organic materials and study of kinetic effects, mainly from proton and carbon-13 spectra. Useful for quantitative analysis but not widely applied. 

PMR spectrometry is an extremely useful technique for the identification and structural analysis of organic compounds in solution, especially when used in conjunction with infrared, ultraviolet, visible and mass spectrometry. Interpretation of PMR spectra is accomplished by comparison with reference spectra and reference to chemical shift tables. In contrast to infrared spectra, it is usually possible to identify all the peaks in a PMR spectrum, although the complete identification of an unknown compound is often not possible without other data. Some examples of PMR spectra are discussed below. 

Identification and structural analysis of organic compounds. Determination of trace impurities in a wide range of inorganic materials (spark source mass spectrometry). 

Used in conjunction with infrared, NMR, UV and visible spectral data, mass spectrometry is an extremely valuable aid in the identification and structural analysis of organic compounds, and, independently, as a method of determining relative molecular mass (RMM). The analysis of mixtures can be accomplished by coupling the technique to GC (p. 114). This was formerly done by using sets of simultaneous equations and matrix calculations based on mass spectra of the pure components. It is well suited to gas... 

A. Benninghoven and W. K. Sichtermann. Detection, Identification, and Structural Investigation of Biologically Important Compounds by Secondary Ion Mass Spectrometry. Anal. Chem., 50(1978) 1180-1184. 

It has been used for the identification and structural analysis of complex compounds. 

ESI-MS-MS permitted unambiguous identification and structure elucidation of compounds detected under NI conditions (halogenated NPECs and NPs), while for NPEOs, detected under positive ionisation conditions no fragmentation was obtained and these compounds were analysed using a single stage MS as [M + Na]+ in selected ion... 

The high sensitivity of hyphenated techniques such as HPLC-MS has also been exploited in the identification and structural studies of flavonoid glucosides [151] and the application of other hyphenated techniques such as LC-MS-MS and LC-NMR for the analysis of plant constituents has been discussed earlier [152],... 

Compared to previously reported instrument configuration, is possible also to couple two different detector systems after 2D-HPLC in order to improve the identification and structural elucidation of targeted compound, for example mass spectrometric and NMR detectors. 

To determine the phase properties of the calcined bimetallic nanoparticles, a detailed x-ray diffraction (XRD) study was carried out. The XRD data of AuPt/C showed that the diffraction patterns for the carbon-supported nanoparticles show a series of broad Bragg peaks, a picture typical for materials of limited structural coherence. Nevertheless, the peaks are defined well enough to allow a definitive phase identification and structural characterization. The diffraction patterns of Au/C and Pt/C could be unambiguously indexed into an fcc-type cubic lattice occurring with bulk gold and platinum. We estimated the corresponding lattice parameters by carefully determining... 

Mass Spectrometric Instrumentation Used in Infusion or Direct Analytical Methods for Chemical Identification and Structure Elucidation. 152... 

This chapter has two aims. First, techniques that use mass spectrometry for the identification and structural elucidation of neuroactive chemicals are reviewed. Second, and with greater emphasis, this chapter attempts to describe the routine use and pitfalls encountered when using mass spectrometry— especially GC/MS and LC/MS—for rapid, specific, quantitative analyses of neuroactive compounds and metabolites in a variety of biological matrices. 

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