Liquid chromatography - mass spectroscop

To investigate the complex metabolic consequences of disease processes, toxic reactions, and genetic manipulation, nonselective but specific analytical approaches are required. Several spectroscopic methods in addition to nuclear magnetic resonance (NMR) can produce metabolic signatures of biomaterials, including mass spectrometry (MS), gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid... 

Hyphenated methods such as gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) and a number of other chromatographic and spectroscopic configurations are perfectly suitable for initial characterization of the impurities. Of course, these methods are not always applicable, especially when the authentic material is needed for purposes of structure confirmation, synthesis, or toxicity studies (this subject is discussed in various chapters of this book also see reference 2). 

The wide range of spectroscopic techniques such as UV, infrared (IR), Gas Chromatography-Mass Spectroscopy (GC-MS), Liquid Chromatography-Mass spectra (LC-MS), Nuclear Magnetic Resonance (NMR), and mass spectra (MS) form the backbone of modem stmctural elucidation studies as mentioned in the Figure 8.2. Prior to the availability of such advanced techniques, ambiguities existed in the determination of stmctures of bioactive compounds. The process of spectroscopic determination should be closely allied to familiarity with the scientific literature. If the compound has not been described, it may be very similar to reported compounds and that may assist in the interpretation of data for the unknown. In this regard, an awareness of the coextractives from the plant may also be of value to determine the stmctures. 

Detailed kinetic studies, product studies, NMR spectroscopic analyses, LC-MS (liquid chromatography-mass spectrometry) chromatography, and Cl and deuterium tracer studies have shown that the homogeneous hydrolysis of 2-chloroethyl ethyl sulfide in water and in 1 1 acetone/water at concentrations above 10 M occurs by the mechanism in Scheme 10. °... 

Spectroscopic techniques used in essential oil analysis comprise ultraviolet and visible spectrophotometry, infrared spectrophotometry (IR), mass spectrometry (MS), and nuclear magnetic resonance spectroscopy (NMR), including the following H-NMR, C-NMR, and site-specific natural isotope fractionation NMR. Combined techniques (hyphenated techniques) employed in essential oil analysis are GC/MS, liquid chromatography/mass spectrometry, gas chromatography/Fourier transform infrared spectrophotometry (GC/FT-IR), GC/FT-IR/MS, GC/atomic emission detector, GC/isotope ratio mass spectrometry, multidimensional GC/MS. 

Detection in SFC can be achieved in the condensed phase using optical detectors similar to those used in liquid chromatography or in the gas phase using detectors similar to those used in gas chromatography. Spectroscopic detectors, such as mass spectrometry and Fourier transform infrared spectroscopy, are relatively easily interfaced to SFC compared to the problems observed with liquid mobile phases (see Chapter 9). The range of available detectors for SFC is considered one of its strengths. 

Pullen, F. S., Swanson, A. G., Newman, M. J. and Richards, D. S., On-line liquid chromatography/nuclear magnetic resonance spectrometry — a powerful spectroscopic tool for the analysis of mixtures of pharmaceutical interest, Rapid Comm. Mass. Spectr., 9, 1003, 1995. 

Figures 4.31(c), 4.36 and 13.3 from Snyder and Kirkland, Introduction to Modern Liquid Chromatography, 2nd edn., (1979) 9.41(a), (b) and (c) from Cooper, Spectroscopic Techniques for Organic Chemists (1980) 9.46 from Millard, Quantitative Mass Spectrometry (1978) 4.17, 4.18, 4.31 (a), 4.33, 4.34(a), 4.37, 4.38, 4.43 and 4.45 from Smith, Gas and Liquid Chromatography in Analytical Chemistry (1988) figures 4.42 and 13.2 from Berridge, Techniques for the Automated Optimisation of Hplc Separations (1985) reproduced by permission of John Wiley and Sons Limited 11.1, 11.5, 11.6, 11.12, 11.13, 11.14, 11.18 and 11.19 from Wendlandt, Thermal Analysis, 3rd edn., (1986) reprinted by permission of John Wiley and Sons Inc., all rights reserved.

Numerous analyses in the quality control of most kinds of samples occurring in the flavour industry are done by different chromatographic procedures, for example gas chromatography (GC), high-pressure liquid chromatography (fiPLC) and capillary electrophoresis (CE). Besides the different IR methods mentioned already, further spectroscopic techniques are used, for example nuclear magnetic resonance, ultraviolet spectroscopy, mass spectroscopy (MS) and atomic absorption spectroscopy. In addition, also in quality control modern coupled techniques like GC-MS, GC-Fourier transform IR spectroscopy, HPLC-MS and CE-MS are gaining more and more importance. 

Principal component analysis is most easily explained by showing its application on a familiar type of data. In this chapter we show the application of PCA to chromatographic-spectroscopic data. These data sets are the kind produced by so-called hyphenated methods such as gas chromatography (GC) or high-performance liquid chromatography (HPLC) coupled to a multivariate detector such as a mass spectrometer (MS), Fourier transform infrared spectrometer (FTIR), or UV/visible spectrometer. Examples of some common hyphenated methods include GC-MS, GC-FTIR, HPLC-UV/Vis, and HLPC-MS. In all these types of data sets, a response in one dimension (e.g., chromatographic separation) modulates the response of a detector (e.g., a spectrum) in a second dimension. 

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