Nuclear magnetic resonance spectroscopy 484 INDEX

When simple Hquids like naphtha are cracked, it may be possible to determine the feed components by gas chromatography combined with mass spectrometry (gc/ms) (30). However, when gas oil is cracked, complete analysis of the feed may not be possible. Therefore, some simple definitions are used to characterize the feed. When available, paraffins, olefins, naphthenes, and aromatics (PONA) content serves as a key property. When PONA is not available, the Bureau of Mines Correlation Index (BMCI) is used. Other properties like specific gravity, ASTM distillation, viscosity, refractive index. Conradson Carbon, and Bromine Number are also used to characterize the feed. In recent years even nuclear magnetic resonance spectroscopy has been... 

SD standard deviation SDE simultaneous distillation extraction SDS sodium dodecyl sulfate SFC solid fat content SFI solid fat index SHAM salicylhydroxamic acid SIM selected ion monitoring SNIF-NMR site-specific natural isotope fractionation measured by nuclear magnetic resonance spectroscopy SP-HPLC straight-phase high-performance liquid chromatography... 

Johnson, L. F. and Jankowski, W. C. (1972). Carbon-13 Nuclear Magnetic Resonance Spectroscopy. A Collection of Assigned, Coded and Indexed Spectra , Wiley-Interscience, New York. 

Contents F. W. WEHRLI and T. NISHIDA, The Use of Carbon-13 Nuclear Magnetic Resonance Spectroscopy in Natural Products Chemistry - G. OHLOFF and I. FLAMENT, The Role of Heteroatomic Substances in the Aroma Compounds of Foodstuffs - A. J. WEIN-HEIMER, C. W. J. CHANG, and J. A. MATSON, Naturally Occurring Cembranes - Author Index - Subject Index. 

Library of Congress Cataloging in Publication Data. Pregosin, P. S. P and C NMR of transition metal phosphine complexes. (NMR, basic principles and progress 16) Bibliography p. Includes index. 1. Nuclear magnetic resonance spectroscopy. 2. Transition metal compounds. 

For some liquid feedstocks such as naphthas, the componential composition is often obtained by gas chromatography (GC) and/or mass spectrometry (MS). For gas oils or heavier feedstocks, it is impossible to obtain the desired analysis. Paraffins, olefins, naphthenes, aromatics (PONA) grouping is sometimes used as a means of feed characterization. For gas oils. Bureau of Mines Correlation Index (BMCI) has been used as a parameter for feed characterization. Since the 1980s, nuclear magnetic resonance (NMR) spectroscopy has been used to characterize heavy feedstocks. 

Terpenoids can be analyzed by the usual methods. For the volatile members of the family, gas chromatography-mass spectrometry (gc-ms) is a particularly useful tool. In laboratories (e.g., those in the major fragrance companies), which are accustomed to analyzing mixtures of volatile terpenoids, gc-ms is the major analytical technique employed and such laboratories will have extensive libraries of mass spectra of terpenoids to assist in this. However, the mass spectral fragmentation patterns of closely related terpenoids are often so similar as to render definitive identification by ms alone, impossible. For these materials and those for which there is no reference (e.g., compounds newly isolated from nature), nuclear magnetic resonance (nmr) spectroscopy is the analytical tool of choice. Physical techniques, e.g., density, refractive index, and optical rotation, are relatively inexpensive and prove useful in quality control. 

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