Hyphenated nuclear magnetic resonance

Strohschein, S., Pursch, M., and Albert, K., Hyphenation of high performance liquid chromatography with nuclear magnetic resonance spectroscopy for the characterization of (3-carotene isomers employing a Cjq stationary phase, J. Pharm. Biom. Anal., 21, 669, 1999. 

Because carotenoids are light- and oxygen-sensitive, a closed-loop hyphenated technique such as the on-line coupling of high performance liquid chromatography (HPLC) together with nuclear magnetic resonance (NMR) spectroscopy can be used for the artifact-free structural determination of the different isomers. 

Wilson ID. 2000. Multiple hyphenation of liquid chromatography with nuclear magnetic resonance spectroscopy, mass spectrometry and beyond. J Chromatogr A 892 315-327. 

T Hyphenated Chromatographic Techniques in Nuclear Magnetic Resonance Spectroscopy... 

Examines hyphenated chromatographic techniques with nuclear magnetic resonance spectroscopy... 

Hyphenated analytical techniques such as LC-MS, which combines liquid chromatography and mass spectrometry, are well-developed laboratory tools that are widely used in the pharmaceutical industry. Eor some compounds, mass spectrometry alone is insufficient for complete structural elucidation of unknown compounds nuclear magnetic resonance spectroscopy (NMR) can help elucidate the structure of these compounds (see Chapter 20). Traditionally, NMR experiments are performed on more or less pure samples, in which the signals of a single component dominate. Therefore, the structural analysis of individual components of complex mixtures is normally time-consuming and less cost-effective. The... 

The hyphenation of capillary electromigration techniques to spectroscopic techniques which, besides the identification, allow the elucidation of the chemical structure of the separated analytes, such as mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR) has been widely pursued in recent years. Such approaches, combining the separation efficiency of capillary electromigration techniques and the information-rich detection capability of either MS or NMR, are emerging as essential diagnostic tools for the analysis of both low molecular weight and macromolecular compounds. 

Many other analytical techniques can be coupled to mass spectrometers. These so-called hyphenated techniques, like GC-MS and LC-MS, include but are not limited to ICP-MS (inductively coupled argon plasma), SCF-MS (supercritical fluid), NMR-MS (nuclear magnetic resonance) and IR-MS (infrared). 

The aim of this text is to introduce the fascinating topic of the hyphenation of chromatographic separation techniques with nuclear magnetic resonance spectroscopy to an interested readership with a background either in organic, pharmaceutical or medical chemistry. The basic principles of NMR spectroscopy, as well as those of separation science, should previously be known to the reader. 

This article treats the benefits, possibilities and drawbacks of supercritical fluid chromatography (SFC) and supercritical fluid extraction (SFE) coupled to nuclear magnetic resonance spectroscopy. After a general overview and consideration of the motivation for such techniques, the design of high-pressure flow probes, as well as the principle experimental set-ups, are described. By means of several applications and comparison to HPLC-NMR, the utility of these hyphenated techniques is demonstrated. 

LC-NMR. Separations using reverse-phase (RP) liquid chromatography are potentially more powerful because samples can be studied without derivatization. Numerous attempts have been made to separate NOM and while most studies exhibit some degree of separation, to date the complete separation of a NOM sample has not been accomplished. Even only partial separation is possible, and it is worth to hyphenate a separation method with structure information-oriented analytical applications. Liquid chromatography combined with nuclear magnetic resonance and preliminary studies with solid-phase extraction were conducted on NOM isolated from freshwater and soil (Simpson et al., 2004). 

Spectroscopy has become a powerful tool for the determination of polymer structures. The major part of the book is devoted to techniques that are the most frequently used for analysis of rubbery materials, i.e., various methods of nuclear magnetic resonance (NMR) and optical spectroscopy. One chapter is devoted to (multi) hyphenated thermograviometric analysis (TGA) techniques, i.e., TGA combined with Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy, gas chromatography, differential scanning calorimetry and differential thermal analysis. There are already many excellent textbooks on the basic principles of these methods. Therefore, the main objective of the present book is to discuss a wide range of applications of the spectroscopic techniques for the analysis of rubbery materials. The contents of this book are of interest to chemists, physicists, material scientists and technologists who seek a better understanding of rubbery materials. 

Elipe, M.V.S., Advantages and disadvantages of nuclear magnetic resonance spectroscopy as a hyphenated technique, Anal. Chim. Acta., 497, 1-25 (2003). 

Korhammer SA, Bernruether A, Hyphenation of high-performance liquid chromatography (HPLC) and other chromatographic techniques (SFC, GPC, GC, CE) with nuclear magnetic resonance (NMR) A review, J. Anal. Chem., 354 131-135, 1996. 

Analytical methods for aluminum can be divided into those that give information about its localization, and those that inform about its quantity. In the first group are nuclear techniques, involving the Al-26 tracer and the Al-27 nuclear magnetic resonance (NMR). In the second group is the well-established technique for aluminum quantification, ETAAS, and a new generation of chromatographic separations coupled with spectrometric detection that allow compartmentalized quantification, the hyphenated systems. 

In general, however, detailed protocols for the direct analysis of stereochemical features by mass spectrometric means have not been achieved so far. Instead, other analytical methods, such as X-ray analysis or nuclear magnetic resonance (NMR), elegantly address these issues [3]. However, with respect to the analysis of trace compounds and in the context of high-throughput analytical methods, it would be beneficial to develop tools for rapid stereochemical assays by mass spectrometric means or hyphenated techniques [4,5]. 

J. A. De Koning, A. C. Hogenboom, T. Lacker, S. Strhoschein, K. Albert, and U. A. Th. Brinkman, On-line trace enrichment in hyphenated liquid chromatography-nuclear magnetic resonance spectroscopy,/. Chromatogr. A 813 (1998), 55-61. 

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