The Principle of Mass Spectrometry

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... 

Mass spectrometry is also extremely useful as a process monitor. Less sophisticated residual gas analyzers (RGA) operating on the principles of mass spectrometry are available for these purposes and for end point detection. For the etching of Si 128-130), poly-Si 130), silicon nitride 130), and Si02 (729), SiF (m/e=85) has been shown to be effective for end-point detection. In addition, (m/e=14) is useful for nitride 129,130) in leak tight systems, while O (m/e =16), CO (m/e =44) and Si" " (m/e=29) are useful for oxide (757). Because of the general nature of mass spectrometry as a diagnostic tool, it should be applicable to etching studies of metals and other semiconductor materials. 

The principles of mass spectrometry of organic compounds are described in a number of excellent reviews and monographs.1-4 Hence, we shall not attempt to present here any theory of the mass-spectral method that is more comprehensive than that necessary for understanding the discussion. 

To benefit general readers, the discussion has been limited to methodologies that are accessible to nonspecialists and that can be carried out on commercially available spectrometers without special modifications. The chapter illustrates the principles of mass spectrometry by demonstrating how various techniques [MALDI, ESI, Fourier transform ion cyclotron resonance (FT-ICR), ion traps, and tandem mass spectrometry (MS-MS)] work. It also provides examples of utilizing mass spectrometry to solve biological and biochemical problems in the field of protein analysis, protein folding, and noncovalent interactions of protein-DNA complexes. 

There are two types of GC gas-solid (adsorption) chromatography and gas-liquid (partition) chromatography. The more important of the two is gas-liquid chromatography (GLC), used in the form of a capillary column. In this chapter, we describe the principles of operation of gas chromatography, the types of GC columns, and GC detectors. The principles of mass spectrometry (MS) are described, along with coupling of the gas chromatograph with a mass spectrometer (GC-MS). 

Mass spectrometry detection in liquid chromatography, like with gas chromatography, has become a powerful analysis tool for sensitive and selective mass detection in characterizing complex samples. Review the principles of mass spectrometry and the types of instruments used for chromatography detection in Chapter 20. 

As the name implies, this is a mass spectrometric technique. The principle of mass spectrometry can be explained briefly with the aid of Figure 4.12, showing the diagram of a double-focusing instrument that is the type used in spark source mass spectrometry. 

The rapid development of mass spectrometric technology and the wide field of applications exclude a complete and comprehensive discussion of mass spectrometric possibilities for trace analysis of metals. Therefore, this report will give a brief outline of the principles of mass spectrometry (MS) and the fundamentals of qualitative and quantitative mass spectrometric analysis with emphasis on recent developments and results. The classical methods of analysis of solids, i.e. spark-source MS and thermal ionization MS, as well as newer methods of metal analysis are described. Focal points in this survey of recently developed techniques include secondary ion MS , laser probe MS , plasma ion source MS gas discharge MS and field desorption MS . Here, a more detailed description is given and the merits of these emerging methods are discussed more explicitly. In particular, the results of the FD techniques in elemental analyses are reviewed and critically evaluated. 

It is hoped that the book will be a good teaching tool of the principles of mass spectrometry to undergraduates and graduates as well as to those with no background in mass spectrometry. The practitioner of mass spectrometry at all levels should also enjoy reading the book. 

M.L. Gross and R. Caprioli (eds), The Encyclopedia of Mass Spectrometry, Elsevier, Amsterdam (2000-2002), 10 vols. E. De Hoffmann and V. Stroobant, Mass Spectrometry Principles and Applications, John Wiley Sons, Ltd, Chichester (2001). 

An electrospray is generally produced by the application of an electric field to a small flow of liquid from a capillary tube toward a counter electrode. The principles of electrospray as applicable to mass spectrometry and the mechanisms involved have been a subject of intense debate over the last decade and have been addressed even before that. This is evident from the discussions in the 2000 issue of the Journal of Mass Spectrometry (e.g., Mora11), the book by Cole,12 and several reviews.8,10 13 14 Here we present a summary encapsulating the relevant observations and direct the readers to the above articles for a more elaborate account. 

The largest increase in experimental measurements on aqueous solutions has been in those designed to furnish information on molecular interactions and order. These techniques, along with the kinds of information which can be derived from them, are outlined in Figure 5. Although the principles behind all these techniques have been known for many years, advances in instrumentation and in data collection have encouraged their widespread application to solutions of all kinds. The use of mass spectrometry to study interactions between isolated solvent and solute molecules has been perfected largely within the past ten years. This topic is reviewed in reference (113). 

Mass spectrometry is the field dealing with separation and analysis of substances according to the masses of the atoms and molecules of which the substance is composed. The principle of mass analysis is that parameters of time and space of the path of a charged particle in a force field in vacuum are dependent on its mass-to-charge ratio (m/z). 

The scope of the use of mass spectrometry in the protein analysis has grown enormously in the past few decades. MS has become an important analytical tool in biological and biochemical research. Its speed, accuracy and sensitivity are unmatched by conventional analytical techniques. The variety of ionization methods permits the analysis of peptide or protein molecules from below 500 Da to as big as 300 Da (Biemann 1990 Lahm and Langen 2000). Basically, a mass spectrometer is an instrument that produces ions and separates them in the gas phase according to their mass-to-charge ratio (m/z). The basic principle of operation is to introduce sample to volatilization and ionization source, and then the molecular fragments from the ionization of the sample are detected by various kinds of detector and the data are analyzed with computer software. 

II. The Basic Principles of Mass Spectrometry of Organic Compounds. 40... 

This present article summarizes the results of these studies as well as related mass spectroscopic data obtained in the author s laboratories as well as some related studies by other workers 4-5>. For a review of the general principles of mass spectrometry the reader is referred to any of several books in this area 6 10> (see also 11-23> on information to be obtained from mass spectra). 

While mass spectrometry cannot provide the detailed structural information that is obtained by NMR and X-ray crystallography, it can, in principle, provide valuable information on the formation and stoichiometry of nonco-valent complexes. There are several key questions that need to be addressed before we can decide whether the advantages of mass spectrometry (sensitivity, speed, and specificity) can be successfully applied to the study of nonco-valent interactions. These questions are... 

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