Field-ionization mass spectrometry

Fast Atom Bombardment Ionization in Mass Spectrometry Field Ionization Kinetics in Mass Spectrometry Glow Discharge Mass Spectrometry, Methods... 

However, in the last decade there has been a tremendous advance in the techniques used for sample preparation and analysis. For instance, in the mass spectrometry field, new interfaces, ionization, and detection techniques were... 

Unlike other techniques of mass spectrometry, field desorption does not require vaporization of the sample prior to ionization. The field desorption technique has been suggested as a method to determine the molecular weights of sub-milligram quantities of involatile substances such as sugar phosphates without derivatization. 

In this book we endeavor to cover most of the topics highlighted in the introduction, and to present (i) technological developments achieved for the coupling of microfluidic systems to MS, both for the ESI and MALDI ionization techniques, (ii) relevant applications of microfluidics-to-MS couplings and (iii) research aiming at miniaturizing the mass spectrometer itself. We hope thereby to give a complete and comprehensive view to the reader of the miniaturization and mass spectrometry field with this collection of chapters. 

CappieUo, A., Famiglini, G., Palma, P., and Siviero, A., Liquid chromatogtaphy-eleciron ionization mass spectrometry fields of application and evalnation of the performance of a Direct—El interface, Mass Spectrom. Rev., 24, 978-989, 2005. 

Glowers, B.H. Steiner, W.E. Dion, H.M. Matz, L.M. Tam, M. Tarver, E.E. Hill, H.H., Evalnation of snlfonylnrea herbicides using high resolntion electrospray ionization ion mobihty qnadmpole mass spectrometry. Field Anal. Ghent. Technol. 2001, 5, 302-312. 

The main difference between field ionization (FI) and field desorption ionization (FD) lies in the manner in which the sample is examined. For FI, the substance under investigation is heated in a vacuum so as to volatilize it onto an ionization surface. In FD, the substance to be examined is placed directly onto the surface before ionization is implemented. FI is quite satisfactory for volatile, thermally stable compounds, but FD is needed for nonvolatile and/or thermally labile substances. Therefore, most FI sources are arranged to function also as FD sources, and the technique is known as FI/FD mass spectrometry. 

Although there has been some controversy concerning the processes involved in field ionization mass spectrometry, the general principles appear to be understood. Firstly, the ionization process itself produces little excess of vibrational and rotational energy in the ions, and, consequently, fragmentation is limited or nonexistent. This ionization process is one of the mild or soft methods available for producing excellent molecular mass information. The initially formed ions are either simple radical cations or radical anions (M ). 

After acceleration through an electric field, ions pass (drift) along a straight length of analyzer under vacuum and reach a detector after a time that depends on the square root of their m/z values. The mass spectrum is a record of the abundances of ions and the times (converted to m/z) they have taken to traverse the analyzer. TOP mass spectrometry is valuable for its fast response time, especially for substances of high mass that have been ionized or selected in pulses. 

Ion-Molecule Reactions. The list of ion-molecule reactions observed by mass spectrometry is highly impressive at this time we can easily count several hundred. Most of these were observed at relatively low pressures and in the presence of a draw-out or pusher field in the ionization chamber. Using this information to account for the radiation chemical product distribution requires one to recognize its restrictions to this use. 

In line with the policy of Advances to provide periodic coverage of major developments in physical methodology for the study of carbohydrates, A. Dell (London) here surveys the use of fast-atom-bombardment mass spectrometry in application to carbohydrates. This technique has achieved rapid prominence as the soft ionization technique of choice for structural investigation of complex carbohydrate sequences in biological samples. The author s extensive personal involvement in this field makes her chapter a critical, state-of-the-art overview for the specialist, as well as a valuable primer for the reader unfamiliar with this technique. 

H.D. Beckey, Principles of Field Ionization and Field Desorption Mass Spectrometry, Pergamon Press, London (1977). 

AFID = alkali-flame ionization detection FID = flame ionization detection FPD = flame photometric detection GC = gas chromatography IGEFET = interdigitated gate electrode field-effect transistor ITMS = ion trap mass spectrometry MIMS = multiphoton ionization mass spectrometry MS = mass spectrometry... 

A two-dimensional picture like that in Fig. 5.1 represents the most common analytical presentation of results however, multi-dimensional pictures can occur, as in mass spectrometry, when measurements are made for the same analyte but with varying ionization energy and/or magnetic field strength. 

Mass spectrometry (MS) in its various forms, and with various procedures for vaporization and ionization, contributes to the identification and characterization of complex species by their isotopomer pattern of the intact ions (usually cation) and by their fragmentation pattern. Upon ionization by the rough electron impact (El) the molecular peak often does not appear, in contrast to the more gentle field desorption (FD) or fast-atom bombardment (FAB) techniques. An even more gentle way is provided by the electrospray (ES) method, which allows all ionic species (optionally cationic or anionic) present in solution to be detected. Descriptions of ESMS and its application to selected problems are published 45-47 also a representative application of this method in a study of phosphine-mercury complexes in solution is reported.48... 

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