Ionization methods, mass spectrometry

Tissue, B. M., Scimedia Mass Spectrometry Ionization Methods, accessed 3/9/2000, http //www.scimedia.com/chem-ed/ms/ftms.htm. 

See also Derivatization of Analytes. Gas Chromatography Column Technology High-Temperature Techniques High-Speed Techniques Detectors Environ-mentai Appiications Forensic Appiications Petro-chemicai Appiications. Mass Spectrometry Ionization Methods Overview Mass Separation Selected Ion Monitoring. 

See also Atomic Mass Spectrometry Inductively Coupled Plasma. Gas Chromatography Mass Spectrometry. Liquid Chromatography Liquid Chromatography-Mass Spectrometry. Mass Spectrometry Ionization Methods Overview Electrospray Stable Isotope Ratio. 

See also Mass Spectrometry Ionization Methods Overview Atmospheric Pressure Ionization Techniques Electrospray Matrix-Assisted Laser Desorption/lonization Time-of-Fiight. Proteins Traditionai Methods of Sequence Determination. Proteomics. 

Both the reliable determination of isotope ratios and the quantitation of trace elements generally accompanied by complete destmction of all molecular entities. Opposed to what is normally desired in organic and bio-organic mass spectrometry, ionization methods in inorganic mass spectrometry therefore use conditions which erase any molecular stmcture, i.e., inorganic mass spectrometry particularly employs high temperature plasmas to achieve atomization prior to ionization and mass analysis [27]. Furthermore, ion-neutral reactions need to be suppressed or their products destroyed in order to ensure isotopic patterns free from interferences with isobars [28,29]. 

Peptide mass fingeiprinting (PMF) is a mass spectrometry based method for protein identification. The protein is cleaved by an enzyme with high specificity (trypsin, Lys-C, Asp-N, etc.) or chemical (CNBr). The peptide mixture generated is analyzed by matrix-assisted laser desorp-tion/ionization (MALDI) or electrospray ionization (ESI)... 

Powell, K.D. Wales, T.E. Fitzgerald, M.C. Thermodynamic stability measurements on multimeric proteins using a new H/D exchange-and matrix-assisted laser desorption/ ionization (MALDl) mass spectrometry-based method. Protein Sci. 2002, 11, 841-851. 

Mass spectrometry has found various applications in the chemistry of zinc-carbon bonds. The availability of a variety of ionization techniques has made possible the identification of different types of organozinc compounds—volatile, neutral, ionic, dimeric, polymetallic, solvent-containing etc. In the majority of the reported cases, molecular species have been observed. The experimental results demonstrated that Zn—C bonds are rather weak and easily cleaved upon or after ionization. It is obvious, however, that expanding mass spectrometry-based methods of analysis of zinc complexes will greatly benefit this field of chemistry, as well as facilitate applications of organozinc compounds to material sciences. 

The development of mass spectrometric ionization methods at atmospheric pressures (API), such as the atmospheric pressure chemical ionization (APCI)99 and the electrospray ionization mass spectrometry (ESI-MS)100 has made it possible to study liquid-phase solutions by mass spectrometry. Electrospray ionization mass spectrometry coupled to a micro-reactor was used to investigate radical cation chain reaction is solution101. The tris (p-bromophenyl)aminium hexachloro antimonate mediated [2 + 2] cycloaddition of trans-anethole to give l,2-bis(4-methoxyphenyl)-3,4-dimethylcyclobutane was investigated and the transient intermediates 9 + and 10 + were detected and characterized directly in the reacting solution. However, steady state conditions are necessary for the detection of reactive intermediates and therefore it is crucial that the reaction must not be complete at the moment of electrospray ionization to be able to detect the intermediates. 

Fast-atom bombardment (FAB) and liquid secondary-ion mass spectrometry (LSIMS) methods make up the category of the particle bombardment ionization. In both methods the analyte is dissolved in a liquid such as glycerol, thioglycerol, m-nitrobenzyl alcohol, or diethanolamine and about 1 1 is placed on a... 

The fifth category of ionization includes the laser ionization mass spectrometry (LIMS) methods. Matrix-assisted laser desorption ionization (MALDI) uses... 

Wingerath, T., Kirsch, D., Kaufmann, R., Stahl, W., and Sies, H. 1999. Matrix-assisted laser desorption ionization postsource decay mass spectrometry (Review). Methods Enzymol. 299 390-408. 

Spark Source Mass Spectrometry. Another method for trace analysis probably should be mentioned and that is spark source mass spectrometry. In this technique, the sample in the form of a solid serves as an electrode and vapors, formed by sparking, are atomized and ionized to metal ions which are separated by a mass spectrometer and measured. The equipment is expensive and good results require the attention of a skilled operator. Even under the best conditions order of magnitude agreement of results is about the best that can be achieved. 

Cancilla, M.T., Penn, S.G. and Lebrilla, C.B. (1998) Alkaline degradation of oligosaccharides coupled with matrix-assisted laser desorption/ionization Fourier transform mass spectrometry a method for sequencing oligosaccharides. Anal. Chem., 70 (4), 663-72. 

A large number of samples (over 80) from various locations inside the cave — both active and inactive speleothems — were analyzed using the Th- U thermal ionization mass spectrometry (TIMS) method and only a brief summary will be given here (see also Spotl et al., 2002). U contents are invariably high (see above) and activity... 

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