Molecular mass spectrometry

ICPMS is uniquely able to borrow a quantitation technique from molecular mass spectrometry. Use of the isotope dilution technique involves the addition of a spike having a different isotope ratio to the sample, which has a known isotope ratio. This is usefiil for determining the concentration of an element in a sample that must undergo some preparation before analysis, or for measuring an element with high precision and accuracy. ... 

Orpiment, Deterioration of Arsenic Sulfide Pigments. Arie Wallert, Molecular Aspects of Ageing in Painted Works of Art, Progress Report 1995-1997, FOM Institute for Atomic and Molecular Physics, Amsterdam, NL, http //www.amolf.nl/research/biomacro molecular mass spectrometry/molart/progress report98.pdf... 

Korobeinichev, O. P., Kuibida, L. V, and Paletsky, A. A., Development and Application of Molecular Mass Spectrometry to the Study of ADN Combustion... 

Esteban-Femandez, D., Montes-Bayon, M., Blanco, G.E., Gomez- Gomez, M.M., Palacios, M.A., Sanz-Medel, A. Atomic (HPLC-ICP-MS) and molecular mass spectrometry (ESl-Q-TOF) to study cii-platin interactions with serum proteins. J. Anal. At. Spectrom. 23, 378-384 (2008)... 

Instead by solvent extraction [207], aroma compounds from aqueous media, e.g. fruit juices, can even be separated and enriched by techniques of solid phase micro extraction (SPME), preferably from the headspace [208] , corresponding devices can often be directly connected to GC systems. These techniques provide the complete spec-tmm of the individual compounds of an aroma. As it will normally not be possible and even not necessary to analyse all components of the complex mixture, the separation of its main compounds may demand a multi-dimensional (MD) gas chromatographic system [209[ as displayed in Fig. 6.14 [210[. Examples for the multi-ele-ment/multi-compound isotope analysis by such systems will be given later (6.2.2.4.4, [211[) they can even integrate the identification of the compounds by molecular mass spectrometry and a simultaneous determination of the enantiomer ratios of isomers [210, 211 [. The importance of enantiomer analysis as a tool for authenticity assessment is extensively treated in chapter 6.2.3. 

Ionization Sources Several different types of ionization sources are available for molecular mass spectrometry. The most widely used sources are listed in Table 31 -2 One of the most common is the electron impact (El) source. In this source, molecules are bombarded with a high-energy beam of electrons. This produces positive ions, negative ions, and neutral species. The positive ions are directed toward the analyzer by electrostatic repulsion. 

In Part VI, Chapter 30 is now a general introduction to separations. It includes solvent extraction and precipitation methods, an introduction to chromatography, and a new section on solid-phase extraction. Chapter 31 contains new material on molecular mass spectrometry and gas chromatography/mass spectrometry. Chapter 32 includes new sections on affinity chromatography and chiral chromatography. A section on LC/MS has been added. A new Chapter 33, Miscellaneous Separation Methods, has been included. It introduces capillary electrophoresis and field-flow fractionation. 

A common speciation scheme after sample preparation involves a fractionation step followed by the element quantification in the fractions obtained. A clear trend exists toward using the techniques that combine separation and detection steps into one operating on-line system. In these coupled techniques, the selectivity is achieved by application of powerful separation modes (different chromatographic or electrophoretic methods), while the use of atomic spectrometric techniques assures high sensitivity of detection. It should be stressed, however, that coupled techniques with element-specific detection do not provide structural information for the species. If the appropriate standards are available, the assignment of chromatographic peaks can be accomplished by spiking experiments. On the other hand, the identification of unknown forms and/or ultimate confirmation of unexpected compounds observed in the sample require the use of complementary techniques (molecular mass spectrometry or NMR). ... 

A mass spectrometer is an instrument that produces ions and separates them according to their mass-lo-charge ratios, m/z. Most of the ions we will discuss are singly charged so that the ratio is simply equal to the mass pumber of the ion. Several types of mass spectrometers are currently available from instrument manufacturers. In this chapter, we describe the three types that are used in atomic mass spectrometry the quadra-pole mass spearomeier. the lime-of-ftighl mass spectrometer. and the doubk-foctising mass spectrometer. Other types of mass spectrometers are considered in Chapter 20. which is devoted to molecular mass spectrometry. I he first column in Table I l-l indicates the types of atomic mass spectrometry in which each of the three types of mass spectrometer is usually applied. 

In this chapter, we lirst describe the nature of molecular mass spectra and dcliiie some terms used In molecular mass spectrometry. We nc.xt consider the various techniques used to form ions from analyte molecules in mass spectrometers and the types of spectra produced by these iccliniqiics. VVe then describe in some detail the various types of mass sjvctrometers Used ill iiiuleculiir mass spectrometry (other than the qiiadru H>le and Linie-of-flight inslrumenis. which received detailed treatment in Section I IB). Finally, we... 

The applications of molecular mass spectrometry are so numerous and widespread that describing them adequately in a brief space is not possible. Table 20-.5 lists... 

The use of molecular mass spectrometry to identify individual organic phos-... 

Molecular Mass spectrometry can be used to determine the molecular formulas of molecules fhat... 

A Molecular Mass Spectra 551 20B Ion Sources 551 20C Mass Spectrometers 563 20D Applications of Molecular Mass Spectrometry 577... 

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