Mass Spectrometric Instrumentation

The promising use of various MALDI- and ESI-MS approaches in proteome research has accelerated many developments in the instrumental design and concepts of mass spectrometry. Novel MS techniques and intriguing combinations of existing instruments have emerged. Nonetheless, the basic principle of measuring the mass-to-charge ratios of analytes remains. 

In this chapter, a description of the working principles of TOP as well as TOP/ TOP and qTOP analyzers is provided. The latter two, illustrated in Pigure 4.1, are hybrid instruments and have already had a big impact on proteomic research. 

If a protein spot cannot successfully be identified by MALDl analysis, peptide sequencing byautomated nano HPLC/FSI MS/MS is an alternative. This provides superior sensitivity due to the preconcentration of peptides on trapping columns (Mitulovic et ah, 2003) and delivers considerably more sequence-specific information at the peptide level. However, nano HPLC coupled online with ESI-tandem MS analysis is much more time-consuming than MALDI-PMF. Therefore, it is predominantly used to efficiently identify complex protein samples which have only been separated partially, e.g., by 1-D PAGE. This case represents the 

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Parallel to the development of mass spectrometric instrumentation and methodologies, the improvements of separation techniques, such as gas chromatography (GC), high performance liquid chromatography (HPLC) and capillary electrophoresis (CE), and of their coupling with MS allowed the study of complex mixtures, that are generally encountered in most studies. 

In the last twenty years, many of the developed and validated high performance liquid chromatography methods with conventional diode array or fluorescence detectors (DAD, FLD) were improved and substituted by new hyphenation with mass spectrometric instrumentation and/or NMR, especially for the analyses of raw materials derived from Natural sources. The main goal of this coupling is achieved by improvement of selectivity and sensitivity of new instrumental configurations [7], Furthermore, with these configurations it is possible to obtain, in only one analysis, the complete chemical structure elucidation, identification and quantification of targeted compounds. 

In principle, mass spectrometry is not suitable to differentiate enantiomers. However, mass spectrometry is able to distinguish between diastereomers and has been applied to stereochemical problems in different areas of chemistry. In the field of chiral cluster chemistry, mass spectrometry, sometimes in combination with chiral chromatography, has been extensively applied to studies of proton- and metal-bound clusters, self-recognition processes, cyclodextrin and crown ethers inclusion complexes, carbohydrate complexes, and others. Several excellent reviews on this topic are nowadays available. A survey of the most relevant examples will be given in this section. Most of the studies was based on ion abundance analysis, often coupled with MIKE and CID ion fragmentation on MS " and FT-ICR mass spectrometric instruments, using Cl, MALDI, FAB, and ESI, and atmospheric pressure ionization (API) methods. 

Mass Spectrometric Instrumentation Used in Infusion or Direct Analytical Methods for Chemical Identification and Structure Elucidation. 152... 

The brief given to us by the editor when we were approached to write the current chapter was to update the landmark 1987 article and thus to contribute a new article on the subject that reflects the rapid subsequent developments in the field of biological mass spectrometry. We have therefore set out to introduce and describe the most commonly available modern mass-spectrometric instrumentation that is used in carbohydrate studies, and to highlight, using a small selection of relevant examples, how it is now typically being used for the analysis of carbohydrates. 

As a final demonstration of new technological achievements, it was recently also demonstrated that gas molecules can be trapped in an electric field on a chip (Meek et al., 2009). Manipulating a packet of ions in a vacuum is quite common practice in mass spectrometric instrumentation, where ions can be collected and analyzed in, for example, ion traps and... 

The SRM acquisition mode allows one to obtain a sensitivity and selectivity gain with respect to SIM. The detection of selected reactions, based on the decomposition reactions of ions that are characteristic of the compounds to be analysed, requires the use of a tandem mass spectrometric instrument. In order to carry out this type of analysis, the spectrometer is set so as to let through only the ions produced by a decomposition reaction in the chosen reaction region for example, the first spectrometer selects the precursor ion with an mp+/z ratio that is characteristic of the compound to be detected, while the second spectrometer selects the fragment ion with an ntf+/z ratio resulting from the characteristic decomposition reaction of the compound to be analysed, mp 1 —> ni(+ + mn, that occurs between the two analysers. 

Ahnell and Koski have reported the observation of ions from CF3CI, one of the molecules employed by Stuckey and Kiser ° to study the F ion. The mass spectrometric instrumentation used by Ahnell and Koski differs from those described above and therefore their observations and results merit careful consideration. 

In addition we will consider the possibility to obtain reliable theoretical information on the preferred attach sites for proton and metal cations and on the potential energy surfaces (PES) that cannot be determined experimentally even with the most modern and sophisticated mass-spectrometric instruments [22,23j. Furthermore, we will propose the way to rationalize some of chemical properties by using the concepts of hardness, softness and other reactivity indices (Fukui functions) for which an exact definition exists only in the framework of DFT 1111. These last fascinating tools can contribute to increase funhemiore the DFT use going in the "core" of molecules to predict and explain basic chemical concepts. 

In order to achieve the highest level of accuracy, special care must be taken in setting up mass spectrometric instrumentation prior to measurement of isotopic ion abundance ratios, as a long stabilisation period may be necessary in order to achieve the highest precision. A major source of imprecision is the instability of the instrument and the electronic signal level must be correctly set and not be subject to drift. In the case of the latest computer controlled instruments such checks can be carried out automatically. 

For one study involving the differentiaton of C3H3 isomers, a Finnigan triple quadrupole mass spectrometer was employed. This type of mass spectrometric instrumentation has been described in several publicatons (23-24) and has been applied to a number of problems (25-26) in analytical chemistry. The first quadrupole is used to select an ion of interest, the second, in an rf-only mode, is used as a trap in which the ion undergoes (in our case reactive) collisions with a selected neutral gas, and the third quadrupole is used to analyze the results of those collisions. Work on structure differentiation was carried out on a VG Analy-... 

Abstract This chapter gives an overview of strategies used in the identification and analysis of environmental transformation products of three important groups of synthetic chemicals pesticides, pharmaceuticals, and personal care products. The characteristics and features of modern mass spectrometric instrumentation coupled to liquid chromatographic separation techniques as well as complementary techniques are presented and examples of their application to the characterization of transformation products of synthetic chemicals are described. Analytical methodologies for the quantitative analysis of the intact parent compounds and their transformation products in the environment are compiled. 

The majority of DClM-MS instruments described to date have been built in-house in a small number of laboratories of leading physical chemists. Because the construction of these instruments requires very significant mechanical, electrical, engineering, and software support, the wider application of the technique has been limited markedly. The laboratories concerned must not only manufacture and integrate the mobility device but must assemble mass spectrometric instrumentation that competes with commercial offerings in terms of sensitivity, ease of use, reliability, capability of interfacing with separation science approaches, and acquisition and processing software. 

Major advancements in mass spectrometric instrumentation (e.g., ESI and MALDI) and electronics (e.g., TOE data handling) have been accompanied by rapid progress in computerization. Older mass spectrometrists may still remember when hand-adjusted potentiometers were used to manipulate the ion beam, and spectra were collected on photographic paper where the peaks had to be counted by hand (using... 

TLC-MS techniques will be reviewed first based on the ion source and second by the analyte type. Chromatographic and mass spectrometric procedures will be described in detail to inform the reader of the possibilities and limitations of a particular technique. The selection of ion source is determined by the analyte type that has been resolved on a TLC plate. Appropriate combinations of ionization methods and analyte types allow one to easily obtain and interpret high quality mass spectra. Therefore, the choice of mass spectrometric instrument is a key step in the process of characterization of compounds using TLC-MS techniques. 

All mass spectrometric instruments contain regions where ionization, mass analysis, and ion detection take place. Mass spectrometry takes place at low pressure all of the mass spectrometric components are contained in a vacuum... 

From the standpoint of mass spectrometric instrumentation, the story of this evolution has taken place on four fronts ... 

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