Mass Spectrometry Basics types

Under the headline of instmmentation we shall mainly discuss the different types of mass analyzers in order to understand their basic principles of operation, their specific properties and their performance characteristics. Of course, this is only one aspect of instmmentation hence topics such as ion detection and vacuum generation will be addressed in brief. As a matter of fact, sample introduction is more closely related to particular ionization methods than to the type of mass analyzer employed, and therefore, this issue is treated in the corresponding chapters on ionization methods. The order of appearance of the mass analyzers in this chapter neither reflects the ever-changing percentage they are employed in mass spectrometry nor does it strictly follow a time line of their invention. Instead, it is attempted to follow a trail of easiest understanding. 

From its very beginnings to the present almost any physical principle ranging from time-of-flight to cyclotron motion has been employed to construct mass-analyzing devices (Fig 4.1). Some of them became extremely successful at the time they were invented, for others it took decades until their potential had fully been recognized. The basic types of mass analyzers employed for analytical mass spectrometry are summarized below (Tab. 4.1). 

The basic principles of absorption spectroscopy are summarised below. These are most obviously applicable to UV and IR spectroscopy and are simply extended to cover NMR spectroscopy. Mass Spectrometry is somewhat different and is not a type of absorption spectroscopy. 

Half-sandwich complexes of the type MesCsEl+X- with El = Ge, Sn and Pb are stable under standard conditions and have been well characterized. However, the corresponding silicon derivatives have only been identified by mass spectrometry. An environment of very low basicity and nucleophilicity will be necessary in order to further stabilize compounds of this type. 

It has been the purpose of this paper to provide an overview of the basic differences and similarities of the various types of Instruments which detect Ionized particles emitted from surfaces by energetic particle bombardment. Since the scope of secondary ion mass spectrometry Is so broad, It is not surprising that no one Instrument has been designed to perform optimally for all types of SIMS analyses. Design aspects of the primary beam, extraction optics, mass spectrometer, detection equipment and vacuum system must be considered to construct an Instrument best suited for a particular purpose. 

Developments in mass spectrometry technology, together with the availability of extensive DNA and protein sequence databases and software tools for data mining, has made possible rapid and sensitive mass spectrometry-based procedures for protein identification. Two basic types of mass spectrometers are commonly used for this purpose Matrix-assisted laser desorption/ionization (MALDI)-time-of-flight (TOF) mass spectrometry (MS) and electrospray ionization (ESI)-MS. MALDI-TOF instruments are now quite common in biochemistry laboratories and are very simple to use, requiring no special training. ESI instruments, usually coupled to capillary/nanoLC systems, are more complex and require expert operators. We will therefore focus on the use of MALDI-... 

The goal of Chapter 6 is to familiarize investigators in biological and medical research with mass spectrometry and its potential applications in these fields, with the anticipation that it will encourage and enable them to utilize MS in their research. An attempt has been made to provide a clear basic description of the modern mass spectrometers and of the most relevant types of experiments that they can perform. Discussed also are the advantages and drawbacks of the different methods in the context of biological research with examples of the ability of mass spectrometry to solve problems in this field of research. 

The basic principle underlying mass spectrometry was formulated by J. J. Thomson (the discoverer of the electron) early in the century. Working with cathode ray tubes, he was able to separate two types of particles, each with a slightly different mass, from a beam of neon ions, thereby proving the existence of isotopes. (Isotopes are atoms of the same element that have slightly different atomic masses due to the presence of differing numbers of neutrons in the nucleus.) The first mass spectrometers were built in 1919 by F. W. Aston and A. J. Dempster. 

The types of tandem mass spectrometers capable of performing MS/MS experiments fall into two basic categories tandem in space and tandem in time. Tandem-in-space instruments have discrete mass analyzers for each stage of mass spectrometry examples include multisector, triple-quadru-pole, and hybrid instruments (instruments having mixed types of analyzers such as a magnetic sector and a quadrupole). Tandem-in-time instruments have only one mass analyzer where each stage of mass spectrometry takes place in the same analyzer but is separated in time via a sequence of events. Examples of this type of instrument include Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers and quadrupole ion traps, described in Chapter 3. 

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