Ionization methods, for mass

Metastable atom bombardment (MAB) is a novel ionization method for mass spectrometry invented by Michel Bertrand s group at the University of Montreal, Quebec, Canada, and described by Faubert et al.38 For the identification of bacteria by MS, MAB has a number of significant advantages relative to more familiar ionization techniques. Electron ionization (El) imparts so much excess energy that labile biomolecules break into very small fragments, from which the diagnostic information content is limited since all... 

Electrospray (ESI) is an atmospheric pressure ionization source in which the sample is ionized at an ambient pressure and then transferred into the MS. It was first developed by John Fenn in the late 1980s [1] and rapidly became one of the most widely used ionization techniques in mass spectrometry due to its high sensitivity and versatility. It is a soft ionization technique for analytes present in solution therefore, it can easily be coupled with separation methods such as LC and capillary electrophoresis (CE). The development of ESI has a wide field of applications, from small polar molecules to high molecular weight compounds such as protein and nucleotides. In 2002, the Nobel Prize was awarded to John Fenn following his studies on electrospray, for the development of soft desorption ionization methods for mass spectrometric analyses of biological macromolecules. ... 

Atmospheric pressure photoionization (APPI) was recently introduced in the world of atmospheric pressure ionization techniques to analyze nonpolar molecules that are not efficiently ionized either by ESI or by APCI. Photoionization (PI) was already exploited some 30 years ago as a detection method for GC and LC, but only in recent times it has been used as an ionization method for mass spectrometry [52],... 

Peptides. One of the applications that has benefited most from the development of soft ionization methods for mass spectrometry has been the analysis of polar biological materials. Peptides, in particular, have been extensively studied by a variety of soft ionization methods, primarily FAB, with excellent results being obtained for peptides in the 1000-10000 dalton range. LD-FTMS also has proved to be very successful for analysis of simple peptides and an examination of these results should help delineate the analytical potential of LD-FTMS in this important area. 

The Laser Desorption Ionization (LDI) was investigated by Franz Hillenkamp and Michael Karas [2, 3], LDI involved sample bombardment with short and intense pulses from a laser light to effect both desorption and ionization of the analyte molecules. It has become a soft desorption ionization method for mass spectrometric analyses of biological macromolecules and small molecular compounds. The MALDI technique was improved by Koichi Tanaka. 

G. J. Van Berkel, An overview of some recent developments in ionization methods for mass spectrometry, Eur. J. Mass Spectrom. 9 (2003), 539-562. 

John B. Fenn, Koichi Tanaka For their development of soft desorption ionization methods for mass spec-trometric analyses of biological macromolecules. ... 

Shiokawa Y, Nakamura M, Hirano Y, Fujii T. Ionization apparatus and ionization method for mass spectrometry. From U.S. Pat Appl Publ. 2002 US 20020053636 A1 20020509, Language English. 

To date, no fewer than five Nobel Prizes have been awarded for work directly related to mass spectrometry J. J. Thomson (Physics, 1906) for theoretical and experimental investigations on the conduction of electricity by gases F. W. Aston (Chemistry, 1922) for discovery, by means of a mass spectrograph, of isotopes, in a large number of nonradioactive elements W. Paul (Physics, 1989) for the development of the ion trap technique and most recently J. B. Fenn and K. Tanaka (Chemistry, 2002) for the development of soft desorption ionization methods for mass spectrometric analyses of biological macromolecules. ... 

Grotemeyer J, Boesl U, Walter K and Schlag EW (1986) A general soft ionization method for mass spectrometry resonance-enhanced multiphoton ionization of biomolecules. Organic Mass Spectrometry 21 645-653. 

Ott, K. H., Soft ionization methods for mass spectrometric analysis of surfactants (in German), Fette, Seifen, Anstrichm., 1985, 87, 377-382. 

In 2002, the Nobel Prize in Chemistry was awarded to Koichi Tanaka and John B. Fenn for. ..their development of soft desorption ionization methods for mass spectrometric analysis of large biopolymers.... The decision of the Nobel Prize Committee caused a controversy, because many scientists... 

Electrospray ionization mass spectrometry (ESI-MS) is an analytical method for mass determination of ionized molecules. It is a commonly used method for soft ionization of peptides and proteins in quadmpole, ion-trap, or time-of-flight mass spectrometers. The ionization is performed by application of a high voltage to a stream of liquid emitted from a capillaty. The highly charged droplets are shrunk and the resulting peptide or protein ions are sampled and separated by the mass spectrometer. 

Resonance ionization methods (RIMS) have also been explored for improving Th ionization efficiency for mass spectrometric measurement (Johnson and Fearey 1993). As shown in Figure 3, two lasers are required, a continuous resonant dye laser for resonance of thorium atoms, and a continuous UV argon laser for transition from resonance to ionization. Consequently, sophisticated laser instrumentation is required for these methods. 

In this chapter we have discussed the successful implementation in our laboratory, for the first time, of the soft (i.e. low energy) electron-impact ionization method for product detection in crossed molecular beams reactive scattering experiments with mass spectrometric detection. Analogous to the approach of soft photoionization by tunable VUV synchrotron radiation,... 

Like sector analyzers, quadrupole analyzers are well suited for continuous ion sources such as ESI, but are not well-suited for pulsed ionization methods. Quadmpole mass spectrometers are generally substantially cheaper and smaller than sector instruments and Qq-TOFs. They are very often used in combination with GC and LC, and single or triple quadmpole mass filters are very common benchtop instruments for routine measurements. 

D. R. Robb, T. R. Covey, and A. P. Bruins. Atmospheric Pressure Photoionization An Ionization Method for Liquid Chromatography-Mass Spectrometry. Anal. Chem., 72(2000) 3653-3659. 

Since then, it has proven to be one of the most successful ionization methods for the mass spectrometric investigation of large molecules, increasing the... 

Note The numerous ionization methods and mass analyzers in use have created a demand for a large number of calibration compounds to suit their specific needs. Therefore, mass calibration compounds will occasionally be addressed later in the chapters on ionization methods. It is also not possible to specify a general level of mass accuracy with external calibration. Depending on the type of mass analyzer and on the frequency of recalibration, mass accuracy can be as high as 1 mmu or as low as 0.5 u. 

Robb, D. B., Covey, T. R., and Bruins, A. P. (2000). Atmospheric pressure photoionization an ionization method for liquid chromatography-mass spectrometry. Anal. Chem. 72, 3653 — 3659. 

The application of molecular SIMS as a sensitive ionization source for nonvolatile and thermally labile molecules compares favorably with other new ionization methods in mass spectrometry such as field desorption (FD), Californium-252 plasma desorption (PD), fast heavy ion induced desorption (FHIID), laser desorp-... 

Ionization Methods/Processes. The recent development of several new ionization methods in mass spectrometry has significantly improved the capability for the analysis of nonvolatile and thermally labile molecules [18-23]. Several of these methods (e.g., field desorption (FD), Californiun-252 plasma desorption (PD), fast heavy ion induced desorption (FHIID), laser-desorption (LD), SIMS, and fast atom bombardment (FAB) or liquid SIMS) desorb and ionize molecules directly from the solid state, thereby reducing the chance of thermal degradation. Although these methods employ fundamentally different excitation sources, similarities in their mass spectra, such as, the appearance of protonated, deprotonated, and/or cationized molecular ions, suggest a related ionization process. 

Ionization method Upper mass limit (amu) for MW information Advantages Disadvantages... 

Laser Desorption Ionization. A pulsed laser beam can be used to ionize samples for mass spectrometry. Because this method of ionization is pulsed, it must be used with either a time of flight or a Fourier transform mass spectrometer (Section 1.4.5). Two types of lasers have found widespread use A COz laser, which emits radiation in the far infrared region, and a frequency-quadrupled neodymium/yttriumaluminum-garnet (Nd/YAG) laser, which emits radiation in the UV region at 266 nm. Without matrix assistance, the method is limited to low molecular weight molecules (<2 kDa). 

---