Matrix-assisted laser desorption/ionization schematics

FigureBl.7.2. Schematic representations of alternative ionization methods to El and PI (a) fast-atom bombardment in which a beam of keV atoms desorbs solute from a matrix (b) matrix-assisted laser desorption ionization and (c) electrospray ionization.

Figure 2.9. Schematic of a matrix-assisted laser desorption/ionization (MALDI) event. The SEM micrograph depicts sinapinic acid-equine myoglobin crystal from a sample prepared according to the dried drop sample preparation method. In the desorption event neutral matrix molecules (M), positive matrix ions (M+), negative matrix ions (M-), neutral analyte molecules (N), positive analyte ions (+), and negative analyte ions (-) are created and/or transferred to the gas phase. Reprinted from A. Westman-Brinkmalm and G. Brinkmalm (2002). In Mass Spectrometry and Hyphenated Techniques in Neuropeptide Research, J. Silberring and R. Ekman (eds.) New York John Wiley Sons, 47-105. With permission of John Wiley Sons, Inc.

Figure 14.1 Schematic view of a mass spectrometer. Its basic parts are ion source, mass analyzer, and detector. Selected principles realized in modern mass spectrometers are assigned El—electron impact. Cl—chemical ionization, FAB—fast atom bombardment, ESI—electrospray ionization, MALDI—matrix-assisted laser desorption/ionization. Different combinations of ion formation with mass separation can be realized.

Figure 4.1 Schematic representations of a time-of-fl ight/time-of-fl ight (TOF/TOF) instrument with a matrix-assisted laser desorption/ionization (MALDI) source (a), and a quadrupole time-of-flight (qTOF) instrument which can be interchangeably...

Fig. 1 Schematic representation of a mass spectrometer depicting its main components and the different modes used. Abbreviations DIP direct insertion probe DEP direct exposure probe GC gas chromatography LC liquid chromatography CE capillary chromatography TEC thin-layer chromatography FEE field-flow fractionation APCI atmospheric pressure ionization El electron impact Cl chemical ionization FAB fast-atom bombardment PD plasma desorption MALDI matrix-assisted laser desorption ionization ED laser desorption TSP thermospray ESI electron spray ionization HSI hypherthermal surface ionization Q quadropole QQQ triple quadropole TOE time-of-fiight FTMS Fourier transform mass spectrometer IT ion trap EM electrom multiplier PM photomultiplier ICR ion cyclotron resonance.

Schematic representation of MALDI (matrix-assisted laser desorption ionization) in conjunction with mass spectromety. A protein salt is mixed into a matrix that is subjected to pulsed laser beams. Small volumes of matrix-bound proteins are aerosolized and stripped of matrix molecules under high vacuum.

A similar but modified approach for low-pressure ion mobility MS was taken by Russell s group. Figure 9.4 shows the schematic of an early matrix-assisted laser desorption ionization (MALDI) IMS-TOF-MS that used a short IMS drift tube at a pressure of 1 to 10 torr of He, resulting in a mobility resolving power of about... 

Fig. 73 Schematic diagram of an ion source for matrix-assisted laser desorption ionization (MALDI-MS)...

A schematic of the basic principles of a matrix-assisted laser desorption/ion source is shown in Figure 2.35. By the interaction of a focused laser beam with short pulses and a suitable matrix, the energy of the photons is transferred to the matrix molecules. In MALDI mostly pulsed UV (e.g., nitrogen, X = 337 nm, pulse duration 3-10 ns), but also IR lasers (e.g., Er YAG, X = 2.94 (xm or C02, X = 10.6(xm with a higher pulse duration of up to 600 ns) are used. The MALDI mass spectra obtained during soft ionization by UV and IR lasers are identical. The energy density... 

Matrix-Assisted Laser Desorption/lonization. In this ionization method, the analyte is combined with a matrix compound, in a molar ratio of l 1000, and evaporated onto a metallic plate. The matrix compound is chosen to absorb strongly at the laser wavelength used. Absorption causes a rapid increase of temperature, allowing vaporization of the sample without extensive fragmentation, which is shown schematically in Figure 15.4. 

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