Laser desorption mass spectrometry LDMS

Laser-desorption mass spectrometry (LDMS) or matrix-assisted laser desorption ionization (MALDI) coupled to a time-of-flight analyzer produces protonated or deprotonated molecular ion clusters for peptides and proteins up to masses of several thousand. 

Automated organic and elemental ion mapping of TLC plates by LMMS techniques, without focus correction, has been reported [802,839]. One of the early TLC-MS scanners used laser desorption combined with Cl detection [807,808]. The use of laser desorption mass spectrometry (LDMS), in connection with TLC separations, allows sampling of a very small area of a spot (ca. 5 im). In this way spot homogeneity can be determined (e.g. in the case of overlapping components), and also leaves the bulk of the material unaffected for further study. An important advantage... 

Applications employing laser ablation of polymers include film deposition and the synthesis of certain organic compounds. Laser beam ablation in conjunction with mass spectrometry is an important tool for polymer analysis, which is referred to as laser desorption mass spectrometry (LDMS). One particular type of LDMS, termed matrix-assisted laser desorption/ionization (MALDI), has contributed essentially to the analysis of proteins (Nobel prize for chemistry to K. Tanaka in 2002) [126,127]. Further information on this subject is available in Ref [4]. 

LDMS Laser desorption mass spectrometry desorption/ionisation... 

This is another field in which the uninitiated can be overwhelmed by acronyms, so some of the most widely used ones are explained here HRMS = high-resolution mass spectrometry HRGC/HRMS = high-resolution gas chromatography/HRMS LC/MS - liquid chromatography/mass spectrometry Cl = chemical ionization FD = field desorption FAB = fast atom bombardment LDMS = laser desorption mass spectrometry. 

Figure 12.9 LDMS spectrum. Reproduced with permission from Balko, L, and J. Allison, The Direct Detection and Identification of Staining Dyes from Security Inks in the Presence of Other Colorants, on Currency and Fabrics, by Laser Desorption Mass Spectrometry, Journal of Forensic Sciences 48 (2003). Copyright 2003 ASTM International. 

Fast-atom bombardment mass spectrometry (FAB-MS) has been applied to the identification of diterpenoid compounds and their oxidation products. Similarly, laser-induced desorption mass spectrometric (LDMS) techniques have been applied to the identification of natural and synthetic organic pigments in microscopic paint samples prepared as cross sections [60]. 

Laser desorption (ionisation) - mass spectrometry (LDMS or one-step LDI-MS) experiments may be manipulated by varying (i) sample presentation (ii) power density, wavelength and pulse duration of the laser desorption technique to ablate the sample and (Hi) mass analyser type combined with a suitable ionisation mode. At variance to MALDI experiments in LDI-MS no matrix is required and no special sample preparation of any kind is necessary. The sample can be subjected to the pulsed desorption laser in a variety of ways. Most commonly, the sample is presented as a solid layer, deposited from solution, on a substrate, which absorbs at the laser wavelength. There is a well-defined threshold, above which successful desorption of neutrals can... 

The current status of laser desorption has recently been reviewed [98], including LDMS [197], LD-FIMS [188,198,199] andLDMS/MS [200]. Van Vaeck et al. [191] have reviewed lasers in mass spectrometry, with emphasis on instrumentation. 

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