Laser Microprobe Mass Spectrometry LAMMA

Infrared and ultraviolet probes for surface analysis are then considered.The applications of IR spectroscopy and Raman microscopy are discussed, and a brief account is also given of laser-microprobe mass spectrometry (LAMMA). 

Among the other soft ionization techniques is laser microprobe mass spectrometry (LAMMA) in which a laser pulse is used to vaporize a small amount of sample, as discussed in a 1982 review (108). Of interest to us is the application to the study of some cobalamins (109). (M + H) and (M - H) ions were observed in the positive and negative ion modes, respectively. However, there were few other high-mass fragments that could be used to impart structural information. 

These workers also investigated eight industrially important high-mass polymers by laser microprobe FTICR. These polymers included PEG 8000, poly(phenylene sulfide) (MW 1.0 x 10 ), poly(vinyl acetate) (MW 6.4 x 10 ), poly(styrene) (MW 2.5 x 10 ), PMMA (MW 4.6 x 10 ), poly(vinyl chloride) (3.7 x 10 ), poly(acrylonitrile) (MW 2.3 x 10 ), and poly(dimethylsiloxane) (MW 4.4 x 10 ). Brenna and Creasy posed the question of whether broadband UV laser microprobe FTICR could be used to identify these polymers, and they also wanted to compare spectra with the more widely used TOF laser microprobe mass spectrometry (LAMMA). Results include the observation of odd-mass ions, carbon clustering (Figure 9.4), stable subunit condensation,... 

Figure 4 Comparison of the positive and negative ion mass spectra recorded using TOF-LMMS from carnidazole (top) and the corresponding N-oxide (bottom). (Reprinted from Van Vaeck L, Van Espen P, Gijbels R, and Lauwers W (1988) Structural characterisation of drugs and oxygenated metabolites by laser microprobe mass spectrometry (LAMMA). Biomedical and Environmental Mass Spectrometry A 6 121-130 Wiley.)...

There are now several different types of machines that are all capable of microanalysis. All have advantages and disadvantages, but the choice of which to use is often governed by expense and availability to a particular institution. Electron probe microanalysis is by far the most popular, but here particle-induced X-ray emission (PIXE), the laser microprobe mass analyzer (LAMMA), electron energy loss spectroscopy (EELS), and secondary ion mass spectrometry (SIMS) are also considered. 

Laser ionization The identification of unknown inclusions in a variety of matrices is very important in an industrial environment. One method used to analyze these unwanted small ( 1-50 pm diameter) inclusions is laser desorption/ionization mass analysis, also known as laser microprobe mass spectrometry and laser microprobe analysis. Trade names used are LIMA (laser ionization mass analyzer) and LAMMA (laser microprobe mass analysis). A variable-power laser is focused on to the inclusion. As discussed above, the desorption/ionization process is very sensitive to the power density of the laser at the sample surface. Firing the laser with an appropriate power setting generates ions containing information about the inclusion, which are then mass-analyzed using TOF-MS. 

Principles and Characteristics Laser microprobe mass spectrometry (LMMS, LAMMS), sometimes called laser probe microanalysis (LPA or LPMA) and often also referred to as laser microprobe mass analysis (LAMMA , Leybold Heraeus) [317] or laser ionisation mass analysis (LIMA , Cambridge Mass Spectrome-try/Kratos) [318], both being registered trademarks, is part of the wider laser ionisation mass spectrometry (LIMS) family. In the original laser microprobe analyser, emitted light was dispersed in a polychro-mator. Improved sensitivity may be obtained by secondary excitation of ablated species with an electric spark. In the mass spectrometric version of the laser microprobe, ions formed in the microplasma... 

Figure 3 Third dimension in pyrolysis mass spectrometry approaches (A) linear programmed thermal degradation mass spectrometry [LPTDMS - third dimension = temperature] (B) collisionally activated dissociation of parent ions coupled with scanning of product ions using tandem mass spectrometry [MS/ MS - third dimension = spectrum of product ions] (C) laser microprobe mass analyser [LAMMA - third dimension = spatial resolution].

The defining attribute of laser microprobe mass spectrometry (LMMS) is the use of a focused laser to irradiate a 5- 10 pm spot of a solid sample at a power density above 10 W cm. The photon solid interaction yields ions which are mass analysed by time of-flight (TOF) or Fourier transform (FT) MS. The technique is sometimes referred to as laser probe microanalysis (LPA or LPMA), laser ionization mass analysis (LIMA) and laser microprobe mass analysis (LAMMA). 

The technique is referred to by several acronyms including LAMMA (Laser Microprobe Mass Analysis), LIMA (Laser Ionisation Mass Analysis), and LIMS (Laser Ionisation Mass Spectrometry). It provides a sensitive elemental and/or molecular detection capability which can be used for materials such as semiconductor devices, integrated optical components, alloys, ceramic composites as well as biological materials. The unique microanalytical capabilities that the technique provides in comparison with SIMS, AES and EPMA are that it provides a rapid, sensitive, elemental survey microanalysis, that it is able to analyse electrically insulating materials and that it has the potential for providing molecular or chemical bonding information from the analytical volume. 

XRD, X-ray diffraction XRF, X-ray fluorescence AAS, atomic absorption spectrometry ICP-AES, inductively coupled plasma-atomic emission spectrometry ICP-MS, Inductively coupled plasma/mass spectroscopy IC, ion chromatography EPMA, electron probe microanalysis SEM, scanning electron microscope ESEM, environmental scanning electron microscope HRTEM, high-resolution transmission electron microscopy LAMMA, laser microprobe mass analysis XPS, X-ray photo-electron spectroscopy RLMP, Raman laser microprobe analysis SHRIMP, sensitive high resolution ion microprobe. PIXE, proton-induced X-ray emission FTIR, Fourier transform infrared. 

Lasers have been used in mass spectrometry for many years. Trace elements in biological samples [90] can be determined by using laser microprobes (LAMMA, laser microprobe mass analyzer) or a combination of laser ablation with ICPMS. For the analysis of bulk materials, techniques such as resonance ionization mass spectrometry (RIMS) and laser ablation MS (LAMS) are employed for a review see [91]. 

AMS = accelerated mass spectroscopy EDTA = ethylene diamine tetra acetic acid GFAAS = graphite furnace atomic absorption spectrometry ICP-AES = inductively coupled plasma - atomic emission spectroscopy NAA = neutron activation analysis ETAAS = electrothermal atomic absorption spectrometry SEC/ICP-MS = size-exclusion chromatography/ICP-AES/mass spectrometry HLPC/ICP-AES = high-performance liquid chromatography/ICP-AES LAMMA = laser ablation microprobe mass analysis NA = not applicable ppq = parts per quadrillion... 

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