Laser microprobe mass analyzer LAMMA

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. 

Schmidt. P.F. (1984). Localization of trace elements with the laser microprobe mass analyzer (LAMMA), Trace Elements in Medicine, 1,13-20 Sherwood. R.A., Rocks, B.F., and Riley, C. (1984). The use of flow-injection analysis (FIA) with atomic absorption detection for the determination of clinically relevant elements. Paper presented at 2nd BNAAS Symposium, Leeds, July 1984 Triebig, G., and Schaller, K.H. (1984). Copper, in Alessio, L, Berlin, A., Boni, M., Roi, R., Biological indicators for the assessment of human exposure to industrial chemicals, p. 57-62, EUR 8903 EN, Commission of the European Communities Van der Vyner, F.L, Verbreuken, A.H., Van Grieken, R.E., and DeBroe, M.E. (1985) Laser microprobe mass analysis A tool for evaluating histochemical staining of trace elements, Clin. Chem., 31. 351... 

Guest, W. H. Recent developments of laser microprobe mass analyzers, lamma-500 and lamma-1000. Int. J. Mass Spectrom. Ion Processes 1984, 60, 189-199. 

The primary methods of analyzing for lead in environmental samples are AAS, GFAAS, ASV, ICP/AES, and XRFS (Lima et al. 1995). Less commonly employed techniques include ICP/MS, gas chromato-graphy/photoionization detector (GC/PID), IDMS, DPASV, electron probe X-ray microanalysis (EPXMA), and laser microprobe mass analysis (LAMMA). The use of ICP/MS will become more routine in the future because of the sensitivity and specificity of the technique. ICP/MS is generally 3 orders of magnitude more sensitive than ICP/AES (Al-Rashdan et al. 1991). Chromatography (GC,... 

In general, in ICP-MS, metal argide ions (MAr+) are observed at lower intensities compared to the dimeric metal oxide ions (MO+). Both ionic species correlate with the bond dissociation energies in the ICP or by the expansion of plasma in the vacuum. A correlation of measured oxide ion intensities (MO+) and experimentally determined or theoretically calculated bond dissociation energies of oxides has been found in laser mass spectra using a LAMMA 500 (laser microprobe mass analyzer, Leybold Hereaus AG, Cologne) by Michiels and Gijbels.52... 

Laser microprobe mass analyzers permit mass spectrometric analysis of very small volumes (0.01-1 pm3) of thin Sections. The method is based on laser induced ion production from a microvolume and analysis of the evaporated ions in a time-of-flight mass-spectrometer. The technique allows detection of all elements and isotopes with a sensitivity approaching the ppm range and an extremely low limit of detection 10 15 to 10-20 g. Transmission type instruments such as the LAMMA 500 are designed for the analysis of particles of 3 pm in diam. The lateral resolution is about 0.5-1 pm. Because the area to be analyzed is selected by an optical microscope, distribution of chemical constituents can be precisely correlated with morphologic structures (Hillenkamp et al., 1982 39), Simons, 198440), Kaufmann, 1984)41 >. 

For example, microprobe analysis of complex samples (laser microprobe mass analysis LAMMA) was performed by using a setup with no expansion chamber and by focusing the laser beam on a small area on the surface of the sample. Although coal and shale samples were successfully analyzed using LAMMA [52], the nature of the bonding in these types of materials cannot be evaluated because it is not clear if a certain compound is the result of desorption or of pyrolysis. More successfully analyzed were the inorganic components of such composite materials where the thermal decomposition was not a concern. 

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]. 

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. 

Of all of the machines used for microanalysis LAMMA seems to be the most problematic. A laser beam is used to disintegrate a spot in the sample, and the material emitted is then analyzed in a mass spectrometer. It has similar lateral resolution to PIXE, and like SIMS can be used to distinguish between isotopes of the same element. It has, however, proved very difficult to quantify, and is destructive to the specimen. One recent investigation (13) ofthe distribution of stable isotopes of calcium, magnesium, and potassium in Norway spruce used three microprobes EDAX at 0.3 pm lateral resolution isotope specific point analysis, using LAMMA at 1.5 pm lateral resolution and isotope specific imaging using SIMS at 1-3 pm lateral resolution. 

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