Analyzers microprobe

The final example cited in this subsection, the use of Raman spectroscopy to the study of pharmaceuticals, is in the area of identification and quantitation of materials in finished pharmaceutical products and formulations. A host of authors, using everything from bench-top laboratory analyzers, microprobes, and fiber-optics sampling devices have demonstrated the use of Raman spectroscopy for identification and quantification [117-122]. Limits of detection and reproducibility for many of the materials studied were reported. 

Laser ionization mass spectrometry or laser microprobing (LIMS) is a microanalyt-ical technique used to rapidly characterize the elemental and, sometimes, molecular composition of materials. It is based on the ability of short high-power laser pulses (-10 ns) to produce ions from solids. The ions formed in these brief pulses are analyzed using a time-of-flight mass spectrometer. The quasi-simultaneous collection of all ion masses allows the survey analysis of unknown materials. The main applications of LIMS are in failure analysis, where chemical differences between a contaminated sample and a control need to be rapidly assessed. The ability to focus the laser beam to a diameter of approximately 1 mm permits the application of this technique to the characterization of small features, for example, in integrated circuits. The LIMS detection limits for many elements are close to 10 at/cm, which makes this technique considerably more sensitive than other survey microan-alytical techniques, such as Auger Electron Spectroscopy (AES) or Electron Probe Microanalysis (EPMA). Additionally, LIMS can be used to analyze insulating sam-... 

XPS spectra were obtained using a Perkin-Elmer Physical Electronics (PHI) 555 electron spectrometer equipped with a double pass cylindrical mirror analyzer (CMA) and 04-500 dual anode x-ray source. The x-ray source used a combination magnesium-silicon anode, with collimation by a shotgun-type collimator (1.). AES/SAM spectra and photomicrographs were obtained with a Perkin-Elmer PHI 610 Scanning Auger Microprobe, which uses a single pass CMA with coaxial lanthanum hexaboride (LaBe) electron gun. 

Analytical electron microscopy (AEM) permits elemental and structural data to be obtained from volumes of catalyst material vastly smaller in size than the pellet or fluidized particle typically used in industrial processes. Figure 1 shows three levels of analysis for catalyst materials. Composite catalyst vehicles in the 0.1 to lOim size range can be chemically analyzed in bulk by techniques such as electron microprobe, XRD, AA, NMR,... 

Pyrite is the most abundant ore mineral. It occurs as euhedral, framboidal, and colloform forms. Abundance of framboidal pyrite increases stratigraphically upwards. Colloform pyrite contains appreciable amounts of As and Cu (Nakata and Shikazono, unpublished), whereas these contents of euhedral and framboidal pyrite are less than the detection limit of an electron microprobe analyzer. Ishizuka and Imai (1998) found that the As content increases toward outer rim and reaches up to 5 wt% in the rim of colloform pyrite from the Fukazawa deposit. 

Because natural stannite contains a considerable amount of zinc, sphalerite contains a considerable amount of iron, and these contents can be easily analyzed using an electron microprobe, a stannite-sphalerite pair is expected to be a useful indicator of formation temperature and sulfur fugacity. 

Scanning patterns and many analytical data obtained by electron-microprobe analyzer reveal that most stannoidite grains are compositionally homogeneous. There is... 

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,... 

Figure 2. Schematic drawing of the AEl IM-20 ion microprobe. The magnetic analyzer and ion counting system are linked to an on-line computer for automated...

A study of the surface helium, neon, and argon in lunar rocks illustrates the sensitivity of the laser microprobe [3]. Lunar rock 12054 was collected from the surface of the moon with known orientation. This rock contains a glass coating which covers the face including a crack. As a result, part of the surface in the crack is never exposed directly to the sun whereas other parts are directly exposed. We made a traverse across the surface analyzing the gas from individual laser pits. Four types of sites were analyzed in this study. 

Selected sphalerite grains (n=15) were mounted and analyzed by electron microprobe. Isotopic analyses of Pb were conducted on galena and sphalerite grains at Carleton University. Sulphur isotope analyses were performed on sphalerite powders at the University of Ottawa. 

Four samples were similarly selected for the EPMA experiments. The samples were dried and embedded in polished epoxy cylindrical plugs. Backscattered electron (BSE) images as well as elemental maps of As, Fe and Ni (EDS/WDS) were collected using a JEOL 8600 Superprobe electron microprobe analyzer (Dept, of Geological Sciences, University of Saskatchewan). 

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. 

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. 

F. Hillenkamp, E. Unsold, R. Kaufmann, and R. Nitsche. A High-Sensitivity Laser Microprobe Mass Analyzer. Appl. Phys., 8(1975) 341-348. 

During investigations we were analyzing samples by methods of X-ray diffraction, electron scanning microscopy, microprobe analysis, atomic force microscopy, high-resolution transmission electron microscopy with preliminary attracting of the another methods including optical microscopy, Raman spectroscopy, thermal analysis and some of others. 

The laser microprobe employs a pulsed laser to vaporize minute amounts of the sample. The vapor temperature, however, in the case of low-power lasers is not sufficient to provide adequate excitation for spectrochemical analysis. The sample vapor is therefore further excited as it passes between two auxiliary electrodes above the sample. The optimum excitation conditions have been examined by Quillfeldt using the commercial laser-microspectral analyzer LMA 1 (Carl Zeiss, Jena). Spectrochemical determinations of Fe,... 

Although this technique is not normally used for thin polymer films for the reasons described before, it can be used for analyzing the surface of polymer composites containing conductive fillers, e.g. carbon fibers. In addition, because of the surface specificity, the sampled area can be maintained almost identically to the beam cross-section so that the scanning Auger microscope (SAM) can have a spatial resolution that is much better than that of microprobe analysis. 

Polished thin sections or iron oxides grains polished in epoxy mounts were analyzed using Universite Laval CAMECA SX-100 5-VVDS electron microprobe under a beam of 15 kV at 100 nA, using a range of natural and synthetic standards. After counting over the peak for 20 to 30 sec, background is measured on both sides for 10 sec. These settings yield minimum detection limits (mdl) as low as 20 ppm for elements such as K, Ca, Al, Si, Ti and Mg, 50 ppm for Mn, Cr and V, 200 ppm for Cu,... 

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