Grazing exit electron probe microanalysis for surface and particle analysis.

We developed a new method of grazing exit electron probe microanalysis (GE-EPMA) and applied it to analyze both Si surfaces and Mg-salt particles. In conventional EPMA, X-rays are detected at an exit (takeoff) angle of approximately 45°. Therefore, when particles collected on a sample carrier are analyzed by EPMA, the X-rays from both the particles and the carrier are detected, although we need only the X-rays emitted from the particle itself. In contrast to this, the X-rays are detected at grazing exit angles in GE-EPMA. The X-rays emitted from deep inside of the sample are not detected under grazing exit conditions, and only X-rays emitted from the surface and the particle are measured. It was found that surface-sensitive analysis of a Si wafer was possible with low background at grazing exit angles. The intensity ratio of O Kα to Si Kα increased near zero degrees, indicating that the Si wafer is covered with a native Si oxide. Moreover, Mg Kα X-rays from a Mg-salt particle, which was deposited on the Si wafer, were detected with a small Si Kα intensity at grazing exit angles of less than 0.5°. By decreasing the exit angle to less than zero, only the top of the particle was observed; therefore, GE-EPMA measurement would make it possible to investigate the surface layer of one particle.

Glow discharge mass spectrometric analysis of atmospheric particulate matter.

A direct current (dc) glow discharge mass spectrometer has been used to analyze atmospheric particulate matter. The sample preparation used is simple and time-saving. The air is sucked by a pump through a single-orifice impactor stage, in which the aerosols are impacted on a metal support, forming a central spot. This metal plate is directly used as a cathode in a dc glow discharge mass spectrometer. Evaluation of the sample loading and of the discharge parameters allowed us to optimize the signal intensity and to minimize its decrease, the latter being a consequence of its consumption by continuous sputtering in the discharge. The available aerosol analysis time could be prolonged to more than 3 h, a time span necessary to perform a multielement analysis using a magnetic sector instrument and long integration times. A NIST reference aerosol was measured to evaluate the quantitative analysis potential. The internal reproducibility was better than 10% RSD, and the limits of detection were estimated to be in the low ppm or sub ppm region. Even without the use of any standards or correction factors, glow discharge mass spectrometry could offer good semiquantitative results, based only on the use of an internal standard.

Laser microprobe mass spectrometry in biology and biomedicine.

An overview is given of laser microprobe mass spectrometry (LMMS) in biology and biomedicine (1989-1993). The present instrumentation and its analytical features are surveyed. Applications are presented with special attention on human and animal tissue samples, as well as plant material. The capabilities of LMMS to study the element distribution in histological sections, to identify the chemical composition of inorganic inclusions and to generate structural information from organic compounds are evidenced.

Laser microprobe mass spectrometric identification of cyclosporin-induced intrarenal microliths in rat.

Using laser microprobe mass analysis (LAMMA), the composition of 'micro-calcifications (dystrophic type)' or 'metastatic calcifications', previously described in rats given high doses of cyclosporin, have been identified. Female Wistar rats given 12.5, 25 or 50 mg kg-1 per day of cyclosporin in olive oil by gastric gavage developed intrarenal calcifications detected by silver nitrate staining (von Kossa) in the outer medulla after two weeks. The calcifications stained red with periodic acid-Schiff reagent and appeared to be intraluminal microliths with concentric laminations. They could be identified by LAMMA as calcium phosphate (hydroxyapatite), indistinguishable from undecalcified bone. These studies indicate that intraluminal obstruction by calcium phosphate microliths, similar to that seen with magnesium depletion or high phosphate diets, may contribute to renal damage in rats given high-dose cyclosporin. LAMMA appears to be an appropriate technique for identifying both the elemental and organic moieities of intrarenal calcium deposits.

Iron, copper, zinc and lead in hair from Sudanese populations of different age groups.

Energy-dispersive X-ray fluorescence was used for the analysis of hair samples from three different age groups of the Sudanese population. Hair samples were digested in a mixture of nitric and perchloric acids and the metals were then precipitated with ammonium pyrrolidine dithiocarbamate. The variations of the Fe, Cu, Zn and Pb content of hair with age were investigated. The averages of the elemental concentrations in each age group were compared with the other age groups and with literature values. The correlation of each pair of elements in the hair samples was also investigated.

Phosphorus, calcium and lead distribution in collagen in lead induced soft tissue calcification. An ultrastructural and X-ray microanalytical study.

Repeated intraperitoneal injections of lead acetate in rats caused a calcification of the skin of the abdomen near the site of the injections. In the lead-induced calcifications, electron dense collagen bundles could be observed. On the surface of the collagen fibrils, needle-like crystals were visible. With energy-dispersive X-ray analysis, phosphorus, calcium and lead were detected in the electron dense collagen bundles. X-ray maps of the P-K alpha, Ca-K alpha, and Pb-L alpha plus Pb-L beta lines showed an equivalent distribution along the collagen fibrils for phosphorus and calcium. The occurrence of the most electron dense areas in the STEM-image was comparable to the lead distribution. A good correlation existed between the structural and the elemental images of the same area. Although the medicinal use of preparations containing lead is no longer recommended, some are still prescribed. From our results we can conclude that they should not be applied to injured or inflamed skin.

Influence of fixation procedures on the microanalysis of lead-induced intranuclear inclusions in rat kidney.

Using Laser Microprobe Mass Analysis (LAMMA), we studied the chemical composition of lead-induced intranuclear inclusions in rat kidney tissue prepared by three different wet chemical fixation procedures for transmission electron microscopy. Fixation with glutaraldehyde-Na2S gave the same results as fixation with glutaraldehyde only: a high lead concentration could be detected. Therefore, for lead strongly bound to proteins, precipitation procedures are not essential. Post-fixation with osmium tetroxide drastically changed the composition of the inclusions: the lead concentration decreased substantially, while sodium, calcium, and barium were introduced. The osmium tetroxide fixative was found to be the source of the contamination. It also contained aluminum, and we suggest that other proteins (e.g., in neurofibrillary tangles) might be able to take up Al out of solution and that care must be exercised in interpreting the microanalytical results of osmium-fixed material. For the microanalysis of the lead inclusions, fixation with glutaraldehyde only provides a good compromise between preservation of the ultrastructure and maintenance of the element distribution.

Characterization of the spheroliths present in primary atypical bandkeratopathy using laser microprobe mass analysis.

Laser microprobe mass analysis was applied to study the chemical composition of spheroliths in the Bowman's membrane of patients suffering from primary atypical bandkeratopathy. The inclusions appear to consist mainly of calcium phosphate.

Ultrastructural localization of aluminium in liver of aluminium maltol-treated rabbits by laser microprobe mass analysis.

By means of laser microprobe mass analysis (LAMMA), we have studied the ultrastructural localization of aluminium in livers of aluminium maltol-treated rabbits. This animal model was developed to study long-term aluminium toxicity using systemic (intravenous) administration of aluminium. We could only detect aluminium in electron-dense inclusion bodies found in large, sometimes multinucleated cells. These results prove that the actual observation of aluminium deposits in liver with LAMMA gives more information than bulk analysis and can be very useful to explore mechanisms of toxicity.

Localization of lead and fluoride in cultured tooth germs by laser microprobe mass analysis.

Trace elements can influence dental health, possibly by altering tooth resistance during preeruptive development. Therefore, it was investigated whether lead and fluoride would be incorporated into the calcifying matrices or the cellular parts of tooth germs in vitro. Using laser microprobe mass analysis, the localization of lead and fluoride was studied in the different layers or tooth germs that had been cultured in a medium to which PbCl2 of NaF had been added in different concentrations. Both elements could only be detected in the dentine layer. Hence, the enamel organ in the secretory stage of tooth development excludes lead and fluoride from the enamel, even when enamel formation by the ameloblasts is visibly disturbed. Furthermore, there seemed to be a process of saturation in the accumulation of lead and fluoride in the dentine.

Use of laser microprobe mass analysis (LAMMA) for localizing multiple elements in soft and hard tissues.

The potential of laser microprobe mass analysis (LAMMA) as a sensitive microanalytical technique was explored in applications relevant to nephrology. Aluminum and associated elements, such as iron, were localized in fresh tissue biopsies obtained from uremic patients treatment by chronic hemodialysis. The LAMMA was applied to serum, liver, bone, and parathyroid glands of such patients. In addition, we used LAMMA to evaluate the specificity and sensitivity of routine histochemistry, in particular on human bone sections stained by the aluminon method. The high, multielemental sensitivity and molecular microprobe potential of LAMMA established important advantages over other microchemical methods forin situ analysis at the micron level in histological sections.

Laser microprobe mass analysis (LAMMA) to verify the aluminon staining of bone.

Triammonium aurin tricarboxylate (aluminon) has been used to localize aluminum in 2 micron sections of undecalcified, methyl methacrylate embedded bone obtained from patients with terminal chronic renal failure. Aluminum appeared in four cases as bright red lines at the mineralized-bone boundary. In two cases, however, purplish lines were found and one patient showed red as well as purplish lines. Laser microprobe mass analysis (LAMMA) identified aluminum at the location of the red lines and both aluminum and iron at the purplish lines. Furthermore, both iron and aluminum were found in histiocytic bone marrow cells, which showed brownish aluminon staining. It appears that when aluminum and iron occur together, aluminon staining may yield aberrant results. This study shows that LAMMA can be used for the identification of elements sought by histochemical methods and thus permits the evaluation of their staining effects.