Embedded ion exchange beads as standards for laser microprobe mass analysis of biological specimens

Abstract

A new Internal standard system based upon Chelex-100 Ion chelating resin beads loaded with various elements Is proposed for laser microprobe mass analysis (LAMMA) of tissue-bound elements In thin sections of biological material. The beads can be coembedded with the biological specimen and cut to the desired thickness. In this way, the standard material is available together with and close to the tissue In the same section, thus avoiding section thickness measurements and specimen exchange. Chelex-100 beads can be loaded with various elements In a controlled way and the spatial elemental distribution Is sufficiently homogeneous for use In microanalysis. The signal reproducibility, the proportionality between the LAMMA response and the elemental concentration, and the Influence of the specimen composition on the LAMMA mass spectra were studied. Chelex-100 was also compared to other types of Ion exchange beads. This versatile standardization technique opens new vistas for quantitative laser microprobe applications In biological and biomedical research.Considerable interest is currently being focused on laser microprobe mass analysis (LAMMA), primarily due to the commercial advent of the LAMMA-500 instrument. A description of this new microanalytical instrument and discussions of its advantages, drawbacks, and applications can readily be found in the literature (1-3). The technique was originally developed for biomedical purposes, but hitherto its impact remained mainly limited to qualitative biological aspects.Absolute quantification of subcellular elemental distributions in biological specimens is, of course, not trivial at all. Structural localization in the uncolored and unstained histological sections is often problematic. Moreover, the LAM-MA spectra of biological preparations can be highly complex, variable, and difficult to interpret: mass interferences arising from organic molecules or fragment ions, both from the specimen itself and from the embedding or supporting media, are often important, while the laser interaction is intricate and complete understanding about laser-induced microplasma

Uptake of aluminium by plant cells

“…The latter technique apparently lacks sufficient sensitivity to measure Al in various subcellular structures and is therefore only suitable for gross localization of Al accumulated in root tissues. When LAMA was used to measure Al in standards (embedded ion-exchange beads), the detection limit was lowered to c. 5 //g g" ( Verbueken et al, 1984).…”

“…Assuming no spectral interferences, a detection limit for Al of c. 1 /ug g~^ (37 nmol g^^) or better can be achieved by SIMS (Linton et al, 1980;Lazof et al, 1994a), a figure which is at least an order of magnitude better than for EDXMA (Chandler, 1979;Linton et al, 1980; but see Marienfeld & Stelzer, 1993, who claimed a detection limit not better than 2-3 //,mol g"^), "Al NMR (Nagata et al, 1991) and LAMMA (Verbueken et al, 1984;Linton et al, 1985), and more than two orders of magnitude better than PIXE (Hult et al, 1992). The latter technique apparently lacks sufficient sensitivity to measure Al in various subcellular structures and is therefore only suitable for gross localization of Al accumulated in root tissues.…”

Laser microprobe mass spectrometric identification of sulfur species in single micrometer-size particles

“…Quantitative or semiquantitative analysis of individual particles is still limited, because of the present scarce knowledge about the laser induced ion formation mechanism and the influence of the particle size, the laser power density, the matrix effects, and the instrumental parameter settings. However research about these topics is currently in progress (3)(4)(5).…”

Comparison of the simplex method with several other methods for background-fitting for electron energy-loss spectral quantification of biological materials

“…However the Log-Log method is faster than the Simplex method. Since their introduction in 1981 for electron probe X-ray microanalyses (EPMA) [9] several aspects have been elucidated also for other analytical techniques [12,14,17].…”