Elemental analysis of renal slices by proton-induced X-ray emission.

Abstract

Methods for analyzing elements in biological samples are important for studying the effects of intoxication. Since its introduction in 1970 (1), proton-induced X-ray emission spectroscopy (PIXE) has been shown to be a powerful, multielemental analysis technique with high sensitivity (2). The PIXE technique involves bombarding a sample with protons which eject innershell electrons of the elements in the sample; the subsequent decay of the induced electronic states results in the emission of X-rays whose energies are characteristic of the elements present in the sample and whose intensities are proportional to the concentrations of these elements. A liquidnitrogen-cooled solid-state Si(Li) detector and a multichannel analyzer are used to determine the energies as well as the intensities of the emitted X-rays, and a computer program identifies the elements present and calculates their concentrations. Although the application of PIXE to biological samples is not new (3), and recent reviews have emphasized the usefulness of this technique (4-7), the optimization of PIXE for use in typical animal toxicity studies has not been described in the toxicology literature. Here we present the optimization of the instrumentation, sample preparation, and the application of PIXE to a disposition study of metals in renal tissue.The implementation of the PIXE technique has been limited mostly to physics and nuclear research laboratories because no commercial instrumentation is available. The proton beams for PIXE are generated by Van de Graaff accelerators that are not in high demand for applications in physics because much higher-energy ion beams are preferred in most nuclear physics research. The availability of high-energy accelerators has therefore made PIXE an attractive alternative to other conventional, multielemental analytical methods. The simultaneous quantification of a large number of elements in a sample makes PIXE an important analytical tool for use in diverse toxicological studies.Overview of PIXE Theory and Technique X-rays are produced as electrons from outer shells rapidly decay to replace innershell electrons ejected by high-energy protons. The energies of the X-ray emissions are characteristic of the elements, and the intensities of the emissions are proportional to the concentrations of the elements in the sample. The useful range of emitted X-ray energies for PIXE is 1-30 keV; the Si(Li) detector is capable of resolving X-ray emissions as closely spaced as 150 eV, and, as a consequence, 20-30 elements can be readily identified and determined simultaneously.An X-ray spectrum of a thin copper film,deposited on a carbon substrate is shown in Figure 1. The dominant features of the spectrum are the copper K. and K X-ray emission lines resulting from the ejection of the K (innermost) shell electrons of copper. The shape of the X-ray emission peaks in the spectrum is primarily Gaussian; the width of the peak is defined by the statistical distribution of the electrical pulses generated by X-ray photons in the Si(L...

Metal Speciation in Environmental and Biological Systems

“…In Figure 4 processing can be completely automated (11,12). Additionally, the proton beam can be focused and areas from 10 um to 100 um can be analyzed for heavy ele?…”

Interseasonal distribution and partitioning of heavy metals in subtidal sediment of Qua Iboe Estuary and associated Creeks, Niger Delta (Nigeria)

“…These results amplified the extent to which metals ions are absorbed by cation exchange within the studied media. It highlighted that non-specific adsorption (cation exchange) depends on many factors such as physicochemical environment (pH, redox status), presence or absence of complexing agent, type of metal (valence, radius) and, the concentrations and properties of metals present (Alloway 1992;Lowe et al 1993;Matagi et al 1998). Cd and Ni showed moderately enhanced speciation percentage in exchangeable and bound to carbonates fractions than Cr and Cu, with Pb having the least percentage.…”

Atomic and Nuclear Analytical Methods

“…has been described by Deconninck (1981). Lowe et al (1993) used PIXE for tissue analysis in a toxicity-disposition study of renal slices exposed to HgCl 2 , CdCl 2 , K 2 Cr 2 O 7 , or NaAsO 2 alone or in a mixture. From this solution, the sample on nucleopore filter is prepared using a micropipette.…”