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Elemental concentrations in micro-PIXE (Particle Induced X-ray Emission) maps of elements in biological tissue slices have been determined using auxiliary information on the sample matrix composition from EBS (Elastic Backscattering Spectroscopy) and STIM (Scanning Transmission Ion Microscopy). The thin sample approximation may be used for evaluating micro-PIXE data in cases, where X-ray absorption in the sample can be neglected and the mass of elements in a selected area can be estimated. The resulting sensitivity amounts to an impressive 10−12 g of the selected elements. Two cases are presented as examples. In the first, we determined the total mass of gold nanoparticles internalized by human monocyte-derived dendritic cells (MDDC). In the second, an inventory of the mass of elements in the micro-particulate material adsorbed at the wall of the lorica of the microzooplankton species Tintinnopsis radix has been created.

In machine workshops and laboratories, specific materials and chemicals are processed and toxic aerosols may be released into air. For protection of the health of employees working in that environment, it is therefore important to gather knowledge about aerosol composition related to specific working activity and to monitor the aerosol concentration levels. An extensive study of this kind was performed in the machine workshop of Jožef Stefan Institute using a combination of time-, particle size- and location-resolved sampling. The majority of samples were analyzed by particle induced X-ray emission (PIXE) and energy dispersive X-ray spectrometry (EDX) techniques and the main results have been described in a separate paper. Here, we concentrate on presenting the results of individual particle analysis of an aerosol emission that is related to a short, unexpected episode related to the restoration of old furniture. Although the activity was identified by a strong correlation of elemental concentrations in a series of samples taken with a 2-h time resolution, the single microparticle analysis of the cascade impactor samples taken over the longer time period offered an additional insight into the corresponding aerosol composition. The analysis of the aerosol size-selected samples revealed strong pair correlations among concentration levels of Ba, Zn, S, Pb and Cl in a number of individual microparticles. The result is explained by the emission of Ba- and Pb-rich aerosol particles in course of removal of the old white paint layers. The former particles appear to originate from white pigment called lithopone, which is a mixture of BaSO4 and ZnS, and the latter group seems to be related to Pattinson's white lead PbCl·OH. Although the individual particle analysis by itself is in principle capable of assigning the emission source, in this case, it was used as an excellent tool to enhance the quality of source characterization. Copyright © 2011 John Wiley & Sons, Ltd.

We recorded a series of spectral maps of a hematite particle by combining a scanning proton microbeam excitation with detection of X-rays by a Si(Li) spectrometer equipped with polycapillary lens. The particle was driven through the sensitive microvolume to allow for a reconstruction of concentration in three dimensions. Beside the description of the experiment, important aspects of data analysis are emphasized to show the potential of the confocal micro-PIXE (Proton Induced X-ray Emission) imaging method: at present, this is limited by the focusing properties of the polycapillary lens.

A detailed report about the confocal experiment and the corresponding data analysis is presented to determine local atomic concentrations in a thick sample with a micrometer resolution. X-ray emission from a quartz substrate, loaded by aerosol particles, was induced by a scanning proton microbeam and observed by an Si(Li) spectrometer whose field of view was narrowed by a polycapillary lens. A series of X-ray images were recorded at different positions of the sample along the microbeam axis when the particles were driven through the sensitive microvolume. The concentrations reconstructed in three dimensions were used to extract penetration profiles of the strongest X-ray emitters (Fe, Ca, S) in an aerosol sample together with the surface profile of the matrix (Si). The results show exponentially dumped depth profiles with characteristic length depending on particle size. Copyright © 2009 John Wiley & Sons, Ltd.

The elemental composition of PM10 aerosols in the vicinity of the open-air bulk terminal in the Port of Koper, Slovenia, was determined. Using a combination of short but intense and longer but relatively simple set-up of sampling points and sampling periods, we studied elemental concentrations ranging from S to Br and Pb due to the presence of the terminal and related activities. We observed a decrease in concentrations with respect to the distance from the source and a long-term correlation of different elemental concentrations detected during the non-stop 2-year sampling period. Two types of filters, Nuclepore and quartz fibre, were used for sampling as being most appropriate for different aims of the project. The filters were irradiated with 2 MeV protons at the PIXE beamline of the Microanalytical Centre at Jozef Stefan Institute (JSI). The elemental concentrations were obtained by analysing the recorded x-ray spectra with the GUPIX code. We found a strong correlation between iron ore transfer and Fe concentration in PM10.

A method of sample surface topography reconstruction is described based on the asymmetry in the X-ray yields acquired by a pair of X-ray detectors positioned at opposite sides of the probing beam. The yield asymmetries in the two simultaneously acquired elemental maps are caused by differences in the X-ray absorption along the X-ray exit route in the sample with a topographically structured surface. The approach presented introduces an asymmetry factor of the X-ray intensity in each of the image pixels to obtain an image asymmetry matrix. The dependence of the asymmetry factor on the local target inclination in the detector plane is calculated for a flat sample surface model. The image asymmetry matrix is then converted into the local inclination angle matrix. As the last step, the surface topography is then reconstructed from the local inclination angle. The method is based on X-ray absorption phenomena and could be applied equivalently in X-ray elemental mapping methods using excitation beams with a well-defined direction in the sample. This includes micro-X-Ray Fluorescence analysis (micro-XRF) and micro-Proton Induced X-ray Emission (micro-PIXE). We demonstrated the method by topographic analysis of engraved metallic samples with stereo-PIXE and compared it with the results of stylus profilometry. The smallest value of the X-ray production depth and the characteristic X-ray attenuation length determines the lateral resolution of the proposed topography reconstruction method.

In a typical micro-PIXE set-up the insertion of an X-ray optic such as a polycapillary half lens, in front of the X-ray detector in combination with the focused charged particle micro-beam creates a confocal geometry and thus a probing-volume. By moving the sample across the probing-volume, spatially resolved characteristic X-ray intensities are detected. The aim of this work is to present a theoretical model that describes the micro-PIXE intensities in confocal geometry in the case of either layered-structured materials or materials composed of major–minor elements exhibiting concentration gradients within depth. The influence of various experimental parameters such as the beam energy, spatial resolution of the X-ray lens, micro-beam dimensions, irradiation and detection angles, as well as the structure (thickness, composition) of the individual layers that compose the analyzed sample, is investigated by means of simulations of the PIXE yield at various positions of the analyzed sample within the probing volume. The advantages and limitations of the micro-PIXE analysis in confocal geometry are presented through examples and discussed, in particular with respect to the differential PIXE analysis.

A novel experimental technique, 3D micro-particle-induced X-ray emission (PIXE) is described in the present paper. 3D Micro-PIXE is realized by using an X-ray optic in front of the detector, thus creating a confocal arrangement together with the focused proton micro-beam. This confocal setup defines a probing volume from which information on elemental distribution is obtained. If a sample is moved through the probing volume, depth-resolved measurements become possible. The confocal setup was characterized with respect to its spatial and depth resolution. As an example of application for this new non-destructive analytical technique, an archaeological ceramic fragment was examined. A first approach to simulate the complex experimental results is performed. The potential of 3D micro-PIXE to provide advanced qualitative information on the elemental distribution in the sample is discussed.