Thick Target PIXE Research Articles

On the direct quantification of celecoxib in commercial solid drugs using the TT-PIXE and TT-PIGE techniques

The quantification of the active ingredient (AI) in drugs is a crucial and important step in the drug quality control process. This is usually performed by using wet chemical techniques like LC–MS, UV spectrophotometry and other appropriate organic analytical methods. In the case of an active ingredient contains specific heteroatoms (F, S, Cl, etc.,), elemental IBA technique can be explored for molecular quantification. IBA techniques permit the analysis of the sample under solid form, without any laborious sample preparation. This is an advantage when the number of sample is relatively large.In this work, we demonstrate the ability of the thick target PIXE (TT-PIXE) and the TT-PIGE techniques for rapid and accurate quantification of celecoxib in commercial drugs. The experimental aspects related to the quantification validity are presented and discussed.

Ni, Cu, Zn and Pb background values determination in representative Lebanese soil using the thick target PIXE technique

Soil contamination by heavy metal ions is one of the most serious environmental problems. The determination of the natural levels or background values of heavy metals in agricultural soils is the first step for soil contamination assessment. The background values of heavy metals should constitute the base serving to evaluate the impact of land use on soil pollution and to determine the trigger values and intervention levels, which is very important for decision makers and planners in the field of land management and land use. In this paper 104 agricultural soil samples collected from the North Lebanon region, covering the soil surface and subsoil horizons and originating from 46 soil profiles, were analyzed using the thick target PIXE (TT-PIXE) technique. The background values for Ni, Cu, Zn and Pb were determined and discussed in relation to their horizon depths and to the soil lithological classes characterizing the studied region. This study is the first attempt to lay the basis for soil assessment based on land quality.

PIXE ANALYSIS OF URBAN ROADSIDE SOIL

In order to study the influence of motor vehicles on a local soil environment, depth profiles of elemental concentration of urban roadside soil were investigated by means of thick-target PIXE analysis. For comparison, we analyzed the soil sampled in a university campus with very low traffic intensity. From the measured depth profiles, it was found that the roadside surface layers up to the depth of approximately 5 cm from the ground level are highly polluted by S and Zn. According to cluster analysis this pollution can be attributed to the deposition of tire dust due to the heavy vehicular traffic volumes on the highways.

Monitoring of chromium, copper and arsenic in contaminated soils using thick-target PIXE

Soil contamination by toxic metal ions is one of the most serious environmental problems today. In this work soil samples from an area where a wood preservation plant has been active were studied. Chromium, copper and arsenic (CCA) are the main metal ions used in preservation of lumber. For the monitoring of these metal ions and of other elements in soil, thick-target PIXE (TTPIXE) has been proved to be a successful method. About 20 elements were quantitatively determined in the soil samples from the contaminated area and from a reference area. The reliability of the results was evaluated by analysing geochemical certified reference materials (CRMs) of chemical compositions similar to the soil samples.

Multi-Element Analysis of Dry-Ashed Honey Samples by Thick-Target PIXE

Honey samples were dry ashed at 550°C and the ashes were directly analysed with the Thick-Target Particle Induced X-ray Emission (TTPIXE) technique. The elements P, K, Ca, Mn, Fe, Ni, Cu, Zn, Pb, Rb and Sr, were analysed quantitatively. The method allowed the determination of concentrations well below 100 ng/g for most of the elements studied. The ash content can be used for characterization of a honey sample. The samples were collected from two areas in Finland and from the Prague region in the Czech Republic. A Cu-Ni smelter, documented as a source of heavy-metal emission, is situated in one of the areas in Finland. A comparison of metal concentrations in ashes of honey samples proved to be useful for environmental monitoring

Analysis of trace elements in trunk wood by thick-target PIXE using dry ashing for preconcentration

Thick-target Particle Induced X-ray Emission (TTPIXE) was used for the quantitative determination of trace-element concentrations in trunk wood. The wood samples were preconcentrated by dry ashing to improve the reliability of the sampling and the sensitivity of the an- alytical method. Samples of Scots pine ( Pinus sylvestris) and Norway spruce (Picea abies) were collected from a polluted area (Harjavalta) as well as from a relatively non- polluted area (Merimasku) in southwestern Finland. The elements studied were P, S, K, Ca, Mn, Fe, Ni, Cu, Pb, Rb, Sr, Ba, Cd and Ag. TTPIXE combined with dry ashing is a sensitive and reliable analytical technique for most ele- ments studied. The method was validified by using sev- eral certified reference materials and also by ICP-MS analysis. Due to the low ash content (0.2-0.4%) in wood a high preconcentration factor can be obtained. Differ- ences in trace-element uptake were observed between the two tree species studied. Trunk wood from the polluted area contained higher concentrations of heavy metal ions.

Main atmospheric heavy metal sources in Portugal by biomonitor analysis

During the months of July and August of 1993 a lichen collection campaign was held in Portugal where about 250 samples were collected and analysed by thick target PIXE and INAA. Results for 43 different elements were obtained and a data base was built and subjected to Monte Carlo aided target transform factor analysis (MCATTFA), method developed at IRI TU Delft. 10 × 10 km coast and 50 × 50 km far from coast sampling grids were used for collection, concentration data as well as factor patterns were extrapolated to the whole country making use of an extinction rule of 1/r 3. In this work we present the results that were obtained based on a reduced data set of 22 elements measured by TTPIXE. The results for INAA data subset and the total data set are presented elsewhere.

DATTPIXE, a computer package for TTPIXE data analysis

Thick target PIXE (TTPIXE) data analysis requires the calculation of an integral (which we call penetration integral) which accounts for the various effects that take place during proton stopping in the target and lead to X-ray emission. This is done by numerical integration and in most TTPIXE work target homogeneity both along the surface and in depth is necessary. This reduces the applicability of the technique in cases as ion implanted, film coated, or other kinds of samples which are by their own nature nonhomogeneous in depth while preserving their surface homogeneity (we call them layered targets). The DATTPIXE main program, which enables the conversion of spectra peak area data into sample concentration values, is being developed so as to be able to face these kinds of problems. Secondary X-ray fluorescence is accounted for and the correction is calculated for each of the layers into which the target is divided for numerical integration. The program was tested by applying it to the analysis of three metal alloy certified reference materials from the British Chemical Standards. The need for secondary X-ray fluorescence corrections and the correctness of the method used are shown.

TRACE ELEMENT ANALYSIS OF WOOD SPECIES USED FOR PAPER MANUFACTURE

Elemental concentrations of light and medium weight elements ranging from about 0.2% to less than 1ppm were determined by thick target PIXE in a variety of South African woods from different localities. Correspondence analysis, using the measured contents of K, Ca, Mn, Fe, Cu, Zn, and Rb, resulted in groupings which were type-dependent and locality-dependent. The possibility of substituting one variety for another in the same group, for paper production, is discussed.

Cation-ratio differences in rock patina on hornfels and chalcedony using thick target PIXE

The ratio of (K + Ca) to Ti in patina layers is time-dependent and decreases with age. Patinas on hornfels and chalcedony artefacts were irradiated by 2 MeV 4He + ions and analysed by Rutherford backscattering and PIXE simultaneously. The patinas on hornfels and basalt showed a self-consistent variation of cation-ratio with typological age up to 128000 years B.P., but the rate of growth was apparently slower on chalcedony.

Yield of L α X-rays from a light element matrix in thick-target PIXE

Yields of L α X-rays from a light element matrix have been measured for elements with atomic number 52 ≤ Z ≤ 92, for incident proton energy of 2.61 MeV. The experimental results have been compared with the results of numerical calculations using L X-ray production cross section data in literature. It is shown that results of such calculations can be used for analytical application using monostandards in thick-target PIXE.

Limits of detection and quantitation in PIXE analysis of thick targets

X-ray spectra induced by the impact of 1–5 MeV protons on pure single-element matrices of carbon, aluminum, silicon, titanium, iron, germanium, molybdenum, silver, tin, ytterbium and lead have been used to investigate analytical detection limits in thick-target PIXE. Particular attention is paid to the choice of appropriate aluminum X-ray filters for suppression of the matrix characteristic X-ray lines and their pile-up peaks, and to the choice of optimum proton energy.

Quantitative PIXE and PIGME analysis of milligram samples of biomineralized tissue in the limpet Patella vulgata

Procedures have been developed to determine, by thick target PIXE and PIGME, the quantitative elemental composition of biological samples with a mass of approximately 1 mg. Systems of particular interest are the biomineralized tissues of chitons and limpets, marine invertebrates of global distribution whose radula teeth and associated tissue contain, variously, inorganic components at different stages of mineralization, e.g. Fe, Ca, P, F, Si, Cu. For the biomineralized teeth and tissue in the limpet Patella vulgata the content of Fe, Ca and P increases rapidly at an early stage of mineralization, while the Si content increases somewhat later. In fully mineralized teeth, the Fe and Si contents are comparable. These data are compared with previous results (Trends Biochem. Sci. 10 (1985) 6) obtained using the Oxford scanning proton microprobe.