Experience in using 3 MeV protons for PIXE application on environmental and biological samples

1. Experience in using 3 MeV protons for PIXE application on environmental and biological samples Ana Pantelica, Constantin Ciortea, Marin Marius Gugiu, Daniela Fluerasu, Dana Elena Dumitriu, Dan Gabriel Ghita, Catalin-Ionut Calinescu Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), 30 Reactorului St., Magurele, Ilfov county, P.O.B. MG-6, 07712, Romania, e-mail: apantel@nipne.ro Opportunities for applied research at the new tandem accelerators of IFIN-HH November 1 - 2, 2012, Bucharest-Magurele, ROMANIA

2. Research Topics experienced by PIXE (3 MeV protons) Environmental pollution studies- Obtaining of information on pollutant elements (S, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br and Pb) in environmental samples, mainly originated by anthropogenic activities (traffic, ferrous, non-ferrous and phosphorous fertilizer industries).- To assess the degree of environmental pollution by a comparison with maximum permissible levels given by the Romanian Regulation bodies Bio-Medical studies - Examination of the content levels of some micro- and macro-elements found in the tumor tissue of patients having skin cancer disease, compared with healthy tissue. - Investigation of the health impactof toxic elements consumed through foodstuffcontaminated by industrial activities.

3. Type of samples investigated by PIXE - tree leaves of vascular plants,to select plant speciescapable to accumulate toxic elements in excessive amounts, being tolerant to them,in the vicinity of large industrial enterprises and in the adjacent areas to improve theair quality in urban areas; - vegetables (different species),grown in the vicinity of industrial platforms,e.g.phosphorous fertilizer industry, iron and steel industry, non-ferrous (Pb-Zn) industry; - lichen biomonitors of bulk (dry and wet) atmospheric deposition; - water samples (tape water, dwell water, groundwater, surface water). - airborne particulate matter (PM10) collected on aerosol filters; - skin samples were collected from cancer patients and controls - blood serum and urine (thyroidal illness).

4. Sample preparation • Thin targets for biological samples (~1 mg·cm-2) are prepared by pipetting on Mylar foil (2.5 µ thickness) volumes of 100-150 µL from a chemically mineralized plant solution, diluted with deionized water. • Yttrium (Y) is added as internal standard, prepared from a Y2O3 nitric solution of 160 µg Y·mL-1. The Y concentration on the pipetted target is about 0.5 %. • The skin samples were freeze-dried before applying the wet chemically treatment. • Thick targets for soil samples are prepared as pellets.

5. Calibration and Analytical Quality Control for PIXE technique were performed by means of standard reference materials of certified element concentrations, which are chemically prepared as thin target samples (Y internal standard was considered a beam flux monitor): - CRM-TMDW (Trace Metals in Drinking Water Standard); CRM-OT (Oyster Tissue); IAEA-V10 (hay); IAEA-393 (green algae); IAEA MA-B-3/TM (fish homogenate); NBS-1575 (pine needles). In addition, standards prepared fromchemical compounds (thin targets) are used to assess experimental Kα/Kβ ratios for different elements present in the samples (e.g. Cl, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn. Certified Reference Materials used for Analytical Quality Control in PIXE analysis

6. Experimental set-up • 3 MeV collimated proton beam (~ 2x2 mm2) at the 9 MV FN Van de Graaff Tandem accelerator of IFIN-HH • The target is placed at an angle of 450 with respect to the incident beam and X-ray detector. • The beam current on the target is about 0.5 - 2 nA. • The transport tubes and the target chamber are maintained at a high vacuum (10-6 mbar). • - X-ray spectra measurements are performed using electronic spectrometric chains, with Si(Li)andHPGE detectorsworking in parallel, and Maestro-32 Ortec acquisition cards mounted in a PC. • - Appropriate absorbers (Al foil) are used to reduce the high peaks of Ca and K in the vegetal, with the scope of reducing pile-up effects and thus improving the analytical sensitivity for higher Z elements (e.g. V, Cr, Fe, Ni and Cu).

7. Scattering chamber Faraday cup Proton beam X-rays Be window Al 30 mm Detector cryostat X-ray detector

8. PIXE experimental set-up

9. 9 MV FN Van de Graaff Tandem accelerator of IFIN-HH

10. X-Ray Detection Efficiency in PIXE experiments

11. Elements determined by PIXE in environmental and biological samples Si(Li) Detector Al, P, S, Cl,K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Pb,Se, Br, Rb, Sr. HPGe Detector K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Pb, Se, Br, Rb, Sr. PIXE technique with 3 MeV protonsis most sensitive for middle-Z elements, due to the relatively high ionization cross-sections, a lower background traceable to the bremsstrahlung of secondary electrons, and high detection efficiency. Its sensitivity is decreasing both for lower- and higher-Z elements. For heavy elements, characterized by smaller ionization cross-sections and lower detection efficiency, PIXE can be completed by NAA.

12. Mn, Fe, Cu, and Zn detection limits for PIXE and INAA techniques applied on IAEA-359 (cabbage) sample.

13. Typical PIXE spectra on environmental and biological samples PAC Bucharest Tandem, October 2, 2009

19. ISAP1, Galati, November 28-29, 2009

21. ISAP1, Galati, November 28-29, 2009

24. Mean elemental concentrations for different sample groups of skin samples: I-control group, II-SCC, III-BCC, IV-MM, V-nevus.

25. Conclusions Biological samples, in particular plants with matrix composed from low-Z elements (H, C, N, O), undetectable by the usual X-ray spectrometers, are very suitable to trace element analysis by PIXE. Due to their relatively high K and Ca contents, attention should be paid to the spectral interferences traceable to escape and summing peaks in the X-ray spectra. These difficulties in spectra processing could be successfully resolved by GUPIX program. Thin-target PIXE offers the possibility to determine elemental concentrations without corrections for X-ray self-absorption and proton stopping in target as it is the case of thick-target PIXE. As disadvantage, a rather difficult target preparation in some cases, as well as the risk of incomplete chemical digestion and/or trace element contamination.

27. References • PIXE analysis of some vegetable species, A. Pantelica, A. Ene, M. Gugiu, C. Ciortea, O. Constantinescu, Rom. Rep. Phys., Vol. 63, No. 4 (2011) 997-1008. • PIXE analysis of multielemental samples, A. Ene, I.V. Popescu, C. Stihi, A. Gheboianu, A. Pantelica, C. Petre, Rom. J. Phys. 55, 7-8, 806-814 (2010). • Revitalization of urban ecosystems through vascular plants: preliminary results from the BSEC-PDF project, Gorelova S. V., Frontasyeva M. V., Yurukova L., M. Coşkun, A. Pantelica, C.J. Saitanis, M. Tomašević,M. Aničić,AGROCHIMICA, 55 (2), 65-84 (2011).

28. Thank you !