Sub-micron Hard X-ray Fluorescence Imaging of Synthetic Elements

• Published in: Analytica chimica acta Vol. 722; pp. 21 - 28
• Main Authors: Jensen, Mark P., Aryal, Baikuntha P., Gorman-Lewis, Drew, Paunesku, Tatjana, Lai, Barry, Vogt, Stefan, Woloschak, Gayle E.
• Format: Journal Article
• Language: English
• Published: 13.02.2012
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2012.01.064

Synchrotron-based X-ray fluorescence microscopy (SXFM) using hard X-rays focused into sub-micron spots is a powerful technique for elemental quantification and mapping, as well as microspectroscopic measurement such as μ-XANES (X-ray absorption near edge structure). We have used SXFM to image and simultaneously quantify the transuranic element plutonium at the L 3 or L 2 edge as well as lighter biologically essential elements in individual rat pheochromocytoma (PC12) cells after exposure to the long-lived plutonium isotope 242 Pu. Elemental maps reveal that plutonium localizes principally in the cytoplasm of the cells and avoids the cell nucleus, which is marked by the highest concentrations of phosphorus and zinc, under the conditions of our experiments. The minimum detection limit under typical acquisition conditions for an average 202 μm 2 cell is 1.4 fg Pu/cell or 2.9 × 10 −20 moles Pu/μm 2 , which is similar to the detection limit of K-edge SXFM of transition metals at 10 keV. Copper electron microscopy grids were used to avoid interference from gold X-ray emissions, but traces of strontium present in naturally occurring calcium can still interfere with plutonium detection using its L α X-ray emission.