Study of the distribution of actinides in human tissues using synchrotron radiation micro X-ray fluorescence spectrometry

Transcription

1 Analytical and Bioanalytical Chemistry Electronic Supplementary Material Study of the distribution of actinides in human tissues using synchrotron radiation micro X-ray fluorescence spectrometry Eva Vergucht, Björn De Samber, Andrei Izmer, Bart Vekemans, Karen Appel, Sergei Tolmachev, Laszlo Vincze, Frank Vanhaecke 1

2 Preparation of formalin-fixed, paraffin-embedded (FFPE) tissues To ensure good conservation of the tissues, all water traces were removed and the tissues were embedded in a medium that later hardened to form a solid matrix. Dehydration was accomplished by using graded alcohol solutions, after which the samples were infiltrated with wax under vacuum. Low pressure guarantees that all air was removed from the tissues, thus inhibiting hole formation in the slices. An overview of the sample treatment steps is given in Table S1 [1]. Table S1 Overview of the sample treatment steps for obtaining formalin-fixed, paraffin-embedded tissues # Process Time range 1 Fixation in neutral buffered formalin* 1 hour for small pieces overnight for larger pieces 2 30 % ethanol 1 hour 3 50 % ethanol 1 hour 4 70 % ethanol 1 hour/overnight 5 Denatured ethanol (96 %) 1 hour 6 Isopropyl alcohol 1 hour 7 Isopropyl alcohol : toluene (1:1) 1 hour 8 Toluene 30 min 9 Paraffin wax at 60 C (under vacuum) overnight * Neutral Buffered Formalin 4% - Formalin 40% 100 ml - Disodium hydrogen phosphate (Na 2 HPO 4 ) 1.78 g - Potassium dihydrogen phosphate (KH 2 PO 4 ) 0.42 g - Add KH 2 PO 4 until ph Add distilled water until 1000 ml 2

3 Free-standing samples The sample slices were mounted onto aluminum supports in a free-standing manner (Fig. S1). Due to the free-standing character, the generation of significant scattering background and the excitation of minor/trace level elements present in the support was prevented. For SR experiments, often silicon-nitride wafers are applied as supporting structures. It should be noted that this type of wafers were not used in this study. Fig. S1 Sample slice mounted free-standing onto an aluminum support 3

4 Data processing flow chart The data processing is split up into multiple parts depending on the input XRF spectra (Fig. S2). Spectral deconvolution was performed by the non-linear non least-squares squares fitting software AXIL, followed by dead time correction and intensity normalization to the Doris ring current.. SR micro micro-xrf LODs were calculated from the NIST SRM 1577c (Bovine liver) measurements. The measurements on the NIST SRM 2910a (HAP) pellets were used for semi-quantitative semi quantitative purposes, based on the construction of calibration curves and subsequent corrections ns for the varying illuminated mass. Note that the calibration curve for Pu was obtained after applying a cross section correction factor of 1.13, since the HAP standards were not spiked with Pu. Fig. S2 Data processing flowchart 4

5 Excitation energies for the elements of interest For the SR micro-xrf experiments the incoming energy was set to 19.5 kev. Using this excitation energy, the main elements of interest (U, Pu and Am) could be excited efficiently by L 3 line excitation. An overview of the exitation energies is presented in Table S2, values were obtained from from the xraylib database [2]. Table S2 Excitation energies for the elements of interest (expressed in kev) U (Z=92) Pu (Z=94) Am (Z=95) K L L L M M M M M

6 Fluorescent spectra of the point measurements on U hot spots (Case 1060) The relevant part of the point measurement spectra of U hot spot 1, 2, 4 and 5 clearly show a very intense U-L α fluorescence peak located at 13.6 kev, thereby confirming the presence of U within the hot spots (Fig. S3). Fig. S3 Overlay of four U point measurement spectra, 17.5 µm m FWHM, 300 s RT 6

7 Confirmation presence Pu in Case 0407 For Case 0407, several point measurements were performed at the position of the Pu hot spots. For plutonium hot spot 6, the relevant part of the fitted spectrum is shown in Fig. S2. In particular, Fig. S2a shows the AXIL-fitted spectrum in case the Pu-L fluorescent lines are not added to the fitting model. It can be clearly seen that the peaks at channel numbers 1200 and 1450 are not fitted correctly which is not the case for the fitted spectrum in Fig. S2b, where the Pu-L fluorescent lines were added to the model. Since the second model correctly fits the XRF spectrum, this thereby clearly confirms that Pu is present within the hot spots observed via the SR micro-xrf measurements. Fig. S4 Detail of the AXIL-fitted spectrum for the point measurement on Pu hot spot 6. (a) Pu-L lines not added to the fitting model. (b) Pu-L lines added to the model resulting in a better fit References 1. Protocols Online. Paraffin Processing of Tissue. preparation/paraffin-processing-of-tissue. Accessed 28 Oct Schoonjans T, Brunetti A, Golosio B, Sanchez del Rio M, Armando Solé V, Ferrero C, Vincze L (2011) The xraylib library for X-ray matter interactions. Recent developments. Spectrochim Acta Part B At Spectrosc 66: