Combination of Total Reflection X-ray Fluorescence (TXRF) analysis with X-ray Absorption Near Edge Structure (XANES) analysis to perform chemical speciation of bioaccumulated arsenic

PEREZ, CARLOS A; MARTINS BRUNA S.; BONGIOVANNI, GUILLERMINA A.

Congreso; 21 International Congress on X-Ray Optics and Microanalysis (ICXOM21); 2011

Brazilian Synchrotron Light Laboratory (LNLS) and the National Laboratory of Biosciences (LNBio)

It is well established that chronic exposure to arsenic can cause cancerous and non-cancerous health hazards. However, epidemiological and experimental evidence suggest that the development of arsenic-related diseases is not only determined by the dosage of exposure, but also by its chemical form. It is generally accepted that the +3 methylated arsenic species are more cyto- and genotoxic, and more potent enzyme inhibitors than both their pentavalent counterparts and the inorganic arsenic species. In this regard, becomes necessary to know chemical species of accumulated arsenic in target organs in order to do more efficient therapy strategies. In previous reports, mapping of As distribution obtained by SR-µXRF showed its accumulation in renal cortex from exposed rats. In order to As speciation, arsenic K-edge XANES measurements in fluorescence mode and grazing incidence geometry (SR-TXRF-XANES) were carried out using the set-up recently developed at the D09B-XRF beamline at the Brazilian Synchrotron Light Laboratory. During the measurements, the excitation energy was tuned in three steps across the arsenic K-edge at 11,867 eV. For step 1, the acquisition time for each spectrum was set to 6 s and the energy range was set from 11800.0 to 11854.0 eV. For step 2, the acquisition times were set to 20 s and the energy range was set from 11856.0 to 11946.5 eV. Finally, for step 3, the acquisition times were set to 6 s and the energy range was set from 11947.0 to 12060.0 eV. By this procedure it was possible to determine that As+5 is the predominant species in the blood (carrier), while As+3 is the predominant accumulated species in the renal cortex. We conclude that SR-XRF-XANES is a new methodology available at LNLS for the successful determination of chemical species in different matrices.