S.M. Simabuco

Synchrotron radiation total reflection for rainwater analysis

Abstract Total reflection X-ray fluorescence analysis excited with synchrotron radiation (SR-TXRF) has been used for rainwater trace element analysis. The samples were collected from four different sites at Campinas City, SP, Brazil. Standard solutions with gallium as internal standard were prepared for the calibration system. Rainwater samples of 10 μl were added to Perspex reflector disks, dried under vacuum and analyzed for 100 s measuring time. The detection limits obtained for K-shell lines varied from 29 ng ml −1 for sulfur to 1.3 ng ml −1 for zinc and copper, while for L-shell the values were 4.5 ng ml −1 for mercury and 7.0 ng ml −1 for lead.

Synchrotron radiation X-ray fluorescence analysis of trace elements in Nerium oleander for pollution monitoring☆

Abstract This works describes the use of synchrotron radiation fluorescence analysis as a technique for monitoring trace elements in bio-indicators for environmental pollution control. The analyses were performed on leaves of Nerium oleander collected in streets with different levels of traffic flow in Rio de Janeiro, Brazil, with one sample from a rural zone. The leaves were collected from adult trees in December and April. The measurement was made with a white beam of synchrotron radiation calibrated with thin samples from MicroMatter. The results indicate that some metals such as Ti, V, Fe and Zn have major content in samples that were collected in places with a high traffic flow, even in the leaves that have been washed. The levels of Mn, Co, Cu and Ni did not show significant differences between the samples. The Pb level also did not vary significantly. This was expected because in Brazil gasoline without Pb has been used for many years. The results seem to indicate that the leaves from Nerium oleander absorb metals from the atmosphere and may be used as an environmental indicator.

Limits of detection of a total reflection x-ray fluorescence system with double reflection module

An X-ray tube with a Mo target and Zr filter, operated at 45 kV/20 mA, was used to excite samples (5 ΜL deposited on a quartz support) and the total reflection angle condition was obtained with a double reflector module built with two 10-cm-long 7-mm-thick quartz crystals placed 50 Μm apart. A high-resolution spectrometer based on a Si(Li) detector coupled to a multichannel analyzer was used for X-ray detection and the spectra were interpreted with the AXIL software.The system was calibrated with standard chemical solutions containing Cr, Fe, Cu, Zn, and Pb, and Y was used as an internal standard to correct eventual geometric errors and high-voltage instabilities of the X-ray generator. The limits of detection were 19, 9, 5, and 4 ng/mL for Cr, Fe, Cu, and Zn, respectively, analyzed through characteristicKkα X-rays, and 7 ng/mL for Pb, throughLkα X-rays, considering 50 ΜL samples deposited and dried on a quartz support, to be excited/ detected for 1000 s.

Quantitative analysis by energy dispersive X-ray fluorescence by the transmission method applied to geological samples

Three certified samples of different matrices (Soil-5, SL-1/IAEA and SARM-4/SABS) were quantitatively analysed by energy dispersive X-ray fluorescence with radioisotopic excitation. The observed errors were about 10-20% for the majority of the elements and less than 10% for Fe and Zn in the Soil-5, Mn in SL-1, and Ti, Fe and Zn in SARM-4 samples. Annular radioactive sources of Fe-55 and Cd-109 were utilized for the excitation of elements while a Si(Li) semiconductor detector coupled to a multichannel emulation card inserted in a microcomputer was used for the detection of the characteristic X-rays. The fundamental parameters method was used for the determination of elemental sensitivities and the irradiator or transmission method for the correction of the absorption effect of characteristic X-rays of elements on the range of atomic number 22 to 42 (Ti to Mo) and excitation with Cd-109. For elements in the range of atomic number 13 to 23 (Al to V) the irradiator method cannot be applied since samples are not transparent for the incident and emergent X-rays. In order to perform the absorption correction for this range of atomic number excited with Fe-55 source, another method was developed based on the experimental value of the absorption coefficients, associated with absorption edges of the elements.

Study on vinasse dynamics in soil usin energy dispersive X-ray fluorescence with radioisotopic excitation

A distribuicao de S, Cl, K e Ca ao longo de perfis de dois solos de diferentes texturas (Podzolico Vermelho Amarelo e Latossolo Vermelho Escuro), tratados com uma dose de vinhaca equivalente a 4000 m3/ha, foi estudada utilizando a fluorescencia de raios X por dispersao de energia, observando-se um acrescimo significativo dos teores destes elementos. O mesmo efeito foi observado nos teores de Cu, Zn, Rb e Sr nos solos tratados com vinhaca em relacao as testemunhas. As concentracoes de Al, Si, Ti, Mn, Fe e Zr tambem puderam ser avaliadas, mas nao houve variacao nos perfis, devido a alta concentracao inicial nos solos acompanhada de baixa concentracao na vinhaca. Na excitacao dos elementos presentes nas amostras de solo tratados ou nao com vinhaca foram empregadas fontes radioativas anelares de Fe-55 e Cd-109, e na deteccao dos raios X caracteristicos um detector semicondutor de Si (Li), acoplado a uma placa analisadora de pulsos multicanal, inserida em um microcomputador.

Matrix characterization using synchrotron radiation X-ray diffraction

Abstract X-ray spectrometry is a non-destructive and multi-elemental technique widely used for elemental analysis. This technique has inherent complexities for quantitative analysis because of matrix effects. Matrix absorption is the most important determining factor when accurate measurements are required for thick samples. Therefore, new methods have to be developed in order to evaluate matrix effects. In this work, the feasibility of using the synchrotron X-ray diffraction for matrix characterization has been investigated. All measurements were performed at the Laboratorio Nacional de Luz Sincrotron (LNLS), in Campinas, Brazil. Diffraction patterns for boric acid and cellulose matrix containing different oxides were recorded. The preliminary results encourage us to examine further the application of X-ray diffraction analysis combined with energy-dispersive X-ray fluorescence analysis for characterization of thick samples.