Characterisation of pure and mixed sulphur compounds by x-ray emission spectroscopy

P. PÉREZ; A. C. CARRERAS; J. TRINCAVELLI

Cabo Frio - Rio de Janeiro - Brasil

Congreso; XI Seminario Latinoamericano de Análisis por Técnicas de Rayos X (SARX 2008); 2008

SARX 2008

Conventionally, x-ray emission spectroscopy is used to determine the concentration of the elements that are present in a sample; nevertheless, the determination of the oxidation state of those elements (speciation) is sometimes very important. For example, SO3 is responsible for the acid rain. This means that some sulphur compounds are very toxic while other ones produce no significant damage at all. In these situations, oxidation state quantification could provide invaluable information [1]. High resolution x-ray spectroscopy makes possible to distinguish changes on the atomic level structure produced by different binding types, as was observed for the Kβ sulphur spectrum by photon incidence [1,2,3]. In addition, a similar study was performed to characterise chemical shifts in the sulphur Kα spectrum by proton incidence [4]. In the present work, the Kβ and Kα sulphur spectra obtained by electron incidence is investigated for different oxidation states. The multiple vacancy satellite lines are dependent on the energy and kind of incident particle and a full characterisation of the sulphur K x-ray spectrum was not previously performed for electron impact, up to our knowledge. Finally, two quantification methods for sulphur compound mixtures are presented. With this purpose, several sulphur compound mixtures of sodium sulphite (S4) and sodium sulphate (S6) were prepared for EPMA. Then, calibration curves were made by plotting certain spectral properties as a function of the compound concentrations.