Determination of toxic metals in clay-minerals by X-ray fluorescence spectrometry

The presence of toxic elements such as Mn, Cr, Co, Ni, As, Se, Cd and Pb have been awakening great interest, because they are frequently found in environmental materials like soils, sediments and waters. The emission of those metals can be, mainly, attributed to industries, thermoelectric plants and urban occupation sources. The study of the contamination of the soils and sediments for toxic metals is important for the preservation and conservation of those resources, once the soil is a component key of the ecosystem for the growth of the plants, degradation and recycling of the dead biomass. A method for determination of those elements in clay minerals was established. It was used x-ray fluorescence spectrometry and fundamental parameters method. This method allows to calculate the theoretical fluorescent intensities from the measured intensities of the elements present in sample, using instrumental sensitivity. The clay fraction was obtained through mineral desegregation, being deposited by gravity on a quartz substrate. This kind of sample preparation allows to obtain thin film samples, reducing drastically the matrix effects. The fundamental parameters method does not need the single element calibration curves, carrying a very fast analysis. The method presented an accuracy lower than 10%, a precision between 0.3 to 2.4% and a determination limit at the 1μg/g (author)