Influence of soil sample grain size on energy dispersive X-ray fluorescence analysis: a comparative study case with three spectrometers

Abstract

This study aims at evaluating the particle size influence on the quantitative Energy Dispersive X-ray Fluorescence data of tropical soils, as well as evaluating the results trueness and precision using different statistical approaches. These objectives were conducted in three spectrometers, a benchtop one, and two portable ones. Certified reference materials were employed in calibration and trueness evaluation. Soil samples were collected, grounded and sieved in particle sizes: macerated (>2 mm), <2, <0.7, <0.3, <0.125, and <0.06 mm. The three spectrometers had different performances and lack of trueness for Potassium and Zinc in the Lab-made spectrometer. Regarding the grain size parameters, the spectrometers responded in different ways. It was identified that the best soil grain size condition for one of the portable spectrometers was <0.06 mm, while for the benchtop and for the other portable spectrometer the best soil grain size was <0.125 mm. In summary, the soil grain size affected the quantitative results in Energy Dispersive X-ray Fluorescence measurements, but it depends on the sensitivity of each spectrometer and the element of interest.