Eu and Tb quantitation in luminescent gamma-ZrP-organometallics compounds by TXRF direct solid procedure

This work presents the analytical procedure developed to quantify Eu and Tb lanthanides by Total-reflection X-Ray Fluorescence (TXRF) by a direct solid method for first time. These rare-earth elements are doping the organic-inorganic hybrid compound gamma-ZrP-TerPy which is currently being investigated as a highly efficient luminescent system. The developed procedure allows for the analysis of very low sample quantities, ca. 5 mg, with an adequate expanded uncertainty, around 8%, and detection limits lower than 0.002 wt% for Eu and Tb. The hereby described direct solid procedure has been tested against the usual quantitative analysis by means of the acid digestion of the samples by TXRF and ICP-MS. Discrepancies as large as one order of magnitude were found between the direct and the acid-digestion measurements. The combination of several unanticipated chemical effects, produced in the conventional digestion procedure of this material, explain its strong loss of Eu and Tb. The thorough optimization of the digestion procedures finally confirmed the validity of the easy and simple direct procedure carried out by TXRF in a solid way without sluggish sample digestion. This research shows once again the versatility and confidence of the quantitative direct solid measurements performed by TXRF.