Uncertainty in the Multielemental Quantification by Total-Reflection X-ray Fluorescence: Theoretical and Empirical Approximation

Nowadays, the subject of the quality assurance of the analytical results is acquiring more and more importance. This work presents a basic theoretical and empirical approximation to the expanded uncertainty associated to the TXRF measurements. Two theoretical models has been proposed and compared systematically with the empirical expanded uncertainty obtained. The main consequences derived of this work are the following; theoretical model B explains with a high degree of agreement the empirical expanded uncertainties associated to the TXRF measurements, while theoretical model A explains partially the instrumental repeatability of the TXRF system. On the other hand, an unexpected U-behavior has been found for the empirical uncertainty in TXRF measurements whose explanation can be due to the sum of several sources of uncertainty not considered like variations of the Compton background or the nonlinearity of the Si(Li) detector quantum efficiency. Additionally, it has been shown that the roughness and small geometrical variations of the sample depositions are the more important uncertaintysourcesintheexperimentalTXRFmeasurements.