Fast, accessible and reliable method for elemental analysis of metals in solution by ED-XRF spectroscopy

The measurement of metals in solution is usually performed using inductive coupled plasma hyphenated techniques or atomic absorption. Although very sensitive and accurate, these analytical techniques are quite expensive and do not allow field measurements. The present work takes advantage of energy-dispersive X-ray fluorescence (ED-XRF) ease-of-use features to determine the concentration of rare earth elements (Y, Pr, Nd, Eu) and others (S, Fe, Ni, Cu, Zn) in aqueous solutions, after appropriate sample treatment. The approach turned out to be a reliable and very convenient procedure for field analysis. The simplicity, speed and reliability of the methodology used combined with the possibility of simultaneous analysis and low cost of the method can be advantageous in industrial context. The approach relies on the suspension of the target solutions in a cellulose matrix that is further converted into a pellet for direct analysis. Calibration curves obtained by regression analysis at 5% significance are shown for a variety of elements (S, Fe, Ni, Cu, Zn, Y, Pr, Nd, Eu) with correlation coefficients between 0.9555 and 0.9980. Higher coefficients of variance were obtained for the calibration of S and Pr due to low sensitivity and the overlapping with the L lines of Nd, respectively. The performed calibrations were not affected by the presence of other analytes in the matrix. Results obtained showed that it is possible to use the proposed methodology to accurately quantify d and f block metals in aqueous solutions by ED-XRF after sequestering the chemical content into a cellulose powder matrix and further processing into a pellet.