Determination of relative rare earth element distributions in very small quantities of uranium ore concentrates using femtosecond UV laser ablation – SF-ICP-MS coupling

Abstract

An alternative analytical method has been developed to determine lanthanide distribution using hundreds of nanograms of uranium ore concentrates (UOCs) by femtosecond ultra-violet laser ablation coupled to inductively coupled plasma sector-field mass spectrometry (fs-UV-LA-ICP-SF-MS). In contrast to the commonly used analytical approach consisting of analysing macroscopic sized samples by standard wet plasma nebulisation ICP-MS, the method developed in this study reduces the amount of sample necessary for analysis by at least three orders of magnitude. As the ablation of micrometric particles produces a short transient signal (5–10 s), optimisation of the method to process such signals is discussed. The absolute limits of detection for the measurement of 14 lanthanides were in the range of 80 to 630 attograms, allowing elemental concentrations close to ppm to be measured in such a small quantity of UOC. Validation of the method was performed by determining the relative distribution of lanthanides in the standard UOC certified reference material, “Bolet” (CETAMA), for which concentrations of 3 lanthanides are certified. The method was also applied to the measurement of the 14 lanthanides in a UOC called “Olympic Dam”. The results were in good agreement with the results obtained from two laboratories for the same sample by a standard wet plasma nebulisation ICP-MS method after chemical purification (U matrix elimination and lanthanide concentration starting from macroscopic amounts of materials) and with data from the literature concerning the lanthanide distribution in the original U-ore.