source:AZO Mining
When the term 'rare earth elements” (REEs) is used, it typically refers to a group of elements including the lanthanide series (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), as well as Sc and Y.
REEs are used extensively in electronics and advanced technologies, which are utilized in: airplanes, automobiles, medical devices, smartphones, television, computers, and camera lenses to name a few. The continual advancement of technologies has increased the demand for REEs, so the search for large deposits of REEs and quality ore material is ongoing.
Raw geological materials containing REEs are typically found in low concentrations. The ability to precisely detect and quantify REEs in geological samples is a critical component of successful geological exploration. This determines the viability of new mining sites, as well as help to expand existing ones.
The common techniques employed to analyze the REEs of geological samples include inductively coupled plasma mass spectrometry (ICP-MS), x-ray fluorescence (XRF), and instrumental neutron activation analyses (INAA). While XRF and INAA have their own advantages and disadvantages, both techniques have poor detection limits when compared to ICP-MS – a vital requirement when detecting low concentrations REEs.
As a result, measuring REEs content by ICP-MS post-sample preparation is the broadest used analytical technique. Using an appropriate sample preparation method – primarily acid digestion or fusion – prior to analysis by ICP-MS is critical in achieving accurate results. A variety of complications can be introduced to the analyzis, depending upon the chosen method of preparation.
The fusion of samples in lithium borate flux is a commonly used preparation technique for matrices that are very refractory, or otherwise hard to digest. In ICP-MS analysis, the high boron and lithium backgrounds in these types of prepared samples can present challenges, which would need addressing. For matrix effects because of the increased amount of total dissolved solids (TDS) in the prepared solution.
In addition, REEs are frequently present in very low concentrations, and many have oxide and isotopic overlaps - these factors require extra considerations. The combination of the All Matrix Solution (AMS, an online argon dilution system)1, second-generation Triple Cone Interface with OmniRing? technology2, four gas channels with on-line gas mixing, Universal Cell Technology (UCT), and multi-quadrupole design of PerkinElmer’s NexION? 5000 ICP-MS, provides many of the tools needed to overcome these issues.
This demonstration note outlines the analysis of three certified reference materials (CRMs) that contain REEs, prepared by fluxing the samples with lithium borate. The samples contain different ore materials all comprised of REEs, and are analogous to exploration samples.