Sample Preparation for Determination of Rare Earth Elements in Geological Samples by ICP-MS: A Critical Review

Microwave-induced combustion of crude oil for further rare earth elements determination by USN–ICP-MS

“…The knowledge of concentration of metals is important to classify crude oils, making possible to differentiate similarities and to predict new reserves. More recently, rare earth elements (REE) have been used for this purpose [4,5]. In general, crude oils present predominantly light REE (La-Sm) than the heavy ones (Eu-Lu) due to the process of crude oil formation in the earth crust [4,6].…”

Hydrofluoride decomposition of natural materials including zirconium-containing minerals

“…Usually, geological sample dissolution of refractory silicates requires hydrofluoric acid and a mixture of oxidizing acids, such as nitric and perchloric, in the case of open acid digestion. Then, the choice of decomposition method depends on the mineralogical composition of the rock [1]. In recent years, a simple, effective, and comparatively safe dissolution method with the use of ammonium fluorides (NH 4 HF 2 or NH 4 F) shows great potential for the digestion of geological samples.…”

Hydrofluoric Acid‐Free Digestion of Geological Samples for the Quantification of Rare Earth Elements by Inductively Coupled Plasma‐Optical Emission Spectrometry

“…Fusion is an effective method for the decomposition of rocks that contain acid‐resistant minerals. However, this method is not regularly used for the quantification of trace elements in geological samples due to the relatively high blank and high TDS in the final solution (Totland et al , Yu et al , Pinto et al , Zhang et al , Helmeczi et al ).…”

“…However, HF is a highly reactive, corrosive and toxic reagent (Manahan ), and its use should be avoided according to one of the principles of ‘Green Chemistry’ that recommends the use of safer chemicals to minimise the potential risk of accidents (Anastas and Kirchhoff ). Furthermore, excess HF may co‐precipitate REEs with complex fluorides of the matrix (Yokoyama et al , Fedyunina et al , Pinto et al , Hu et al ), leading to low analytical recoveries. HF also damages the glass and quartz fittings of the measurement equipment.…”

“…However, these methods may present certain disadvantages or may not be employed for all types of samples. The repeated additions of HNO 3 (Eggins et al 1997, Yokoyama et al 1999, Yu et al 2001 or HClO 4 (Takei et al 2001, Hu et al 2013, Magaldi et al 2018) and HF evaporation steps may be time-consuming (Pinto et al 2012), besides the disadvantage of exposure to hazardous HF vapours. Furthermore, this method cannot be employed for samples containing (Mg + Ca)/Al ratios < 1, because of the trace element co-precipitation with AlF 3 (Takei et al 2001).…”