Recent trends in sample preparation methods and plasma-based spectrometric techniques for the determination of rare earth elements in geological and fossil fuel samples

Sample preparation is the most crucial step in any analytical method of determination. The main goal of sample preparation is to isolate or pre-concentrate target analyte from complex matrix, to ensure compatibility of the desired analyte with the detection technique of interest. Most plasma-based spectrometric techniques cannot succeed with high matrix interferences. The favored sample preparation method must follow the Green Analytical Chemistry Principles (i.e., short duration, environmentally friendly reagents, less energy consumption, microliter volume, robust, simple, cost-effective, etc.). Rare earth elements (REEs) naturally occur in complex matrices (fossil fuels and geological materials) at trace concentration levels. Therefore, this review evaluates various sample preparation methods that have been frequently reported for the determination of REEs in geological and fossil fuel samples using plasma-based analytical techniques such as inductively coupled plasma optical emission spectroscopy and inductively coupled plasma mass spectrometry. Moreover, the determination of these REEs is examined according to whether the samples were acid digested, heat digested, or extracted prior to REEs spectrometric determination. Lastly, the merits and demerits of each sample preparation method are extensively discussed and the recent trends on the development of plasma-based techniques for REEs determination in geological and fossil fuel samples are addressed.

Automated summary

This study evaluates various sample preparation methods for the determination of rare earth elements in geological and fossil fuel samples, focusing on whether acid digestion, heat digestion, or extraction were performed prior to REEs spectrometric determination. The principles of Green Analytical Chemistry are proposed as guiding principles for sample preparation, and the advantages and disadvantages of each method are extensively discussed.