Direct determination of lanthanides by LIBS in REE-rich ores: comparison between univariate and DoE based multivariate calibrations with respect to spectral resolution

Abstract

Laser-induced breakdown spectroscopy (LIBS) was used to detect rare-earth elements (REEs) – Ce, La, Nd, Pr, Sm – in ores. The problems of significant overlapping of REE lines in LIBS...

Atomic spectrometry update – a review of advances in environmental analysis

“…The LOD for La was 7.2 ppm. A specially designed set of calibration standards was employed 203 for the direct LIBS determination of lanthanides in REE-rich niobium and uranium ores. The content of each REE in the calibration set covered two orders of magnitude and analytical lines were selected through thermodynamic modelling of the LIBS spectra.…”

Determination of Ce and La in REE-rich ores using handheld LIBS and PLS regression

“…5 However, both techniques require complex and timeconsuming sample preparation and equipment, therefore, cannot be used for rapid analysis outside the laboratory. 6 Direct determination of REEs without sample decomposition is possible using several techniques, such as laser ablation with ICP-MS, 7,8 instrumental neutron activation analysis (INAA), 9,10 X-ray uorescence in wavelength dispersive mode (WDXRF) 11,12 and energy dispersive one (EDXRF), 12,13 laser-induced breakdown spectroscopy (LIBS), 14,15 etc. Geochemical exploration with sample sorting in situ requires the semi-quantitative determination of REEs using handheld/portable spectral systems.…”

“…47 There are several approaches to construct DoE, among them: (1) full factorial design, 48 requiring excessive number of samples to cover all possible relations of concentrations of analytes to completely ll the hyperspace; (2) fractional factorial design, 49 which can reduce the number of required experiments; (3) an orthogonal matrix design proposed by Brereton and successfully used by Shulyumova et al 50 to solve a problem of line overlapping (e.g., As/Pb characteristic lines) common for total reection X-ray uorescence (TXRF); 51 (4) the uniform distribution of experimental points in a multidimensional space developed by Kirsanov et al 52 to analyze lanthanides in aqueous solutions using TXRF; 53 (5) Latin hypercube sampling, rst proposed by McKay et al, 54 which allowed us to construct DoE with extremely low correlation (<0.03) between any pair of ve REEs and applied to XRF and LIBS analysis of REE-rich ores. 12,14 Therefore, our study aims to close the gap on the evaluation of the potential of the handheld LIBS (SciAps Z-300, USA) as a tool for quantication of major REEs (lanthanum and cerium) in real REEs-rich niobium and uranium ores of geological origin with the use of multivariate PLS regression with the aim of developing strategy of the rapid screening analysis. In order to make sure that we avoid systematic errors in the results of the PLS regression we utilized the DoE previously described by us 12,14 to determine several REEs (Ce, La, Nd, Pr, Sm) in ores by laboratory XRF and LIBS systems.…”

“…12,14 Therefore, our study aims to close the gap on the evaluation of the potential of the handheld LIBS (SciAps Z-300, USA) as a tool for quantication of major REEs (lanthanum and cerium) in real REEs-rich niobium and uranium ores of geological origin with the use of multivariate PLS regression with the aim of developing strategy of the rapid screening analysis. In order to make sure that we avoid systematic errors in the results of the PLS regression we utilized the DoE previously described by us 12,14 to determine several REEs (Ce, La, Nd, Pr, Sm) in ores by laboratory XRF and LIBS systems. We believe that the results of this study will allow cheaper, sensitive and accurate, direct determination of La and Ce in ore analysis using the Z-300 analyzer which could be highly benecial in developing of instruments for rapid in-line monitoring and geological survey.…”

“…, As/Pb characteristic lines) common for total reflection X-ray fluorescence (TXRF); 51 (4) the uniform distribution of experimental points in a multidimensional space developed by Kirsanov et al 52 to analyze lanthanides in aqueous solutions using TXRF; 53 (5) Latin hypercube sampling, first proposed by McKay et al , 54 which allowed us to construct DoE with extremely low correlation (<0.03) between any pair of five REEs and applied to XRF and LIBS analysis of REE-rich ores. 12,14…”