Analytical methodology to elemental quantification of weathered terrestrial analogues to meteorites using a portable Laser-Induced Breakdown Spectroscopy (LIBS) instrument and Partial Least Squares (PLS) as multivariate calibration technique

Abstract

The present work is focused on the in situ quantitative analysis of Si, Al, Mg, Ca, Ba, Na, and Fe, present in weathered terrestrial analogues to meteorites (black steel slag and impact glasses), using a portable Laser Induced Breakdown Spectroscopy (LIBS) instrument. For that purpose, several standards pellets of known elemental concentrations were manufactured. The elemental and molecular homogeneity of the pellets was studied by means of Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM-EDS) and Raman spectroscopy. This check was always made before the LIBS analysis. Univariate and multivariate (Partial Least Squares (PLS) regression) calibration approaches on LIBS spectra were selected as initial calibration models. After a comparison between both approaches, the former was discarded due to the poor linearity of the calibration curves, and PLS regression was chosen to treat the LIBS spectra as the multivariate calibration approach (in the ultraviolet (UV) and infrared (IR) spectral ranges). Predictive capabilities of each calibration model were evaluated by calculating regression coefficient (r), number of PLS factors (rank), relative errors of cross validation (RMSECV), residual predictive deviation (RPD) and the Bias value. At the end, the simultaneous use of both ranges of wavelengths was demonstrated to be more fruitful rather than using the individual ones, probably due to the higher number of emission lines, number of spectral variables and the PLS latent variables for each element. Moreover, a Reference Material was used as external validation, obtaining satisfactory results in the determination of elements. The predictive ability of the PLS models was evaluated on samples of Darwin Glasses (Australia), Libyan Desert Glasses (Western Desert of Egypt) and black steel slag residues (steelworks of Basque Country). The obtained results were in concordance with the range of composition measured also by X-ray Fluorescence Spectrometer (ED-XRF). Our 2 methodology is a good, rapid, simple and cost-effective alternative for in situ analysis of these terrestrial analogues over other techniques.

Handheld Laser Induced Breakdown Spectroscopy Instrumentation Applied to the Rapid Discrimination between Iron Meteorites and Meteor‐Wrongs

“…Very recently a portable handheld LIBS instrument, associated with a multivariate calibration treatment of the LIBS spectra acquired in the ultraviolet (UV) and infrared (IR) spectral ranges, was used successfully for the in situ quantitative measurement of Si, Al, Mg, Ca, Ba, Na and Fe mass fractions in weathered terrestrial meteorite analogues (black steel slag and impact glasses; Gómez‐Nubla et al . ). In particular, the LIBS predicted concentrations were in good agreement with the certified concentrations measured by X‐ray fluorescence (XRF).…”

Integrated Laser-Induced Breakdown Spectroscopy (LIBS) and Multivariate Wavelet Tessellation: A New, Rapid Approach for Lithogeochemical Analysis and Interpretation

“…Gómez-Nubla et al (2018) [25] present a rapid, simple and cost-effective alternative for in situ analysis of terrestrial analogues to meteorites utilizing handheld LIBS equipment. Harmon et al (2019) [7] through a series of case studies show the wide potential of LIBS in mineral exploration, prospect evaluation, deposit exploitation, and quality control in mining activities.…”

Combination of Multi-Energy Calibration (MEC) and Laser-Induced Breakdown Spectroscopy (LIBS) for Dietary Supplements Analysis and Determination of Ca, Mg and K

“…All the traditional calibration methods previously mentioned present drawbacks for analysis of complex samples, being in some cases necessary the application of other strategies such as multivariate calibration [25][26][27][28][29] and matrix-matching procedures. [30][31][32] Since 2011, nontraditional calibration methods, such as standard dilution analysis (SDA), [30][31][32][33] interference standard method (ISM) [34][35][36] and multi-energy calibration (MEC), 37 have been applied for quantitative analysis by inductively coupled plasma (ICP) optical emission spectrometry (OES), high-resolution continuum source (HR-CS) flame atomic absorption spectrometry (FAAS), ICP-mass spectrometry (MS) and microwave induced plasma (MIP) with OES.…”