Determination of elemental composition of shale rocks by laser induced breakdown spectroscopy

Abstract

In this study laser induced breakdown spectroscopy (LIBS) is used for elemental characterization of outcrop samples from the Marcellus Shale. Powdered samples were pressed to form pellets and used for LIBS analysis. Partial least squares regression (PLS-R) and univariate calibration curves were used for quantification of analytes. The matrix effect is substantially reduced using the partial least squares calibration method. Predicted results with LIBS are compared to ICP-OES results for Si, Al, Ti, Mg, and Ca. As for C, its results are compared to those obtained by a carbon analyzer. Relative errors of the LIBS measurements are in the range of 1.7 to 12.6%. The limits of detection (LOD) obtained for Si, Al, Ti, Mg and Ca are 60.9, 33.0, 15.6, 4.2 and 0.03 ppm, respectively. An LOD of 0.4wt% was obtained for carbon. This study shows that the LIBS method can provide a rapid analysis of shale samples and can potentially benefit depleted gas shale carbon storage research.

Real-Time Analysis of Potassium in Infant Formula Powder by Data-Driven Laser-Induced Breakdown Spectroscopy

“…The R 2 of area (C) is also not satisfactory for quantification even it is slightly higher than the two peaks above-mentioned. The reason is that the univariate analysis is compromised by both matrix effect and sample complexity (Hou et al, 2016 ; Sanghapi et al, 2016 ). It is therefore expected that the multivariate analysis could improve the calibration performance through latent projection instead of univariate regression, and PLS was chosen as it is mostly adopted in multivariate calibration.…”

Calibration Methods of Laser-Induced Breakdown Spectroscopy

“…There is no doubt that the multivariate analysis is superior to univariate analysis. This has been proven by numerous researchers, for instance, the analysis of rocks [49], rare earth elements [38], glass [50], cerium oxide [51], alloy steel [52], liquid steel [53], soil [54,55], soybean oil [56], PZT (Lead Zirconate Titanate) ceramics [57], Pb in navel orange [58], Marcellus Shale [59], tailing cores [60], geologically diverse samples [49], steel melt [61], slurry [62], iron ore [63] and pellets of plant materials [64].…”

Investigations of Laser Produced Plasmas Generated by Laser Ablation on Geomaterials. Experimental and Theoretical Aspects

“…Each of these moments are defined by three different types of ejection mechanism which lead to the formation of three independent plasma structures [34,36,42,43]. In such a context the dynamics of fast plasma structure generated though Coulomb explosion mechanism would be described by relations (5), (7) and (8) while the dynamics of the slow structure generated through thermal ejection mechanisms are given by relations (6), (7) and (9). The reasoning behind this association is given by the fact that the nondifferentiable behavior of the laser ablation plasmas is induced through the collision process between the ejected particles in each plasma structure.…”

“…As such differential absorption by the material and by the particle vapor, or the matrix effect [7] can strongly affect the properties of the resultant plasma (usually confined to a few mm from the sample and expanding with high velocities). The matrix effect issues are shown to be overcome by different sample preparation techniques (i.e., in the form of pressed pelletized powder [8] or, with much better results, fused glass), however these are breaking on the main advantage of LIBS-reduced time consuming sample preparation-which is lost and the operational costs are higher due to the special equipment needed. The implementation of LIBS technique on soils needs also to consider the influences of compression force, moisture, and total content of easily ionized elements on line intensities and electron density were studied and because dramatic changes occur, the recommendations were to use dry samples as much as possible and observe plasma as early it can be done in order to minimize the matrix effects on results [9].…”