LIBS Core Scanner Review/Optimization of laser-induced breakdown spectroscopy for rapid geochemical analysis

Optimization of laser-induced breakdown spectroscopy for rapid geochemical analysis[1][edit | edit source]

Abstract: Laser-induced breakdown spectroscopy (LIBS) is demonstrated as a quantitative technique for geochemical analysis. This study demonstrates the applicability of LIBS to bulk elemental analysis of igneous rock powders. LIBS spectra of 100 igneous rocks with highly varying compositions were acquired at 9 m standoff distance under Mars atmospheric conditions. LIBS spectra were modeled using partial least squares regressions to predict major element compositions. A series of comparative tests determined the most effective methodologies for pre-processing of spectral and compositional data, and choice of calibration set. In the best cases, calculated 1−σ errors are 1.6 wt.% SiO2, 1.5 wt.% Al2O3, 0.4 wt.% TiO2, 1.2 wt.% Fe2O3T, 1.6 wt.% MgO, 0.02 wt.% MnO, 1.1 wt.% CaO, 0.5 wt.% Na2O, 0.2 wt.% P2O5, and 0.4 wt.% K2O, with totals near 100%. The largest improvement came as a result of scaling the elemental distributions to equalize the ranges of variability. Optimal predictions for this data set were produced with calibration set compositions input as weight % oxides and not atomic fractions. Predictions were also improved when calibration sets represented the smallest range of compositional variability possible, and completely encompassed the compositional range encountered. Multiple calibration sets relevant to different rock types are preferred over a single all-encompassing calibration set. Baseline removal and transforming spectral data by their first derivative do not improve predictions and can even have negative effects. These results are directly applicable to spectra that will be acquired by the ChemCam experiment on Mars Science Laboratory, but also apply more broadly to terrestrial LIBS applications.

• Elem. distributions scaled
• Quantification units as oxides
• PLS

Analysis of Minerals and Rocks by Laser-Induced Breakdown Spectroscopy[2][edit | edit source]

Abstract: Laser-induced breakdown spectroscopy (LIBS) technique was applied for rapid analysis of major and minor elements composing geological samples including minerals, rocks, and a soil sample. The plasma was produced in air at atmospheric pressure by focusing on the targets a pulsed infrared Nd:YAG laser in open-path configuration. The emitted light in the UV-Vis was analyzed by a compact LIBS system to measure spectral emission lines of Si, Al, Fe, Ca, Na, K, Mg, C, Cu, Mn, and Ti. The experimental issues relevant for the analysis of the different samples were investigated by taking into account their peculiar features: drilling through a weathered layer, roughness and grain-size considerations, statistical averaging, and accuracy of the measurements. In this approach, the characterization of the samples was achieved by studying the relative variations of the emission intensities of each element normalized with respect to an internal standard. The present study shows the usefulness of LIBS as a tool for reliable identification of field samples.

• Non-gated
• Errors due to: matrix, surf. roughness, grain size, inhomogenities, laser fluc. FL, regio of plasma plume
• Internal standard norm. with N

Testing a portable laser-induced breakdown spectroscopy system on geological samples[3][edit | edit source]

Abstract: This paper illustrates the potentialities of a home-made portable LIBS (laser-induced breakdown spectroscopy) instrument in Earth sciences, more particularly in geochemically recognizing (i) tephra layers in lacustrine sediments and (ii) fossilization processes in ammonites. Abundances for selected lines of Al, Ca, Fe, Ti, Ba and Na were determined in lacustrine chalk sediments of the Jura, where the Laacher See Tephra (LST) layer is recorded. A statistical treatment of elemental maps produced from the section of a sedimentary column containing the LST event allows instrumental conditions to be optimized. Accumulating spectra from close shot positions gives better results than multiplying shots at the same location. A depth profile method was applied to study ammonite fossilization (pyritization, phosphatization) processes. Depth variations of Fe, Ca, Al intensities, and Fe/Ca and Al/Ca ratios provide indications about pyritization, but phosphatization processes cannot be determined with our device.

• home-made portable LIBS

Cores and Core Logging for Geoscientists[4][edit | edit source]

Abstract: Cores and Core Logging for Geoscientists is essential reading for all geologists and environmental and engineering geoscientists who deal with core or results coming from core. This book is an update from the first-edition paperback version published almost 20 years earlier titled Cores and Core Logging for Geologists. As the title implies, the second edition broadens the scope to the larger "geoscience" audience, which is a reflection of the growing field of professionals using core data since the publication of the first edition.

• Basic knowledge about cores and core sampling

Applications of laser-induced breakdown spectroscopy for geochemical and environmental analysis: A comprehensive review[5][edit | edit source]

Abstract: Applications of laser-induced breakdown spectroscopy (LIBS) have been growing rapidly and continue to be extended to a broad range of materials. This paper reviews recent application of LIBS for the analysis of geological and environmental materials, here termed "GEOLIBS" . Following a summary of fundamentals of the LIBS analytical technique and its potential for chemical analysis in real time, the history of the application of LIBS to the analysis of natural fluids, minerals, rocks, soils, sediments, and other natural materials is described.

• List of LIBS attributes
• Fundamentals
• Different applications
• Signal statistics

Laser-Induced Breakdown Spectroscopy for Rapid Elemental Analysis of Drillcore[6][edit | edit source]

Abstract: The elemental and mineralogical contents of rock drillcore can be analyzed using a variety of methods. For efficient exploration the characterization of the drillcore should be performed rapidly, so that the further drillings can be better planned and unnecessary costs can be reduced. In this paper, laser-induced breakdown spectroscopy (LIBS) is studied as a potential rapid on-line method for automated elemental analysis of drillcore. The method is based on a pulsed laser beam that transforms a small volume of the sample into plasma. Individual elements in the plasma have characteristic emission patterns detectable by a spectrometer. Based on the measured spectra the amount of different elements in the sample can be estimated. Drillcore samples from a gold mine in Finland are used as test cases in this study. The LIBS measurements are compared to laboratory analysis results as well as to hyperspectral imaging results obtained in the short-wave infrared region. It is shown that the LIBS method can produce similar elemental concentrations as the laboratory measurements. Moreover, based on the elemental contents, some minerals can be identified and the LIBS information can be used to confirm and complete the results of the hyperspectral analysis. However, the spot size of the LIBS measurement is very small, meaning that a large number of measurements must be taken to reach a representative sampling result for large drillcore volumes. On the other hand, high spatial resolution is easily achieved.

• Drill core on conveyor
• XRF and SWIR for comparison
• Line scan
• Suurikuusikko samples
• PCA

Handbook of Laser-Induced Breakdown Spectroscopy[edit | edit source]

Abstract: Starting from fundamentals and moving through a thorough discussion of equipment, methods, and techniques, the Handbook of Laser-Induced Breakdown Spectroscopy provides a unique reference source that will be of value for many years to come for this important new analysis method. The authors, with a total of over 60 years of experience in the LIBS method, use a combination of tutorial discussions ranging from basic principles up to more advanced descriptions along with extensive figures and photographs to clearly explain topics addressed in the text. In this second edition, chapters on the use of statistical analysis and advances in detection of weapons of mass destruction have been added. Tables of data related to analysis with LIBS have been updated. The Handbook of Laser-Induced Breakdown Spectroscopy, Second Edition: provides a thorough but understandable discussion of the basic principles of the method based on atomic emission spectroscopy, including recently available data leading to better characterization of the LIBS plasma; presents a discussion of the many advantages of the method along with limitations, to provide the reader a balanced overview of capabilities of the method; describes LIBS instrumentation ranging from basic set-ups to more advanced configurations; presents a comprehensive discussion of the different types of components (laser, spectrometers, detectors) that can be used for LIBS apparatuses along with suggestions for their use, as well as an up-to-date treatment of the newest advances and capabilities of LIBS instruments; presents the analytical capabilities of the method in terms of detection limits, accuracy, and precision of measurements for a variety of different sample types; discusses methods of sampling different media such as gases, liquids, and solids; presents an overview of some real-world applications of the method, with new emphasis on sampling of biologically and physically dangerous materials; provides an up-to-date list of references to LIBS literature along with the latest detection limits and a unique list of element detection limits using a uniform analysis method; provides annotated examples of LIBS spectra which can serve as references for the general reader and will be especially useful for those starting out in the field.

• Fundamentals of LIBS

Ore characterization, process mineralogy and lab automation a roadmap for future mining[edit | edit source]

Abstract: Mineralogical laboratory technology has undergone seismic shifts since the introduction of automated mineral analyzers and other quantitative tools such as XRD Rietveld analysis. During the last 25 years, these changes have positioned mineralogical data into the front line of ore characterization, process control and plant optimization. The continuous deterioration of ore quality in regard to grade, hardness, finer particle sizes and the increase of metallurgical complexities have made modern process mineralogy an integral part of new project development. In addition, it has supported improvement of existing plants and the better utilization of tailings or other residues. Automation in mineralogical (and chemical) laboratories from sample preparation to analysis has been the baseline for these improvements. This paper will highlight key benchmarks of mineralogical work from ore characterization to advanced process mineralogy including the increasing importance of mineralogical mine site laboratories. A roadmap for the future of operations-oriented process mineralogy will be provided.

• Overall description of analytical needs in mining

Laser-induced breakdown spectroscopy expands into industrial applications[7][edit | edit source]

Abstract: This paper presents R&D activities in the field of laser-induced breakdown spectroscopy for industrial applications and shows novel LIBS systems running in routine operation for inline process control tasks. Starting with a comparison of the typical characteristics of LIBS with XRF and spark-discharge optical emission spectrometry, the principal structure of LIBS machines embedded for inline process monitoring will be presented. A systematic requirement analysis for LIBS systems following Ishikawa's scheme was worked out. Stability issues are studied for laser sources and Paschen-Runge spectrometers as key components for industrial LIBS systems. Examples of industrial applications range from handheld LIBS systems using a fiber laser source, via a set of LIBS machines for inline process control tasks, such as scrap analysis, coal analysis, liquid slag analysis and finally monitoring of drill dust.

• Ishikawa diagram for a LIBS system
• Different applications
• imperatives for industrial LIBS applications

Good practices in LIBS analysis: Review and advices[8][edit | edit source]

Abstract: This paper presents a review on the analytical results obtained by laser-induced breakdown spectroscopy (LIBS). In the first part, results on identification and classification of samples are presented including the risk of misclassification, and in the second part, results on concentration measurement based on calibration are accompanied with significant figures of merit including the concept of accuracy. Both univariate and multivariate approaches are discussed with special emphasis on the methodology, the way of presenting the results and the assessment of the methods. Finally, good practices are proposed for both classification and concentration measurement.

• Good article for selecting the classification and regression algorithms
• Good talk about figures of merit

Laser-Induced Breakdown Spectroscopy (LIBS) applied to terrestrial and extraterrestrial analogue geomaterials with emphasis to minerals and rocks[9][edit | edit source]

Abstract: Thanks to its unique, unprecedented and very appealing analytical capabilities and performances, the Laser-Induced Breakdown Spectroscopy (LIBS) technique has expanded rapidly in the last two decades in several fields of academic and applicative research, including the study of geomaterials. This review mainly consists of two parts, the first one provides a general and brief summary and discussion of the basic theory and principles of LIBS, the experimental set-up of conventional laboratory bench-top and portable, remote and stand-off configurations, the main methodologies of qualitative and quantitative LIBS analysis with the support of chemometric approaches, and the advantages and disadvantages of the technique. The second part aims to provide a comprehensive, detailed and adjourned at-my-best overview of the huge work done on LIBS applications to the study of geomaterials with focus on minerals and rocks. In particular, results obtained on element detection and quantification, identification, discrimination, classification, provenance, weathering and alteration of minerals, igneous, sedimentary and metamorphic rocks, gemstones, mine ores, archeological artifacts and speleothems, are reviewed and briefly discussed. The enormous efforts and remarkable progresses made in the last decade by several research groups on the potential and viable use of LIBS on robotic vehicles for studying meteorites and planetary analogue terrestrial rocks in simulated planetary conditions, have also been reviewed.

• Very usefull review article

A Review of Laser-Induced Breakdown Spectroscopy for Analysis of Geological Materials[10][edit | edit source]

Abstract: Laser-induced breakdown spectroscopy (LIBS) as an analytical technique has been developing into a versatile tool in various fields because of its distinct abilities, especially the simple, rapid, in situ detection of any material (solid, liquid, or gas). Following a brief description of LIBS instrumentation, the recent development in the field of geology is reviewed, including the qualitative and quantitative analysis of geological materials, as well as the LIBS application in some specific fields to the analysis of ores, extraterrestrial materials, speleothems, marine sediments, and fluid inclusion.

• Calib and calib-free LIBS
• Ore analysis
• Nice review

Fast mineral identification using elemental LIBS technique[11][edit | edit source]

Abstract: Rapid and on-line scanning of rock and drillcore samples gives fast results that can be used to ease the decision-making process during exploration and to guide the future drilling activities without delays. Recently, faster and more efficient ore characterization by combining various laser-based and contactless measurement techniques has drawn tremendous attention in research. However, complexity of different measurement setups and the difference between the sources of light make it non-economic and complicated for industry. Considering the wide range of the elements which can be detected by Laser-Induced Breakdown Spectroscopy and bearing in mind that LIBS is a very simple spectroscopic technique, the importance of applying LIBS for fast scanning purposes is certified. This study proposes a simple statistical analysis technique leading to mineral identification from the elemental results of LIBS. It is shown that LIBS can be used for calibrating and giving complementary information to other fast scanning techniques like Laser-Induced Fluorescence imaging. The application of the point-wise LIBS measurement technique for online and fast estimation of the minerals abundance from the surface of the rock and drillcore samples is discussed.

• LIF + LIBS
• Core samples
• SVD

Application of Handheld Laser-Induced Breakdown Spectroscopy (LIBS) to Geochemical Analysis[12][edit | edit source]

Abstract: While laser-induced breakdown spectroscopy (LIBS) has been in use for decades, only within the last two years has technology progressed to the point of enabling true handheld, self-contained instruments. Several instruments are now commercially available with a range of capabilities and features. In this paper, the SciAps Z-500 handheld LIBS instrument functionality and sub-systems are reviewed. Several assayed geochemical sample sets, including igneous rocks and soils, are investigated. Calibration data are presented for multiple elements of interest along with examples of elemental mapping in heterogeneous samples. Sample preparation and the data collection method from multiple locations and data analysis are discussed.

• Showcasing the ability of HH-LIBS

Chemical mapping of mine waste drill cores with laser-induced breakdown spectroscopy (LIBS) and energy dispersive X-ray fluorescence (EDXRF) for mineral resource exploration[edit | edit source]

Abstract: Resource estimation for metals in mine tailings and ore deposits requires many samples, usually in the form of drill cores. In order to detect zones of metal enrichment or depletion as well as different lithological zones in such cores, two different core scanning methods were tested on three drill core metres from tailings of a former Pb–Zn mine to obtain chemical information. The results provide an objective basis for further sub-sampling of the taken drill cores and help reduce the amount of samples and therefore the costs for further investigations. For the determination of element concentrations a prototype of a core scanner working with laser-induced breakdown spectroscopy (LIBS) was tested and the results were compared to data from a commercially available ITRAX core scanner, working with energy-dispersive X-ray fluorescence (EDXRF). Apart from a smooth surface, no complex sample preparation was necessary. Peak intensities of selected elements determined by the two scanners were calibrated by means of linear regression (LR) and partial least squares (PLS) regression with respect to bulk geochemical wavelength-dispersive XRF (WDXRF) analysis results of representative core samples. The application of PLS compensates for matrix effects in LIBS and EDXRF and improves prediction accuracy for most elements, compared to LR. In general, prediction ability of PLS models is slightly higher for EDXRF results than for LIBS. The advantage of the LIBS core scanner is the high spatial resolution and the ability to create two-dimensional (2D) element distribution images as well as phase or mineral distribution maps of the drill core at larger scales. Within the analysed tailing cores metal-rich layers with concentrations up to a maximum of 2.2% Pb + Zn + Cu, could be detected by both core scanning methods. Since these layers are not visible by the human eye, the used core scanning methods are appropriate methods for mineral exploration.

• Two scanning methods tested (LIBS, EDXRF)
• Pb-Zn mine (tailings)
• Provides basis for sub-samling (less samples, lower costs)
• Prototype of LIBS-scanner tested against ITRAX
• Linear reg. and PLS (PLS compensates Matrix eff.)
• LIBS adv. High spatial res. & 2d-images
• List of current core logging methods
• List of elemental mapping techniques
• Gamma-ray (K ,U, Th), XRF(Al-U), EDXRF not available in 1m long
• LIBS often used in material sci. but not geo, only few research groups
• Results semi-quantitative
• "Chemical matrix effects can occur in the LIBS plasma, when a species, present in the sample, inhibits the ionization of another species of much lower ionization potential"
• Phycical M-eff. Also explained
• "Therefore, the emission intensity of one element measured in two different matrixes does not necessarily represent the real element concentration, and a simple linear correlation of element intensity and real element concentration is not possible."
• Univariate cal. Not efficient
• User mainly interested in distribution of minerals
• The scanner is able to map 1m x 2.5 cm
• Five shots accum.
• Echelle spec. 285-964nm, Nd:YAG 1064, 11 ns, 55mJ
• Delay 1.5-1.7µs
• Pb, Zn, Cu, Ni, Co, Si, Al, K, Na, Ca, Mg, Fe, Mn, Ti, Ba, and S were investigated.
• Elemental lines listed
• Normalization with total energy, only listed peaks were used and areas integrated
• Validation with WDXRF
• Data was Checked for saturation or bg-noice
• 2-3 lines per element
• Outlier removal 2 std
• Quartz giving matrix effect?

Rapid Analysis of Geological Drill‐Cores with LIBS[edit | edit source]

Abstract: Spectroscopy — the study of interaction between electromagnetic radiation and matter — is a continually developing branch of science that facilitates a number of research and industrial applications. As a state‐of‐the‐art technique, spectroscopy offers many experimental possibilities to acquire compositional information of inorganic materials, including core samples, minerals and geological specimens. Laser‐induced breakdown spectroscopy (LIBS), which provides fast, accurate and high‐resolution measurements, is one such spectroscopic technique. LIBS is primarily suited for phase‐independent, simultaneous, qualitative and quantitative analysis of samples, dovetailing the technique perfectly with geological standards.

• EDXRF limitations
• High res. 8-9h, low res. 30 min
• 200*20 mm samples
• Proto can accept whole casing
• 100 Hz laser
• Regions of interest

Development of seafloor mineral processing for Seafloor Massive Sulfides[edit | edit source]

Abstract: Seafloor Massive Sulfides (SMSs), which are formed from hydrothermal fluids vented from seafloor, have been expected as one of future mineral resources. The authors have proposed the concept of seafloor mineral processing, where valuable minerals contained in SMS ores are separated on seafloor. Experimental studies were carried out to apply conventional mineral processing technologies such as ball mill grinding and column flotation to seafloor mineral processing. Experimental studies suggest that these technologies would be applicable to seafloor mineral processing. In addition, application of Laser-Induced Breakdown Spectroscopy (LIBS) to in-situ measurement of metal grade of ore particles in the mineral processing system was investigated. By adapting seafloor mineral processing to the mining scheme of SMSs, the mining costs are expected to be reduced significantly.

Signal and noise in Laser Induced Breakdown Spectroscopy: An introductory review[13][edit | edit source]

Abstract: Laser Induced Breakdown Spectroscopy (LIBS) has become a very popular technique for elemental analysis thanks to its ease of use. However, LIBS users often report poor repeatability of the signal, due to shot-to-shot fluctuations, and consequent not satisfactory limits of detection. In many practical cases, these shortcomings are difficult to control because the signal is affected by several noise sources that cannot be reduced simultaneously. Hopefully, there is a large amount of knowledge, accumulated during several decades, that can provide guidelines to reduce the effect of the single sources of fluctuations. Experimental setup and measurement settings can be optimized on purpose. Spectral data can be processed in order to better exploit the information contained. In the current paper several approaches to improve the analytical figures-of-merit are reviewed and the respective advantages and drawbacks are discussed.

Sensor-based real-time resource model reconciliation for improved mine production control – a conceptual framework[14][edit | edit source]

Abstract: The flow of information and consequently the decision-making along the chain of mining from exploration to beneficiation typically occurs in a discontinuous fashion over long time spans. In addition, due to the uncertain nature of the knowledge about the deposit and its inherent spatial distribution of material characteristics, actual production performance in terms of produced ore grades and quantity and extraction process efficiency often deviate from expectations. Reconciliation exercises to adjust mineral resource models and planning assumptions are performed with timely lags of weeks, months or even years. With the development of modern Information and Communication Technology over the last decade, literally a flood of data about different aspects of the production process is available in a real-time manner. For example, sensor technology enables online characterisation of geochemical, mineralogical and physical material characteristics on conveyor belts or at working faces. The ability to utilise the value of this additional information and feed it back into resource block models and planning assumptions opens up new opportunities to continuously control the decisions made in production planning to increase resource recovery and process efficiency. This leads to a change in paradigm from a discontinuous to a near real-time reserve reconciliation and model updating, which calls for suitable modelling and optimisation methodologies to quantify prior knowledge in the resource model, to process and integrate information from different sensor-sources and accuracy, back propagate the gain in information into resource models and efficiently optimise operational decisions real time. This contribution introduces the concept of an integrated closed-loop framework for Real-Time Reserve management incorporating sensor-based material characterisation, geostatistical modelling under uncertainty, modern data assimilation methods for a sequential model updating and mining system simulation and optimisation. Selected aspects of the framework are demonstrated in an illustrative case study.

• The need for sensor technologies in mining

Singular value decomposition approach to the yttrium occurrence in mineral maps of rare earth element ores using laser-induced breakdown spectroscopy[15][edit | edit source]

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been used in analysis of rare earth element (REE) ores from the geological formation of Norra Kärr Alkaline Complex in southern Sweden. Yttrium has been detected in eudialyte (Na15 Ca6(Fe,Mn)3 Zr3Si(Si25O73)(O,OH,H2O)3 (OH,Cl)2) and catapleiite (Ca/Na2ZrSi3O9·2H2O). Singular value decomposition (SVD) has been employed in classification of the minerals in the rock samples and maps representing the mineralogy in the sampled area have been constructed. Based on the SVD classification the percentage of the yttrium-bearing ore minerals can be calculated even in fine-grained rock samples.

• Core samples
• Samples with REEs
• SVD with +- classification

Megapixel multi-elemental imaging by Laser-Induced Breakdown Spectroscopy, a technology with considerable potential for paleoclimate studies[16][edit | edit source]

Abstract: Paleoclimate studies play a crucial role in understanding past and future climates and their environmental impacts. Current methodologies for performing highly sensitive elemental analysis at micrometre spatial resolutions are restricted to the use of complex and/or not easily applied techniques, such as synchrotron radiation X-ray fluorescence micro-analysis (μ-SRXRF), nano secondary ion mass spectrometry (nano-SIMS) or laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Moreover, the analysis of large samples (>few cm²) with any of these methods remains very challenging due to their relatively low acquisition speed (~1–10 Hz), and because they must be operated in vacuum or controlled atmosphere. In this work, we proposed an imaging methodology based on laser-induced breakdown spectroscopy, to perform fast multi-elemental scanning of large geological samples with high performance in terms of sensitivity (ppm-level), lateral resolution (up to 10 μm) and operating speed (100 Hz). This method was successfully applied to obtain the first megapixel images of large geological samples and yielded new information, not accessible using other techniques. These results open a new perspective into the use of laser spectroscopy in a variety of geochemical applications.

• Amazing pictures
• Autofocus

Analysis of gold in rock samples using laser-induced breakdown spectroscopy: Matrix and heterogeneity effects Rifai, Kheireddine, et al. "Analysis of gold in rock samples using laser-induced breakdown spectroscopy: matrix and heterogeneity effects." Spectrochimica Acta Part B: Atomic Spectroscopy 134 (2017): 33-41.[edit | edit source]

Abstract: We used the laser-induced breakdown spectroscopy (LIBS) technique to determine the concentration of gold in rock samples. 44 reference materials (mostly compressed fine powders) of various chemical compositions, with a quasi-homogeneous concentration of gold varying from 0 to 1000 ppm, were used to establish the calibration curve for the Au I 267.59 nm line. A chemometric study based on the principal component analysis (PCA) showed that ~ 83% of the LIBS spectra variations are attributable to the presence of iron in the samples. Two distinct branches were obtained in the calibration curve: one for Si-rich samples (< 5% of iron) and one for Fe-rich samples (> 13% of iron) with limits of detection of 0.8 ppm and 1.5 ppm, respectively. Different normalization schemes of the gold signal were tested in order to reduce the matrix effects. The LIBS analysis was performed on various mineral samples of practical interest, namely two Si-rich uncompressed ore powders, fine and granular, and three bulk drill cores. The fluctuations in the gold concentration measurements appear to be about two times greater in the granular powder (5–10%) than in the fine one (2–5%). A detailed mapping of the gold concentration on a solid drill core was also performed, revealing multiscale heterogeneity of the gold distribution on the surface of the sample.

• Nice 3D-map
• Calib. curve from powders
• Also core samples
• Standard lab result can have huge error

Quantitative methods for compensation of matrix effects and self-absorption in Laser Induced Breakdown Spectroscopy signals of solids[17][edit | edit source]

Abstract: This paper reviews methods to compensate for matrix effects and self-absorption during quantitative analysis of compositions of solids measured using Laser Induced Breakdown Spectroscopy (LIBS) and their applications to in-situ analysis. Methods to reduce matrix and self-absorption effects on calibration curves are first introduced. The conditions where calibration curves are applicable to quantification of compositions of solid samples and their limitations are discussed. While calibration-free LIBS (CF-LIBS), which corrects matrix effects theoretically based on the Boltzmann distribution law and Saha equation, has been applied in a number of studies, requirements need to be satisfied for the calculation of chemical compositions to be valid. Also, peaks of all elements contained in the target need to be detected, which is a bottleneck for in-situ analysis of unknown materials. Multivariate analysis techniques are gaining momentum in LIBS analysis. Among the available techniques, principal component regression (PCR) analysis and partial least squares (PLS) regression analysis, which can extract related information to compositions from all spectral data, are widely established methods and have been applied to various fields including in-situ applications in air and for planetary explorations. Artificial neural networks (ANNs), where non-linear effects can be modelled, have also been investigated as a quantitative method and their applications are introduced. The ability to make quantitative estimates based on LIBS signals is seen as a key element for the technique to gain wider acceptance as an analytical method, especially in in-situ applications. In order to accelerate this process, it is recommended that the accuracy should be described using common figures of merit which express the overall normalised accuracy, such as the normalised root mean square errors (NRMSEs), when comparing the accuracy obtained from different setups and analytical methods

• Figures of merit
• Different normalizations
• SA-corrections
• PCR & PLS
• ANN

Univariate and multivariate analyses of rare earth elements by laser-induced breakdown spectroscopy<ref>Bhatt, Chet R., Fang Y. Yueh, and Jagdish P. Singh. "Univariate and multivariate analyses of rare earth elements by laser-induced breakdown spectroscopy." Applied optics 56.8 (2017): 2280-2287.<ref>[edit | edit source]

Abstract: Univariate and multivariate analyses of six rare earth elements [cerium (Ce), europium (Eu), gadolinium (Gd), neodymium (Nd), samarium (Sm), and yttrium (Y)] have been performed using data from laser-induced breakdown spectroscopy (LIBS). Binary mixtures of oxide forms of each rare earth element in an Al2O3 matrix with their concentrations varying from 1% to 10% by weight in powder form were used as working samples for univariate analysis. For multivariate analysis, complex mixtures of oxides of all these six rare earth elements and Al2O3 in powder form, where the concentration of each element oxide was varied from 1% to 50% by weight one by one, were used to record LIBS spectra. Optimum values of gate delay, gate width, and laser energy were used to get spectra from these samples and spectra were used to develop calibration models. The limits of detection for Ce, Eu, Gd, Nd, Sm, and Y were calculated to be 0.098%, 0.052%, 0.077%, 0.047%, 0.250%, and 0.036%, respectively, from the calibration curves.

Detection of contaminants in ore samples using laser-induced breakdown spectroscopy<ref>Gondal, Mohammed A., et al. "Detection of contaminants in ore samples using laser-induced breakdown spectroscopy." Journal of Environmental Science and Health Part A 42.7 (2007): 879-887.<ref>[edit | edit source]

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been applied for the determination of contaminants present in ore samples. The plasma was generated by focusing a pulsed Nd:YAG laser radiation at 1064 nm wavelength on the ore sample collected from one of the open-pit mines located in Saudi Arabia. The concentrations in this ore sample of different elements of environmental significance like Cu, Cr, Ca, Mg, Zn, Ti, Si, Fe and Al were determined by spectral analysis. Parametric dependence for improvement of LIBS sensitivity was carried out. The LIBS results were compared with the results obtained using other analytical techniques such as the inductively coupled plasma emission spectroscopy (ICP-AES). Limits of detection (LOD) of our LIBS system were also calculated for the elements under investigation.