TY - JOUR A1 - Völker, Tobias A1 - Gornushkin, Igor B. T1 - Mass and mole fractions in calibration-free LIBS N2 - This technical note highlights the fact that CF-LIBS algorithms work in mole fractions, while results of spectrochemical analysis are usually reported in mass fractions or mass percent. Ignoring this difference and not converting mole fractions to mass fractions can lead to errors in reported concentrations determined by the CF-LIBS method and inadequate comparison of these concentrations with certified concentrations. Here, the key points of the CF-LIBS algorithm are reproduced and the formulae for converting a mole fraction to a mass fraction and vice versa are given. Several numerical examples are also given, which show that the greater the difference between the molar mass of an individual element in a sample and the average molar mass, the greater the discrepancy between the mole and mass fractions. KW - Spectroscopy KW - Analytical Chemistry KW - LIBS KW - Calibration PY - 2024 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-598611 SN - 0267-9477 VL - 39 IS - 4 SP - 1030 EP - 1032 PB - Royal Society of Chemistry (RSC) AN - OPUS4-59861 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Völker, Tobias A1 - Gornushkin, Igor B. T1 - Extension of the Boltzmann plot method for multiplet emission lines N2 - The Boltzmann plot method is widely used to determine the temperature of laser induced plasma. It involves the use of individual lines that are not easy to find in complex spectra and/or in the spectral range available. If the number of such lines is not enough to build a reliable Boltzmann plot, overlapping lines are often used, which are separated by software. However, line separation is a rather imprecise procedure, which, in addition, requires significant computational costs. This study proposes an extension of the Boltzmann plot method that allows a specific group of unresolved lines to be included in a Boltzmann plot without the need to separate them. This group of lines are multiplets, lines of the same element with similar upper and lower transition states. The multiplet lines along with the individual lines are included in the algorithm, which also includes a correction for self-absorption and is used to determine the plasma temperature. The algorithm is tested on synthetic spectra which are consistent with the model of a homogeneous isothermal plasma in local thermodynamic equilibrium and is shown to be superior to the standard Boltzmann plot method both in more accurate determination of the plasma temperature and in a significant reduction in the computational time. The advantages and disadvantages of the method are discussed in the context of its applications in laser induced breakdown spectroscopy. KW - LIBS KW - Spectroscopy KW - Boltzmann plot KW - Multiplet KW - Spectral overlap PY - 2023 U6 - https://doi.org/10.1016/j.jqsrt.2023.108741 SN - 1879-1352 VL - 310 SP - 1 EP - 5 PB - Elsevier AN - OPUS4-58058 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Völker, Tobias A1 - Gornushkin, Igor B. T1 - Investigation of a method for the correction of self-absorption by Planck function in laser induced breakdown spectroscopy N2 - The electron density and temperature of a laser-induced plasma can be determined from the width and intensity of the spectral lines, provided that the corresponding optical transitions are optically thin. However, the lines in laser induced plasma are often self-absorbed. One of the methods of correction of this effect is based on the use of the Planck function and an iterative numerical calculation of the plasma temperature. In this study, the method is further explored and its inherent errors and limitations are evaluated. For this, synthetic spectra are used that fully correspond to the assumed conditions of a homogeneous isothermal plasma at local thermodynamic equilibrium. Based on the error analysis, the advantages and disadvantages of the method are discussed in comparison with other methods of self-absorption correction. KW - LIBS KW - Self-absorption KW - Planck function PY - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b43-572677 SN - 0267-9477 SP - 1 EP - 6 PB - Royal Society of Chemistry (RSC) AN - OPUS4-57267 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Völker, Tobias A1 - Wilsch, Gerd A1 - Gornushkin, Igor B. A1 - Kratochvilo, L. A1 - Pořízka, P. A1 - Kaiser, J. A1 - Millar, S. A1 - et al., T1 - Interlaboratory comparison for quantitative chlorine analysis in cement pastes with laser induced breakdown spectroscopy N2 - Concrete structures experience severe damage during service, for example due to pitting corrosion of rebars caused by the ingress of chlorine (Cl) into the porous concrete structure. The ingress can be monitored using laser-induced breakdown spectroscopy (LIBS), a recently introduced civil engineering technique used to detect Cl in concrete structures in addition to conventional wet chemistry methods. The key advantages of LIBS are high spatial resolution, which is important when analyzing heterogeneous concrete samples, as well as the almost complete absence of sample preparation. To assess LIBS as a reliable analytical method, its accuracy and robustness must be carefully tested. This paper presents the results of an interlaboratory comparison on the analysis of Cl in cement paste samples conducted by 12 laboratories in 10 countries. Two sets of samples were prepared with Cl content ranging from 0.06 to 1.95 wt% in the training set and 0.23–1.51 wt% in the test set, with additional variations in the type of cement and Cl source (salt type). The overall result shows that LIBS is suitable for the quantification of the studied samples: the average relative error was generally below 15%. The results demonstrate the true status quo of the LIBS method for this type of analysis, given that the laboratories were not instructed on how to perform the analysis or how to process the data. KW - LIBS KW - Interlaboratory comparison KW - Round robin test KW - Cement KW - Chlorine PY - 2023 U6 - https://doi.org/10.1016/j.sab.2023.106632 SN - 0584-8547 VL - 202 SP - 1 EP - 8 PB - Elsevier B.V. AN - OPUS4-57102 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Maher, C. A1 - Schazmann, B. A1 - Gornushkin, Igor B. A1 - Rurack, Knut A1 - Gojani, Ardian T1 - Exploring an Application of Principal Component Analysis to LaserInduced Breakdown Spectroscopy of Stainless-Steel Standard Samples as a Research Project N2 - Laser-induced breakdown spectroscopy (LIBS) and principal component analysis (PCA) are frequently used for analytical purposes in research and industry, but they seldom are part of the chemistry Curriculum or laboratory exercises. This case study paper describes the combined application of LIBS and PCA during a research internship for an undergraduate student. The instructional method applied was based on a one-on-one mentorship, in which case the learner was engaged in a Research work. The learning activities included theoretical introductions to the LIBS and PCA methods, numerical simulation, experiments, and data analysis. The study covered three main topics: analysis of LIBS spectra, application of PCA for clustering, and use of PCA for experimental design. The realization of the study was instructive for all parties involved: from the mentorship point of view, it is concluded that the topics can be covered during an internship or developed into a one semester long research-based module of a chemistry program or a final year project. The student, on the other hand, developed profound technical skills in performing experiments and using PCA software for data analysis. KW - LIBS KW - PCA PY - 2021 U6 - https://doi.org/10.1021/acs.jchemed.1c00563 VL - 98 SP - 3237 EP - 3244 PB - American Chemical Society Publications CY - USA AN - OPUS4-53515 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gaft, M. A1 - Nagli, L. A1 - Gornushkin, Igor B. A1 - Raichlin, Y. T1 - Review on recent advances in analytical applications of molecular emission and modelling N2 - The review mainly deals with two topics that became important in applications of laser-induced breakdown spectroscopy (LIBS) in recent years: the emission of halogen- and rare-earth-containing molecules and selective excitation of molecules by molecular laser-induced fluorescence (MLIF). The first topic is related to the emission of alkaline-earth diatomic halides MX, M = Ca, Mg, Ba, Sr and X = F, Cl, Br, and I and rare-earth element (REE) oxides LaO, YO, and ScO. These molecules form in laser-induced plasma (LIP) soon after its ignition and persist for a long time, emitting broad bands in a visible part of the spectrum. They are best detected after relatively long delay times when emission from interfering plasma species (atoms and ions) has already been quenched. Such behavior of molecular spectra allows of using, for their detection, inexpensive CCD detectors equipped with simple electronic or mechanical shutters and low-resolution spectrometers. A main target for analysis by molecular spectroscopy is halogens; these elements are difficult to detect by atomic spectroscopy because their most intense atomic lines lie in the vacuum UV. Therefore, in many situations, emission from CaF and CaCl may provide a substantially more sensitive detection of F and Cl than emission from elemental F and Cl and their ions. This proved to be important in mining and concrete industries and even Mars exploration. A similar situation is observed for REEs; their detection by atomic spectroscopy sometimes fails even despite the abundance of atomic and ionic REEs' lines in the UV-VIS. For example, in minerals and rocks with low concentrations of REEs, emission from major and minor mineral elements hinders the weak emission from REEs. Many REEs do not form molecules that show strong emission bands in LIP but can still be detected with the aid of LIP. All REEs except La, Y, and Sc exhibit long-lived luminescence in solid matrices that is easily excited by LIP. The luminescence can be detected simultaneously with molecular emission of species in LIP within the same time and spectral window. The second topic is related to the combination of MLIF and LIBS, which is a technique that was proved to be efficient for analysis of isotopic molecules in LIP. For example, the characteristic spectral signals from isotopic molecules containing 10B and 11B are easier to detect with MLIF-LIBS than with laser ablation molecular isotopic spectrometry (LAMIS) because MLIF provides strong resonance excitation of only targeted isotopes. The technique is also very efficient in detection of halogen molecules although it requires an additional tunable laser that makes the experimental setup bulky and more expensive. KW - Plasma induced luminescence KW - Molecular emission KW - Laser induced plasma KW - Plasma modeling KW - Molecular analysis KW - LIBS PY - 2020 U6 - https://doi.org/10.1016/j.sab.2020.105989 VL - 173 SP - 105989 PB - Elsevier B. V. AN - OPUS4-51420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Gottlieb, Cassian A1 - Gojani, Ardian A1 - Völker, Tobias A1 - Günther, Tobias A1 - Gornushkin, Igor B. A1 - Wilsch, Gerd A1 - Günster, Jens T1 - Investigation of grain sizes in cement-based materials and their influence on laser-induced plasmas by shadowgraphy and plasma imaging N2 - The effect of particle grain sizes in different cement-based mixtures on the laser-induced plasma evolution is studied using two experimental methods: (i) temporal and spatial evolution of the laser-induced shock wave is investigated using shadowgraphy and two-dimensional plasma imaging, and (ii) temporal and spatial distribution of elements in the plasma is investigated using two-dimensional spectral imaging. This study is motivated by the interest in applying laser-induced breakdown spectroscopy (LIBS) for chemical analysis of concrete, and subsequently obtain information related to damage assessment of structures like bridges and parking decks. The distribution of grain sizes is of major interest in civil engineering as for making concrete different aggregate grain sizes defined by a sieving curve (64mm to 0.125 mm) are needed. Aggregates up to a size of 180 μm can be excluded from the data set, therefore only the amount of small aggregates with a grain size below 180 μm must be considered with LIBS. All components of the concrete with a grain size smaller than 0.125mm are related to the flour grain content. Tested samples consisted of dry and hardened cement paste (water-cement ratio w/z=0.5), which served as a reference. Aggregate mixtures were made by adding flour grains (size 40 μm) and silica fume (size 0.1 μm) in different ratios to cement: 10%, 30%, 50% and 60%, all combined to the remaining percentage of dry or hydrated cement. The visualization results show that a dependance in the evolution of the plasma as a function of sample grain size can be detected only in the initial stages of the plasma formation, that is, at the initial 3 μs of the plasma life. Spectral information reveals the elemental distribution of the silicon and calcium in plasma, in both neutral and ionized form. Here also, a significant effect is observed in the first 1 μs of the plasma lifetime. KW - LIBS KW - Cement-based materials KW - Particle size KW - Shadowgraphy KW - Plasma imaging PY - 2020 U6 - https://doi.org/10.1016/j.sab.2020.105772 VL - 165 SP - 105772 PB - Elsevier B.V. AN - OPUS4-50319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gornushkin, Igor B. T1 - Laser induced plasma as a chemical reactor: how feasible? N2 - A goal of this work is to apply the model, which was initially developed for laser induced plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates. Also, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy. T2 - 1st workshop on Tandem LIBS/LA-ICP-MS CY - BAM, Berlin, Adlershof DA - 18.11.2019 KW - LIBS KW - Laser induced plasma KW - Plasma modeling KW - Plasma chemical reactor PY - 2019 AN - OPUS4-49776 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gornushkin, Igor B. A1 - Shabanov, Sergej V. A1 - Völker, Tobias A1 - Kepes, Erik A1 - Wolsch, Gerd A1 - Baudelet, M. T1 - Molecule formation in calcium carbonate and calcium hydroxide libs plasmas: model and experiment N2 - Analysis of calcium hydrate and calcium carbonate samples and their mixtures is important for archeology, anthropology, and geology. Laser-induced plasma spectroscopy (LIBS) is a suitable tool for such the analysis as it allows for in- and on-line real time chemical assays. LIBS is inherently a technique for atomic analysis; however, since recently, it is also used for molecular analysis. The information attained by the latter is mainly related to “secondary” chemistry that deals with re-association of atoms and ions into molecules at long delay times (≥10 μs) after the initial breakdown. Even though the direct information about the initial molecular content in the target may be lost, the molecular analysis by LIBS can still be useful to assess the composition of samples. In this work, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled and compared to experiment. The model is based on the assumption that all ionization processes and chemical reactions are at local thermodynamic equilibrium. A chemical composition of argon-calcium-oxygen and argon-calcium-hydrogen plasmas is studied as a function of plasma temperature and pressure. It is established that more than twenty simple and composite molecules and ions can be formed in the course of chemical reactions. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy. T2 - SciX 2019 CY - Palm Springs, USA DA - 13.10.2019 KW - Plasma diagnostics KW - LIBS KW - Laser induced plasma KW - Plasma modeling PY - 2019 AN - OPUS4-49775 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Gornushkin, Igor B. A1 - Shabanov, Sergej V. A1 - Sennikov, P. T1 - Modeling equilibrium chemistry in laser induced plasmas and plasma chemical reactors N2 - A goal of this work is to apply the model, which was initially developed for laser induced plasmas, to plasmas used in chemical reactors, in particular, the inductively-coupled-RF discharge plasma. The model predicts equilibrium chemical compositions of reaction mixtures as functions of plasma temperature and stoichiometry of reactants. The mixtures investigated are BCl3/H2/Ar and BF3/H2/Ar where Ar serves as the plasma-forming gas and H2 as a binding agent which binds the active species Cl and F and Cl- and F-containing intermediates to produce gaseous B and its condensate. An additional goal is to obtain information about intermediate reaction products for different ratios of BCl3/H2 and BF3/H2 and at different temperatures and different Ar flow rates. Also, chemical reactions in laser induced plasmas (LIPs) created on calcium hydrate and calcium carbonate targets in argon are modeled. The results are compared with those obtained by means of the equilibrium model based on the minimization of Gibbs free energy. T2 - SciX 2019 CY - Palm Springs, USA DA - 13.10.2019 KW - LIBS KW - Laser induced plasma KW - Plasma modeling PY - 2019 AN - OPUS4-49774 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -