Chemometrics and Spectroscopic Analyses of Peganum harmala Plant’s Seeds by Laser‐Induced Breakdown Spectroscopy

In the present work, the rapid identification of elements and their relative chemical com‐ position in various Peganum harmala seed samples were investigated using a calibration‐free laser‐ induced breakdown spectroscopy technique (CF‐LIBS). A pulsed Nd:YAG laser‐source with a 5 ns pulse‐duration, and 10 Hz pulse repetition rates providing 400 and 200 mJ energy at 1064 and 532 nm wavelength, respectively, was focused on the Peganum harmala seed samples for ablation. A LIBS 2000+ spectrometer within the wavelength range (200 to 720 nm), emission‐spectra were recorded. The measured spectra of the Peganum harmala sample gives spectral lines of Carbon (C), Magnesium (Mg), Lithium (Li), Sodium (Na), Calcium (Ca), Silicon (Si), Iron (Fe), Strontium (Sr), Copper (Cu), Potassium (K), and Lead (Pb). A CF‐LIBS technique has been employed for the compositional study of the elements exist in the Peganum harmala seed samples. The measured results demonstrate that C, Mg, and Ca are found to be major elements in the Peganum harmala seed samples with composi‐ tions of ~36.64%, ~24.09%, and ~19.03%, respectively. Along with the major elements, the elements including Li, Na, Si, K, Fe, and Sr were identified as minor elements with compositions of ~2.87%, ~2.33%, ~3.72%, ~7.17%, ~2.83%, and ~1.14%, respectively. Besides Cu (~8.07 μg/g), and Pb (~1.10 μg/g) elements were observed as trace elements exist in the Peganum harmala seed samples. Further‐ more, the electron number density including the plasma excitation‐temperature were calculated using the stark‐broadening line profile method and the Saha–Boltzmann plot method, respectively. The plasma parameters versus laser‐irradiance and the distance from the sample were further in‐ vestigated. Moreover, a principal component analysis (PCA) method was also utilized to the spec‐ tral data obtained by using LIBS to discriminate various seed samples with four classes, namely, α, β, γ, and Δ. Three principal‐components (PCs) calculated from eigenvalues of score matrix de‐ scribed 87.6%, 4.6%, and 2.5% of total variance for PC1, PC2, and PC3, respectively. The LIBS spec‐ tral data variance covered by the initial 3 PCS was found as ~94.7% of total variance. The PCA results have successfully demonstrated the different classes of the Peganum harmala seed samples based on the different doping compositional ratios of the Zn element. This study confirmed the feasibility and ability of LIBS and PCA for the rapid analysis of Peganum harmala seed samples. Finally, the results achieved using CF‐LIBS were incorporated with those obtained from the XRF and EDX an‐ alytical techniques

Rare Earth Elements analysis to identify anthropogenic signatures at Valle del Serpis (Spain) Neolithic settlements

Due to their particular geochemical properties and stability Rare Earth Elements (REE) can act as a ‘fingerprint’ for soils, and as a consequence have been employed in a variety of different archaeological scenarios in order to identify past human activities.In this study, for the first time, we apply REE signatures in different Spanish Neolithic settlements, all located in the Valle del Serpis region. More than 100 Neolithic settlements have been identified in this area, and most of these open sites are characterised by dark brown strata that are in contrast with the light brown soils of the valley. These dark brown deposits are usually covered by paleosols and have been interpreted as markers of anthropogenic activities. However, in order to demonstrate whether these strata are anthropogenic or natural features requires a better understand-ing of soil development processes. A total of fifty samples were taken across six different sites, and from each site the sam-pling was carried out at different depths through 3m deep sections. Four sites are clearly associated with archaeological findings (sites BF, LP, PB and AC); another one is from a natural section near the Neolithic site of Mas d’Is (MD) and has been radiocarbon dated to the beginning of the Holocene (7751-7611 cal BC); and the last corresponds to a place of uncertain attribution (BK). Major, minor and trace elements including REE were determined using XRF and ICP- MS, with Principal Components Analysis (PCA) used to statistically analyze these data. Results were then compared with the strata soil properties analysed by XRD and particle size analysis, and cross-referenced with archaeological data to aid interpretation. The results demonstrate that REE analyses provide significant details regarding anthropogenic activities and strata development history, and in this instance confirm and elaborate on the archaeological interpretation that these dark brown deposits are evidence of a region-wide agricultural system in the Neolithic Valle del Serpis

The source of the building stones from the Sagunto Castle archaeological area and its surroundings

A multidisciplinary study was carried out on the building stones of the masonries belonging to the Castle of Sagunto (Valencia, Spain), an important historical and archeological complex, characterized by several construction phases from the Roman Period to the Modern Ages. For the first time, the stones of the Sagunto Castle have been analysed to determine their chemical, mineralogical and petrographic features, the main physical and mechanical properties, and to understand their decay, use and recycling dynamics in the different building during the entire occupational period. Geochemical and mineralogical analyses employing X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffraction (XRD) were carried out together with optical and electronic microscope analysis to observe the stone macro- and micro-structures. The collected data were processed by Principal Component Analysis (PCA) to highlight differences among the studied structures. The results show that the stones employed to build Sagunto`s structures during the different historical periods are related to a specific quarried area located nearby Sagunto Castle hill and differences between the studied samples are mostly related to the conservation state of the buildings. Therefore, geochemical analyses confirm the origin of the raw materials, while petrographic and physical analyses have been useful to evaluate the conservation state of the studied Sagunto Castle structures

Methodology and applications of elemental mapping by laser induced breakdown spectroscopy

In the last few years, LIBS has become an established technique for the assessment of elemental concentrations in various sample types. However, for many applications knowledge about the overall elemental composition is not sufficient. In addition, detailed information about the elemental distribution within a heterogeneous sample is needed. LIBS has become of great interest in elemental imaging studies, since this technique allows to associate the obtained elemental composition information with the spatial coordinates of the investigated sample. The possibility of simultaneous multi-elemental analysis of major, minor, and trace constituents in almost all types of solid materials with no or negligible sample preparation combined with a high speed of analysis are benefits which make LIBS especially attractive when compared to other elemental imaging techniques. The first part of this review is aimed at providing information about the instrumental requirements necessary for successful LIBS imaging measurements and points out and discusses state-of-the-art LIBS instrumentation and upcoming developments. The second part is dedicated to data processing and evaluation of LIBS imaging data. This chapter is focused on different approaches of multivariate data evaluation and chemometrics which can be used e.g. for classification but also for the quantification of obtained LIBS imaging data. In the final part, current literature of different LIBS imaging applications ranging from bioimaging, geoscientific and cultural heritage studies to the field of materials science is summarized and reviewed. 2020 The Authors. Published by Elsevier B.V

Laser Spectroscopy for Atmospheric and Environmental Sensing

Lasers and laser spectroscopic techniques have been extensively used in several applications since their advent, and the subject has been reviewed extensively in the last several decades. This review is focused on three areas of laser spectroscopic applications in atmospheric and environmental sensing; namely laser-induced fluorescence (LIF), cavity ring-down spectroscopy (CRDS), and photoluminescence (PL) techniques used in the detection of solids, liquids, aerosols, trace gases, and volatile organic compounds (VOCs)

A Spatial Heterodyne Spectrometer for Raman Imaging and Remote Spectroscopy

Raman and Laser-Induced Breakdown Spectroscopy (LIBS) are optical techniques that provide information about the chemical makeup of a sample without any preparation or physical contact with it. For this reason, Raman and LIBS spectrometers are among the instruments selected for NASA’s Mars 2020 rover mission and are being considered for future missions to the Jovian moons, asteroids and comets. Such future missions will require smaller, more ruggedized Raman and LIBS spectrometers, and the new type of spectrometers discussed here, the spatial heterodyne Raman and LIBS spectrometers are being developed for this purpose. The SHS is a wide-field, Fourier transform, stationary grating interferometer with no moving parts, that is well-suited for miniature Raman and LIBS spectrometers. The spectral resolution of the SHS is not strongly dependent upon entrance aperture size, so the footprint can be very small while still allowing for high resolution spectral measurements. The SHS has a large entrance aperture and a wide acceptance angle that provides much higher light throughput than a dispersive slit-based spectrometer of comparable resolution. Lastly, because the SHS has no moving parts and the spectral resolution is not strongly tied to its size, it can be built monolithically making it both small and robust. This thesis explores alternative optical configurations of the SHS collection optics that are useful for miniaturizing or extending the capabilities of a remote SHS Raman or LIBS system. A lightweight, low cost Fresnel lens was compared to that of a high-quality telescope for standoff signal collection. This takes advantage of the wide field of view of the SHS, which makes the collection efficiency very forgiving of the quality of the collection optics. We observed that the signal collected by the Fresnel lens, which weighed less than 1% of a comparable glass lens, was only about four times less than that of the telescope. This suggests that Fresnel optics would be useful in applications where size and weight are restricted, such as in instruments designed for spacecraft and planetary landers. In other studies, a new hyperspectral Raman imaging technique is demonstrated using a spatial heterodyne Raman spectrometer with a microlens array, where the entire hypercube of spatial and spectral information is obtained in a single measurement. Raman images for a variety of sample types are demonstrated where complete Raman spectra, at spectral ranges from 1200 cm-1 to 2800 cm-1, were acquired independently at each spatial point, for 60 to \u3e500 unique spatial points, in a single spectral acquisition. The spectral resolution of the Raman spectra acquired for each spatial point in the images varied from 32 cm-1 to 148 cm-1, dependent on the grating and system magnification and the resolution of the detector. Calculations show that this technique can be extended to include more than 10,000 spatial points with a spectral resolution of 20 cm-1, over a large spectral range