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Spectrochimica Acta
Pergamon Press
Spectrochimica Acta

Pergamon Press

0584-8547

Spectrochimica Acta/Journal Spectrochimica Acta
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    Multi-elemental analysis of oil renewable fuel feedstock

    Martinez S.Sanchez R.Todoli J.-L.Lefevre J....
    28页
    查看更多>>摘要：? 2022 Elsevier B.V.The use of oils and fats, mainly from non-edible or used sources, microalgae, plastic wastes, and lignocellulosic residues as feedstock to elaborate different kinds of renewable fuels (biodiesel, hydrotreated vegetable oils, pyrolysis oils, and bio-oils) is increasing with the aim of implementing a circular and dynamic economy. Quality control of these materials involves the quantification of trace elements. Their presence, even at trace levels, leads to environmental concerns, fuel instabilities and may impact the performance of combustion engines. Therefore, in order to circumvent these problems, accurate and sensitive analytical techniques are required to control the level of these elements with good precision. The present manuscript will review different analytical tools used to analyze these samples. Because of their high sensitivity, low limits of detection, wide dynamic range, and in some cases the capability of carrying out multi-elemental analyses, the review is mainly focused on inductively coupled plasma techniques. Furthermore, sample preparation procedures (e.g., direct dilution, emulsification, extraction, and matrix decomposition) are elaborated. At the end of the work, suggestions on procedures for multi-elemental determination in the aforementioned samples are provided.
      原文链接:
    • NSTL
    • Elsevier

    Laser-ablation absorption spectroscopy: Reviewing an uncommon hyphenation

    Merten J.
    13页
    查看更多>>摘要：? 2022 Elsevier B.V.Absorption spectroscopy hyphenations of the laser-induced plasma have been attempted by a handful of groups since the early 1990s. Despite the measurement's relatively long history, there are few reviews and the details of the experiment remain somewhat opaque. Though the early experiments were directed at understanding laser-induced deposition physics, more recent measurements have begun to bend absorption spectroscopy to plasma diagnostics with an eye to analytical chemistry applications of laser ablation. This review discusses the benefits and difficulties of the different experimental approaches in addition to analytical and plasma characterization applications. Because the laser-induced plasma is so different from the usual atomic reservoirs used for atomic absorption spectroscopy, the assumptions of the Beer-Lambert Law are also discussed. Finally, with several groups currently working in the field, I provide an outlook for the future of the measurements.
      原文链接:
    • NSTL
    • Elsevier

    Sulphur variations in annually layered stalagmites using benchtop micro-XRF

    Wang H.Rich A.M.Bhattacharyya S.Akter R....
    9页
    查看更多>>摘要：? 2022 Elsevier B.V.Variation of sulphur in annually laminated stalagmites can be used to infer the impact of past volcanic activities, anthropogenic pollution, and climate change due to increased bushfire activity. The synchrotron radiation micro-X-Ray fluorescence (SR-XRF) microprobe is a powerful tool to analyse and image sulphur recorded in stalagmites with micrometre resolution. However, access to SR-XRF beamlines can be limited, so researchers must select the most promising stalagmites for imaging. Benchtop micro-XRF is an effective tool for trace elemental analysis of speleothem samples and is a candidate for routine laboratory measurement of sulphur along stalagmite laminae and screening for SR-XRF. This study describes a protocol using matrix-matched standards to measure annual variations of sulphur at trace to percent level along the laminae of two Western Australian stalagmites, one of which already having been analysed using SR-XRF. Parameters that affected quantitation include X-ray tube voltage and current, spot size of the X-ray beam and stalagmite surface roughness and porosity. The use of a 20 μm X-ray spot size provides sub-annual spatial resolution that can be completed in an overnight scan. The features in a 1000 point micro-XRF analysis of sulphur along a 20 mm transect show good consistency with SR-XRF microprobe data. Micro-XRF mapping was also performed to produce chemical images on the stalagmite and compared with Raman and X-ray diffraction (XRD) to confirm that the stalagmite is exclusively calcite, with no aragonite, and that the source of sulphur in the samples was gypsum and anhydrite. Regions of very high sulphur in the micro-XRF maps were found to be artefacts due to diffraction of the incident beam but these could be efficiently removed by using a multiple point statistics approach to produce a clean image suitable for analysis of the laminae. This work shows the potential of micro-XRF for routine analysis of sulphur in stalagmites, and to streamline sample characterisation before SR-XRF imaging.
      原文链接:
    • NSTL
    • Elsevier

    Microliter-stirred sample setup for X-ray spectroscopy analysis of nanomaterials in suspension

    Fanselow R.Wach A.Blachucki W.Szlachetko J....
    7页
    查看更多>>摘要：? 2022 The AuthorsAnalysis of samples in the liquid environment using X-ray spectroscopy techniques is a very attractive approach as it provides specimen characterization in its native conditions thanks to the penetrating properties of X-rays. However, very often due to challenging synthesis procedures and the high cost of specimens it is difficult to obtain a sample in quantities for optimal measurement. Additionally, nanoparticles (NPs) aqueous suspensions are often not stable and undergo agglomeration and sedimentation processes that can be avoided either by sonication or sample stirring. Relatively small sample volumes and intrinsic agglomeration processes make X-ray spectroscopy measurements challenging especially when long periods are needed for the collection of high-quality data. To address both issues, we developed dedicated sample system that allows measurements down to few tens of μL of the liquid sample with capability of continuous stirring of the suspension. The X-ray spectroscopy measurements of ZnO nanoparticles suspension in water showed a stable signal for hours of acquisition time. On the other hand, in the absence of stirring, agglomeration and subsequent sedimentation processes were visible already within few minutes with maximum sedimentation rate of 2.5% of concentration loss in the beam field per minute.
      原文链接:
    • NSTL
    • Elsevier

    Screening of uranium contamination on waste surfaces using X-ray fluorescence analysis

    Yoshii H.Takamura K.Uwatoko T.Sakai Y....
    4页
    查看更多>>摘要：? 2022X-ray fluorescence (XRF) analysis is useful for detecting radionuclides with long half-lives, such as most isotopes of uranium (234U, 235U, and 238U), as the detection of uranium by radiation measurements can be difficult. Therefore, we propose energy dispersive X-ray fluorescence (EDXRF) analysis as a method for the rapid screening of pollution from substances that are contaminated with uranium-containing water droplets. Sealed uranium-containing filter paper, which was used as the contaminated area model, was layered on top of a rubber plate to simulate a rubber plate whose surface was contaminated with uranium. The measured EDXRF spectra revealed a U Lα peak at the tail of a strong Br Kβ peak, and the contribution of this U Lα peak was extracted by peak fitting. The obtained results suggested a linear relationship between the uranium concentration of the filter paper and the signal intensity of the U Lα peak. The proposed method is more sensitive than the α-particle counting method for long half-life radionuclides, and can be used at uranium handling facilities.
      原文链接:
    • NSTL
    • Elsevier

    Validation of an Energy Dispersive X-Ray Fluorescence method for small sample intake in a wide range of matrices. Application to the analysis of saffron

    Ghidotti M.Papoci S.de la Calle Guntinas M.B.
    9页
    查看更多>>摘要：? 2022 The AuthorsMulti-elemental analyses using Energy Dispersive X-Ray Fluorescence have proven their efficacy in food authentication, but sample intake can be a drawback in the analysis of expensive matrices such as saffron. In this work, small sample holders and the double pellet method (a thin sample layer on a wax pellet) were combined to determine 19 elements of interest in food analysis, using only 1 g of sample. The trueness of these two approaches was evaluated with 17 different organic matrix reference materials of lichen, wheat flour, rice flour, bran, brown bread, cabbage, vegetable feed, pine needles, and spinach, tomato and tobacco leaves. In the analyses of reference materials, double pellets provided accurate results (recovery 100%) for Mg, Al, Si, P, Cl, S, K, Ca, Cr, Mn and Fe, but the penetration of the radiation into the wax layer of the double pellet hindered quantitative recovery for heavier elements. Contrarily, small sample holders were less accurate for the very light elements (Mg, Al and Si) but the recovery was satisfactory (> 80%) for the remaining ones, including the heavier elements (Cu, Zn, Rb, Sr, Cd and Ba). Ni and Br determinations were affected by a possible matrix dependent interference. With some few exceptions, the precision and the limits of quantification for the different elements in saffron, are comparable to those that characterise the analyses with standard pellets. The method was validated to analyse 21 Iranian saffron samples collected on the EU market.
      原文链接:
    • NSTL
    • Elsevier

    Mineral classification of lithium-bearing pegmatites based on laser-induced breakdown spectroscopy: Application of semi-supervised learning to detect known minerals and unknown material

    Muller S.Meima J.A.
    15页
    查看更多>>摘要：? 2022Mineral exploration and active mining relies on extensive drilling campaigns that produce large numbers of drill cores. LIBS is ideally suited for their fast and effective measurement, but matrix effects complicate quantitative geological LIBS applications due to the extensive amount of different minerals, rock types, and lithologies, as well as all textural and optical parameters increasing physical matrix effects. This is challenging for the application of LIBS in geological exploration, since LIBS data processing highly depends on matrix-matched models. The fast acquisition of new data is in conflict with the large amount of existing minerals and lithologies. As a result, new appearances are common during ongoing drilling campaigns, resulting in incomplete train sets for supervised classification and quantification. This paper presents a novel semi-supervised learning (SSL) classification model to resolve related issues by separating known minerals in geological drill cores based on a set of train samples, while also detecting unknown material, i.e. new lithologies and/or minerals not in the train set. Using a combination of supervised Linear Discriminant Analysis (LDA) and semi-supervised One-Class Support Vector Machines (OC-SVM), main minerals and known accessory minerals were effectively separated from unknown material in LIBS mappings of Spodumene and Muscovite pegmatite, as well as from Metagreywacke in drill cores from the Rapasaari lithium deposit in Finland. Self-learning was applied to automatically increase the number of train samples, which effectively decreased the number of unknowns due to physical matrix effects in coherent crystals. Validation with respect to the main minerals revealed an almost perfect classification of albite, spodumene, K-feldspar, quartz, and muscovite. Measurement points of Metagreywacke, which were only included in the test set, were correctly detected as unknown. Transferring the developed model onto LIBS mappings and drill core profile measurements displayed excellent classification results for main and accessory minerals included in the train set. Mixed spectra at mineral borders, as well as accessory minerals not in the train set were correctly identified as unknown.
      原文链接:
    • NSTL
    • Elsevier

    Dynamic thin-film microextraction method using cellulose platforms modified with silver nanoparticles for preconcentration of volatile hydride-forming elements prior to inductively-coupled plasma mass spectrometry determination

    de la Calle I.Lourido-Grovas A.Lavilla I.Bendicho C....
    10页
    查看更多>>摘要：? 2022 The AuthorsIn this work, a novel preconcentration method was developed for As, Sb and Bi following trapping of their volatile hydride derivatives onto cellulose-based platforms modified with Ag nanoparticles for ultrasensitive determination by inductively-coupled plasma mass spectrometry (ICP-MS). A continuous flow hydride generation system was coupled to a gas-liquid separation unit integrated with the preconcentration platform. AsH3, SbH3 and BiH3 were retained onto the silver nanoparticles (AgNPs) modified cellulose substrate upon catalytic decomposition. After a 10 min preconcentration time, enrichment factors of 16, 9 and 26 for As, Sb and Bi were obtained, respectively. These values can be increased when needed by a factor of three applying a preconcentration time of 30 min. Elution of analytes trapped onto AgNPs with 0.1 M HNO3 (As, Sb) or 1 M HNO3 (Bi) was performed and metal content in the eluates was measured by ICP-MS. Detection limits of 15, 2 and 1 ng/L for As, Sb and Bi were obtained, respectively. Repeatability values expressed as relative standard deviation (%) was in the range of 1.2–2.7%. Other hydrides tried (i.e. SeH2 and TeH2) did not provide suitable performance owing to inefficient desorption from the cellulose substrate. Simulated water matrices mimicking the major composition of freshwater, seawater, wastewater and groundwater were analyzed, recoveries being in the range of 80–106%.
      原文链接:
    • NSTL
    • Elsevier

    Evaluation of plasma condition, concentration effect, position effect, and nickel-doping method on non-matrix-matched Fe isotopic analysis by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry

    Xu L.Yang J.-H.Xie L.-W.Wang H....
    9页
    查看更多>>摘要：? 2022 Elsevier B.V.This study investigated the influences of plasma condition, concentration effect, ablation position and on-line addition of an aqueous Ni standard for non-matrix-matched Fe isotopic analysis by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry (fs LA–MC–ICP–MS). Deviations up to ~0.7‰ in δ56Fe values caused by non-matrix-matched analyses were difficult to eliminate under dry plasma condition even with fs-LA. However, the nebulized water after the ablation cell efficiently reduces or eliminates the matrix-dependent fractionation of Fe isotopes without reducing signal intensity. Furthermore, concentration- and position-dependent fractionation of Fe isotopes was not observed under wet plasma condition. For instrumental mass bias correction, the standard–sample bracketing (SSB) method and SSB with Ni doping (SSB + Ni) were performed in the presence of nebulized water with fs LA–MC–ICP–MS. Results indicate that both the SSB and SSB + Ni methods are sufficient to correct for instrumental mass bias under wet plasma condition, with the SSB + Ni method being more effective in calibrating short-term fluctuations in mass bias with improved external reproducibility of ~0.15‰ (2SD) for δ56Fe values. Compared to SN–MC–ICP–MS, deteriorated precision offered by fs LA–MC–ICP–MS may represent a major limitation for some applications relying upon precise Fe isotope ratio measurements. This approach for non-matrix-matched analysis of Fe isotopes by fs LA–MC–ICP–MS under wet plasma condition combined with the SSB + Ni method allows for more flexibility in tracing detailed geological processes with large Fe isotope fractionation of a wide range of solids. Relatively precise and accurate Fe isotopic compositions of potential reference materials of Balmat pyrite (δ56Fe = ?1.32 ± 0.12‰, δ57Fe = ?1.91 ± 0.20‰; 2SD, n = 166) and PZH12–24 ilmenite (δ56Fe = ?0.38 ± 0.15‰, δ57Fe = ?0.57 ± 0.23‰; 2SD, n = 134) were obtained using this analytical protocol, consistent with reference values obtained by solution nebulization (SN)–MC–ICP–MS within analytical uncertainties (Balmat pyrite: δ56Fe = ?1.30 ± 0.04‰, δ57Fe = ?1.94 ± 0.07‰, 2SD, n = 3; PZH12–24 ilmenite: δ56Fe = ?0.38 ± 0.06‰, δ57Fe = ?0.55 ± 0.07‰, 2SD, n = 6).
      原文链接:
    • NSTL
    • Elsevier