查看更多>>摘要：Laser-induced breakdown spectroscopy allows fast chemical analysis of light elements without significant sample preparation, turning it into a promising technique for on-site mining operations. Still, the performance for quantification purposes remains its major caveat, obstructing a broader application of the technique. In this work, we present an extensive comparison of the performances of distinct algorithms for quantification of Lithium in a mining prospection stage, using spectra acquired with both a commercial handheld device and a laboratory prototype. Covering both linear and non-linear methodologies, the results show that, when covering a wide range of concentrations typical on a mining operation, non-linear methodologies manage to achieve errors compatible with a semi-quantitative performance, offering performances better than those obtained with linear methods, which are more affected by saturation and matrix effects. The findings enclosed offer support for future applications in the field and may possibly be generalized for other elements of interest in similar mining environments.
Iria Rujido-SantosM. Estela del Castillo BustoIsabel Abad-Alvaro
11页
查看更多>>摘要：The low limits of detection and information regarding the concentration and size distribution of nanoparticles provided by single particle inductively coupled plasma mass spectrometry (spICP-MS) has been taken in advance for assessing released silver nanoparticles from (nano)textiles (nanosilver textiles). The releasing procedure consisted of using orbital-horizontal shaking (100 rpm, 20 °C, 30 min) and ultrapure water (10 mL) as an extractant, and it was found to guarantee silver nanoparticles stability (silver nanoparticle concentration and size distribution). Stability of released silver nanoparticles was further investigated at several filtration (0.22, 0.45 and 5.0 μm) and centrifugation conditions, stages required for fluff removal after extraction and just before spICP-MS determinations. Filtration using 5.0 μm filters was found to not affect silver nanoparticles concentrations and size distributions. The extractive procedure plus spICP-MS has shown a limit of detection and a limit of quantification for silver nanoparticle number concentration of 4.59 × 10~4 and 1.53 × 10~5 silver nanoparticles per gram of textile, respectively, whereas a limit of detection in size of 12 nm was obtained. Repeatability of the overall procedure was 14% (silver nanoparticle concentration) and 6% (mean silver nanoparticle size). Similarly, analytical recovery assays using standard silver nanoparticles of 20, 40, and 60 nm led to recoveries within the 102-113% range. The high degree of fixation of the AgNPs to the fabric and the softness of the extraction process to guarantee the integrity of the nanoparticles has led to a non-quantitative extraction (extraction percentages between 0.3 and 9.0% depending on the textile sample). However, the methodology developed has proven to be highly efficient for the characterization of the extracted AgNPs, and robust since the stability of the released AgNPs during the extraction procedure.
查看更多>>摘要：Koc x-ray emission induced by 2 MeV protons in thick Ti metal, TiO, Ti2O3, TiO2, MgTiO3, FeTiO3, TiC, TiN, TiB2, Cr metal, Cr2O3, CrO2, CrO3, K2Cr2O7 targets was measured using a wavelength dispersive spectrometer employing Johansson geometry to study chemical sensitivity of X-ray spectra. In the spectra the main Kα1 and Kα2 components as well as the KαL~1 multiple ionization satellites were clearly resolved. The Kα1 and Kα2 peak positions and widths were extracted direcdy from the measured spectra in a consistent way. The results were compared with the existing data obtained by proton and photon induced ionization mechanisms, with the results of multiplet calculations, and with the observed chemical effects found in the related experimental Kp spectra measured on the same Ti and Cr compounds at earlier times. The results obtained confirm linear correlations of the Kα1 first moments (M1) and the Ka center of gravity energy shifts with the central metal formal oxidation state, as well as between the Kα1 line widths and the Kα1 - Kβ1 M1 and/or centre of gravity energy shifts. The Ka energy shifts calculated by multiplet structure method for Cr compounds agreed with the experimentally obtained trends.
查看更多>>摘要：In the present work, the sensitivity and repeatability of the emission spectra have been investigated using nano-enhanced laser-induced breakdown spectroscopy (NELIBS). The colloidal solution of copper nanoparticles was produced by using the laser ablation technique at the fundamental wavelength of Nd: YAG laser at 100 mJ and deposited on the surface of standard aluminum alloy in different concentrations. With varying laser irradiances (10 GW/cm~2 to 35 GW/cm~2) and nanoparticles surface concentration (6.4 μL/cm~2 to 57.7 μL/cm~2), emission spectra were acquired from laser-induced plasma. On average the signal enhancement up to 50 times was achieved at a laser irradiance of 28.3 GW/cm~2 and at NPs concentration of 45 μL/cm~2. A decrease in relative standard deviations (RSD) from 28% to 16% for manganese and 18% to 10% for aluminum emission lines was achieved at laser irradiance of 10.5 GW/cm~2 and surface concentration of 19.2 μL/cm~2.
查看更多>>摘要：Today, we acquire larger and larger spectroscopic imaging data sets on complex samples. Even before proceeding with a spectroscopic analysis, we often have information concerning for example the presence of major compounds. However, we are not in the same position regarding the presence and location of minor compounds and traces in the sample, while this is generally a more interesting piece of information. Modern spectroscopic imaging uses chemometric tools that allow the simultaneous exploration of the entire spectral range available. These well-tested tools, such as principal component analysis, often exploit the variance contained in the data set to extract maximum chemical information. In general, we can say that these approaches are quite efficient but they are not completely adapted to the characteristics of the data acquired during a spectral imaging experiment. Indeed, such data sets have generally a limited signal to noise ratio and minor compounds and traces are often present on a small number of pixels compared to the total number in the considered data set. It is then quite possible that these compounds are present in a sample but not detected by the chosen multivariate tool. The goal of this work is to introduce an approach called Interesting Features Finder (IFF) able to retrieve minor compounds and traces independently of the variance they may express in the spectral data set. Like other state of the art methods, it uses the notion of convex hull but with the great advantage of working directly on the raw data, without prior projection to reduce their dimensionality. By means of a synthetic spectral data set and a micro-LIBS (laser-induced breakdown spectroscopy) imaging one acquired on a sample taken in Antarctica, we will show the potential of this approach in terms of sensitivity of detection of compounds but also of robustness against noise.
NSTL