查看更多>>摘要：Determination of thiomersal was made by the temporally selective photo-degradation, mediated by graphene quantum dots (GQDs) and TiO(2 )nanoparticles (GQDs-TiO2 ) composite, producing the Hg0 quantified by atomic absorption spectrometry (AAS) using a multipass detection cell. The UV photo-reactor was directly adapted to the mercury dedicated spectrometer with samples mixed, into quartz tube, to a solution (buffered at pH 4.0) containing formic acid (1% v/v) and the dispersed GQDs-TiO2 (0.18 mg L-1). Hg-0 temporal profile from thiomersal was detected after 16 min of UV exposure. Different kinetics of Hg0 releasing allowed speciation as the Hg0 from other mercurial species were produced at different times. Analytical linear range was from 15 ng L-1 (LOD) up to 1000 ng L-1. Temporal separation of Hg-0 formation was confirmed by gas chromatography coupled to atomic fluorescence spectrometry, also indicating that thiomersal is firstly degraded to ethylmercury before turning into Hg2+ and then into Hg-0. The method was applied in the determination of thiomersal in vaccines and residual levels of Hg2+ and ethylmercury were also detected.
查看更多>>摘要：Alkali and alkaline earth metals incorporated in rocks can indicate past water activities. Their precise determination with laser-induced breakdown spectroscopy (LIBS) is required for geological investigations on Earth as well as on Mars. In previous studies, laboratory standard samples in the form of pressed powder pellets were used to train univariate or multivariate regression models. Although various chemical compositions of the used samples cover the chemical and mineralogical diversities of the rocks encountered in field measurements, the difference in physical forms between the laboratory standards and the real samples analyzed in situ leads to the physical matrix, which dramatically reduces the prediction performance of the models for real samples. The present work performs a systematic study of the influences of the chemical and physical matrix effects, and develops multivariate regression models based on machine learning and transfer learning to effectively correct these effects. The experiment involved a set of 27 fully characterized natural rocks. A part of each rock was prepared in a pressed powder pellet, while another part was left in its raw state. LIBS spectra recorded from pellets were first used to train multivariate regression models based on a machine learning approach combining feature selection and back-propagation neural network (BPNN). The trained models were tested respectively by independent pellets and raw rocks with and without counterpart pellets in the training sample set. An effective correction of the chemical matrix effect was observed for the models when tested with pellets. While the tests with raw rocks revealed the influence of the physical matrix effect on the prediction performance of the models. Transfer learning was then introduced by including a part of the raw rocks in the training sample set, leading to a significant improvement of the prediction performances for raw rocks, with root mean square errors of prediction (RMSEPs) of 1.6, 18, 101, and 162 wt. ppm respectively for Li, Rb, Sr, and Ba.
查看更多>>摘要：The interactions of gold nanoparticles (AuNPs) with blood represents the first systemic clearance barrier that these particles face in-vivo. Assessment of this interaction is of particular interest in evaluating the efficacy and kinetics of AuNP delivery in various tissues or organs. Total reflection X-ray fluorescence (TXRF) spectroscopy offers multielemental quantification of trace-level concentrations through internal standardization. In this work, we investigate different sample preparation procedures to determine an appropriate method that would allow accurate quantification of AuNPs in blood matrix. Whole blood, plasma and red blood cells samples were doped with La internal standard and certified Au solution. The samples were prepared as is and diluted with water in ratios of 1:1, 1:5 and 1:10. In order to extend the investigation to AuNPs, samples were also doped with 10 nm reference material AuNPs and diluted with aqua regia in ratios of 1:1, 1:5, 1:10. Our results demonstrate that near 100% recovery of Au concentration can be obtained with the appropriate dilutant and dilution ratio. This work facilitates TXRF's transition into AuNP research as it offers an easy-to-use analytical toolbox that can accurately quantify AuNPs in blood.
查看更多>>摘要：We study the effect of complementary spectral information based on combined LIBS (laser-induced breakdown spectroscopy) and Raman spectroscopy, including 3 options of LIBS, Raman and LIBS-Raman, on the improved classification accuracy of meat tissues of beef, mutton and pork. The BPNN (back propagation neural network) with input variables optimized by RF (random forest) was used to classify the 3 kinds of meat tissues. The model confusion matrix, Precision, Recall, Kappa, MAE (Mean absolute error), RMSE (Root mean square error) and other parameters were obtained by 10-fold cross-validation method to evaluate the 3 classification models, and the results of the three methods were compared. The results showed that the combined LIBS-Raman model has the highest classification accuracy of up to 99.42%, and superior to the other 2 separate methods in terms of model consistency and confidence degree, indicating that the combined LIBS-Raman method has significantly improved the recognition ability and classification accuracy of meat tissues, which took the advantage of utilizing the complementary spectral information obtained by both methods. Therefore, the combination of LIBSRaman and BPNN is a fast and robust method for meat tissue identification.
查看更多>>摘要：The SuperCam instrument, aboard NASA's Perseverance rover, provides for the first time the hardware capability for time-resolved spectroscopy on Mars. As a consequence, in addition to the atomic and molecular emissions routinely recorded by SuperCam LIBS, plasma-induced luminescence (PIL) features could theoretically also be observed, within the sample, potentially improving the detection capabilities for some minor elements, compared to LIBS. PIL has been studied in terrestrial conditions but not yet examined under Martian atmospheric conditions. Since atmospheric conditions have previously been shown to strongly affect plasma emissions, they may also have a significant influence on PIL. This study aims at assessing the feasibility of PIL spectroscopy in Martian atmospheric conditions. To do so, we investigate the influence of atmospheric pressure and composition on PIL emissions, compared to plasma emissions. We demonstrate that PIL emission can be observed in simulated Martian conditions, despite its lower intensity compared to terrestrial conditions. Moreover, PIL features exhibiting millisecond-range decay have been observed once plasma emissions have decreased significantly; with our experimental conditions, it is achieved with a temporal delay of 200 mu s after plasma initiation and a gate of 20 ms. Shorter-lived PIL features have not been observed, possibly due to spectral interference with plasma emissions.
查看更多>>摘要：Complementary methods are introduced to laser-induced breakdown spectroscopy measurement systems in order to provide complete information about the investigated sample, phenomena beyond laser-matter interaction and evolution of laser-induced plasmas and its properties. Another use of such complementary signals is in their potential use for signal standardization. So far one additional method is used at a time to achieve this goal, be it direct imaging of the plasma, shadowgraphy method, measurement of the sound signal or energy of the laser pulse. In this work we were able to record all above mentioned data at the same time as the LIBS spectra or even energy of the individual laser pulses. This allowed us to observe correlation between all the data with optical emission signal of laser induced plasmas. Each data pair is represented by correlation coefficient, where the average value of correlation coefficients R-2 is 0.87. After correcting the data with the energy of laser pulse and optical emission signal, we achieved average value of the correlation coefficients R(2 )0.98.
查看更多>>摘要：In this study, we used optical emission spectroscopy (OES) as a diagnostic tool in a Duo-Plasmaline surface-wave discharge. Argon plasma emission is recorded in order to calculate the electron density ne and the electron temperature Te in argon gas at a pressure range of 10-30 Pa. To describe argon emission, a corona model using different line ratios is compared to a more complete collisional-radiative model (CRM). It has been found that metastable states play an important role in the population model via electron impact excitation and radiation trapping and should be taken into account for the considered pressure range. The obtained parameters are in the range of 1.4 eV for the electron temperature and 5 x 1016 m(-3) for the electron density.
查看更多>>摘要：Automobile exhaust catalysts containing only Pd have significant advantages over other types of catalysts, including exceptionally high activity at low temperatures, superior thermal stability at high temperatures, and resistance to sulfur toxicity. The present study employs the electron probe microanalysis (EPMA) technique to determine the trace elemental Pd in such catalysts. The particle size distribution and homogeneity of Pd in synthesised standard samples were studied after ball milling, which improved the sample uniformity. Furthermore, the impact of measurement parameters on the analysis precision was investigated. It was found that the optimal conditions are an acceleration voltage of 18 kV, a beam current of 140 nA, and a beam spot size of 40 mu m. To avoid potential background interference when choosing background positions in the ZAF method, a calibration curve was established with a correlation coefficient higher than 0.99. This analysis method can be of substantial significance in the production process of automobile exhaust catalysts and in the recovery of precious metals from spent catalysts. Therefore, there is high potential to expand the applications of EPMA in this field.
Cureatz, Daniel J. T.Kavcic, MatjazPetric, MarkoIsakovic, Kristina...
10页
查看更多>>摘要：Wavelength-dispersive X-ray spectrometry is used to examine the influence of multiple ionization satellites induced by 3-5 MeV energy helium ion beams upon the accuracy of particle-induced X-ray emission analysis (PIXE). The work extends our prior study of elements magnesium, aluminum and silicon and their oxides to elements phosphorus, chlorine, potassium, calcium, titanium and chromium and, for the latter two, their oxides. Fitting of the spectra with Voigtian peaks enables construction of a database that comprises the mean energies and the relative intensities of up to four distinct satellite groupings. This database provides an empirical means for inclusion of one peak per satellite group when modelling energy-dispersive spectra. This is a useful step towards improving the accuracy of PIXE analysis of materials using helium beams; an example of this is provided using a spectrum recorded by the Curiosity rover on Mars.
Alcaraz-Pelegrina, J. M.Sarsa, A.Dimitrijevic, M. S.Yubero, C....
9页
查看更多>>摘要：Laboratory plasmas can be characterized by Optical Emission Spectroscopy techniques by using Hydrogen Balmer series lines. The line shape is the result of the convolution of the several internal process occuring in plasma. The Stark effect over the Hydrogen emitter atom has been studied in a limited range of plasma parameters, obtaining a profile which is the result of a sum of a given number of Lorentzian functions for the H alpha and H beta line. In this paper, we have extended this analysis to cover a wide range of plasma conditions for the H alpha line. The number of Lorentzian functions depends on the contribution of ion collisions around the Hydrogen emitter atom and their mobility in comparison with that of electrons.
NSTL
Elsevier