Spectrochimica Acta Part B: Atomic Spectroscopy最新文献

LAMIS is a known technique for isotopic shift analysis of light elements, such as B, C, etc. Its application for heavy molecules has been studied less. We proved that vibrational and rotational transitions A(1–0), A(1–2), and A(2–1) of GdO in Laser-Induced Plasma exhibit apparent differences between natural GdO, ¹⁵⁶GdO, and ¹⁵⁸GdO emissions. The absolute values are in the 0.4–0.5 cm⁻¹ range. Besides its adequate spectral resolution, the Demon HR Double Echelle Monochromator proved its sensitivity for isotopic analysis of Rare Earth Elements.

A new approach to the quantitative determination of sulfate sulfur in soils and sediments by wavelength-dispersive X-ray fluorescence spectrometry in combination with partial least squares (PLS) regression has been investigated. The quantitative analysis of sulfate sulfur was carried out by analyzing the spectra in the S-Kα and S-Kβ regions of sulfur spectral lines. The study shows that the differences in the spectra in both regions can be used for quantitative analysis of sulfate sulfur in the presence of sulfur in other forms. The obtained information can be used for quantitative express analysis of sulfur forms in objects of various nature.

A comprehensive model equation for the measurement of elemental mass fractions in solid materials using the direct standardization method of Instrumental Neutron Activation Analysis was developed. The extensive modelling established for the single comparator standardization was revised and changed for the direct standardization to obtain a complete mathematical description of the measurand by physical and chemical quantities having dimensions in SI units. The model equation is presented both in case measurement and standard samples are measured in the same γ-counting position and in different γ-counting positions. The first was successfully applied for the quantitative determination of As mass fraction in a seafood matrix with a percent level relative uncertainty. The SI traceability of the result is established by a traceable standard via the measurement equation and the uncertainty budget compiled to highlight the input quantities that contribute most to the combined uncertainty.

A method with broad applicability for evaluating the content of As, Sb Bi, Hg, Cd, Cu, Zn, Sr, Mn, Ni, Cr, Co and Pb was developed for the characterization of recyclable (bio)polymeric materials of various types and origins based on high-resolution continuum source atomic absorption spectrometry after high-pressure microwave-assisted wet digestion in H₂SO₄–HNO₃–H₂O₂ mixture. The limits of detection (LODs) for As, Sb Bi and Hg were in the range 0.005–0.020 mg kg⁻¹ after chemical vapour generation and quartz tube atomization, while for the other elements determined in air-acetylene flame were 0.1–1.5 mg kg⁻¹. The recoveries were in the range 95–105% with extended uncertainty of 9–21% (k = 2). Plastics of polyethylene terephthalate, polypropylene, polyethylene, epoxy resin, polyvinyl chloride and acrylonitrile butadiene styrene showed higher concentrations of the studied elements, but variable depending on the element, nature and origin of the polymeric materials. Biopolymeric or hybrid polymeric materials could represent a risk for at least one of the elements (As, Sb, Bi and Zn). The recycling of plastics from electronic products, medical activity, food and cosmetics packaging, office supplies and toys generate recyclable materials with concentrations of As, Sb, Bi, Cu and Zn higher than agriculture, domestic activities, and constructions, in which As and Sb were below the method LODs. Chromium, Co and Pb were below LOD in all samples. However, in all the (bio)polymeric recyclable materials considered in this study, the concentrations of the elements were below the limits imposed by European regulations, regardless of their origin and use. Tukey's statistical test showed both significant and not significant differences (p > 0.05) among the content of elements in materials with concentration above the LODs of the method.

Eu isotope ratio can be precisely measured by MC-ICP-MS using a Sm isotope pair as spike for normalization. The standard chemical reagent NIST3117a exhibits almost no Eu isotope fractionation regardless of the kind of Sm isotope pairs used in normalization. However, Eu isotope fractionation can appear even in high purity Eu chemical reagents due to Gd and Ba impurities, interference with Sm isotope pair or use of different sample introduction methods. The Eu isotope fractionation in highly fractionated igneous rocks or feldspar minerals can arise from Gd and Ba impurities left by incomplete chemical separation. This study describes a modified, optimal method for accurately and precisely determining the degree of Eu isotope fractionation in highly fractionated Si-rich igneous rocks and Ba-rich feldspar. Ba oxide effects on Sm, Eu and Gd isotopes were monitored by MC-ICP-MS using different wet and dry plasma conditions for sample introduction. The Gd impurities exerts more influence than Ba impurities on Eu isotope ratios. The highly fractionated igneous rocks and feldspar materials showed consistent enrichment in the lighter Eu isotope (¹⁵¹Eu) which becomes a negative Eu isotopic value relative to NIST3117a. Results showed that highly purified Eu solutions from reagents containing no detectable Gd and Ba gave consistent Eu isotopic values regardless of Sm isotope pair (e.g., ¹⁴⁷Sm¹⁴⁹Sm, ¹⁴⁷Sm¹⁵²Sm, ¹⁴⁷Sm¹⁵⁴Sm, ¹⁴⁹Sm¹⁵⁴Sm, ¹⁵⁰Sm¹⁵⁴Sm) used in normalization. In order to obtain the best estimates of Eu isotope fractionation in different kinds of geological materials (including Si- and Ba-rich materials), Ba and Gd matrix must be completely removed and the Eu isotopic values calculated using four or more Sm spike isotope pairs.

Some compounds, including the monoterpenes, are difficult to be analyzed by chemical ionization mass spectrometry (CI-MS) mass spectrometry because of having distinct chemical features of unsaturated bonds in relatively large molecule, which is responsible for occurring fragmentation of molecular ions. A direct detection of monoterpenes, including monocyclic, bicyclic and oxygenated (acyclic), was carried out using a soft plasma ionization (SPI) source combined with a q-mass spectrometer (q-MS). Detectable signals for monoterpenes were examined in an ambient air discharge plasma when varying the discharge parameters, such as discharge pressure (0.4–3.0 kPa) and sample/carrier pressure ratio (R = 5–100%). Furthermore, to consider the ionization reactions in detail, nitrogen gas was also used as the discharge gas (carrier gas). Monoterpenes, including cross-linked bicyclic (α-pinene and β-pinene) and oxygenated (linalool, geraniol, nerol and eucalyptol), in which their simple spectrum patterns can be obtained with little or no fragmentation at an ambient air pressure of several kPa, has successfully conducted by the pulsed dc SPI-MS. To our knowledge, this is the first report demonstrating that the spectrum pattern of monoterpenes could be directly detected without any complicated fragmentation of analyte ions in the SPI source.

The aim of the study is to extend the list of spectral lines of atomic and single ionized holmium (Ho) into the near infrared wavelength range up to 1750 nm. Spectra of a Ho hollow cathode discharge lamp with neon or argon as buffer gases have been measured with a Fourier Transform spectrometer in different spectral ranges. In total, the range from 700 nm to 1750 nm i.e. from $5710{\mathrm{cm}}^{-1}$ to $14280{\mathrm{cm}}^{-1}$ has been covered. A total of almost 800 spectral lines were detected. Based on the known energy levels of atom and ion Ho, 589 lines could be classified as Ho I transitions and 31 lines as Ho II transitions. The remaining 171 lines could mostly be classified as different Ho I or Ho II, based on different signal-to-noise ratios in spectra measured with different buffer gases. In the wavelength range from 1200 nm to 1750 nm, a list of Ho lines is presented for the first time. In the wavelength range from 700 nm to 1200 nm 216 lines had not been listed in literature up to now.

Thermal decomposition behavior of two kinds of Pt salts, namely, H₂PtCl₆ and Pt(NH₃)₄Cl₂, on amorphous SiO₂ and γ-Al₂O₃ under air to prepare supported platinum catalysts up to 773 K was investigated by in-situ laboratory X-ray absorption fine structure (XANES/EXAFS) and UV–Vis spectroscopy. Changing the oxidation state of platinum species and the coordination environment, the migration to vacant sites or aggregation process on the surface were discussed. The supported H₂PtCl₆ was reduced to Pt²⁺ species under air flow around 573 K by eliminating Cl/O ligand atoms until 573 K. High-temperature treatment caused the re-oxidation of the supported Pt species on Al₂O₃, but it did not affect the oxidation state of SiO₂-supported species. The formed platinum oxychloride on Al₂O₃ was stable under air, but it partly decomposed to atomic-like species above 673 K, followed by migration on the surface, trapping at the cation vacant site because of its defect spinel structure. The lattice oxygen atoms of Al₂O₃ adjacent to Pt atom captured might cause the re-oxidation, and molecular oxygen was not the oxidant. The partly formed atomic-like species migrates on the SiO₂ surface, followed by aggregation to form metallic Pt particles above 573 K.

The existence of signal uncertainty remains the biggest obstacle in quantitative chemical analysis of laser-induced breakdown spectroscopy (LIBS), in which the original signal optimization is a key and difficult problem to overcome for a long time in the past, present, and future. In this review, we investigated the existing methods for optimizing original signals and briefly introduced the process of laser-produced plasma, sources of spectral uncertainty, and evaluation parameters. In addition, we summarized and proposed four optimization scenarios, including energy injection, spatial confinement, experimental environment, and technology fusion, aiming to improve the accuracy and reliability of LIBS in quantitative analysis of the chemical element composition of substances. Finally, we conducted an in-depth discussion on the existing problems of the current LIBS signal optimization scenarios and reflected on its further development. This work not only provides theoretical guidelines and practical suggestions for researchers to use LIBS technology, but also has great significance for promoting the practical application of signal optimization.