High-resolution Absorption Research Articles

Accurate absorption intensities of ozone in a wide IR spectral range from experimental measurements and ab initio calculations

Recent results of a long-term effort of Tomsk-Reims research teams on accurate intensity data obtained from high-resolution absorption spectra of ozone suitable for the atmospheric remote sensing in a wide IR range are summarized. This includes vibronic bands corresponding to the transitions towards triplet electronic states near 1 µm, and vibration-rotation bands covering the far-infrared and near-infrared ranges.

The CLEAR X-ray emission spectrometer available at the CLAESS beamline of ALBA synchrotron.

The CLEAR X-ray emission spectrometer installed at the CLAESS beamline of the ALBA synchrotron is described. It is an energy-dispersive spectrometer based on Rowland circle geometry with 1 m-diameter circle. The energy dispersion is achieved by the combination of a diced analyzer crystal and a unidimensional detector. A single unconventional dynamically bent analyzer crystal (Si 111) permits a wide energy range to be covered, just by exploiting its different reflections (333, 444, 555, 777, 888): 6-22 keV, with a spectrometer efficiency that decreases above 11 keV because of the Si detector thickness (Mythen, 350 µm), while the relative scattering intensities for the Si 333, 444, 555, 777 and 888 reflections correspond to 36, 40, 21, 13 and 15, respectively. The provided energy resolution is typically below 1-2 eV and depends on the beam size, working Bragg angle and reflection exploited. In most cases the energy dispersion ranges from 10 to 20 eV and can be enlarged by working in the out-of-Rowland geometry up to 40 eV. The spectrometer works in full backscattering geometry with the beam passing through the two halves of the analyzer. The vacuum beam path and the particular geometry allow a typical average noise of only 0.5 counts per second per pixel. The spectrometer is mainly used for measuring emission lines and high-resolution absorption spectra, with a typical scanning time for highly concentrated systems of around half an hour, including several repeats. The intrinsic energy dispersion allows systematic collection of resonant X-ray emission maps by measuring high-resolution absorption spectra. Moreover, it allows spectra to be measured on a single-shot basis. Resonant inelastic X-ray scattering experiments to probe electronic excitations are feasible, although the spectrometer is not optimized for this purpose due to the limited energy resolution and scattering geometry provided. In that case, to minimize the quasi-elastic line, the spectrometer is able to rotate along the beam path. Advantages and disadvantages with respect to other existing spectrometers are highlighted.

RE3+-Doped Ca3(Nb,Ga)5O12 and Ca3(Li,Nb,Ga)5O12 Crystals (RE = Sm, Dy, and Pr): A Review of Current Achievements.

Spectroscopic characteristics of RE3+ ions (RE = Sm, Dy, and Pr) doped in partially disordered Ca3Nb1.6875Ga3.1875O12-CNGG and Ca3Li0.275Nb1.775Ga2.95O12-CLNGG crystals are reviewed in detail to assess their prospects as laser crystals with emission in the visible spectral domain. All investigated crystals were grown using the Czochralski crystal growth technique. High-resolution absorption and emission measurements at different temperatures, as well as emission dynamics measurements, were performed on the grown crystals. The spectroscopic and laser emission characteristics of the obtained crystals were determined based on the Judd-Ofelt parameters. The obtained results indicate that CNGG:RE3+ and CLNGG:RE3+ (RE = Sm, Dy, and Pr) crystals can be promising materials for lasers in the visible range.

Determination of thallium in vegetative plant leaves near industrial areas by high-resolution continuum source electrothermal atomic absorption spectrometry after salt induced cloud point extraction

A rapid analytical procedure is described for the separation and pre-concentration of ultra trace level thallium from the microwave assisted nitric acid digests of plant samples and determination using high resolution continuum source electrothermal atomic absorption spectrometry (HR-CS-ETAAS). The method is based on the extraction of ionic thallium spices formed in-situ in the nitric acid digests of plant leaves with Triton X-100 micelles, in presence of HCl and NaCl. The hydrophobic solubilising sites of Triton X-100 micelles are used for the pre-concentration of hydrophobic species of thallium from bulk aqueous phase into a small surfactant rich phase. The main parameters affecting the extraction process are evaluated and optimized. A rapid temperature program completed within 15 s is used for the determination of thallium using a permanent ZrIr modifier. Under the optimized conditions, the pre-concentration factor and limit of detection are 25 and 0.05 ng mL−1, respectively. A characteristic mass of 12 pg is obtained on measuring the integrated absorbance with central pixel ±1. The recoveries are in the range of 95–99% at 1 ng mL−1 with 2–3% relative standard deviation. The accuracy of the method is verified by analyzing certified reference materials such as BCR 060 aquatic plant and NIST 1572 citrus leaves. The obtained values are in good agreement with the certified values. The procedure is also applied to real samples such as spinach, cabbage, aquatic, and tobacco plant leaves collected near thermal power plants and industrial areas.

Broadband soft X-ray source from a clustered gas target dedicated to high-resolution XCT and X-ray absorption spectroscopy.

The development of the broad-bandwidth photon sources emitting in the soft X-ray range has attracted great attention for a long time due to the possible applications in high-resolution spectroscopy, nano-metrology, and material sciences. A high photon flux accompanied by a broad, smooth spectrum is favored for the applications such as near-edge X-ray absorption fine structure (NEXAFS), extended X-ray absorption fine structure (EXAFS), or XUV/X-ray coherence tomography (XCT). So far, either large-scale facilities or technologically challenging systems providing only limited photon flux in a single shot dominate the suitable sources. Here, we present a soft, broad-band (1.5 nm - 10.7 nm) soft X-ray source. The source is based on the interaction of very intense laser pulses with a target formed by a cluster mixture. A photon yield of 2.4 × 1014 photons/pulse into 4π (full space) was achieved with a medium containing Xe clusters of moderate-size mixed with a substantial amount of extremely large ones. It is shown that such a cluster mixture enhances the photon yield in the soft X-ray range by roughly one order of magnitude. The size of the resulting source is not beneficial (≤500 µm but this deficit is compensated by a specific spectral structure of its emission fulfilling the specific needs of the spectroscopic (broad spectrum and high signal dynamics) and metrological applications (broad and smoothed spectrum enabling a sub-nanometer resolution limit for XCT).

Valence Transitions in Yb1+xIn1−xCu4 Studied by High-resolution X-ray Absorption Spectroscopy, X-ray Diffraction, and Photoelectron Spectroscopy

Temperature- and pressure-induced valence transitions in the Yb-rich compounds Yb1+xIn1−xCu4 were studied directly by the high-resolution x-ray absorption spectroscopy. We observed a correlation between the temperature dependence of χT and the Yb valence which could be described by the Anderson model, where χ and T are magnetic susceptibility and temperature, respectively. The valence transition temperature of Yb1+xIn1−xCu4 was found to be insensitive to the chemical pressure compared to to the case of YbIn1−xAgxCu4. This difference could be attributed to the difference in the electronic structure above the Fermi level. The shift of Tv to higher temperatures with increasing x in Yb1+xIn1−xCu4 is interpreted to be caused by the stronger hybridization contributed by the additional Yb site at the In site. Hydrostatic pressure dependence of the Yb valence in Yb1.06In0.94Cu4 showed an anomaly. The Yb valence decreased at the pressure range of 5–20 GPa where an anomaly was also observed in the pressure dependence of the lattice constant.

Ti3AlC2 max phase- graphene oxide (GO) nanocomposite for selective solid phase microextraction of palladium in environmental samples and medical appliances prior to its detection with high-resolution continuum source flame atomic absorption spectrometry (HR-CS-FAAS)

Palladium is an important metal as it has a wide range of applications in different fields but can cause cancer in human beings. Therefore, precise quantification of palladium is important. For this purpose, new material Ti3AlC2 max phase having unique properties like high stability, thermal conductivity and environmental friendly has been synthesized. To increase its surface area of Ti3AlC2 max phase, graphene oxide (GO) has been incorporated to form Ti3AlC2 max phase GO nanocomposite. Ti3AlC2 max phase GO nanocomposite was used as solid phase extracting material for microextraction and preconcentration of Pd(II) in environmental samples and medical appliances. Characterization of the adsorbent was achieved by using fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and surface area analyzer (SAA). All the parameters that influence the extraction efficiency of the adsorbent like solution pH, amount of adsorbent, volume of sample, vortex time, desorption condition and interferences effect were determined and optimized. The limit of detection (0.327 µg/L) and limit of quantification (1.09 µg/L) show that the method is highly sensitive. The relative standard deviation was calculated as 5.48 % for five repeated measurements, which shows that the developed method is reproducible. The method is highly efficient with large values of preconcentration factor (20) and enhancement factors (20). The method was validated by applying the method to real water samples, soil samples and medical appliances with satisfied recovery results (94–106 %).

Crystal and electronic structures of BiS2 -based compounds Sr0.5X0.5FBiS2 (X=rare earth) under pressure: Correlation with the change in the superconductivity from unconventional to conventional

${\mathrm{Sr}}_{1\ensuremath{-}x}{X}_{x}{\mathrm{FBiS}}_{2}$ $(X:\text{rare earth})$ is considered to show a pressure-induced structural transition around 1 GPa where the superconductivity changes from unconventional in the low-pressure phase to conventional in the high-pressure phase with increasing the superconducting transition temperature (${T}_{c}$). We clarified the monoclinic crystal structure ($P{2}_{1}/m$) in the high-pressure phase which is the same as the high-pressure phase of $X{\mathrm{O}}_{1\ensuremath{-}x}{\mathrm{F}}_{x}\mathrm{Bi}{Y}_{2}$ ($Y$: chalcogen) systems. We performed high-resolution x-ray absorption spectroscopy (XAS) to study the electronic structure of ${\mathrm{Sr}}_{1\ensuremath{-}x}{X}_{x}{\mathrm{FBiS}}_{2}$ systematically, indicating the Bi charge state of nearly $3+$. The pressure dependence of the XAS spectra of ${\mathrm{Sr}}_{0.5}{\mathrm{La}}_{0.5}{\mathrm{FBiS}}_{2}$ and ${\mathrm{Sr}}_{0.5}{\mathrm{Nd}}_{0.5}{\mathrm{FBiS}}_{2}$ indicate a large change in the electronic structure around the structural transition pressure, which corresponded to the transition from semiconductorlike to more metallic states. The increase of the empty states of Bi $s$ and $d$ (${t}_{2g}$) bands above the Fermi level was observed in the high-pressure phase. Density functional theory calculations showed that the density of the states at the Fermi level did not show a significant change in the high-pressure phase, where higher ${T}_{c}$ was observed.

Ag modified ZnO nanoflowers for the dispersive micro-solid-phase extraction of lead(II) from food and water samples prior to its detection with high-resolution continuum source flame atomic absorption spectrometry

Ag modified ZnO nanoflowers were synthesized by using hydrothermal method and used as dispersive micro-solid phase extractant for separation and preconcentration prior to its flame atomic absorption spectrometric detection. The Ag modified ZnO nanoflowers has been characterized by FT-IR, XRD, FESEM, EDX and BET. The factors effecting extraction efficiency like pH, Adsorbent dose, sample volume, eluent concentration, eluent volume was optimized. Matrix effects were also studied. The limit of detection and preconcentration factor (PF) were calculated as 8.52 μg L−1, and 100, respectively. The presented dispersive micro-solid phase extraction technique was validated using GBW07424 (GSS-10) soil and GBW07425 (GSS-11) soil certificated reference materials (CRMs) with satisfactory recovery results. The presented dispersive micro-solid-phase extraction (d-μSPE) procedure was successfully applied to food and water samples.

Major chemical carcinogens and health exposure risks in some therapeutic herbal plants in Nigeria.

People of all ages and genders utilize herbal medicine to treat varieties of problems all around the world. The accumulation of Cd and Cr in therapeutic herbs (Adansonia digitata, Psidium guajava, and Carica papaya) can lead to a variety of health complications. These leaf extracts are used to treat varieties of ailments, including cancer, in the northern Nigerian states of Borno, Jigawa, and Kano. The researchers employed high-resolution continuous source atomic absorption spectrometry. The statistical parameters such as mean, range, minimum and maximum were computed along with one-way analysis of variance (ANOVA) to assess activity concentrations of Major Chemical Carcinogens (MCCs) in the herb extracts from the three states. The result demonstrated substantial statistical variation in the concentration of Chromium between groups with C. papaya (F = 190.683, p = 0.000), P. guajava (F = 5.698, p = 0.006), A. digitata (F = 243.154, p = 0.000). The post hoc test revealed that the C. papaya and A. digitata observed concentrations were statistically significant across the three states (p = 0.000). It was observed that there is no statistically significant difference between concentrations of the extracts between Kano and Borno states for P. guajava (p = 0.686). For Cd, the one-way ANOVA showed significant statistically variation in the concentration between groups with C. papaya (F = 77.393, p = 0.000), P. guajava (F = 4.496, p = 0.017), A. digitata (F = 69.042, p = 0.000). The post hoc test with multiple comparisons revealed that the activity concentration of all extracts was statistically significant across the three states (p<0.05). The target risk quotient (THQ) for Cd was more than unity in A. digitata and C. papaya, except for P. guajava from Borno State. The probable cancer risk was observed for consumption of plant extracts as a result of Cr and Cd.

Crystal Phase, Electronic Structure, and Surface Band Bending of (InxGa1–x)2O3 Alloy Wide-Band-Gap Semiconductors

Ga2O3 is emerging as a promising wide-band-gap semiconductor for high-power electronics and deep ultraviolet optoelectronics. Alloying Ga2O3 with In2O3 leads to the modulation of the band gaps and possible carrier confinement achieved at the heterointerface. In this work, we report a systematic study on the crystallographic phase, electronic structure, and surface band bending of (InxGa1–x)2O3 thin films over the whole composition range of 0 ≤ x ≤ 1 grown on α-Al2O3 (0001) substrates by pulsed laser deposition. It was found that with In content x < 0.2, a monoclinic β-phase of an (InxGa1–x)2O3 film is epitaxially grown on Al2O3 (0001), while a bixbyite phase of the (InxGa1–x)2O3 film grows when x ≥ 0.8. When 0.2 ≤ x < 0.8, a mixed β-phase and bixbyite phase coexist. The evolution of electronic structures of the (InxGa1–x)2O3 films was examined by high-resolution X-ray photoemission spectroscopy (XPS) and optical absorption spectroscopy. For the β-phase films, the optical band gaps decrease from 4.96 eV for Ga2O3 to 4.43 eV for x = 0.4, while for bixbyite (InxGa1–x)2O3, the optical band gaps slightly increase from 3.57 eV for In2O3 to 3.70 eV for x = 0.8. Detailed electronic structure study indicates that the decrease of band gaps of (InxGa1–x)2O3 with an increase of In content mainly results from the upper movement of the valence band edge because the shallow In 4d orbitals introduce a hybridized state with O 2p at the top of the valence band. In addition, the presence of surface electron accumulation (i.e., downward band bending) was identified at the surface region of the (InxGa1–x)2O3 films with x ≥ 0.6, which would provide an opportunity to modulate the surface electronic properties for device applications.

Influence of catalase encapsulation on Cobalt@Nanoporous carbon with multiwall shell for supercapacitor and polyurethane synthesis using carbon dioxide

Enzyme encapsulated ZIFs exhibit significant host–guest synergism and protect the relative activity of the enzymes. Elucidation of metallic active sites including the nature of electronics and valance state has been forefront in energy conversion studies supported by high-resolution transmission electron microscopy and synchrotron X-ray absorption fine structure (XAFS) spectrogram. Here, we access metallic cobalt (Co) sites that were set by pyrolysis of catalase encapsulated ZIF-67 (cat@ZIF-67) at a high temperature (700 °C) to obtain cat@ZIF-67-NC. The local environment of Co-sites from X-ray photoelectron spectroscopic (XPS) and extended X-ray absorption fine structure (EXAFS) analysis suggests the presence of Co sites in a metallic valance state. HR-TEM and STEM analysis further revealed the Co particles encapsulated with multiwall shell morphology as support. An activity reversal is witnessed, where cat@ZIF-67-NC exhibited higher activity in CO2-cycloaddition-polymerization but was found weaker in capacitance than ZIF-67-NC for 3-electrode supercapacitor applications. The ZIF-67-NC has exhibited maximum Cs of 223 F/g at a scan rate of 5 mV/s, which retained about 87 F/g on increasing scan rate to 200 mV/s, in contrast to cat@ZIF-67-NC with a Cs value of 133.4 F/g at 5 mV/s with improved retention (58 % at 200 mV/s). The contrasting nature of cat-ZIF-67-NC and ZIF-67-NC in supercapacitor and CO2 cycloaddition-polymerization originates from encapsulated catalase in ZIF-67 based on XPS and EXAFS analysis. The electronic configuration and surface composition analysis using EXAFS and XPS techniques revealed the presence of metallic Co-sites responsible for supercapacitor and CO2-cycloaddition-polymerization. An influence of encapsulated catalase is evident in a decrease in the capacitance for cat@ZIF-67-NC due to metallic Co-sites. Co-sites in cat-ZIF-67-NC are more active in producing polyurethane by a non-isocyanate route via CO2-cycloaddition.

Application of MgF2 as a new sorbent for preconcentration and isolation of sulphur in food samples before the determination by molecular absorption spectrometry

This study proposes, for the first time, the development of an analytical method using the new sorbent - magnesium fluoride (MgF2) and ultrasound-assisted dispersive micro solid-phase extraction (UA DMSPE) for accurate preconcentration and isolation of sulphur in food samples. The further determination was conducted with high-resolution continuum source electrothermal molecular absorption spectrometry (HR-CS ET MAS). The main UA DMSPE parameters were investigated. Satisfying extraction efficiencies were obtained using 10 mL of sample solution, 20 mg of MgF2 and 20 s extraction time. The limit of detection and the preconcentration factor were 0.001 μg mL−1 and 18, respectively, and no matrix effect was observed. The relative standard deviation (RSD) was 2–13%. The proposed method was applied, inter alia, to corn flakes and flour, dried raisins and goji berries as well as different types of tea leaves. The accuracy of the developed method was evaluated by analysis of certified reference materials: mixed polish herbs (INCT-MPH-2), soya bean flour (INCT-SBF-4), tea leaves (INCT-TL-1), wheat (NCS ZC73009) and corn (NCS ZC73010). Sulphur concentrations determined in these materials were in satisfactory agreement with the certified values (recoveries in the range of 94% to 101%).

Operando High Energy Resolution Fluorescence Detected (HERFD) X-Ray Absorption Spectroscopic Study of Toyota Mirai Gen.1 Catalysts

The development of proton exchange membrane fuel cells (PEMFCs) have received increasing attention for its potential to get rid of dependence on fossil fuels and curb carbon emissions. However, the application of PEMFC has been limited by the consumption of platinum due to the sluggish kinetics of the cathode reaction and limiting platinum resources. It is well-known that the oxygen species generated on the Pt surface hiders ORR reaction at high potential region. Therefore, it is very important to evaluate the interaction between the oxygen species and the catalyst based on the electronic structure. However, the differences in XAFS spectra due to the presence of oxygen species are relatively small, and conventional detection methods, such as transmittance and total fluorescence yield, have difficulty distinguishing differences in electronic structure because the fine structure of the spectra is filled in by the lifetime width of the Pt 2p 3/2 core hole. In contrast, the new high-energy-resolution fluorescence-detection X-ray absorption spectroscopy (HERFD-XAS) monochromatized fluorescence lines (e.g., Pt Lα1), which are broadened only by Pt 3d 5/2 (~2.4 eV) rather than by Pt 2p 3/2 (~5.2 eV) core hole lifetime, are used to monitor core High-resolution X-ray absorption spectra with extended hole lifetimes can now be extracted. The present study covers conventional platinum catalysts supported on Vulcan carbon and TOYOTA MIRAI Gen.1 catalysts. The HERFD-XAS method was applied to elucidate the cause of the superior electrochemical properties of the TOYOTA MIRAI Gen.1 catalyst. o perando Pt LIII edge HERFD-XAS measurements were performed on Pt/C and TOYOTA MIRAI Gen.1 catalysts under oxygen reduction conditions, and the high energy resolution revealed the interaction of oxygen species with the Pt surface.Pt/C (29.1 wt %; TEC10V30E, average particle size of 3 nm, observed by TEM) catalyst was purchased from TKK Co. Ltd., Japan. The Pt/C catalyst ink contained water and 2-propanol in a 3:2 ratio (99.99%, FUJIFILM Wako Pure Chemical Corporation, Japan), and the amount of Pt/C was adjusted to form a 20 μg carbon cm–2 catalyst layer after dropping 10 μL on a glassy carbon RDE (GC RDE, HOKUTO DENKO, Japan; 0.196 cm2 area). TOYOTA MIRAI Gen.1 catalyst was also prepared by the above-mentioned preparation method. operando XAS measurements for Pt LΙΙΙ-edge of the catalysts were carried out at BL39XU of SPring-8, Hyogo, Japan. Prior to the experiments, the samples were electrochemically cleaned by CV in the range 0.0–1.1 V (vs. RHE). The electrode potential was swept cathodically from 0.5 to 1.1 V (vs. RHE).Figure 1 shows the results for in situ HERFD-XAS spectra of Pt and MIRAI Gen.1 catalyst. For both samples, the white line intensity changes depending on the adsorption conditions. The obtained HERFD-XAS spectra were decomposed into oxidized (Pt-OH) and reduced (Pt metal) components. The ratio of the peak area intensity of the two components is proportional to the surface coverage assuming similar charge transfer among the catalysts. It is noted that enhancement of oxidation is significantly suppressed on MIRAI Gen.1 catalysts. Figure 1. operando HERFD-XAS spectra for (a) TOYOTA MIRAI Gen.1 catalyst. (b) Pt/C (TEC10V30E) Acknowledgement This work was supported by a NEDO FC-Platform project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

A new class of variable-radii diffraction optics for high-resolution x-ray spectroscopy at the National Ignition Facility (invited).

A new class of crystal shapes has been developed for x-ray spectroscopy of point-like or small (a few mm) emission sources. These optics allow for dramatic improvement in both achievable energy resolution and total throughput of the spectrometer as compared with traditional designs. This class of crystal shapes, collectively referred to as the Variable-Radii Spiral (VR-Spiral), utilize crystal shapes in which both the major and minor radii are variable. A crystal using this novel VR-Spiral shape has now been fabricated for high-resolution Extended X-ray Absorption Fine Structure (EXAFS) experiments targeting the Pb-L3 (13.0keV) absorption edge at the National Ignition Facility. The performance of this crystal has been characterized in the laboratory using a microfocus x-ray source, showing that high-resolution high-throughput EXAFS spectra can be acquired using this geometry. Importantly, these successful tests show that the complex three-dimensional crystal shape is manufacturable with the required precision needed to realize the expected performance of better than 5eV energy resolution while using a 30mm high crystal. An improved generalized mathematical form for VR-Spiral shapes is also presented allowing improved optimization as compared to the first sinusoidal-spiral based design. This new formulation allows VR-Spiral spectrometers to be designed at any magnification with optimized energy resolution at all energies within the spectrometer bandwidth.

Vibrational Structure of a High-Resolution UV Absorption Spectrum of Methyl Vinyl Ketone in the Gas Phase

Vibrational Structure of a High-Resolution UV Absorption Spectrum of Methyl Vinyl Ketone in the Gas Phase

Determination of metallic elements in foods for enteral nutrition of chronic renal patients by atomic absorption spectrometry after extraction induced by emulsion breaking

This article describes the analysis of aluminum (Al), cadmium (Cd), copper (Cu), molybdenum (Mo), and lead (Pb) in foods for enteral nutrition of chronic renal patients by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) after extraction induced by emulsion breaking. The following wavelengths were used for the detection of analytes 309.2713 nm for Al, 228.8018 nm for Cd, 324.7540 nm for Cu, 313.2594 nm for Mo, and 217.0005 nm for Pb. The detection limits for the methods were 0.022 mg kg−1 for Al, 0.0003 mg kg−1 for Cd, 0.001 mg kg−1 for Cu, 0.009 mg kg−1 for Mo, and 0.002 mg kg−1 for Pb. The precision ranged from 7.3% to 7.8%, 5.1% to 6.3%, 2.5% to 3.8%, 2.8% to 3.4%, and 6.2% to 7.3% for Al, Cd, Cu, Mo, and Pb, respectively. The accuracy of the method was evaluated through recovery tests, which ranged from 92.2% for Cd to 107.2% for Al. Cadmium concentrations in analyzed samples are below the limit allowed by Brazilian legislation (0.01 mg kg−1). However, two samples presented Pb concentration (samples 4 and 5) above the allowed limit (0.01 mg kg−1). Furthermore, all samples analyzed in this work showed relatively considerable quantities of Al (0.72–1.66 mg kg−1), and the concentrations of Cu (samples 3 and 4) and Mo (samples 1 and 5) were obtained were higher than those presented by the manufacturers. The proposed methods for the quantitative determination of the analytes of interest by HR-CS GFAAS after extraction induced by emulsion breaking in foods for enteral nutrition of chronic renal patients proved to be simple, fast, and efficient.

A laser-absorption sensor for in situ detection of biofuel blend vapor in engine intakes

A novel, mid-infrared laser-absorption sensor was developed for measurements of biofuel blend (E85) vapor in the intake runner of a single-cylinder internal combustion engine. The sensor used two mid-infrared interband cascade lasers to target a region of strong E85 absorbance near 3.35 µm. The lasers were co-aligned and fiber-coupled into the engine, and a two-color, online-offline differential absorption strategy was used to provide sensitive measurements of E85 vapor mole fraction and reject interference due to beam-steering and fuel droplet spray. An intensity-modulation spectroscopy (IMS) sensing scheme was employed to reject low-frequency additive noise and allow for frequency-domain multiplexing of the two lasers. High-resolution E85 absorption cross-section measurements were conducted in a static cell at a range of intake-relevant conditions. Validation experiments were performed in a laboratory setting to demonstrate sensor accuracy and noise rejection capability. The sensor was deployed on a single-cylinder development engine during dynamometer testing to provide time-resolved E85 vapor mole fraction measurements at a measurement rate of 40 kS/s, which corresponds to one measurement per crank angle degree at 6700 rpm. Time-resolved and average sensor measurements provide key performance insights for the development of intake systems in high-performance internal combustion engines.

Low-J Transitions in Band of Buffer-gas-cooled CaOH

Calcium monohydroxide radical (CaOH) is receiving an increasing amount of attention from the astrophysics community as it is expected to be present in the atmospheres of hot rocky super-Earth exoplanets as well as interstellar and circumstellar environments. Here, we report the high-resolution laboratory absorption spectroscopy on low-J transitions in band of buffer-gas-cooled CaOH. In total, 40 transitions out of the low-J states were assigned, including 27 transitions that have not been reported in previous literature. The determined rotational constants for both ground and excited states are in excellent agreement with previous literature, and the measurement uncertainty for the absolute transition frequencies was improved by more than a factor of 3. This will aid future interstellar, circumstellar, and atmospheric identifications of CaOH. The buffer-gas-cooling method employed here is a particularly powerful method to probe low-J transitions and is easily applicable to other astrophysical molecules.

Determination of Silver in Environmental Samples by High-resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry after Preconcentration on Bentonite

Determination of Silver in Environmental Samples by High-resolution Continuum Source Graphite Furnace Atomic Absorption Spectrometry after Preconcentration on Bentonite