Absorption Spectroscopy Techniques Research Articles

Development and validation of Graphite Furnace Atomic Absorption Spectrometry method and its application for clinical evaluation of blood lead levels among occupationally exposed lead smelting plant workers.

The growing interest in estimating the blood lead levels, for early detection of lead exposure, warranted a need for a validated analytical method for trace levels estimation of lead. The present study aimed to develop an analytical method for detecting trace amounts to elevated levels of lead in human blood using the Graphite Furnace Atomic Absorption Spectrometry technique and its application in evaluating blood lead levels among occupationally exposed individuals. The method validation was performed with standard test parameters including linearity, recovery, precision, method detection limit, and limit of quantification. The validation results for each performance parameter were in agreement with acceptable criteria as per standard guidelines. The correlation was observed as optimum linear (R2 = 0.998) between absorbance and lead concentration range from 0 to 10µg/dL. The recoveries for spiked samples ranged between 95 and 105%. The calculated value for the method detection limit was 0.16µg/dL and the limit of quantification was 0.51µg/dL. The precision for all spiked concentrations was below 10% of the relative standard deviation. Evaluation of lead exposure among occupationally exposed individuals revealed the study population had found average blood lead level (42.80 ± 12.47µg/dL), which was above the upper acceptable limit suggested by Occupational Safety and Health Administration, USA. The majority of system-specific symptoms were observed among study groups having mean blood lead levels above 40µg/dL. However, sociodemographic status and employment factors were found possible determinants of the prevalence of high blood lead levels.

Comparison of Digestion Methods Using Atomic Absorption Spectrometry for the Determination of Metal Levels in Plants

Trace metal elements (TMEs) are among the most important types of pollutants in the environment. Therefore, a precise determination of these contaminants in several environmental components is required for the safety assurance of living organisms. Spectroscopic analysis is an efficient technique employed to detect and determine TME contents in numerous samples. Hence, to achieve reliable and accurate results when using spectroscopic analysis, samples should be carefully prepared. In the present study, the comparison of eight digestion methods of five vegetal samples was carried out to quantify Cd, Mn, Al and Mg contents using the atomic absorption spectroscopy technique. According to the extraction techniques used in this study, results showed an outstanding difference in TME levels determined in the same vegetal sample. The results obtained indicated that the highest Mn concentrations were recorded when using the mixture of HNO3-HClO4 in the studied species: atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279 compared to all other methods. Regarding the extraction of Cd, our results showed that heated extraction using different acids (HNO3-H2SO4-HClO4, HCl-HNO3, HNO3-HClO4, HNO3-H2SO4, HNO3-HCl-HClO4 and HNO3-HCl-H2SO4) was the most efficient in atriplex portulacoides, arthrocnemum indicum, olea europaea BCR-62, ulva lactuca and ulva lactuca BCR-279. Similarly, these heated acid digestion techniques (efficient for Cd) showed the highest levels of Al in atriplex portulacoides and arthrocnemum indicum. However, for the Mg extraction, our results revealed that the effectiveness of the method used depended on the plant species studied. Regarding these findings, the efficiency of metal quantification by AAS depends on the digestion procedure, the metallic ion to determine and the plant species.

Performance of micro-beam X-ray absorption spectroscopy at beamline 7.2W of Synchrotron Light Research Institute

Performance of micro-beam X-ray absorption spectroscopy at beamline 7.2W of Synchrotron Light Research Institute

Lidar sounding of carbon dioxide and water vapor with absorption spectroscopy techniques

A possibility of monitoring greenhouse gases (CO2 and H2O) along horizontal paths in the troposphere with two-channel near-IR lidar system based on an absorption spectroscopy measurement technique is estimated. The main units and components of the IR lidar under development are described. A backscattered signal is simulated in the informative range of IR lidar for sensing target greenhouse gases.

Retrieval and Regional Distribution Analysis of Ammonia, Sulfur Dioxide and Nitrogen Dioxide in the Urban Environment Using Ultraviolet DOAS Algorithm

Aiming at the in situ and mobile observation of urban environmental air pollution, a portable instrument using ultraviolet spectrum retrieval algorithm was developed based on the basis of Differential Optical Absorption Spectroscopy (DOAS) and multiple-pass cell technique. Typical trace gas pollutants, NH3, SO2, and NO2, were explored using their optical spectral characteristics in deep ultraviolet wavelength range from 210 to 215 nm. The gas concentration was retrieved by Lambert-Beer's law and nonlinear least square method. With an optimized optical alignment, the detection limits of NH3, SO2, NO2 were estimated to be 2.2, 2.3, and 36.2 ppb, respectively. The system was used in carrying out some cruise observations in Chengdu, China. During the entire period, the polluted gases showed varied distribution and typical daily average concentrations of NH3, SO2, NO2 were 23.2, 3.5, and 106.0 ppb, respectively. The contributions from different sources were analyzed combined with the HYSPLIT model. Results show that the portable DOAS system is a convenient and effective tool for regional distribution measurement and pollution source monitoring.

Effect of substrate on interfacial electronic properties of ferrocene thin films

Effect of substrate on interfacial electronic properties of ferrocene thin films

In situ grown high-valence Mo-doped NiCo Prussian blue analogue for enhanced urea electrooxidation.

Mo-doped NiCo Prussian blue analogue (PBA) electrocatalysts self-supported on Ni foam are elaborately designed, which exhibit a low potential of 1.358 V (vs. RHE) to reach 100 mA cm-2 for catalyzing the urea oxidation reaction (UOR). The incorporation of high-valence Mo (+6) modifies the electronic structure and improves the electron transfer ability. Using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) techniques, we confirm the effect of Mo doping on the NiCo PBA electronic structure.

A near infrared H2S leakage detection system based on WDO-ELM using a digital lock-in amplifier combined with discrete wavelet transform filter

A near infrared H2S leakage detection system based on WDO-ELM using a digital lock-in amplifier combined with discrete wavelet transform filter

Beta decay along the N=Z line and its relevance in rp-process and X-Ray bursts

Nucleosynthesis in Type I X-ray bursts (XRB) proceeds eventually through the rp-process near the proton drip-line. Several N=Z nuclei act as waiting points in the reaction network chain. Astrophysical calculations of XRB light curves depend upon the theoretical modelling of the beta decays of interest, with the N=Z waiting points 64Ge, 68Se, 72Kr, 76Sr, and their second-neighbours N=Z+2 being key nuclei in this context. We have carried out different experimental campaigns at ISOLDE (CERN) to determine the B(GT) distributions, in the decay of several N=Z, N=Z+2 and their daughters, of particular relevance in rp-process calculations. To this aim the Total Absorption Spectroscopy technique is applied. Here we present results on the beta decay of 64Ga and the status of the analysis of 64Ge. Our results provide benchmarks for testing and constraining models under terrestrial conditions that can be used later for predictions in stellar environments.

Optimization of beam arrangement for tunable diode laser absorption tomography reconstruction based on fractional Tikhonov regularization

Beam arrangement with limited projections based on tunable diode laser absorption spectroscopy is the key to achieving a more accurate two-dimensional reconstruction of the combustion. Using fractional calculus theory, a beam optimization method based on fractional Tikhonov regularization is proposed. The beam arrangement function based on fractional Tikhonov regularization is established by extending the standard Tikhonov regularization to fractional modes. The genetic algorithm is used to analyze the calculation results of different orders in a range of (0, 1), and the beam arrangement is obtained. Using 20 laser beams to scan the characteristic absorption spectrum of H<sub>2</sub>O in the near-infrared band 7185.6 cm<sup>–1</sup>, modeling the calculations in a 10×10 element discrete tomography domain, and comparing the reconstruction results of the five beam arrangements for different Gaussian distribution models, the beam arrangement based on fractional Tikhonov regularization shows more obvious advantages. This design method proposed in this work is valuable for the theoretical study of the optimal design of two-dimensional measurement beams based on the tunable diode laser absorption spectroscopy technique, which can promote the application of this technique in the two-dimensional reconstruction of complex engine combustion and combustion efficiency improvement.

Noise Immune Absorption Profile Extraction for the TDLAS Thermometry Sensor by Using an FMCW Interferometer

Tunable diode laser absorption spectroscopy techniques usually utilize direct absorption spectroscopy (DAS) to measure absorbance profiles for temperature measurements. The DAS method is sensitive to thermal noises and fails to work in harsh application cases. A noise immune method is proposed for robust temperature measurement by using coherent detection and retroflected optical alignment. The absorption spectrum is shifted to a high-frequency band of MHz level away from ambient noises. The optical alignment suppresses thermal radiations along the laser path. Gas temperatures were measured in cases of both laboratory and porotype setup of aeroengine, i.e., the steady and the harsh states. Transition lines of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O at 7182.94 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , 7185.59 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , and 7444.35 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> were selected for performance evaluations of target molecules, i.e., of water vapor. Performance comparisons were made with the DAS method for temperature detection. In a steady-state case, standard deviations of the proposed method were below 0.9 K at SNR of 25 dB, while those of the DAS method were above 3.9 K. In an onsite harsh application case, the fluctuations of path-averaged temperatures obtained by the proposed method were also smaller. The coherent detection and retroflected alignment enable better performance in hostile cases.

High precision measurement of spectroscopic parameters of H&lt;sub&gt;2&lt;/sub&gt;S in 6320—6350 cm&lt;sup&gt;–1&lt;/sup&gt; band

As a highly corrosive and highly toxic gas, hydrogen sulfide (H&lt;sub&gt;2&lt;/sub&gt;S) is an important intermediate product or pollutant in many fields such as chemical industry, energy and environment. Accurate online measurement of its concentration is of great significance for process control and production safety. Tunable diode laser absorption spectroscopy (TDLAS), as a quantitative absorption spectroscopy technique, is suitable for high-precision on-line measurement of H&lt;sub&gt;2&lt;/sub&gt;S concentration in atmospheric environmental monitoring and industrial processes control. Considering that most of the spectroscopic parameters of H&lt;sub&gt;2&lt;/sub&gt;S in the HITRAN2020 database are mainly calculated based on semi-empirical theoretical model and the experimental data to support them are lacking. In this work, direct absorption spectroscopy (DAS) method is firstly used to measure the absorption spectra of H&lt;sub&gt;2&lt;/sub&gt;S in the band of 6320–6350 cm&lt;sup&gt;–1&lt;/sup&gt;. Six groups of characteristic lines with strong absorption and relative independence are selected as the target transitions for experimental measurement. Then, the wavelength modulation-direct absorption (WM-DAS) method with no calibration and high signal-to-noise ratio is used to measure the absorbances of the six groups of transitions under different pressures. Voigt, Raution and quadratic speed-dependent Voigt profiles fit the measured absorbances by least squares method in order to obtain the spectroscopic parameters such as the collision broadening coefficient, line strength and Dicke narrowing coefficient. And the minimum standard deviation of residual error of absorbances is 7×10&lt;sup&gt;–5&lt;/sup&gt;. The measurement uncertainty of each line strength is less than 2%, and the uncertainty of collision broadening coefficients, Dicke narrowing coefficients and the speed-dependent coefficients are all less than 10%. This work is helpful in improving the H&lt;sub&gt;2&lt;/sub&gt;S spectral database and providing the spectral data basis for the high-precision measurement of H&lt;sub&gt;2&lt;/sub&gt;S concentration.

Determination of Heavy Metals in Cocoa Products Consumed in Nairobi County Kenya

Cocoa is an important cash crop obtained from the beans of the Theobroma cacao tree belonging to the family Malvaceae. Its products are rich in several classes of phenolic compounds such as Flavanols, procyanidins, and anthocyanins. These compounds are attributed to copious health benefits. In addition to the bioactive compounds, cocoa contains heavy metals whose origin and levels depend on natural and anthropogenic activities. Beyond permissible limits, these metals are linked to deleterious damage to several systems in the human body. This study aims to determine the concentration of some heavy metals in Cocoa products and compare the levels with the permissible exposure limits stipulated by international health agencies. This was achieved by wet digestion of the strategically sampled cocoa products and their analysis using the atomic absorption spectrometry technique. The average concentration of Lead (Pb), Copper (Cu), Zinc (Zn), and Manganese (Mn) in cocoa powder was 0.154±0.021, 0.270±0.037, 0.794±0.063, and 0.334±0.015 respectively. The average concentration of Pb, Cu, Zn, and Mn in cocoa butter was 0.329±0.008, 0.028±0.038, 0.116±0.075, and 0.124±0.008 respectively. The average concentration of Pb, Cu, Zn, and Mn in chocolate milk was 0.463±0.003, 0.042±0.066, 0.296±0.015, and 0.162±0.010 respectively. Cadmium levels were below the detection limit in all the samples. The results obtained in all the samples were within the WHO and KEBS permissible levels in food products.

A Green Product Using Selective Compound for Susceptible Assessment of Copper in Blood Serum

A highly reliable approach for assessment of copper(II) in blood serum samples using an organic molecule 4-(3-hydroxyphenylazo)resorcinol, 4-HAR was developed. The paper presents the synthesis of 4-HAR, which serves as probe for definite species. 4-HAR was characterized with the FT-IR, UV-visible, 1H-NMR, 13C-NMR and mass analysis, thermal TG and DSC techniques. After examining its interactions with more than twenty-five metal ions, it was found that 4-HAR showed reaction only with copper(II), giving a distinct green color at λmax 603 nm. Experimental conditions for the reaction of 4-HAR with copper(II) were optimized. A calibration curve was created and the exhibition range of concentration obeyed Beer's Law from 0.30 to 16 μg.mL-1 with correlation coefficient of r = 0.9986, and value of the molar absorption coefficient, ε, being 3314 L.mol- 1.cm-1. The analytical method was used to determine copper(II) levels in several blood serum samples. The amounts of copper(II) found in the sera samples were compared with flame atomic absorption spectrometry technique, and the results were found to be highly reliable. Based on validation, the new approach can be utilized for assurance quality purposes with a high degree of confidence.

Synthesis of Stereoregular Uniform Oligomers Possessing a Dense 1,2,3-Triazole Backbone

Recent remarkable progress of precision polymerization techniques has allowed researchers to synthesize polymers of controlled molecular weight, tacticity, and monomer sequence with narrow distributions. However, it is still a challenging subject to synthesize uniform polymers and oligomers, which possess specific molecular weight, tacticity, and monomer sequence. Utilizing the advantages of t-butyl 4-azido-5-hexynoate (tBuAH), which we designed recently, for the synthesis of uniform polymers and oligomers, uniform oligomers of different stereoregularities possessing a dense 1,2,3-triazole backbone were synthesized using optically active tBuAH precursors by iterative procedures containing azidation, deprotection of the protecting group, and copper(I)-catalyzed azide–alkyne cycloaddition (CuAAC). The stereoregular uniform oligomers were characterized in the solid state by powder X-ray diffraction (PXRD) and in the solution state by pulse-field-gradient spin-echo (PGSE) NMR, ultraviolet (UV) absorption, and circular dichroism (CD) spectroscopic techniques. While the solubility of stereoregular uniform oligomers was investigated using common organic solvents, gelation was observed for solutions of two octamers of different stereoregularities in some solvents, e.g., toluene, tetrahydrofuran (THF), acetone, and methanol. It is noteworthy that the intermolecular attractive interaction depended on the stereoregularity in aprotic polar solvents, i.e., THF and acetone, presumably because of the different polarities of octamers.

Characterization of Binding Properties of Cr(Phen)3 3+ and Ru(Phen)3 2+ Complexes with Human Lactoferrin.

This work presents research about [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ interaction with human lactoferrin (HLf), a key carrier protein of ferric cations. The photochemical and photophysical properties of [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ have been widely studied in the last decades due to their potential use as photosensitizers in photodynamic therapy (PDT). The behavior between the complexes and the protein was studied employing UV-visible absorption, fluorescence emission and circular dichroism spectroscopic techniques. It was found that both complexes bind to HLf with a large binding constant (Kb ): 9.46 × 104 for the chromium complex and 4.16 × 104 for the ruthenium one at 299 K. Thermodynamic parameters were obtained from the Van't Hoff equation. Analyses of entropy (ΔS), enthalpy (ΔH) and free energy changes (ΔG) indicate that these complexes bind to HLf because of entropy-driven processes and electrostatic interactions. According to circular dichroism experiments, no conformational changes have been observed in the secondary and tertiary structure of the protein in the presence of any of the studied complexes. These experimental results suggest that [Cr(phen)3 ]3+ and [Ru(phen)3 ]2+ bind to HLf, indicating that this protein could act as a carrier of these complexes in further applications.

Cis-difunctionalized 21-telluraporphyrin building blocks and their use in the synthesis of (BODIPY)2-telluraporphyrin triad

A series of cis-difunctionalized 21-telluraporphyrins containing two functionalized meso-aryl groups such as [Formula: see text]-iodophenyl, [Formula: see text]-bromophenyl, [Formula: see text]-cyanophenyl, [Formula: see text]-nitrophenyl and [Formula: see text]-trimethylsilyl ethynylphenyl groups in cis-fashion were synthesized by condensing one equivalent of 16-telluratripyrrin with two equivalents of functionalized benzaldehyde and three equivalents of pyrrole in CH2Cl2 under acid catalyzed porphyrin forming conditions. The cis-difunctionalized 21-telluraporphyrins were thoroughly characterized by HR-MS, 1D and 2D NMR, and absorption spectroscopic techniques. To show the use of cis-difunctionalized 21-telluraporphyrin building blocks, the covalently linked (BODIPY)2-telluraporphyrin triad was synthesized by coupling cis-diiodophenyl 21-telluraporphyrin with meso-ethynylphenyl BODIPY under Pd(0) coupling conditions and afforded (BODIPY)2-telluraporphyrin triad in 24% yield. The NMR and absorption studies of the triad indicated that the telluraporphyrin and BODIPY moieties interact weakly in the (BODIPY)2-telluraporphyrin triad and retain their individual characteristic features. The steady-state fluorescence and DFT studies indicated a possibility of charge transfer between 21-telluraporphyrin and BODIPY units in the triad.

XANES Studies of Zinc Tin Oxide Films Deposited by Atomic Layer Deposition: Revealing Process-Structure Relationships for Amorphous Oxide Semiconductors

Amorphous oxide semiconductors have grown in technological relevance in displays, information technology, energy, and catalysis. Recent research efforts have converged on the need to develop design principles for the electronic structure of these materials. Here, we systematically vary the cation composition and annealing temperatures of zinc tin oxide films using atomic layer deposition (ALD) and study their process-structure relationships with synchrotron X-ray absorption near-edge spectroscopy (XANES). Measurements of the O K-edge, Sn M-edge, and Zn L-edge are analyzed with ab initio and nonlinear statistical modeling to understand the changes in geometric and electronic structure of the films. A key finding from this approach is the ability to measure the changes in the relative contribution of the Zn and Sn s orbitals to the density of states near the conduction band minimum. Furthermore, we identify and delineate critical process-structure design principles when working with amorphous oxide semiconductor (AOS) material systems: (1) use of complementary diffraction and absorption spectroscopy techniques to characterize the as-deposited coordination environment; (2) accounting for gradual and abrupt changes in coordination environment as a function of processing parameters (stoichiometry, annealing, etc.); (3) revealing and exploiting the relevant knowledge and interdependence of coordination environments, orbital hybridizations, the density of states, and band structures. In the future, this multimodal X-ray analysis and modeling framework can be applied to understand the process-structure relationships needed to optimize AOS performance in devices.

Temperature‐dependent kinetics of the reactions of CH2OO with acetone, biacetyl, and acetylacetone

AbstractTemperature‐dependent rate constants for the reactions of CH2OO with acetone (Ac), biacetyl (BiAc), and acetylacetone (AcAc) have been measured over the range 275–335 K using a flash photolysis, transient absorption spectroscopy technique. The measurements were performed at a total pressure of ∼80 Torr in N2 bath gas, which corresponds to the high‐pressure limit for these reactions. All three reactions show linear Arrhenius plots with negative temperature dependences. Rate constants increase in the order Ac &lt; AcAc « BiAc across the temperature range; at 295 K the rate constants are kAc = (4.8 ± 0.4) × 10–13 cm3 s–1, kAcAc = (8.0 ± 0.7) × 10–13 cm3 s–1, and kBiAc = (1.10 ± 0.09) × 10–11 cm3 s–1. Sensitivity to temperature, characterized by the magnitude of the negative activation energy, increases in the order AcAc &lt; BiAc &lt; Ac (Ea/R values of –1830 ± 170 K, –1260 ± 170 K, and –460 ± 180 K, respectively). CBS‐QB3 calculations show that the Ac and BiAc reactions proceed via formation of an entrance channel complex followed by 1,3‐dipolar cycloaddition to form secondary ozonide products via a submerged transition state. For the BiAc reaction, the rate limiting step appears to be rearrangement of a long‐range van der Waals complex into the short‐range complex that subsequently leads directly to the cycloaddition transition state with a very low energy barrier. The calculations show that two reaction pathways are competitive for AcAc with nearly identical transition state free energies (ΔG° = +10.1 kcal mol–1 at 298 K) found for cycloaddition at the C=O and at the C=C site of the dominant enolone tautomer. The weak temperature dependence observed is likely due to competition between these pathways.

Synthesis, crystal structure, and chromotropism properties of Dihalo N-2-ethanolpicolylamine copper(II)

Synthesis, crystal structure, and chromotropism properties of Dihalo N-2-ethanolpicolylamine copper(II)