Search

The use of mid-fi eld infrared spectroscopy in combination with chemometric algorithms for the identifi cation of cephalosporin antibiotics in the form of injectable powders is demonstrated. III generation cephalosporins have been selected as objects of the study: ceftriaxone, ceftazidime, cefotaxime, which are widely used in pharmaceutical practice. IR spectra of the medical preparations have been recorded using an FT-801 Fourier transform IR spectrometer with an attenuated total refl ection (ATR) attachment. The results have been processed in the Microsoft Excel computer package with the XLSTAT add-in using the principal component analysis (PCA), the k-means method and agglomerative hierarchical clustering (AНC). It has been shown that using these algorithms it is possible to identify the studied cephalosporin antibiotics from diff erent manufacturers. In the PCA method, points corresponding to samples are located in separate quadrants depending on the nature of the antibiotic. The k-means method has been used to divide antibiotics into classes; diff erences are also visible in the classes themselves, depending on the manufacturer. The clearest separation of cephalosporins is observed when data are presented using the AHC method in the form of a dendrogram.

Bound states in the continuum (BICs) are localized electromagnetic modes within the continuous spectrum of radiating waves. Due to their infinite lifetimes without radiation losses, BICs are driving research directions in lasing, non‐linear optical processes, and sensing. However, conventional methods for converting BICs into leaky resonances, or quasi‐BICs, with high‐quality factors typically rely on breaking the in‐plane inversion symmetry of the metasurface and often result in resonances that are strongly dependent on the angle of the incident light, making them unsuitable for many practical applications. Here, an emerging class of BIC‐driven metasurfaces is numerically analyzed and experimentally demonstrated, where the coupling to the far field is controlled by the displacement of individual resonators. In particular, both all‐dielectric and metallic as well as positive and inverse displacement‐mediated metasurfaces sustaining angular‐robust quasi‐BICs are investigated in the mid‐infrared spectral region. Their optical behavior with regard to changes in the angle of incidence is investigated and experimentally shows their superior performance compared to two conventional alternatives: silicon‐based tilted ellipses and cylindrical nanoholes in gold. These findings are anticipated to open exciting perspectives for bio‐sensing, conformal optical devices, and photonic devices using focused light. [ABSTRACT FROM AUTHOR]

We propose that the observed enrichment of sulfur at the surface of Mercury (up to 4 wt.%) is the product of silicate sulfidation reactions with a S‐rich reduced volcanogenic gas phase. Here, we present new experiments on the sulfidation behavior of olivine, diopside, and anorthite. We investigate these reaction products, and those of sulfidized glasses with Mercury compositions previously reported, by mid‐IR reflectance spectroscopy. We investigate both the reacted bulk materials as powders as well as cross‐sections of the reaction products by in situ micro‐IR spectroscopy. The mid‐IR spectra confirm the presence of predicted reaction products including quartz. The mid‐IR reflectance of sulfide reaction products, such as CaS (oldhamite) or MgS (niningerite), is insufficient to be observed in the complex run products. However, the ESA/JAXA BepiColombo mission to Mercury will be able to test our hypothesis by investigating the correlated abundances of sulfides with other reaction products such as quartz. Plain Language Summary: The surface of the planet Mercury is enriched in sulfur, with abundances of up to 4 wt.%. Sulfur on Mercury has previously been interpreted to occur in magmatic sulfide phases. We propose an alternative mechanism for the enrichment of S on Mercury, whereby reduced S‐rich gases react with silicate minerals to form sulfides and quartz. We carried out sulfidation experiments on silicate minerals and glasses and used mid‐infrared spectroscopy to characterize the products of these reactions. The upcoming ESA/JAXA BepiColombo mission to Mercury will allow us to test the sulfidation hypothesis and provide constraints on the origin of the S enrichment on the planet's surface. Key Points: S‐enrichment on the surface of Mercury by sulfidation of silicate mineralsMid‐IR spectroscopy allows the identification of quartz as a main reaction product in mineral and glass sulfidationBepiColombo's Mercury Radiometer and Thermal Infrared Spectrometer instrument will test the sulfidation hypothesis by mapping the surface of Mercury in the mid‐IR spectral range [ABSTRACT FROM AUTHOR]

In this work the study of the green pigments employed by ancient Romans in the decoration of 50 wall fragments from buildings of different ages located in seven archaeological sites of the Augustean X Regio (Venetia et Histria) is presented. The pigments are green earths—celadonite and glauconite, the latter associated to variable amounts of smectites—as found through mid-Infrared Fourier Transform Spectroscopy and as confirmed by Principal Component Analysis. The investigation was performed in suitable spectral ranges that while accounting for all the most intense absorptions of green earths allowed to minimize the influence of absorptions due to accessory minerals in the pigment ores or to the mineral species contained in the preparatory layers of the painted fragments (carbonates, quartz, kaolinite and gypsum) and sampled with the pigment. Three commercial green pigments consisting of the minerals celadonite and glauconite were also considered to check the soundness of the approach followed for the identification of the historical pigments and the reliability of the results obtained. For the first time it is shown that Principal Component Analysis is an effective tool to confirm the results of conventional spectroscopic analysis of the two green earths celadonite and glauconite. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) originates from a complex mixture of organic materials, and to better understand its role in soil functions, one must characterise its chemical composition. However, current methods, such as solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy, are time‐consuming and expensive. Diffuse reflectance spectroscopy in the visible, near infrared and mid‐infrared regions (vis–NIR: 350–2500 nm; mid‐IR: 4000–400 cm−1) can also be used to characterise SOC chemistry; however, it is difficult to know the frequencies where the information occurs. Thus, we correlated the C functional groups from the 13C NMR to the frequencies in the vis–NIR and mid‐IR spectra using two methods: (1) 2‐dimensional correlations of 13C NMR spectra and the diffuse reflectance spectra, and (2) modelling the NMR functional C groups with the reflectance spectra using support vector machines (SVM) (validated using 5 times repeated 10‐fold cross‐validation). For the study, we used 99 mineral soils from the agricultural regions of Sweden. The results show clear correlations between organic functional C groups measured with NMR and specific frequencies in the vis–NIR and mid‐IR spectra. While the 2D correlations showed general relationships (mainly related to the total SOC content), analysing the importance of the wavelengths in the SVM models revealed more detail. Generally, models using mid‐IR spectra produced slightly better estimates than the vis–NIR. The best estimates were for the alkyl C group (R2 = 0.83 and 0.85, vis–NIR and mid‐IR, respectively), and the O/N‐alkyl C group was the most difficult to estimate (R2 = 0.34 and 0.38, vis–NIR and mid‐IR, respectively). Combining 13C NMR with the cost‐effective diffuse reflectance methods could potentially increase the number of measured samples and improve the spatial and temporal characterisation of SOC. However, more studies with a wider range of soil types and land management systems are needed to further evaluate the conditions under which these methods could be used. Highlights: Diffuse reflectance spectroscopy was used to characterise and model SOC functional chemistry.NMR derived C functional groups could be modelled with vis‐NIR and mid‐IR diffuse reflectance spectra.The methods allow for characterisation of SOC chemical composition on whole mineral soil samples.The approach can improve the spatial and temporal characterisation of SOC composition. [ABSTRACT FROM AUTHOR]

Background and Objectives: The fiber-based evanescent-wave mid-IR spectroscopy is a prospective tool for the real-time remote chemical analysis of various substances, which have their vibrational spectra in the mid-IR spectral range. Chalcogenide fibers transparent in the mid-IR are considered as the most suitable sensing elements of the fiber-based mid-IR spectroscopic sensors. Earlier, to describe light fields in a chalcogenide fiber embedded into an absorbing medium, a ray optics approach based on the approximation of weak absorption of the medium was used. However, this approach is not applicable for the mid-IR spectroscopy of liquids since the absorption coefficients of liquids in the mid-IR can be of the order of 103 cm-1. As the difference of refractive indices of a chalcogenide glass (2.4–3.4) and a liquid (1.28–1.35) is large, the weakly guiding approximation widely used to design the fiber-optic information networks is not applicable for the sensing elements modeling. Development of a reliable mathematical model of light fields in the chalcogenide sensing elements is an urgent problem. In this paper, a detailed analysis of such a mathematical model based on the electromagnetic theory of optical fibers is presented. Materials and Methods: A multimode single-index chalcogenide fiber embedded into an absorbing liquid is considered as a sensing element of a fiber-based spectroscopic sensor. For this sensing element, a model of a infinite cylindrical waveguide with a uniform core and an infinite uniform cladding with a complex-valued refractive index is proposed. To describe light fields in the sensing element, a mathematical model based on solution of a boundary value problem for Helmholtz equations in a rigorous electrodynamic formulation is developed. For classification of the boundary value problem solutions, a complex plane of a fiber mode parameter in the cladding is used. Eigenwaves obtained by solution of the boundary value problem that satisfies the condition of exponential decay in the waveguide cross-section at infinity are identified as evanescent modes of the waveguide. The power of the modes is decreasing along the waveguide due to the external absorption. In computer modeling of the evanescent modes, an eigenvalue equation written for the modes parameters is solved numerically. As an absorbing liquid, pure acetone is chosen. The absorption coefficient of acetone, obtained experimentally, is used to evaluate the imaginary part of its refractive index. Results: Specificity of the boundary value problem formulation in application to the light fields in sensing elements of the fiber-based spectroscopic sensors has been revealed. A mathematical model of evanescent modes of a chalcogenide sensing element has been elaborated by using the rigorous electrodynamic approach. This model has been applied to calculate the longitudinal and transverse power flows of the HEvm evanescent modes in the cross-section of a chalcogenide fiber immersed into the pure acetone. It was demonstrated that in the rigorous mathematical model, the transverse power flows of evanescent modes are specifically nonzero. With the given parameters of the chalcogenide sensing element and the absorbing medium, the density of the transverse components of the power flow at a specified peak wavelength of an absorption band of acetone was 3–4 orders of magnitude lower than the longitudinal component density. Conclusion: The mathematical model of light fields in chalcogenide sensing elements for the mid-IR spectroscopy has been developed with account of the large difference in the refractive indices of the chalcogenide fiber core and the external medium having large absorption coefficients. Applicability of the mathematical model based on the rigorous electrodynamic approach was confirmed previously in our works where the results of computer modeling fit the experimental data obtained in the chalcogenide fiber based spectroscopic measurements.

Acquisition of classical absorption spectra of liquids in the mid-IR range with quantum cascade lasers (QCLs) is often limited in sensitivity by noise from the laser source. Alternatively, measurement of molecular dispersion (i.e., refractive index) spectra poses an experimental approach that is immune to intensity fluctuations and further offers a direct relationship between the recorded signal and the sample concentration. In this work, we present an external cavity quantum cascade laser (EC-QCL) based Mach–Zehnder interferometer setup to determine dispersion spectra of liquid samples. We present two approaches for acquisition of refractive index spectra and compare the qualitative experimental results. Furthermore, the performance for quantitative analysis is evaluated. Finally, multivariate analysis of a spectrally complex mixture comprising three different sugars is performed. The obtained figures of merit by partial least squares (PLS) regression modelling compare well with standard absorption spectroscopy, demonstrating the potential of the introduced dispersion spectroscopic method for quantitative chemical analysis. [ABSTRACT FROM AUTHOR]

Sum-frequency spectrum of non-selective (multi-line) CO laser radiation generated in ZnGeP 2 crystal under noncritical spectral phase-matching conditions was experimentally studied with spectral resolution of ∼0.1 cm−1. The number of spectral lines for this spectrum was found to be about an order of magnitude larger than for previously reported one. Its spectral structure looked like a broadband mid-IR comb of multi-line groups having complicated substructure. That is attractive for the atmosphere sounding by both differential absorption technique and absorption line profile spectroscopy. A list of the atmosphere gases and pollutants that could be detected by these procedures was considered. An opportunity of absorption line profile measuring by means of CO laser sum-frequency comb was experimentally demonstrated for CO 2 molecules. [ABSTRACT FROM AUTHOR]

Abstract A new spectroscopic predictor for estimating ignition characteristics including derived cetane number is proposed for hydrocarbon fuels. This spectroscopic predictor is the ratio of room temperature absorbance of unreacted fuel vapor at 3.41 and 3.39 μ m, termed here as the "3.41/3.39 absorption ratio." Its wide availability and applicability are demonstrated for a range of pure hydrocarbons, mixtures of pure hydrocarbons, and distillate and synthetic jet fuels. Quasi-linear calculation methods are provided for practical use. Spectroscopic and kinetic interpretations are provided based on the fraction of –CH 2 – hydrogen relative to all carbon-bonded hydrogen. In addition, the correlations between the proposed predictor and ignition delay time and C 2 H 4 yield are presented and discussed to exhibit the predictor's potential as a fuel screening tool. [ABSTRACT FROM AUTHOR]

Highlights • Planetary distances and a definition of life thwart resolution of the Fermi paradox. • Electromagnetic radiation is the best medium for probing exoplanets for signs of life. • Mid-IR spectroscopy is the most informative region of the electromagnetic spectrum. • Moon-based mid-IR spectra yield more information about life than any other platform. • Current estimates for a lunar platform are 10-fold lower than previous estimates. Abstract The failure to resolve the 70 year old Fermi paradox has been limited by the vastness of the Universe, the inability to search even a fraction of the Universe in a reasonable time period, and the lack of agreement on the criteria for life. We suggest that one approach is to use cyclical perturbations of thermodynamic equilibria on exoplanets within range of the most powerful mid-infrared (mid-IR) telescopes as a general screening tool for the possible existence of any form of life. We argue that the optimal platform for such a mid-IR search is on the Earth's moon. [ABSTRACT FROM AUTHOR]

Abstract Soil microbes link aboveground and belowground ecosystem processes by modulating nutrient retention, recycling, and availability to plants. The diversity and abundance of soil microbes are influenced by biotic and edaphic factors such as plant communities and soil chemistry. Despite this general understanding, relatively few details are known about how soil microbial community structure responds to changing plant communities and soil chemistry associated with secondary forest succession. To address these gaps, we used 16S rRNA gene sequencing to investigate how diversity, composition and abundance of soil prokaryotic communities differed among five successional stages at two soil depths in a temperate forest, and then related these differences with soil properties. Oligotrophic prokaryotic taxa were more common in earlier successional stages, and community diversity declined at later forest successional stages. Prokaryotic diversity was consistently higher in topsoil than subsoil. Prokaryotic community composition varied with respect to soil organic matter (SOM) properties. The relative abundances of specific carbon (C) functional groups (e.g., aliphatic C groups, aromatic C groups and polysaccharides) revealed by mid-IR spectroscopy were strongly related with prokaryotic community composition. Overall, this study revealed that changes in soil prokaryotic community structure (diversity, composition and taxa abundance) paralleled changes in plant communities and soil chemistry associated with forest succession, and that these changes can be inferred through changes in SOM properties. Graphical abstract Image 1 Highlights • Forest succession and soil depth influence soil prokaryote community structure. • Subsoil prokaryotic community diversity declined at late stage of forest succession. • SOM quantity and quality are major drivers of soil prokaryotic community structure. • Changing SOM drives a shift from soil copiotrophs to oligotrophs during succession. [ABSTRACT FROM AUTHOR]

The aim of the present study was to estimate genetic parameters for calcium (Ca), phosphorus (P) and titratable acidity (TA) in bovine milk predicted by mid-IR spectroscopy (MIRS). Data consisted of 2458 Italian Holstein−Friesian cows sampled once in 220 farms. Information per sample on protein and fat percentage, pH and somatic cell count, as well as test-day milk yield, was also available. (Co)variance components were estimated using univariate and bivariate animal linear mixed models. Fixed effects considered in the analyses were herd of sampling, parity, lactation stage and a two-way interaction between parity and lactation stage; an additive genetic and residual term were included in the models as random effects. Estimates of heritability for Ca, P and TA were 0.10, 0.12 and 0.26, respectively. Positive moderate to strong phenotypic correlations (0.33 to 0.82) existed between Ca, P and TA, whereas phenotypic weak to moderate correlations (0.00 to 0.45) existed between these traits with both milk quality and yield. Moderate to strong genetic correlations (0.28 to 0.92) existed between Ca, P and TA, and between these predicted traits with both fat and protein percentage (0.35 to 0.91). The existence of heritable genetic variation for Ca, P and TA, coupled with the potential to predict these components for routine cow milk testing, imply that genetic gain in these traits is indeed possible.

We report on mid-IR spectroscopic measurements performed with rapidly tunable external cavity quantum cascade lasers (EC-QCLs). Fast wavelength tuning in the external cavity is realized by a microoptoelectromechanical systems (MOEMS) grating oscillating at a resonance frequency of about 1 kHz with a deflection amplitude of up to 10 deg. The entire spectral range of the broadband QCL can therefore be covered in just 500 µs, paving the way for real-time spectroscopy in the mid-IR region. In addition to its use in spectroscopic measurements conducted in backscattering and transmission geometry, the MOEMS-based laser source is characterized regarding pulse intensity noise, wavelength reproducibility, and spectral resolution. [ABSTRACT FROM AUTHOR]

Output characteristics of the evanescent wave sensor have been studied in experiment by measurement of the transmittance of a chalcogenide fiber submerged into an aqueous solution of acetone in the range of wavelengths 5–9 μm. The minimum concentration of 1 mol% of acetone has been detected at the wavelengths of 7.33 μm and 8.18 μm. By using a theoretical approach based on the electromagnetic theory of optical fibers, we have revealed that dependence of the transmittance logarithm versus the length of the fiber immersed into the solution is not linear because of the greater attenuation of the evanescent modes having greater radial orders. As calibration curves of the higher-order modes are steeper they are more suitable for the sensitive detection of chemicals. Water absorption as a factor limiting the sensitivity of spectroscopic measurements in mid-infrared has been discussed. [ABSTRACT FROM AUTHOR]

Molecular complexes formation in diethyl ether-chloroform liquid solution is investigated by Mid-IR absorbance spectroscopy. The spectra were measured in spectral ranges of 1000–1550 cm −1 and 2650–3100 cm −1 . 2D correlation analysis of spectral data indicates the presence of a third component in the solution. Excess spectroscopy shows that maximum of complex concentration is concentrated at around of 55% (vol.) of diethyl ether. 2D codistribution analysis supports such conclusion and provides the order of species distribution. Three-components MCR decomposition of spectral data was performed for the determination of concentration and spectral profiles of mixture components. Spectral transformations due to intermolecular interactions are in full agreement with those calculated according to density functional theory with B3LYP functional and cc-pVTz basis set for the case of equimolecular complex. [ABSTRACT FROM AUTHOR]

The aim of the present study was to estimate genetic parameters for calcium (Ca), phosphorus (P) and titratable acidity (TA) in bovine milk predicted by mid-IR spectroscopy (MIRS). Data consisted of 2458 Italian Holstein−Friesian cows sampled once in 220 farms. Information per sample on protein and fat percentage, pH and somatic cell count, as well as test-day milk yield, was also available. (Co)variance components were estimated using univariate and bivariate animal linear mixed models. Fixed effects considered in the analyses were herd of sampling, parity, lactation stage and a two-way interaction between parity and lactation stage; an additive genetic and residual term were included in the models as random effects. Estimates of heritability for Ca, P and TA were 0.10, 0.12 and 0.26, respectively. Positive moderate to strong phenotypic correlations (0.33 to 0.82) existed between Ca, P and TA, whereas phenotypic weak to moderate correlations (0.00 to 0.45) existed between these traits with both milk quality and yield. Moderate to strong genetic correlations (0.28 to 0.92) existed between Ca, P and TA, and between these predicted traits with both fat and protein percentage (0.35 to 0.91). The existence of heritable genetic variation for Ca, P and TA, coupled with the potential to predict these components for routine cow milk testing, imply that genetic gain in these traits is indeed possible. [ABSTRACT FROM PUBLISHER]

Dielectric metasurfaces governed by bound states in the continuum (BIC) are actively investigated for achieving high-quality factors and strong electromagnetic field enhancements. Traditional approaches reported for tuning the performance of quasi-BIC metasurfaces include tuning the resonator size, period, and structure symmetry. Here we propose and experimentally demonstrate an alternative approach through engineering slots within a zigzag array of elliptical silicon resonators. Through analytical theory, three-dimensional electromagnetic modeling, and infrared spectroscopy, we systematically investigate the spectral responses and field distributions of the slotted metasurface in the mid-IR. Our results show that by introducing slots, the electric field intensity enhancement near the apex and the quality factor of the quasi-BIC resonance are increased by a factor of 2.1 and 3.3, respectively, in comparison to the metasurface without slots. Furthermore, the slotted metasurface also provides extra regions of electromagnetic enhancement and confinement, which holds enormous potential in particle trapping, sensing, and emission enhancement.

Abstract: This study integrated physical, chemical, and molecular techniques to assess relationships between soil bacterial community structures and the quantity and quality of soil organic carbon (SOC) at the soil microenvironment scale (e.g., within different aggregate size-fractions). To accomplish this goal, soil samples (0–5 cm) were collected from the Texas High Plains region under a variety of dryland and irrigated cropping systems. The soil was separated into macroaggregates, microaggregates, and silt + clay fractions that were analyzed for (1) bacterial diversity via pyrosequencing of the 16s rRNA gene and (2) SOC quantity and quality using a combustion method and mid-infrared diffuse reflectance spectroscopy (mid-IR), respectively. Results from pyrosequencing showed that each soil microenvironment supported a distinct bacterial community. Similarly, mid-IR data revealed distinct spectral features indicating that these fractions were also distinguished by organic and mineral composition. Macroaggregates showed relatively high abundance of Actinobacteria (excluding order Rubrobacteriales) and α-Proteobacteria and contained the most SOC. Microaggregates showed high relative abundance of Rubrobacteriales and the least amount of SOC. Predominance within the soil microenvironment and correlations along the mid-IR spectra were different between members of the order Rubrobacteriales compared with all other members of the Actinobacteria phyla, suggesting they have different ecological niches. Mid-IR results revealed microaggregates had greater absorbance in the 1370–1450 cm−1 region for phenolic and alkyl groups (possibly recalcitrant C). Silt + clay fractions were distinguished by Gemmatimonadetes and OP10 phyla, which positively correlated with spectral absorption in the1250–1150 cm−1 range (indicating both degradable and recalcitrant C forms). In contrast to general diversity index measurements, distributions of the more rare bacterial phyla (phyla representing <6% of the identified population) were more important for differentiating between communities in soil microenvironments. To our knowledge, this is the first study to investigate soil bacterial communities among soil aggregates using pyrosequenging and to associate these communities to specific soil C chemistries as indicated by mid-IR absorbance. [Copyright &y& Elsevier]

Abstract: A multilamination micromixer for time resolved infrared spectroscopy, optimized by fluid simulations is characterized by fluidic means for different flow rates. The mixer is fabricated with silicon micromachining techniques. Using four instead of two lamination layers yields a reduction of the diffusion length and decreases mixing time significantly. Measurement results show the ultrafast mixing performance of this micromixer (<1ms for aqueous solutions) with high uniformity. An infrared measurement (mid-IR spectral range, 3–10μm) proves the applicability of the device to monitor fast (bio)chemical reactions. The mixer operates in a high dynamic range enabling the investigation of a variety of chemical reaction kinetics in the time range of 10–300ms. A high yield in fabrication is achieved due to well controlled processes. Easy chip handling and higher pressure durability is provided by a dedicated custom chip holder. [Copyright &y& Elsevier]

Abstract: A novel method is presented for the rigorous propagation of uncertainties in initial concentrations and in dosing rates into the errors in the rate constants fitted by multivariate kinetic hard-modelling of spectroscopic data using the Newton–Gauss–Levenberg/Marquardt optimisation algorithm. The method was successfully validated by Monte-Carlo sampling. The impact of the uncertainties in initial concentrations and in the dosing rate was quantified for simulated spectroscopic data based on a second and a formal third order rate law under batch and semi-batch conditions respectively. An important consequence of this study regarding optimum experimental design is the fact that the propagated error in a second order rate constant is minimal under exact stoichiometric conditions or when the reactant with the lowest associated uncertainty in its initial concentration is in a reasonable excess (pseudo first order conditions). As an experimental example, the reaction of benzophenone with phenylhydrazine in THF was investigated repeatedly (17 individual experiments) by UV–vis and mid-IR spectroscopy under the same semi-batch conditions, dosing the catalyst acetic acid. For all experiments and spectroscopic signals, reproducible formal third order rate constants were determined. Applying the proposed method of error propagation to any single experiment, it was possible to predict 80% (UV–vis) and 40% (mid-IR) of the observed standard deviation in the rate constants obtained from all experiments. The largest contribution to this predicted error in the rate constant could be assigned to the dosing rate. The proposed method of error propagation is flexible and can straightforwardly be extended to propagate other possible sources of error. [Copyright &y& Elsevier]

Instrumentation is reported for rapid, on-line quantitative analysis of the gaseous effluent from a heterogeneously catalyzed reaction. Absorption bands over the mid-infrared (IR) range 4000–580 cm−1 have been used to quantify, in less than 2 min, the major gaseous products of the hydrogenation of carbon monoxide (Fischer-Tropsch synthesis) using partial least squares (PLS) methodology. The fast analysis capability of the IR technique coupled to a single channel microreactor enables the approach of a Fischer-Tropsch catalyst to steady-state to be investigated by sampling the products every 2 min for 3 h on-stream. Coupling IR spectroscopy and chemometrics in this manner will allow a wide range of heterogeneously catalyzed reactions to be analyzed in very short times, a key requisite for high throughput catalyst testing. [Copyright &y& Elsevier]

The first infrared spectroscopy in the 3–13 micron region has been obtained of several persistent Leonid meteor trains with two different instrument types, one at a desert ground-based site and the other on-board a high-flying aircraft. The spectra exhibit common structures assigned to enhanced emissions of warm CH4, CO2, CO and H2O, which may originate from heated trace air compounds or materials created in the wake of the meteor. This is the first time that any of these molecules has been observed in the spectra of persistent trains. Hence, the mid-IR observations offer a new perspective on the physical processes that occur in the path of the meteor at some time after the meteor itself has passed by. Continuum emission is observed also, but its origin has not yet been established. No 10 micron dust emission feature has been observed. [ABSTRACT FROM AUTHOR]

In previous studies, we have shown that gas-phase mid-infrared spectra can be used to estimate the properties of hydrocarbon fuels. Specifically, the spectrum around 3.4 μm and regularized linear models were utilized to estimate various physical and chemical properties of hydrocarbon fuels. In this study, we use a generalized linear model with grouped-Lasso regularization to characterize the average fuel structure in terms of the fractions of each functional group type and provide a new strategy to approach the property estimation problem. The robustness of this structure characterization method against low spectral resolution and high multiplicative noise in FTIR spectra are studied and presented. Two property estimation models, i.e. a linear and a nonlinear additive model, are presented as demonstrations of estimating properties from functional group numbers. [ABSTRACT FROM AUTHOR]

Exposure to asbestos fibres is related to a number of severe lung diseases, and therefore, rapid, accurate and reliable in situ or on-site asbestos detection in real-life samples is of considerable importance. This work presents a comprehensive investigation of all six types of asbestos by mid-infrared ATR–FTIR, NIR spectroscopy and Raman microspectroscopy. Our studies demonstrate that for practical applications, NIR spectroscopy is potentially the most powerful method for asbestos identification in materials utilised by the construction industry. By focusing on the narrow spectral region, 7300–7000 cm−1 (~1370–1430 nm, overtones of O‒H vibrations), which is highly specific to these materials, and optimising the sensitivity and resolution of the instrumentation, we have been able to discriminate and identify each of the six types of asbestos with the level of detection significantly better than 1 wt%. Furthermore, straightforward computational analysis has allowed for automated objective evaluation of the spectroscopic data. ga1 • Six types of asbestos are characterised by mid-IR, NIR and Raman spectroscopy. • NIR spectroscopy is established as a powerful method for asbestos identification. • The key experimental parameters for NIR detection of asbestos are determined. • Each type of asbestos can be differentiated with the detection level of ~0.1 wt%. • Rapid, objective and reliable detection of asbestos in real-life materials is shown. [ABSTRACT FROM AUTHOR]

• Small, cost-effective mid-IR sensor for nitrate in aqueous solutions based on a 3D-printed ATR-IR filtometer. • ATR crystals were coated mesoporous silica functionalized with trimethylammonium groups. • Enrichment factors of up 1600 and 1.2 mg L−1 limits of detection were achieved. Strong anion-exchange materials carry a positive charge that allows them to trap and concentrate anions while releasing other anions. Here, we introduced a quaternary ammonium anion exchange group into mesoporous silica films coated on attenuated total reflection (ATR) crystals to enrich nitrate from aqueous phase in the volume probed by the evanescent field. The ion-exchange and enrichment capabilities of the films were characterized using FTIR spectroscopy. Thereby fast analyte enrichment and full sensor recovery were observed. In addition, high enrichment factors of up to 1600 were achieved. After characterization, these coated ATR crystals were used in a dedicated ATR-IR filtometer comprising a Fabry-Pérot filter detector unit and a miniaturized thermal emitter with a overall dimensions of only 80 mm × 120 mm × 70 mm. The filter covered the spectral region between 1250–1800 cm−1 allowing for recording IR spectra of nitrate enriched into the mesoporous silica film. The sensor was calibrated using the Langmuir adsorption model as calibration function. From this a limit of detection of 1.2 mg L−1 was derived for the ATR-IR filtometer. This emphasizes the high potential of functionalized mesoporous silica films combined with low-cost filtometers for portable water sensors. [ABSTRACT FROM AUTHOR]

• ATR crystals were coated with functionalized mesoporous silica with different pore sizes. • Enrichment factors of up 32,000 and 3–7 ppmv limits of detection achieved. • Modified silica allowed for sensing in the fingerprint region without water vapor interferences. Sensitivity of evanescent wave sensing of gaseous species can be vastly increased by enrichment materials that locally concentrate the analyte on the sensor. Here, we investigate functionalized mesoporous silica films as versatile enrichment layer for sensing volatile organic compounds (VOCs) from gas-phase. Attenuated total reflection (ATR) crystals were coated with silica films of different pore sizes and their capability to enrich three different aromatic hydrocarbons from a vapor stream was studied by means of Fourier Transform infrared (FTIR) spectroscopy. Thereby, single-digit ppmv limits of detection (LOD) were achieved with an effective path length of only 6.3 μm. The selectivity introduced by the functionalization of the silica films effectively minimized interferences of water vapor, which gave access to the spectral fingerprint region between 1550 and 1450 cm−1. This allowed to discriminate and quantify toluene, p -xylene and 1,2,4-trimethylbenzene in multicomponent mixtures at high humidity. Fast response and regeneration times and enrichment factors up to 32 000 showcase the high potential of this material for evanescent wave sensing. [ABSTRACT FROM AUTHOR]