Showing papers in "Applied Spectroscopy in 2017"
TL;DR: The literature in the field is reviewed, the published Raman spectroscopy studies of erythrocytes, leucocytes, platelets, plasma, and whole blood are collated, and general conclusions on the state of the field are drawn.
Abstract: Blood is a bodily fluid that is vital for a number of life functions in animals. To a first approximation, blood is a mildly alkaline aqueous fluid (plasma) in which a large number of free-floating red cells (erythrocytes), white cells (leucocytes), and platelets are suspended. The primary function of blood is to transport oxygen from the lungs to all the cells of the body and move carbon dioxide in the return direction after it is produced by the cells' metabolism. Blood also carries nutrients to the cells and brings waste products to the liver and kidneys. Measured levels of oxygen, nutrients, waste, and electrolytes in blood are often used for clinical assessment of human health. Raman spectroscopy is a non-destructive analytical technique that uses the inelastic scattering of light to provide information on chemical composition, and hence has a potential role in this clinical assessment process. Raman spectroscopic probing of blood components and of whole blood has been on-going for more than four decades and has proven useful in applications ranging from the understanding of hemoglobin oxygenation, to the discrimination of cancerous cells from healthy lymphocytes, and the forensic investigation of crime scenes. In this paper, we review the literature in the field, collate the published Raman spectroscopy studies of erythrocytes, leucocytes, platelets, plasma, and whole blood, and attempt to draw general conclusions on the state of the field.
188 citations
TL;DR: This review includes the principles of NIR spectroscopy, pre-processing methods, and multivariate analyses used for quantitative and qualitative purposes in the meat sector and the challenges of using NIRS technology in commercial applications.
Abstract: Consumer demand for quality and healthfulness has led to a higher need for quality assurance in meat production This requirement has increased interest in near-infrared (NIR) spectroscopy due to the ability for rapid, environmentally friendly, and noninvasive prediction of meat quality or authentication of added-value meat products This review includes the principles of NIR spectroscopy, pre-processing methods, and multivariate analyses used for quantitative and qualitative purposes in the meat sector Recent advances in portable NIR spectrometers that enable new online applications in the meat industry are shown and their performance evaluated Discrepancies between published studies and potential sources of variability are discussed, and further research is encouraged to face the challenges of using NIRS technology in commercial applications, so that its full potential can be achieved
141 citations
TL;DR: It has been found that drying and re-humidification leads to intensity changes of absorption bands of the carbohydrate backbone, but does not impair the identification of the fiber type by library search or cluster analysis.
Abstract: This work was sparked by the reported identification of man-made cellulosic fibers (rayon/viscose) in the marine environment as a major fraction of plastic litter by Fourier transform infrared (FT-IR) transmission spectroscopy and library search. To assess the plausibility of such findings, both natural and man-made fibers were examined using FT-IR spectroscopy. Spectra acquired by transmission microscopy, attenuated total reflection (ATR) microscopy, and ATR spectroscopy were compared. Library search was employed and results show significant differences in the identification rate depending on the acquisition method of the spectra. Careful selection of search parameters and the choice of spectra acquisition method were found to be essential for optimization of the library search results. When using transmission spectra of fibers and ATR libraries it was not possible to differentiate between man-made and natural fibers. Successful differentiation of natural and man-made cellulosic fibers has been achieved for FT-IR spectra acquired by ATR microscopy and ATR spectroscopy, and application of ATR libraries. As an alternative, chemometric methods such as unsupervised hierarchical cluster analysis, principal component analysis, and partial least squares-discriminant analysis were employed to facilitate identification based on intrinsic relationships of sample spectra and successful discrimination of the fiber type could be achieved. Differences in the ATR spectra depending on the internal reflection element (Ge versus diamond) were observed as expected; however, these did not impair correct classification by chemometric analysis. Moreover, the effects of different levels of humidity on the IR spectra of natural and man-made fibers were investigated, too. It has been found that drying and re-humidification leads to intensity changes of absorption bands of the carbohydrate backbone, but does not impair the identification of the fiber type by library search or cluster analysis.
119 citations
TL;DR: The review shows that the properties of Raman have been successfully exploited to deliver unique and useful analytical solutions, particularly for online process monitoring, and shows that its inherent susceptibility to fluorescence interference and the weakness of the Raman effect mean that it can never be a panacea.
Abstract: The production of active pharmaceutical ingredients (APIs) is currently undergoing its biggest transformation in a century. The changes are based on the rapid and dramatic introduction of protein- and macromolecule-based drugs (collectively known as biopharmaceuticals) and can be traced back to the huge investment in biomedical science (in particular in genomics and proteomics) that has been ongoing since the 1970s. Biopharmaceuticals (or biologics) are manufactured using biological-expression systems (such as mammalian, bacterial, insect cells, etc.) and have spawned a large (>€35 billion sales annually in Europe) and growing biopharmaceutical industry (BioPharma). The structural and chemical complexity of biologics, combined with the intricacy of cell-based manufacturing, imposes a huge analytical burden to correctly characterize and quantify both processes (upstream) and products (downstream). In small molecule manufacturing, advances in analytical and computational methods have been extensively exploited to generate process analytical technologies (PAT) that are now used for routine process control, leading to more efficient processes and safer medicines. In the analytical domain, biologic manufacturing is considerably behind and there is both a huge scope and need to produce relevant PAT tools with which to better control processes, and better characterize product macromolecules. Raman spectroscopy, a vibrational spectroscopy with a number of useful properties (nondestructive, non-contact, robustness) has significant potential advantages in BioPharma. Key among them are intrinsically high molecular specificity, the ability to measure in water, the requirement for minimal (or no) sample pre-treatment, the flexibility of sampling configurations, and suitability for automation. Here, we review and discuss a representative selection of the more important Raman applications in BioPharma (with particular emphasis on mammalian cell culture). The review shows that the properties of Raman have been successfully exploited to deliver unique and useful analytical solutions, particularly for online process monitoring. However, it also shows that its inherent susceptibility to fluorescence interference and the weakness of the Raman effect mean that it can never be a panacea. In particular, Raman-based methods are intrinsically limited by the chemical complexity and wide analyte-concentration-profiles of cell culture media/bioprocessing broths which limit their use for quantitative analysis. Nevertheless, with appropriate foreknowledge of these limitations and good experimental design, robust analytical methods can be produced. In addition, new technological developments such as time-resolved detectors, advanced lasers, and plasmonics offer potential of new Raman-based methods to resolve existing limitations and/or provide new analytical insights.
108 citations
TL;DR: Improved protocols using multiple path lengths to determine the optical constants n/k for dozens of liquids, including inorganic, organic, and organophosphorus compounds are developed.
Abstract: For optical modeling and other purposes, we have created a library of 57 liquids for which we have measured the complex optical constants n and k. These liquids vary in their nature, ranging in pro...
74 citations
TL;DR: These findings show that the precision in peak position and intensity can be improved significantly by fitting the measured Raman peaks with appropriate profiles, and significant errors were still observed in the results from fitting of weak and wide Raman bands having unnormalized intensity/FWHM ratios lower than 200 counts/cm−1.
Abstract: Fitting experimentally measured Raman bands with theoretical model profiles is the basic operation for numerical determination of Raman peak parameters. In order to investigate the effects of peak modeling using various algorithms on peak fitting results, the representative Raman bands of mineral crystals, glass, fluids as well as the emission lines from a fluorescent lamp, some of which were measured under ambient light whereas others under elevated pressure and temperature conditions, were fitted using Gaussian, Lorentzian, Gaussian-Lorentzian, Voigtian, Pearson type IV, and beta profiles. From the fitting results of the Raman bands investigated in this study, the fitted peak position, intensity, area and full width at half-maximum (FWHM) values of the measured Raman bands can vary significantly depending upon which peak profile function is used in the fitting, and the most appropriate fitting profile should be selected depending upon the nature of the Raman bands. Specifically, the symmetric Raman bands of mineral crystals and non-aqueous fluids are best fit using Gaussian-Lorentzian or Voigtian profiles, whereas the asymmetric Raman bands are best fit using Pearson type IV profiles. The asymmetric O-H stretching vibrations of H2O and the Raman bands of soda-lime glass are best fit using several Gaussian profiles, whereas the emission lines from a florescent light are best fit using beta profiles. Multiple peaks that are not clearly separated can be fit simultaneously, provided the residuals in the fitting of one peak will not affect the fitting of the remaining peaks to a significant degree. Once the resolution of the Raman spectrometer has been properly accounted for, our findings show that the precision in peak position and intensity can be improved significantly by fitting the measured Raman peaks with appropriate profiles. Nevertheless, significant errors in peak position and intensity were still observed in the results from fitting of weak and wide Raman bands having unnormalized intensity/FWHM ratios lower than 200 counts/cm-1.
62 citations
TL;DR: It is found that the width, intensity, and area of bands in the ATR FT-IR spectra of minerals have explicit dependence on the particle size, and at least a proportion of the moisture could be very adhesive to the particles due to the band shift towards lower wavenumbers in the IR range of 3000–3620 cm–1.
Abstract: This study focuses on particle size effect on monomineralic powders recorded using attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy. Six particle size fractions of qu...
56 citations
TL;DR: Important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering are presented and described with some background physics.
Abstract: Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.
52 citations
TL;DR: The goal of this work is the determination of the amount of main scattering components, the fat droplets and the casein micelles, by understanding the light propagation in homogenized milk and in raw milk.
Abstract: Dairy products play an important role in our daily nutrition. As a turbid scattering medium with different kinds of particles and droplets, each alteration of these components changes the scattering properties of milk. The goal of this work is the determination of the amount of main scattering components, the fat droplets and the casein micelles, by understanding the light propagation in homogenized milk and in raw milk. To provide the absolute impact of these milk components, the geometrical and optical properties such as the size distribution and the refractive index (RI) of the components have to be examined. We determined the reduced scattering coefficient μs' and the absorption coefficient μa from integrating sphere measurements. By use of a collimated transmission setup, the scattering coefficient μs was measured. Size measurements were performed to validate the influence of the fat droplet size on the results of the scattering properties; also, the RI of both components was determined by the said coefficients. These results were used to determine the absolute impact of the milk components on the scattering behavior. By fitting Mie theory calculations on scattering spectra μs and μs' from different raw milk samples, it was possible to get reliable values for the concentrations of fat and casein and for the size of the fat droplets. By destroying the casein micelles, it was possible to separate the influence of the different scattering components on scattering behavior.
50 citations
TL;DR: This focal point review ofSum frequency generation vibrational spectroscopy studies at buried polymer interfaces is focused on and the essential theoretical background of SFG-VS is covered.
Abstract: Sum frequency generation vibrational spectroscopy (SFG-VS) has become one of the most appealing technologies to characterize molecular structures at interfaces In this focal point review, we focus on SFG-VS studies at buried polymer interfaces and review many of the recent publications in the field We also cover the essential theoretical background of SFG-VS and discuss the experimental implementation of SFG-VS
39 citations
TL;DR: A thin-walled nanofluidic sample cell concept that has advanced the discovery horizons of ultrafast spectroscopy and of electron microscopy investigations of in-liquid samples; and a unique class of thin-film-based nanofLUidic devices, designed around a nanopore, with expansive prospects for single molecule sensing are highlighted.
Abstract: We present a review of the use of selected nanofabricated thin films to deliver a host of capabilities and insights spanning bioanalytical and biophysical chemistry, materials science, and fundamental molecular-level research. We discuss approaches where thin films have been vital, enabling experimental studies using a variety of optical spectroscopies across the visible and infrared spectral range, electron microscopies, and related techniques such as electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and single molecule sensing. We anchor this broad discussion by highlighting two particularly exciting exemplars: a thin-walled nanofluidic sample cell concept that has advanced the discovery horizons of ultrafast spectroscopy and of electron microscopy investigations of in-liquid samples; and a unique class of thin-film-based nanofluidic devices, designed around a nanopore, with expansive prospects for single molecule sensing. Free-standing, low-stress silicon nitride membranes are a canonical structural element for these applications, and we elucidate the fabrication and resulting features-including mechanical stability, optical properties, X-ray and electron scattering properties, and chemical nature-of this material in this format. We also outline design and performance principles and include a discussion of underlying material preparations and properties suitable for understanding the use of alternative thin-film materials such as graphene.
TL;DR: The evaluation of Raman spectroscopy using random forest (RF) for the analysis of dengue fever in the infected human sera and accuracy, sensitivity, specificity, and accuracy have been calculated in comparison to normally performed IgM capture ELISA.
Abstract: This work presents the evaluation of Raman spectroscopy using random forest (RF) for the analysis of dengue fever in the infected human sera. A total of 100 dengue suspected blood samples, collected from Holy Family Hospital, Rawalpindi, Pakistan, have been used in this study. Out of these samples, 45 were dengue-positive based on immunoglobulin M (IgM) capture enzyme-linked immunosorbent assay (ELISA) tests. For highlighting the spectral differences between normal and infected samples, an effective machine learning system is developed that automatically learns the pattern of the shift in spectrum for the dengue compared to normal cases and thus is able to predict the unknown class based on the known example. In this connection, dimensionality reduction has been performed with the principal component analysis (PCA), while RF is used for automatic classification of dengue samples. For the determination of diagnostic capabilities of Raman spectroscopy based on RF, sensitivity, specificity, and accuracy have been calculated in comparison to normally performed IgM capture ELISA. According to the experiment, accuracy of 91%, sensitivity of 91%, and specificity of 91% were achieved for the proposed RF-based model.
TL;DR: The laser-induced breakdown spectroscopy technique used for analyzing the composition of an ancient Roman mortar gives well interpretable results in very short times, without any reduction in the dimensionality of the system.
Abstract: The laser-induced breakdown spectroscopy (LIBS) technique was used for analyzing the composition of an ancient Roman mortar (5th century A.D.), exploiting an experimental setup which allows the determination of the compositions of binder and aggregate in few minutes, without the need for sample treatment. Four thousand LIBS spectra were acquired from an area of 10 mm2, with a 50 µm lateral resolution. The elements of interest in the mortar sample (H, C, O, Na, Mg, Al, Si, K, Ca, Ti, Mn, Fe) were detected and mapped. The collected data graphically shown as compositional images were interpreted using different statistical approaches for the determination of the chemical composition of the binder and aggregate fraction. The methods of false color imaging, blind separation, and self-organizing maps were applied and their results are discussed in this paper. In particular, the method based on the use of self-organizing maps gives well interpretable results in very short times, without any reduction in the dime...
TL;DR: The results showed the superiority of using normalization for predictions of minor elements when the predicted sample and those in the training set had matrices with similar SiO2 contents, and normalization also mitigates differences in spectra arising from laser/sample coupling effects and the use of different energy densities.
Abstract: Obtaining quantitative chemical information using laser-induced breakdown spectroscopy is challenging due to the variability in the bulk composition of geological materials. Chemical matrix effects...
TL;DR: The production of pyocyanin is found to depend both on the growth carbon source and on the specific strain of P. aeruginosa studied, and production in the laboratory strain grown with glucose was below the limit of detection of SERS.
Abstract: Surface enhanced Raman spectroscopy (SERS) imaging was used in conjunction with principal component analysis (PCA) for the in situ spatiotemporal mapping of the virulence factor pyocyanin in communities of the pathogenic bacterium Pseudomonas aeruginosa. The combination of SERS imaging and PCA analysis provides a robust method for the characterization of heterogeneous biological systems while circumventing issues associated with interference from sample autofluorescence and low reproducibility of SERS signals. The production of pyocyanin is found to depend both on the growth carbon source and on the specific strain of P. aeruginosa studied. A cystic fibrosis lung isolate strain of P. aeruginosa synthesizes and secretes pyocyanin when grown with glucose and glutamate, while the laboratory strain exhibits detectable production of pyocyanin only when grown with glutamate as the source of carbon. Pyocyanin production in the laboratory strain grown with glucose was below the limit of detection of SERS. In addition, the combination of SERS imaging and PCA can elucidate subtle differences in the molecular composition of biofilms. PCA loading plots from the clinical isolate exhibit features corresponding to vibrational bands of carbohydrates, which represent the mucoid biofilm matrix specific to that isolate, features that are not seen in the PCA loading plots of the laboratory strain.
TL;DR: The results confirm that the Raman mineral:matrix bone composition parameter correlates strongly to ash fraction and to its IR counterpart, confirming the biological relevance of the chemical standards and the characterization techniques.
Abstract: Raman and Fourier transform infrared (FT-IR) spectroscopic imaging techniques can be used to characterize bone composition. In this study, our objective was to validate the Raman mineral:matrix rat...
TL;DR: This paper discusses the nascent developments of spatially heterodyne spectroscopy, a method that seeks to circumnavigate a serious drawback of most spectrometers – very small optical throughput – through the use of interferometers.
Abstract: The goal of this review article is to provide a description of recent and novel laser-induced breakdown spectroscopy (LIBS) applications and developments, especially those discussed during the NASL...
TL;DR: Data analysis using disrelation mapping applied to Fourier transform infrared (FT-IR) spectroscopic images suggests that the blends of PMMA and PEG are partially miscible at the molecular level and these intermolecular interactions are affected by the quantity of the terminal –OH groups of the PEG.
Abstract: A novel technique called disrelation spectroscopic imaging describes the process of identifying an area where a coordinated or out-of-phase change in pattern of spectral absorbance occurs. Disrelation mapping can be viewed as a spatial filter based on the well-established two-dimensional (2D) correlation function to highlight specific areas where disrelated variation occurs between ν1 and ν2. Disrelation intensity develops only if the spectral absorbance measured at ν1 and ν2 vary out of phase with each other within a specific spatial area. The disrelation mapping locates regions where absorbance varies in a dissimilar manner because of the contribution from species of different physical or chemical origins. Consequently, it becomes possible to probe onset of molecular interactions or presence of intermediate forms between components, which is not fully detected by the conventional visualizations based on a single wavenumber. Data analysis using disrelation mapping applied to Fourier transform infrared (FT-IR) spectroscopic images is presented in this study. Data sets of FT-IR spectroscopic images of blends of poly(methyl methacrylate) (PMMA) and polyethylene glycol (PEG) were subjected to the disrelation mapping. It was found that the disrelation intensity between 1730 and 1714 cm-1 becomes especially acute around the spatial boundary between PMMA and PEG domains within the studied blend sample. Thus the band at 1730 cm-1 most likely represents the C=O stretching mode of the C=O···H-O species due to the intermolecular hydrogen bonding between PMMA and PEG. The appearance of such disrelation is more noticeable in the PEG-rich region, for the PEG with low molecular weight. Consequently, it suggests that the blends of PMMA and PEG are partially miscible at the molecular level and these intermolecular interactions are affected by the quantity of the terminal -OH groups of the PEG.
TL;DR: The SWIR imaging spectral technique was found to have a highly favorable effect on the extraction of line features from drawings and on the identification of colors, classification of paintings, and extraction of hidden information.
Abstract: Spectral analysis is one of the main non-destructive techniques used to examine cultural relics. Hyperspectral imaging technology, especially on the shortwave infrared (SWIR) band, can clearly extract information from paintings, such as color, pigment composition, damage characteristics, and painting techniques. All of these characteristics have significant scientific and practical value in the study of ancient paintings and other relics and in their protection and restoration. In this study, an ancient painting, numbered Gu-6541, which had been found in the Forbidden City, served as a sample. A ground-based SWIR imaging spectrometer was used to produce hyperspectral images with high spatial and spectral resolution. Results indicated that SWIR imaging spectral data greatly facilitates the extraction of line features used in drafting, even using a single band image. It can be used to identify and classify mineral pigments used in paintings. These images can detect alterations and traces of daub used in painting corrections and, combined with hyperspectral data analysis methods such as band combination or principal component analysis, such information can be extracted to highlight outcomes of interest. In brief, the SWIR imaging spectral technique was found to have a highly favorable effect on the extraction of line features from drawings and on the identification of colors, classification of paintings, and extraction of hidden information.
TL;DR: Experimental measurement of refractive indices and absorption coefficients of styrene acrylonitrile and Bakelite in the spectral range of 0.2–2.0 THz for the first time and it is demonstrated that by combining principle component analysis (PCA) with THz time-domain spectroscopy one can differentiate such polymers.
Abstract: Polymers are among the most commonly used materials in our everyday life. They are generally transparent to terahertz (THz) radiation, but are quite difficult to differentiate using optical techniques as few or no characteristic features exist in the spectral range of 94% variance with a distribution of 72.45%, 11.52%, and 9.38%, respectively.
TL;DR: The results obtained were used to determine the stratigraphy of six instruments, obtain new information about the materials involved in the finishing processes employed in Cremona, and elucidate the technological relationship among the procedures adopted in the violin making workshops during the considered period.
Abstract: Historical bowed string instruments exhibit acoustic features and aesthetic appeal that are still considered inimitable. These characteristics seem to be in large part determined by the materials u...
TL;DR: SDA results were compared with values obtained with the traditional methods of external calibration, internal standardization (IS), and standard additions (SA) in MIP OES determinations and it was found that the SDA method presents superior precision and accuracy compared to the traditional calibration methods.
Abstract: In this work, we evaluate the application of microwave-induced plasma optical emission spectrometry (MIP OES) to determine of Al, Cr, Co, Cu, Fe, Mn, Ni and Zn in children's cough syrup, eye drops, and oral antiseptic using standard dilution analysis (SDA). The SDA method is simple, with only two calibration solutions prepared per sample. The first solution (S1), composed of 50% sample +50% of a standard solution, is introduced into the plasma and the analytical signals are monitored in a time-resolved fashion. Then, the second solution (S2), composed of 50% sample +50% blank, is poured into the vial containing S1. As the solutions mix, the analytical signals gradually drop to a stable baseline. The calibration curve is computed by plotting the ratio of the analyte signal (SA) over the internal standard signal (which is also part of S1) (SIS) on the y-axis, versus the inverse of the IS concentration on the x-axis (i.e., SA/SIS versus 1/CIS). In this study, SDA results were compared with values obtained with the traditional methods of external calibration (EC), internal standardization (IS), and standard additions (SA) in MIP OES determinations. The precision (represented as percent RSD) for SDA showed values in the range of 2.50-8.00% for all samples, while conventional calibration methods showed RSDs in the range of 6.40-32.50% for EC, 8.30-21.80% for IS, and 5.20-17.40% for SA. The LODs calculated for SDA are below the maximum limits allowed by the major pharmaceutical regulatory agencies, and presents superior precision and accuracy compared to the traditional calibration methods. Considering its simplicity and efficiency, SDA is an important new tool for accurate analyses of pharmaceuticals.
TL;DR: The unique spectra originating from the biofilms of three pathogenic microorganisms and the spectral changes as a result of time-dependent concentration fluctuations of biomolecular species in their biofilmms allow not only identification but also discrimination of biofilm using principal component analysis.
Abstract: Biofilm formation is a defense mechanism for microorganisms to survive under both natural and stress conditions. Clinically relevant microorganisms threaten patient health through biofilm formation on medical devices and implants. It is very important to identify biofilm formation in order to suppress their pathogenic activities in early stages. With the aim for better understanding biofilm formation and possibility of detection, in this study, biofilm formation of clinically important microorganisms, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Candida albicans are monitored with surface-enhanced Raman scattering (SERS). The SERS spectra were collected by mapping a dried droplet area where a volume of colloidal silver nanoparticle (AgNP) suspension is placed on microorganism culture plate. The spectral changes on the SERS spectra with increasing incubation time of the model microorganisms from 4 to 120 h are monitored. The unique spectra originating from the biofilms of three pathogenic microorganisms and the spectral changes as a result of time-dependent concentration fluctuations of biomolecular species in their biofilms including carbohydrates, lipids, proteins, and genetic materials allow not only identification but also discrimination of biofilms using principal component analysis.
TL;DR: This work constructed the first deep ultraviolet (UV) Raman standoff wide-field imaging spectrometer using a photonic crystal to select Raman spectral regions for detection and estimates detection limits of ∼1 µg/cm2 for PETN and AN films under these experimental conditions.
Abstract: We constructed the first deep ultraviolet (UV) Raman standoff wide-field imaging spectrometer. Our novel deep UV imaging spectrometer utilizes a photonic crystal to select Raman spectral regions for detection. The photonic crystal is composed of highly charged, monodisperse 35.5 ± 2.9 nm silica nanoparticles that self-assemble in solution to produce a face centered cubic crystalline colloidal array that Bragg diffracts a narrow ∼1.0 nm full width at half-maximum (FWHM) UV spectral region. We utilize this photonic crystal to select and image two different spectral regions containing resonance Raman bands of pentaerythritol tetranitrate (PETN) and NH4NO3 (AN). These two deep UV Raman spectral regions diffracted were selected by angle tuning the photonic crystal. We utilized this imaging spectrometer to measure 229 nm excited UV Raman images containing ∼10-1000 µg/cm2 samples of solid PETN and AN on aluminum surfaces at 2.3 m standoff distances. We estimate detection limits of ∼1 µg/cm2 for PETN and AN films under these experimental conditions.
TL;DR: Initial results have shown that this molten salt aerosol–LIBS system has a great potential as an analytical technique for measuring the molten salt electrolyte used in this UNF reprocessing technology.
Abstract: In the pyrochemical separation of used nuclear fuel (UNF), fission product, rare earth, and actinide chlorides accumulate in the molten salt electrolyte over time. Measuring this salt composition in near real-time is advantageous for operational efficiency, material accountability, and nuclear safeguards. Laser-induced breakdown spectroscopy (LIBS) has been proposed and demonstrated as a potential analytical approach for molten LiCl-KCl salts. However, all the studies conducted to date have used a static surface approach which can lead to issues with splashing, low repeatability, and poor sample homogeneity. In this initial study, a novel molten salt aerosol approach has been developed and explored to measure the composition of the salt via LIBS. The functionality of the system has been demonstrated as well as a basic optimization of the laser energy and nebulizer gas pressure used. Initial results have shown that this molten salt aerosol-LIBS system has a great potential as an analytical technique for measuring the molten salt electrolyte used in this UNF reprocessing technology.
TL;DR: This review summarizes the state of the art of analytical methods while highlighting tools for the assessment of quality assessment of the results, such as the production and evaluation of certified reference materials (CRMs) and the availability of specific proficiency testing (PT) programmes.
Abstract: Here we review recent developments in analytical proposals for the assessment of inorganic arsenic (iAs) content in food products. Interest in the determination of iAs in products for human consumption such as food commodities, wine, and seaweed among others is fueled by the wide recognition of its toxic effects on humans, even at low concentrations. Currently, the need for robust and reliable analytical methods is recognized by various international safety and health agencies, and by organizations in charge of establishing acceptable tolerance levels of iAs in food. This review summarizes the state of the art of analytical methods while highlighting tools for the assessment of quality assessment of the results, such as the production and evaluation of certified reference materials (CRMs) and the availability of specific proficiency testing (PT) programmes. Because the number of studies dedicated to the subject of this review has increased considerably over recent years, the sources consulted and cited here are limited to those from 2010 to the end of 2015.
TL;DR: In this paper, a seemingly simple problem, design of an ultraviolet, visible, and near-infrared spectrometer, is used to show the reasoning behind the trade-offs in instrument design.
Abstract: Designing a spectrometer requires knowledge of the problem to be solved, the molecules whose properties will contribute to a solution of that problem and skill in many subfields of science and engineering. A seemingly simple problem, design of an ultraviolet, visible, and near-infrared spectrometer, is used to show the reasoning behind the trade-offs in instrument design. Rather than reporting a fully optimized instrument, the Yin and Yang of design choices, leading to decisions about financial cost, materials choice, resolution, throughput, aperture, and layout are described. To limit scope, aspects such as grating blaze, electronics design, and light sources are not presented. The review illustrates the mixture of mathematical rigor, rule of thumb, esthetics, and availability of components that contribute to the art of spectrometer design.
TL;DR: An optical diagnostic technique to determine the order and concentration of lithium polysulfides in lithium–sulfur (Li–S) battery electrolytes has been developed using attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy.
Abstract: An optical diagnostic technique to determine the order and concentration of lithium polysulfides in lithium–sulfur (Li–S) battery electrolytes has been developed. One of the major challenges of lithium–sulfur batteries is the problem of polysulfide shuttling between the electrodes, which leads to self-discharge and loss of active material. Here we present an optical diagnostic for quantitative in situ measurements of lithium polysulfides using attenuated total reflection Fourier transform infrared (FT-IR) spectroscopy. Simulated infrared spectra of lithium polysulfide molecules were generated using computational quantum chemistry routines implemented in Gaussian 09. The theoretical spectra served as a starting point for experimental characterization of lithium polysulfide solutions synthesized by the direct reaction of lithium sulfide and sulfur. Attenuated total reflection FT-IR spectroscopy was used to measure absorption spectra. The lower limit of detection with this technique is 0.05 M. Measured spect...
TL;DR: Raman spectroscopy is applied to investigate the structural composition and the conformational heterogeneity of both full-length p53 and its DNA binding domain (DBD), in different solvent environments and is identified as a label-free, real-time and non-invasive detection method.
Abstract: The intrinsically disordered protein p53 has attracted a strong interest for its important role in genome safeguarding and potential therapeutic applications. However, its disordered character makes difficult a full characterization of p53 structural architecture. A deep knowledge of p53 structural motifs could significantly help the understanding of its functional properties, in connection with its complex binding network. We have applied Raman spectroscopy to investigate the structural composition and the conformational heterogeneity of both full-length p53 and its DNA binding domain (DBD), in different solvent environments. In particular, a careful analysis of the Amide I Raman band, which is highly sensitive to protein secondary structure elements such as α-helices, β-sheets and random coils, has revealed the presence of extended random coils in p53 and predominant β-sheet regions in its DBD. In addition, this analysis has allowed us to explore the ensemble of interchanging conformations in both p53 and its DBD, highlighting a higher conformational heterogeneity in p53 than in its DBD. Furthermore, by applying a principal components analysis, we have identified the principal spectral markers in both p53 and DBD samples. The combination of the two approaches could be insightful for the study of intrinsically disordered proteins, by offering increased versatility and wide application as a label-free, real-time and non-invasive detection method.
TL;DR: All the models are reliable, with high accuracy for predicting lignin in sugarcane, and significantly reduce the time to perform the analysis, the cost and the chemical reagent consumption, thus optimizing the entire process.
Abstract: The building of multivariate calibration models using near-infrared spectroscopy (NIR) and partial least squares (PLS) to estimate the lignin content in different parts of sugarcane genotypes is pr...