Showing papers in "Applied Spectroscopy in 2021"

Exploration of Principal Component Analysis: Deriving Principal Component Analysis Visually Using Spectra.

Abstract: Spectroscopy rapidly captures a large amount of data that is not directly interpretable. Principal component analysis is widely used to simplify complex spectral datasets into comprehensible information by identifying recurring patterns in the data with minimal loss of information. The linear algebra underpinning principal component analysis is not well understood by many applied analytical scientists and spectroscopists who use principal component analysis. The meaning of features identified through principal component analysis is often unclear. This manuscript traces the journey of the spectra themselves through the operations behind principal component analysis, with each step illustrated by simulated spectra. Principal component analysis relies solely on the information within the spectra, consequently the mathematical model is dependent on the nature of the data itself. The direct links between model and spectra allow concrete spectroscopic explanation of principal component analysis , such as the scores representing "concentration" or "weights". The principal components (loadings) are by definition hidden, repeated and uncorrelated spectral shapes that linearly combine to generate the observed spectra. They can be visualized as subtraction spectra between extreme differences within the dataset. Each PC is shown to be a successive refinement of the estimated spectra, improving the fit between PC reconstructed data and the original data. Understanding the data-led development of a principal component analysis model shows how to interpret application specific chemical meaning of the principal component analysis loadings and how to analyze scores. A critical benefit of principal component analysis is its simplicity and the succinctness of its description of a dataset, making it powerful and flexible.

Raman Spectroscopy for the Analysis of Microplastics in Aquatic Systems

Abstract: Raman spectroscopy is gaining ground in the analysis of microplastics, especially due to its high spatial resolution that allows the investigation of small plastic particles, whose numeric abundanc...

Infrared Spectroscopy of Blood

Abstract: The magnitude of infectious diseases in the twenty-first century created an urgent need for point-of-care diagnostics. Critical shortages in reagents and testing kits have had a large impact on the ability to test patients with a suspected parasitic, bacteria, fungal, and viral infections. New point-of-care tests need to be highly sensitive, specific, and easy to use and provide results in rapid time. Infrared spectroscopy, coupled to multivariate and machine learning algorithms, has the potential to meet this unmet demand requiring minimal sample preparation to detect both pathogenic infectious agents and chronic disease markers in blood. This focal point article will highlight the application of Fourier transform infrared spectroscopy to detect disease markers in blood focusing principally on parasites, bacteria, viruses, cancer markers, and important analytes indicative of disease. Methodologies and state-of-the-art approaches will be reported and potential confounding variables in blood analysis identified. The article provides an up to date review of the literature on blood diagnosis using infrared spectroscopy highlighting the recent advances in this burgeoning field.

Hydration Shells of DPPC Liposomes from the Point of View of Terahertz Time-Domain Spectroscopy:

Abstract: Analysis of structural and dynamic properties of water in suspensions of liposomes composed from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in three phase states (gel, rippled gel, liquid c...

Theoretical Simulation of Near-Infrared Spectrum of Piperine: Insight into Band Origins and the Features of Regression Models.

Abstract: We investigated the near-infrared spectrum of piperine using quantum mechanical calculations. We evaluated two efficient approaches, DVPT2//PM6 and DVPT2//ONIOM [PM6:B3LYP/6-311++G(2df, 2pd)] that yielded a simulated spectrum with varying accuracy versus computing time factor. We performed vibrational assignments and unveiled complex nature of the near-infrared spectrum of piperine, resulting from a high level of band convolution. The most meaningful contribution to the near-infrared absorption of piperine results from binary combination bands. With the available detailed near-infrared assignment of piperine, we interpreted the properties of partial least square regression models constructed in our earlier study to describe the piperine content in black pepper samples. Two models were compared with spectral data sets obtained with a benchtop and a miniaturized spectrometer. The two spectrometers implement distinct technology which leads to a profound instrumental difference and discrepancy in the predictive performance when analyzing piperine content. We concluded that the sensitivity of the two instruments to certain types of piperine vibrations is different and that the benchtop spectrometer unveiled higher selectivity. Such difference in obtaining chemical information from a sample can be one of the reasons why the benchtop spectrometer performs better in analyzing the piperine content of black pepper. This evidenced direct correspondence between the features critical for applied near-infrared spectroscopic routine and the underlying vibrational properties of the analyzed constituent in a complex sample.

Comparison of Surface-Enhanced Raman Scattering Properties of Serum and Urine for the Detection of Chronic Kidney Disease in Patients.

Abstract: Chronic kidney disease (CKD) affects more than 10% of the global population and is associated with significant morbidity and mortality. In most cases, this disease is developed silently, and it can progress to the end-stage renal failure. Therefore, early detection becomes critical for initiating effective interventions. Routine diagnosis of CKD requires both blood test and urinalyses in a clinical laboratory, which are time-consuming and have low sensitivity and specificity. Surface-enhanced Raman scattering (SERS) is an emerging method for rapidly assessing kidney function or injury. This study was designed to compare the differences between the SERS properties of the serum and urine for easy and simple detection of CKD. Enrolled for this study were 126 CKD patients (Stages 2–5) and 97 healthy individuals. SERS spectra of both the serum and urine samples were acquired using a Raman spectrometer (785 nm excitation). The correlation of chemical parameters of kidney function with the spectra was examined using prinicpal component analysis (PCA) combined with linear discriminant analysis (LDA) and partial least squares (PLS) analysis. Here, we showed that CKD was discriminated from non-CKD controls using PCA–LDA with a sensitivity of 74.6% and a specificity of 93.8% for the serum spectra, and 78.0% and 86.0 % for the urine spectra. The integration area under the receiver operating characteristic curve was 0.937 ± 0.015 (p < 0.0001) for the serum and 0.886 ± 0.025 (p < 0.0001) for the urine. The different stages of CKD were separated with the accuracy of 78.0% and 75.4% by the serum and urine spectra, respectively. PLS prediction (R2) of the serum spectra was 0.8540 for the serum urea (p < 0.001), 0.8536 for the serum creatinine (p < 0.001), 0.7500 for the estimated glomerular filtration rate (eGFR) (p < 0.001), whereas the prediction (R2) of urine spectra was 0.7335 for the urine urea (p < 0.001), 0.7901 for the urine creatinine (p < 0.001), 0.4644 for the eGFR (p < 0.001) and 0.6579 for the urine microalbumin (p < 0.001). In conclusion, the accuracy of associations between SERS findings of the serum and urine samples with clinical conclusions of CKD diagnosis in this limited number of patients is similar, suggesting that SERS may be used as a rapid and easy-to-use method for early screening of CKD, which however needs further evaluation in a large cohort study.

Multivariate Analysis Aided Surface-Enhanced Raman Spectroscopy (MVA-SERS) Multiplex Quantitative Detection of Trace Fentanyl in Illicit Drug Mixtures Using a Handheld Raman Spectrometer:

Abstract: Recently there has been upsurge in reports that illicit seizures of cocaine and heroin have been adulterated with fentanyl. Surface-enhanced Raman spectroscopy (SERS) provides a useful alternative to current screening procedures that permits detection of trace levels of fentanyl in mixtures. Samples are solubilized and allowed to interact with aggregated colloidal nanostars to produce a rapid and sensitive assay. In this study, we present the quantitative determination of fentanyl in heroin and cocaine using SERS, using a point-and-shoot handheld Raman system. Our protocol is optimized to detect pure fentanyl down to 0.20 ± 0.06 ng/mL and can also distinguish pure cocaine and heroin at ng/mL levels. Multiplex analysis of mixtures is enabled by combining SERS detection with principal component analysis and super partial least squares regression discriminate analysis (SPLS-DA), which allow for the determination of fentanyl as low as 0.05% in simulated seized heroin and 0.10% in simulated seized cocaine samples.

Characterization of Synthetic Hydroxyapatite Fibers Using High-Resolution, Polarized Raman Spectroscopy.

Abstract: In the Raman spectrum of B-type carbonated apatites, the ν1 CO32– mode (at ∼1070 cm–1) overlaps the ν3 PO43– band The latter is readily observed where the CO32– content is low (up to ∼3 wt%) The CO32– content of bone is considerably higher (∼7–9 wt%) As a result, the ν3 PO43– band becomes completely obscured The 1000–1100 cm–1 spectral range of carbonated apatite is frequently considered a combined ν3 PO43– and ν1 CO32– region Here, high-resolution polarized Raman spectroscopy (step size of 074 ± 004 cm–1) provides new insights into synthetic hydroxyapatite (HAp) obtained as micrometer-sized fibers Compared to bone mineral (deproteinized bovine bone), spectral features of HAp fibers are highly resolved In particular, the ν3 PO43– band resolves into nine distinct sub-components: 1028, 1032, 1040, 1043, 1047, 1053, 1055, 1062, and 1076 cm–1 Parameters including full width half-maximum, intensity, area fraction, intensity ratio, and area fraction ratio vary between parallel and perpendicular polarized configurations It is likely that the ν1 CO32– band of B-type carbonated apatites may contain a small but not insignificant contribution from the 1076 cm–1 sub-component of the ν3 PO43– band Furthermore, the 1076 cm–1/1047 cm–1 ratio changes between parallel and perpendicular scattering configurations, suggesting that the contribution of the 1076 cm–1 sub-component may vary as a function of local orientation of bone mineral, thus skewing the ν1 CO32– band and compromising accurate estimation of carbonate-to-phosphate ratios in B-type CO32– substituted apatite

Application of Infrared Reflectance Spectroscopy on Plastics in Cultural Heritage Collections: A Comparative Assessment of Two Portable Mid-Fourier Transform Infrared Reflection Devices.

Abstract: Plastics have been increasingly used to create modern and contemporary art and design, and nowadays, museum collections hold numerous objects completely or partially made of plastics. However, the preservation of these materials is still a challenging task in heritage conservation, especially because some plastics show signs of degradation shortly after their production. In addition, different degradation mechanisms can often take place depending on the plastic composition and appropriate environmental and packaging conditions should be adopted. Therefore, methods for in situ and rapid characterization of plastic artifacts' composition are greatly needed to outline proper conservation strategies. Infrared (IR) spectroscopy, such as attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), is a well-established method for polymeric material analysis. However, ATR FT-IR requires an intimate contact with the object, which makes its application less appropriate for the in situ investigation of fragile or brittle degraded plastic objects. Mid-FT-IR reflectance spectroscopy may represent a valid alternative as it allows in situ measurements with minimum or even no contact, and IR data can be acquired rapidly. On the other hand, spectral interpretation of reflectance spectra is usually difficult as IR bands may appear distorted with significant changes in band maximum, shape, and relative intensity, depending on the optical properties and surface texture of the material analyzed. Presently, mid-FT-IR reflection devices working in external reflection (ER FT-IR) and diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) modes have been used in cultural heritage research studies. As the collected vibrational information depends on the optical layout of the measuring system, differences between ER FT-IR and DRIFT spectra are thus expected when the same polymer is analyzed. So far, ER FT-IR and DRIFT spectroscopy have been individually explored for the identification of plastic objects, but comparative studies between the application of two reflectance FT-IR modes have not been presented yet. In this work, the use of two portable FT-IR spectrometers equipped with ER FT-IR and DRIFTS modes were compared for plastics identification purposes for the first time. Both references of polymeric materials and historical plastic objects (from a Portuguese private collection) were studied and the differences between ER FT-IR and DRIFT spectra were discussed. The spectra features were examined considering the two different optical geometries and analytes' properties. This new insight can support a better understanding of both vibrational information acquired and practical aspects in the application of the ER FT-IR and DRIFTS in plastic analysis.

Calibration of the SHERLOC Deep Ultraviolet Fluorescence-Raman Spectrometer on the Perseverance Rover.

Abstract: We describe the wavelength calibration of the spectrometer for the scanning of habitable environments with Raman and luminescence for organics and chemicals (SHERLOC) instrument onboard NASA’s Pers...

Chemometrics and Experimental Design for the Quantification of Nitrate Salts in Nitric Acid: Near-Infrared Spectroscopy Absorption Analysis

Abstract: Implementing remote, real-time spectroscopic monitoring of radiochemical processing streams in hot cell environments requires efficiency and simplicity. The success of optical spectroscopy for the ...

ISREA: An Efficient Peak-Preserving Baseline Correction Algorithm for Raman Spectra.

Abstract: A critical step in Raman spectroscopy is baseline correction. This procedure eliminates the background signals generated by residual Rayleigh scattering or fluorescence. Baseline correction procedures relying on asymmetric loss functions have been employed recently. They operate with a reduced penalty on positive spectral deviations that essentially push down the baseline estimates from invading Raman peak areas. However, their coupling with polynomial fitting may not be suitable over the whole spectral domain and can yield inconsistent baselines. Their requirement of the specification of a threshold and the non-convexity of the corresponding objective function further complicates the computation. Learning from their pros and cons, we have developed a novel baseline correction procedure called the iterative smoothing-splines with root error adjustment (ISREA) that has three distinct advantages. First, ISREA uses smoothing splines to estimate the baseline that are more flexible than polynomials and capable of capturing complicated trends over the whole spectral domain. Second, ISREA mimics the asymmetric square root loss and removes the need of a threshold. Finally, ISREA avoids the direct optimization of a non-convex loss function by iteratively updating prediction errors and refitting baselines. Through our extensive numerical experiments on a wide variety of spectra including simulated spectra, mineral spectra, and dialysate spectra, we show that ISREA is simple, fast, and can yield consistent and accurate baselines that preserve all the meaningful Raman peaks.

Vibrational Spectroscopy for Detection of Diabetes: A Review

Abstract: Type II diabetes mellitus (T2DM) is a metabolic disorder that is characterized by chronically elevated glucose caused by insulin resistance. Although T2DM is manageable through insulin therapy, the disorder itself is a risk factor for much more dangerous diseases including cardiovascular disease, kidney disease, retinopathy, Alzheimer's disease, and more. T2DM affects 450 million people worldwide and is attributed to causing over four million deaths each year. Current methods for detecting diabetes typically involve testing a person's glycated hemoglobin levels as well as blood sugar levels randomly or after fasting. However, these methods can be problematic due to an individual's levels differing on a day-to-day basis or being affected by diet or environment, and due to the lack of sensitivity and reliability within the tests themselves. Vibrational spectroscopic methods have been pursued as a novel method for detecting diabetes accurately and early in a minimally invasive manner. This review summarizes recent research, since 2015, which has used infrared or Raman spectroscopy for the purpose of developing a fast and accurate method for diagnosing diabetes. Based on critical evaluation of the reviewed work, vibrational spectroscopy has the potential to improve and revolutionize the way diabetes is diagnosed, thereby allowing for faster and more effective treatment of the disorder.

Effects of Laser Beam Focusing Characteristics on Laser-Induced Breakdown Spectra.

Abstract: The impact of altering laser focusing conditions on laser-induced breakdown spectroscopy experiments is investigated under ambient Earth laboratory and simulated Martian atmospheres. Experiments were performed in which the focal spot size was varied on a sample by altering the lens to sample distance with respect to targets of interest. Samples investigated include aluminum, copper, and steel. Specific neutral and ionic transitions of each sample were monitored. Atomic and ionic emissions show different intensity peak distributions along the varying lens to sample distance. Ionic species have peak emissions when laser plasma is initiated with a focused spot within the sample in ambient Earth laboratory air, while atomic emissions have peak intensities several millimeters deeper into a sample. In simulated Martian atmospheres, atomic emissions are observed to peak when the laser is focused within the sample, while ionic emissions have peak intensities when the laser is focused near the surface of a sample.

Total Phosphorus Determination in Soils Using Laser-Induced Breakdown Spectroscopy: Evaluating Different Sources of Matrix Effects.

Abstract: Laser-induced breakdown spectroscopy (LIBS) is a potential alternative to wet chemical methods for total soil phosphorus determination, but matrix effects related to physical and chemical sample pr...

Comparison of Raman and near-infrared chemical mapping for the analysis of pharmaceutical tablets

Abstract: Raman and near-infrared (NIR) chemical mapping are widely used methods in the pharmaceutical industry to understand the distribution of components within a drug product. Recent advancements in instrumentation have enabled the rapid acquisition of high-resolution images. The comparison of these techniques for the analysis of pharmaceutical tablets has not recently been explored and thus the relative performance of each technique is not currently well defined. Here, the differences in the chemical images obtained by each method are assessed and compared with scanning electron microscopy with energy dispersive X-ray microanalysis (SEM-EDX), as an alternative surface imaging technique to understand the ability of each technique to acquire a chemical image representative of the sample surface. It was found that the Raman data showed the best agreement with the spatial distribution of components observed in the SEM-EDX images. Quantitative and qualitative comparison of the Raman and NIR images revealed a very different spatial distribution of components with regards to domain size and shape. The Raman image exhibited sharper and better discriminated domains of each component, whereas the NIR image was heavily dominated by large pixelated domains. This study demonstrated the superiority of using Raman chemical mapping compared with NIR chemical mapping to produce a chemical image representative of the sample surface using routinely available instrumentation to obtain a better approximation of domain size and shape. This is fundamental for understanding knowledge gaps in current manufacturing processes; particularly relating the relationship between components in the formulation, processing condition, and final characteristics. By providing a means to more accurately visualize the components within a tablet matrix, these areas can all be further understood.

Authentication of Antibiotics Using Portable Near-Infrared Spectroscopy and Multivariate Data Analysis.

Abstract: Counterfeit medicines represent a global public health threat warranting the development of accurate, rapid, and nondestructive methods for their identification. Portable near-infrared (NIR) spectroscopy offers this advantage. This work sheds light on the potential of combining NIR spectroscopy with principal component analysis (PCA) and soft independent modelling of class analogy (SIMCA) for authenticating branded and generic antibiotics. A total of 23 antibiotics were measured “nondestructively” using a portable NIR spectrometer. The antibiotics corresponded to six different active pharmaceutical ingredients being: amoxicillin trihydrate and clavulanic acid, azithromycin dihydrate, ciprofloxacin hydrochloride, doxycycline hydrochloride, and ofloxacin. NIR spectra were exported into Matlab R2018b where data analysis was applied. The results showed that the NIR spectra of the medicines showed characteristic features that corresponded to the main excipient(s). When combined with PCA, NIR spectroscopy could distinguish between branded and generic medicines and could classify medicines according to their manufacturing sources. The PCA scores showed the distinct clusters corresponding to each group of antibiotics, whereas the loadings indicated which spectral features were significant. SIMCA provided more accurate classification over PCA for all antibiotics except ciprofloxacin which products shared many overlapping excipients. In summary, the findings of the study demonstrated the feasibility of portable NIR as an initial method for screening antibiotics.

Prediction of α-Lactalbumin and β-Lactoglobulin Composition of Aqueous Whey Solutions Using Fourier Transform Mid-Infrared Spectroscopy and Near-Infrared Spectroscopy.

Abstract: Characterization and quantification of individual whey proteins are of crucial importance to many industrial dairy processes. Labor intensive wet-chemical methods are still being used for this purpose, but a rapid quantification method for individual whey proteins is highly desired. This work investigate the utility of Fourier transform mid-infrared spectroscopy and Fourier transform near-infrared spectroscopy for rapid quantification of the two main whey proteins (β-lactoglobulin and α-lactalbumin) in complex aqueous whey solutions simulating production process streams. MIR and NIR spectra obtained on whey samples with known and varying amounts of the proteins of interest and are used to develop partial least squares prediction models. Selection of informative wavelength regions allowed for prediction of β-lactoglobulin and α-lactalbumin concentrations with very high precision and accuracy (root mean square error of cross-validation, or RMSECV, of 0.6% and R2 of 0.99 for NIR), demonstrating the potential of being implemented for rapid in-line monitoring of protein composition in industrial whey streams. Two-dimensional MIR-NIR correlation spectroscopy is used to identify the most informative parts of the NIR spectra in relation to protein secondary structure. In addition multivariate curve resolution is applied to the MIR data to resolve mixture spectra and to elucidate the spectral ranges that were most useful in distinguishing between the two whey proteins. The study concludes that NIR spectroscopy has potential for accurate in-line protein quantification and overall secondary protein structure quantification which open new possibilities for in-line industrial applications.

Estimation of the Relative Abundance of Quartz to Clay Minerals Using the Visible-Near-Infrared-Shortwave-Infrared Spectral Region.

Abstract: Quartz is the most abundant mineral on the earth’s surface. It is spectrally active in the longwave infrared (LWIR) region with no significant spectral features in the optical domain, i.e., visible...

Intermolecular Interactions in the Polymer Blends Under High-Pressure CO2 Studied Using Two-Dimensional Correlation Analysis and Two-Dimensional Disrelation Mapping.

Abstract: Exposing polymers to high-pressure and supercritical CO2 is a useful approach in polymer processing. Consequently, the mechanisms of polymer–polymer interaction under such conditions are worthy of ...

Sub-Surface Molecular Analysis and Imaging in Turbid Media Using Time-Gated Raman Spectral Multiplexing.

Abstract: Obtaining molecular information deeper within optically turbid samples is valuable in many applications. However, in many cases this is challenging, in particular when the sample elicits strong laser-induced fluorescence emission. Here, we investigated the use of time-gated and micro-spatially offset Raman spectroscopy (micro-SORS) based on spectral multiplexing detection to obtain sub-surface molecular analysis and imaging for both fluorescing and non-fluorescing samples. The multiplexed spectral detection achieved with a digital micromirror device (DMD) allowed fast acquisition of the time-gated signals to enable three-dimensional Raman mapping (raster scanning in the lateral x,y plane and using time-of-flight calibration for the axial z-direction). Sub-millimeter resolution molecular depth mapping was achieved with dwell times on the order of seconds per pixel. To suppress fluorescence backgrounds and enhance Raman bands, time-gated Raman spectroscopy was combined with micro-SORS to recover Raman signals of red pigments placed behind a layer of optically turbid material. Using a defocusing micro-SORS approach, both fluorescence and Raman signals from the surface layers were further suppressed, which enhanced the Raman signals from the deeper sublayers containing the pigment. These results demonstrate that time-gated Raman spectroscopy based on spectral multiplexed detection, and in combination with micro-SORS, is a powerful technique for sub-surface molecular analysis and imaging, which may find practical applications in medical imaging, cultural heritage, forensics, and industry.

Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

Abstract: Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an ...

Fiber Optic Reflection Spectroscopy-Near-Infrared Characterization Study of Dry Pigments for Pictorial Retouching.

Abstract: A deep comprehension of composition of pigments, employed nowadays in the field of pictorial retouch is considered essential for a deeper knowledge of their behavior with time once applied on artifacts. A commercially available set consisting of 27 pigments employed for the conservation of both historical and contemporary artworks has been characterized through Reflectance Spectroscopy in the VIS and NIR spectral range. The pigments included in the investigated set are classified into four categories: (i) dyes and colors from plants, (ii) modern pigments, (iii) pigments of own production and historical pigments, and (iv) natural earths. Recorded spectra were interpreted with the aim to detect existing coloring and filling phases and obtained results were compared with available data sheets: some inconsistencies were found, as well as lack of some compounds among the reported ones. Attributions were found for many features, even if in some cases detailed information for a comparison was not found in the literature, especially regarding NIR spectra. The proposed paper aims to provide a useful tool for the study of real artworks with a detailed overview of material characteristics in the visible and near infrared spectral range.

Intensity Enhancement of a Two-Dimensional Asynchronous Spectrum Without Noise Level Fluctuation Escalation Using a One-Dimensional Spectra Sequence Change.

Abstract: Previously, we demonstrated that the intensities of cross-peaks in a two-dimensional asynchronous spectrum could be enhanced using sequence change of the corresponding one-dimensional spectra. This...

Interband Cascade Laser Arrays for Simultaneous and Selective Analysis of C1-C5 Hydrocarbons in Petrochemical Industry.

Abstract: The detection and measurement of hydrocarbons are of high interest for a variety of applications, for example within the oil and gas industry from extraction throughout the complete refining process, as well as for environmental monitoring and for portable safety devices. This paper presents a highly sensitive, selective, and robust tunable laser analyzer that has the capability to analyze several components in a gas sample stream. More specifically, a multi-gas system for simultaneous detection of C1 to iC5 hydrocarbons, using a room temperature distributed feedback interband cascade laser array, emitting in the 3.3 µm band has been realized. It combines all the advantages of the tunable laser spectroscopy method for a fast, sensitive, and selective in-line multicomponent tunable laser analyzer. Capable of continuous and milliseconds fast monitoring of C1-iC5 hydrocarbon compositions in a process stream, the analyzer requires no consumables (e.g., purging, carrier gas) and no in-field calibration, enabling a low cost of ownership for the analyzer. The system was built based on an industrial GasEye series platform and deployed for the first time in field at Preem refinery in Lysekil, Sweden, in autumn 2018. Results of the measurement campaign and comparison with gas chromatography instrumentation are presented.

Two-Trace Two-Dimensional Correlation Spectroscopy Study of the Crystallization Behavior of Bioplastics:

Abstract: A pair of attenuated total reflection infrared (ATR IR) spectra obtained during the crystallization of bioplastic copolymer poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate] or PHBHx from the m...

A Monolithic Spatial Heterodyne Raman Spectrometer: Initial Tests

Abstract: A monolithic spatial heterodyne Raman spectrometer (mSHRS) is described, where the optical components of the spectrometer are bonded to make a small, stable, one-piece structure. This builds on pre...

Features of Measuring Low CO Concentrations in N2-Containing Mixtures at Different Temperatures Using Spontaneous Raman Spectroscopy.

Abstract: Raman spectroscopy is a promising tool for combustion processes optimization, due to the possibility of rapid determination of the exhaust gases composition. An important gas component in this task is carbon monoxide whose emission limits vary from 100 to 200 parts per million (ppm), depending on the heat generator technology. However, for the correct determination of its concentration from the sample Raman spectrum, it is necessary to take into account the contribution of nitrogen lines intensity due to their mutual overlap. This paper discusses a technique for deriving carbon monoxide intensity based on fitting the nitrogen spectrum at various temperatures. It is shown that ignoring the Herman–Wallis factors in the fitting procedure lead to an additional measurement error, which increases with temperature and exceeds 350 ppm at T = 1800 K.

Detecting Minerals and Organics Relevant to Planetary Exploration Using a Compact Portable Remote Raman System at 122 Meters

Abstract: Raman spectroscopy is a technique that can detect and characterize a range of molecular compounds such as water, water ice, water-bearing minerals, and organics of particular interest to planetary science The detection and characterization of these molecular compounds, which are indications of habitability on planetary bodies, have become an important goal for planetary exploration missions spanning the solar system Using a compact portable remote Raman system consisting of a 532 nm neodymium-doped yttrium aluminum garnet- (Nd:YAG-) pulsed laser, a 3-in (762 cm) diameter mirror lens and a compact spectrograph with a miniature intensified charge coupled device (mini-ICCD), we were able to detect water (H2O), water ice (H2O-ice), CO2-ice, hydrous minerals, organics, nitrates, and an amino acid from a remote distance of 122 m in natural lighting conditions To the best of our knowledge, this is the longest remote Raman detection using a compact system The development of this uniquely compact portable remote Raman system is applicable to a range of solar system exploration missions including stationary landers for ocean worlds and lunar exploration, as they provide unambiguous detection of compounds indicative of life as well as resources necessary for further human exploration

Single-Molecule Fluorescence Techniques for Membrane Protein Dynamics Analysis.

Abstract: Fluorescence-based single-molecule techniques, mainly including fluorescence correlation spectroscopy (FCS) and single-molecule fluorescence resonance energy transfer (smFRET), are able to analyze the conformational dynamics and diversity of biological macromolecules. They have been applied to analysis of the dynamics of membrane proteins, such as membrane receptors and membrane transport proteins, due to their superior ability in resolving spatio-temporal heterogeneity and the demand of trace amounts of analytes. In this review, we first introduced the basic principle involved in FCS and smFRET. Then we summarized the labeling and immobilization strategies of membrane protein molecules, the confocal-based and TIRF-based instrumental configuration, and the data processing methods. The applications to membrane protein dynamics analysis are described in detail with the focus on how to select suitable fluorophores, labeling sites, experimental setup, and analysis methods. In the last part, the remaining challenges to be addressed and further development in this field are also briefly discussed.