Applied Spectroscopy

doi: 10.1177/00037028221150570pmid: 36599819

Daigle, Jean-François; Foster, Mathieu; Caron, Guillaume; Amyotte, Adrien; Pudo, Dominik; Théberge, Francis

doi: 10.1177/00037028221124907pmid: 36217960

In light of the widespread use of high-energy lasers (HELs) for a variety of purposes, for example, standoff (>100 m) applications, will require the ability to monitor in real time the interaction with processed materials. While multiple sensing methods have been successfully developed for industrial HEL systems operating at close range, they are not compatible with the unique requirements of long-distance applications. Here, high-energy laser–induced oxidation spectroscopy (HELIOS) is demonstrated on carbon steel coupons as an efficient standoff assessment method compatible with long distance HEL applications. Acute monitoring of spectral features from thermally excited iron atoms and oxides, corroborated with real-time temperature measurements, reveals the interaction mechanisms at play.

Meuse, Curtis W.; Rubinson, Kenneth A.

doi: 10.1177/00037028221134128pmid: 36200904

Circular dichroism (CD) measurements help characterize optically active molecules and higher-order biomolecular structures. The harmonization of interlaboratory CD measurements requires minimizing measurement uncertainties and determinate errors. Most CD measurements utilize a single-wavelength intensity measurement at a spectral peak to calibrate the intensities of the ultraviolet wavelength range. However, such a single-wavelength calibration is inherently less precise than using the CD instrument's spectrum over the entire measured spectral range. A more thorough and informative calibration can be achieved by remapping the spectrum into what we call a spectral similarity plot. This process allows a straightforward, quantitative evaluation of the shape congruence between two spectra over the full spectral range. While preliminary analyses suggest spectral similarity plots can be utilized with a variety of different spectrometry methods, here we illustrate the process applied to circular dichroism. Spectral similarity plots are highly sensitive to deviations due to differences in concentration, pathlength, source and detector properties, circular polarization balance, as well as wavelength nonlinearities and shifts. Deviations in these properties can be quantitated by a linear least squares fit of the remapped data. The remapping enables protocols to correct spectra toward congruence between two spectra. The spectra similarity comparison provides an objective, unambiguous test of the CD instrument quality when, for example, compared to a carefully calibrated system as shown in the examples described in the text.

Marchetti, Mario; Mechling, Jean-Michel; Janvier-Badosa, Sarah; Offroy, Marc

doi: 10.1177/00037028221135065pmid: 36220774

The addition of water is used to past by internal post-curing of hardening cement. Hydration and curing of cementitious are widely identified by non-destructive 1H nuclear magnetic resonance (NMR) measurements of transverse relaxation time and self-diffusion. However, those non-destructive analytical methodologies do not give a truly chemical characterization of the cement matrix during the hydration and curing process. Indeed, the NMR studies only the water dynamics of hydrating cement with internal post-curing. Recent research indicated chemometrics coupled with Raman spectroscopy allows for a better understanding of chemical processes. Recent advances in computing gave industries and research centers the opportunity to generate cost effective data. In this work, an original method is presented, which uses both a data analysis and a non-invasive, non-destructive Raman monitoring of the hydration reaction of a Portland cement. Data was then analyzed by means of chemometrics methods (principal components analysis (PCA), independent components analysis (ICA), and multivariate curve resolution-alternated least-squares (MCR-ALS) with SIMPLe-to-use Interactive Self-modelling Mixture Analysi (SIMPLISMA) and Orthogonal Projection Approach (OP initialization). Results were compared to the ones obtained with thermogravimetric analysis of this cement paste. Besides the consistency of results from both analytical measurements, chemometrics coupled to Raman spectroscopy accurately revealed the details of the setting without any samples collection. The acquisition frequency allowed a proper identification of the occurrence of each of the various phases involved in the hydration and setting process.

Thomas, Brian; Anderson, Kevin; De Silva, Imesha; Verbeck, Guido; Taylor, Stephen

doi: 10.1177/00037028221135634pmid: 36253880

The analysis of collagen stability is of interest in forensics, archaeology, and molecular paleontology. Collagen decay rates are often measured by thermal kinetic studies that employ liquid chromatography mass spectrometry (LC-MS) to assay collagen quantities. However, these kinetic studies generally focus on measuring the decreasing levels of collagen instead of an exact molecular concentration of each sample. Thus, attenuated total reflection Fourier transform infrared (ATR FT-IR) spectroscopy can offer a simpler and less expensive alternative to LC-MS. The application of a new protocol to determine decreasing amounts of bone collagen in artificially decayed porcine and bovine bone was assessed. The protocol uses a forensic application of ATR FT-IR spectroscopy on size-restricted bone powder from three uniformly high temperature conditions. Also, for the first time, collagen-specific second-harmonic generation (SHG) imaging was also applied to artificially aged bone to add an independent, qualitative perspective to parallel FT-IR assessments. SHG images and ATR FT-IR spectra together reveal the same orderly bone collagen decay as found in previous thermal kinetic studies. Resulting Arrhenius plots with r2 values > 0.95 suggest that the ATR FT-IR-based protocol has potential as a precise and simple tool for measuring bone collagen decay rates. The results are significant for applications of thermal kinetic studies, and our protocol can serve as an inexpensive, precise, and pragmatic means of evaluating bone collagen stability within an array of conditions.

Jakubek, Ryan S.

doi: 10.1177/00037028221126197pmid: 36065940

Detailed information on the physics and chemistry of a sample can be derived from Raman band parameters. However, the Raman band observed by the detector contains artifacts from the instrument, complicating analysis of these details. To obtain Raman data that can be directly correlated to sample properties and to compare Raman spectra across instrumentation, instrumental effects must be accounted for. This is commonly performed for homogeneously broadened bands by determining the contribution of the slit function to the spectrum. However, there is currently no method for understanding instrumental effects on inhomogeneously broadened bands or a method to account for these effects when examining data and comparing data across instruments, though these analyses are commonplace. This shortfall injects an unknown error into the analyses and comparisons of inhomogeneously broadened Raman bands. This work derives a method of modeling inhomogeneous Raman bands as a continuum of homogeneous Raman bands spanning the width of the stochastic fluctuation energy well that causes inhomogeneous broadening. This model is combined with previous work to examine the effects of the slit function, intrinsic Raman band, stochastic energy well, homogeneously broadened Raman band, and slit width band parameters on the inhomogeneously broadened Raman band parameters. This model, for the first time, provides a quantitative description of the experimental parameters that effect the inhomogeneous Raman bands.

Artesani, Alessia; Lamuraglia, Raffaella; Menegazzo, Federica; Bonetti, Stefano; Traviglia, Arianna

doi: 10.1177/00037028221133404pmid: 36190333

This work demonstrates terahertz time-domain spectroscopy (THz-TDS) in reflection configuration on a class of inorganic and mineral pigments. The technique is validated for pictorial materials against the limitations imposed by the back-reflection of the THz signal, such as weak signal intensity, multiple signal losses and distortion, as well as the current scarce databases. This work provides a detailed description of the experimental procedure and method used for the determination of material absorption coefficient of a group of 10 pigments known to be used in ancient frescoes, that are, Cu-based (azurite, malachite, and Egyptian blue), Pb-based (minium and massicot), Fe-based (iron oxide yellow, dark ochre, hematite, and Pompeii red) pigments and mercury sulfide (cinnabar), and classified the vibrational modes of the molecular oxides and sulfides for material identification. The results of this work showed that the mild signal in reflection configuration does not limit the application of THz-TDS on inorganic and mineral pigments as long as (i) the THz signal is normalized with a highly reflective reference sample, (ii) the secondary reflected signals from inner interfaces are removed with a filtering procedure, and (iii) the limitations at high frequencies imposed by the dynamic range of the instrument are considered. Under these assumptions, we were able to differentiate molecular phases of the same metal and identify azurite, Egyptian blue, minium, and cinnabar, isolating the molecular vibrations up to 125 cm−1. The established approach demonstrated to be reliable, and it can be extended for the study of other materials, well beyond the reach of the heritage domain.

Paukshtis, Evgeniy A.; Chesnokov, Vladimir V.; Glazneva, Tatiana S.

doi: 10.1177/00037028221134118pmid: 36331040

Formic acid is considered as a promising hydrogen carrier and can be used as a source of hydrogen in the processing of heavy oil fractions such as tar. The interaction of formic acid with tar was studied by infrared Fourier transform spectroscopy via special technique using a mirror substrate. The infrared (IR) spectra were interpreted considering density functional theory (DFT) calculations. It was shown that formic acid dissolved in tar in three forms, as dimers, monomers of cis- and trans-configurations, hydrogen-bonded to the aromatic rings of the tar compounds, and as free-rotating gas molecules (microbubbles in the tar bulk). The research performed provides an opportunity and methodological base for studying the process of tar conversion in the presence of formic acid into gasoline fractions at temperatures up to 300 oC.

English, Caitlyn M.; Kitzhaber, Zechariah B.; Sanim, Kazi Ragib I.; Kalaitzakis, Michail; Kosaraju, Bhanuprakash; Pinckney, James L.; Hodgson, Michael E.; Vitzilaios, Nikolaos I.; Richardson, Tammi L.; Myrick, Michael L.

doi: 10.1177/00037028221126748

Farquharson, Stuart; Brouillette, Carl; Shende, Chetan; Farquharson, Duncan; Morrison, Chad

doi: 10.1177/00037028221130789pmid: 36138573

NASA has been developing and testing a water recovery system for over two decades to minimize the amount of water required for long duration human space missions. A key system component is the total organic carbon analyzer (TOCA) that determines if the recovered water is below the toxicology-defined health limit of 5 mg/L TOC and is safe to drink. The TOCA is composed of a liquid phase loop and a gas phase loop. The TOCA employs an oxidizer to convert the organics in the liquid phase to carbon dioxide (CO2) and a liquid–gas separator to isolate the CO2 for measurement in the gas phase by infrared spectroscopy. In an effort to reduce the consumables, mass, volume, and power of the system, we investigated the ability of surface-enhanced Raman spectroscopy (SERS), and Raman spectroscopy to measure 5 mg/L carbon in water. The SERS measurement employed silver colloids to increase sensitivity, while the Raman measurements used multiple mirrors to increase sensitivity. Here, we present SERS measurements of carbonate (CO3=) at 3 mg/L carbon and Raman measurements of CO2 at 9 mg/L carbon in the effluent water of a new oxidizer being developed for a future TOCA. Both SERS and Raman techniques can determine TOC in the liquid phase, eliminating the need for the gas phase loop and associated supplies and replacement components, which could effectively decrease the size and weight of the current TOCA by as much as 50%.