Rapid on-site analysis of soil microplastics using miniaturized NIR spectrometers: Key aspect of instrumental variation.

Contamination by microplastics, a global environmental concern, demands effective monitoring. While current methods focus on characterizing the smallest particles, their low throughput hinders practical assessment. Miniaturized near-infrared (NIR) spectroscopy offers high-throughput capabilities and rapid on-site analysis, potentially filling this gap.

Characterization and classification of oleogels and edible oil using vibrational spectroscopy in tandem with one-class and multiclass chemometric methods.

Oleogel represents a promising healthier alternative to act as a substitute for conventional fat in various food products. Oil selection is a crucial factor in determining the technological properties and applications of oleogels due to their distinct fatty acid composition, molecular weight, and thermal properties, as well as the presence of antioxidants and oxidative stability. Hence, the relevance of monitoring oleogel properties by non-destructive, eco-friendly, portable, fast, and effective techniques is a relevant task and constitutes an advance in the evaluation of oleogels quality.

The Application of Handheld Near-Infrared Spectroscopy and Raman Spectroscopic Imaging for the Identification and Quality Control of Food Products.

The following investigations describe the potential of handheld NIR spectroscopy and Raman imaging measurements for the identification and authentication of food products. On the one hand, during the last decade, handheld NIR spectroscopy has made the greatest progress among vibrational spectroscopic methods in terms of miniaturization and price/performance ratio, and on the other hand, the Raman spectroscopic imaging method can achieve the best lateral resolution when examining the heterogeneous composition of samples. The utilization of both methods is further enhanced via the combination with chemometric evaluation methods with respect to the detection, identification, and discrimination of illegal counterfeiting of food products.

Correction: Bigi et al. Waste Orange Peels as a Source of Cellulose Nanocrystals and Their Use for the Development of Nanocomposite Films. 2023, , 960.

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Rapid Determination of the Total Petroleum Hydrocarbon Content of Soils by Handheld Fourier Transform Near-Infrared Spectroscopy.

For successful soil remediation and hydrocarbon exploration operations, determining the total petroleum hydrocarbon (TPH) content of soils is an indispensable process step. This paper reports on the performance of a handheld Fourier transform near-infrared (FT-NIR) spectrometer for rapid and quantitative determination of TPH content of soils from two different sites by diffuse reflection measurements. For rapid decisions for exploration work or environmental site assessment projects, a quick─preferably on-site─determination of TPH content is valuable.

Waste Orange Peels as a Source of Cellulose Nanocrystals and Their Use for the Development of Nanocomposite Films.

To date, approximately 30-50% of food is wasted from post-harvesting to consumer usage. Typical examples of food by-products are fruit peels and pomace, seeds, and others. A large part of these matrices is still discarded in landfills, while a small portion is valorized for bioprocessing.

Hand-Held Near-Infrared Spectroscopy for Authentication of Fengdous and Quantitative Analysis of Mulberry Fruits.

Recently, miniaturization of Raman, mid-infrared (MIR) and near-infrared (NIR) spectrometers have made substantial progress, and marketing companies predict this segment of instrumentation a significant growth rate within the next few years. This increase will be based on a more frequent implementation for industrial quality and process control and a broader adoption of spectrometers for in-the-field testing, on-site measurements, and every-day-life consumer applications. The reduction in size, however, must not lead to compromises in measurement performance and the hand-held instrumentation will only have a real impact if spectra of comparable quality to laboratory spectrometers can be obtained.

Quantitative Analysis of Organic Liquid Three-Component Systems: Near-Infrared Transmission versus Raman Spectroscopy, Partial Least Squares versus Classical Least Squares Regression Evaluation and Volume versus Weight Percent Concentration Units.

The band shapes and band positions of near-infrared (NIR) and Raman spectra change depending on the concentrations of specific chemical functionalities in a multicomponent system. To elucidate these effects in more detail and clarify their impact on the analytical measurement techniques and evaluation procedures, NIR transmission spectra and Raman spectra of two organic liquid three-component systems with variable compositions were analyzed by two different multivariate calibration procedures, partial least squares (PLS) and classical least-squares (CLS) regression. Furthermore, the effect of applying different concentration units (volume percent (%V) and weight percent (%W) on the performance of the two calibration procedures have been tested.

Rapid Determination of Nutritional Parameters of Pasta/Sauce Blends by Handheld Near-Infrared Spectroscopy.

Nowadays, near infrared (NIR) spectroscopy has experienced a rapid progress in miniaturization (instruments < 100 g are presently available), and the price for handheld systems has reached the < $500 level for high lot sizes. Thus, the stage is set for NIR spectroscopy to become the technique of choice for food and beverage testing, not only in industry but also as a consumer application. However, contrary to the (in our opinion) exaggerated claims of some direct-to-consumer companies regarding the performance of their "food scanners" with "cloud evaluation of big data", the present publication will demonstrate realistic analytical data derived from the development of partial least squares (PLS) calibration models for six different nutritional parameters (energy, protein, fat, carbohydrates, sugar, and fiber) based on the NIR spectra of a broad range of different pasta/sauce blends recorded with a handheld instrument.

Quantitative analysis of a pharmaceutical formulation: Performance comparison of different handheld near-infrared spectrometers.

Notwithstanding the first developments of miniaturized vibrational spectrometers more than a decade ago, only recently real handheld near-infrared (NIR) spectrometers (<200 g) became commercially available at significantly reduced costs compared to other portable systems. While on the one hand this development was driven by the consumer request for every-day-life applications by non-experts, on the manufacturer side it was supported by the availability and potential of new technologies such as micro-electromechanical systems (MEMS). In the present communication calibration spectra of a solid pharmaceutical formulation consisting of two excipients and three active ingredients, acetylsalicylic acid (ASA), ascorbic acid (ASC) and caffeine (CAF), have been measured with four handheld NIR spectrometers based on different monochromator principles and have subsequently been used to develop partial least squares (PLS) models for the quantitative determination of the active ingredients.

Identification Performance of Different Types of Handheld Near-Infrared (NIR) Spectrometers for the Recycling of Polymer Commodities.

For sustainable utilization of raw materials and environmental protection, the recycling of the most common polymers-polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS)-is an extremely important issue. In the present communication, the discrimination performance of the above polymer commodities based on their near-infrared (NIR) spectra measured with four real handheld (<200 g) spectrometers based on different monochromator principles were investigated. From a total of 43 polymer samples, the diffuse reflection spectra were measured with the handheld instruments.

2DCOS and PCMW2D analysis of FT-IR/ATR spectra measured at variable temperatures on-line to a polyurethane polymerization.

In the present communication the potential of 2DCOS analysis and the spin-off technique perturbation-correlation moving window 2D (PCMW2D) analysis is illustrated with reference to spectroscopic changes observed in a data set recorded by in-line fiber-coupled FT-IR spectroscopy in the attenuated total reflection (ATR) mode during a polyurethane solution polymerization at different temperatures. In view of the chemical functionalities involved, hydrogen bonding plays an important role in this polymerization reaction. Based on the 2DCOS and PCMW2D analysis, the sequence of hydrogen bonding changes accompanying the progress of polymerization and precipitation of solid polymer can be determined.

Real-time analysis of the polymerization kinetics of 1,4-butanediol and 4,4'-diphenylmethanediisocyanate by fiber-coupled Fourier transform infrared spectroscopy.

Polyurethanes are a polymer class with large property diversity. However, despite their extreme technical importance, only few research data regarding the on-line analysis and the derivation of kinetic polymerization data are available in the literature. The present work focuses on the in-line monitoring of the solution polymerization of 4,4'-diphenylmethanediisocyanate and 1,4-butanediol by fiber-coupled FT-IR spectroscopy in the attenuated total reflection (ATR) mode at variable temperatures and the interpretation of the spectral changes as a function of polymerization progress.

Comparative Variable Temperature Studies of Polyamide II with a Benchtop Fourier Transform and a Miniature Handheld Near-Infrared Spectrometer Using 2D-COS and PCMW-2D Analysis.

The main objective of this communication is to compare the performance of a miniaturized handheld near-infrared (NIR) spectrometer with a benchtop Fourier transform near-infrared (FT-NIR) spectrometer. Generally, NIR spectroscopy is an extremely powerful analytical tool to study hydrogen-bonding changes of amide functionalities in solid and liquid materials and therefore variable temperature NIR measurements of polyamide II (PAII) have been selected as a case study. The information content of the measurement data has been further enhanced by exploiting the potential of two-dimensional correlation spectroscopy (2D-COS) and the perturbation correlation moving window two-dimensional (PCMW2D) evaluation technique.

Spectra Transfer Between a Fourier Transform Near-Infrared Laboratory and a Miniaturized Handheld Near-Infrared Spectrometer.

The aim of this contribution is to demonstrate the transfer of spectra that have been measured on two different laboratory Fourier transform near-infrared (FT-NIR) spectrometers to the format of a handheld instrument by measuring only a few samples with both spectrometer types. Thus, despite the extreme differences in spectral range and resolution, spectral data sets that have been collected and quantitative as well as qualitative calibrations that have been developed thereof, respectively, over a long period on a laboratory instrument can be conveniently transferred to the handheld system. Thus, the necessity to prepare completely new calibration samples and the effort required to develop calibration models when changing hardware platforms is minimized.

Evaluating the Molecular Interaction of Organic Liquid Mixtures Using Near-Infrared Spectroscopy.

The near-infrared transmission spectra of two organic liquid three-component systems of variable compositions were investigated in detail. To evaluate the interaction of the different components in the two systems the experimental spectra of the pure components were compared to mathematically constructed "pure component" spectra. Though usually the correlation coefficient (CC) and Manhattan distance (MD) are used to measure the similarity of spectra, in the present investigations principal component analysis (PCA) was found to be a more effective tool to investigate the difference between these spectra and derive parameters characterizing the interaction between the different components.

Variable-temperature Fourier transform near-infrared imaging spectroscopy of the deuterium/hydrogen exchange in liquid D₂O.

In the present publication, the deuterium/hydrogen (D/H) exchange of liquid D2O exposed to water vapor of the surrounding atmosphere has been studied by variable-temperature Fourier transform near-infrared (FT-NIR) imaging spectroscopy. Apart from the visualization of the exchange process in the time-resolved FT-NIR images, kinetic parameters and the activation energy for this D/H exchange reaction have been derived from the Arrhenius plot of the variable-temperature spectroscopic data.

Temperature-dependent Fourier transform infrared spectroscopy and Raman mapping spectroscopy of phase-separation in a poly(3-hydroxybutyrate)-poly(L-lactic acid) blend.

Variable-temperature Fourier transform infrared spectroscopy (FT-IR) and Raman spectroscopic mapping measurements were applied to study the phase separation of a poly(3-hydroxybutyrate) (PHB)-poly(L-lactic acid) (PLA) (50 : 50 wt.%) polymer-blend film as a function of temperature between 25 and 175 °C. Because of the better band separation compared with the fundamental absorptions, the first overtones of the ν(C=O) bands of PHB and PLA were used to evaluate the temperature-dependent FT-IR images as PLA-PHB and PHB-PLA band-ratio contour plots, respectively.

Water uptake of poly(2-N-alkyl-2-oxazoline)s: temperature-dependent Fourier transform infrared (FT-IR) spectroscopy and two-dimensional correlation analysis (2DCOS).

A library of poly(2-oxazoline)s with varying length of the alkyl side-chain has been investigated by variable-temperature Fourier transform infrared (FT-IR) spectroscopy. These polymers are suitable for studies of structure-property relationships as their cationic ring-opening polymerization and the relatively facile monomer synthesis enable a control of the molecular structure. In this contribution, the number of carbon atoms in the linear side-chain is systematically varied from a short methyl to a long nonyl group.

Sequential identification of model parameters by derivative double two-dimensional correlation spectroscopy and calibration-free approach for chemical reaction systems.

A sequential identification approach by two-dimensional (2D) correlation analysis for the identification of a chemical reaction model, activation, and thermodynamic parameters is presented in this paper. The identification task is decomposed into a sequence of subproblems. The first step is the construction of a reaction model with the suggested information by model-free 2D correlation analysis using a novel technique called derivative double 2D correlation spectroscopy (DD2DCOS), which enables one to analyze intensities with nonlinear behavior and overlapped bands.

Activation and thermodynamic parameter study of the heteronuclear C=O···H-N hydrogen bonding of diphenylurethane isomeric structures by FT-IR spectroscopy using the regularized inversion of an eigenvalue problem.

The doublet of the ν(C=O) carbonyl band in isomeric urethane systems has been extensively discussed in qualitative terms on the basis of FT-IR spectroscopy of the macromolecular structures. Recently, a reaction extent model was proposed as an inverse kinetic problem for the synthesis of diphenylurethane for which hydrogen-bonded and non-hydrogen-bonded C=O functionalities were identified. In this article, the heteronuclear C=O···H-N hydrogen bonding in the isomeric structure of diphenylurethane synthesized from phenylisocyanate and phenol was investigated via FT-IR spectroscopy, using a methodology of regularization for the inverse reaction extent model through an eigenvalue problem.

Variable-temperature Fourier transform near-infrared (FT-NIR) Imaging spectroscopy of the diffusion process of butanol(OD) into polyamide 11.

Time-resolved Fourier transform near-infrared (FT-NIR) spectroscopic imaging was applied to the diffusion process of butanol(OD) into polyamide 11 (PA11) with a novel sheet-structured variable-temperature-controlled sample holder in order to demonstrate the significant differences of diffusion rate below and above the glass transition temperature of PA11. The diffusant butanol(OD) was chosen for two reasons: (1) it allows the diffusion front to be monitored by the intensity decrease of a NH-specific absorption band of PA11 due to the NH/ND isotope exchange and (2) under the measurement conditions the diffusion of butanol(OD) into PA11 takes place in an experimentally manageable time frame. Apart from the in situ visualization of the diffusion front in the time-resolved FT-NIR images, the type of diffusion and the diffusion coefficient of butanol(OD) into PA11 have been determined.

Solvent interactions in methanol/N, N-dimethylamide binary systems studied by Fourier transform infrared-attenuated total reflection (FT-IR/ATR) and two-dimensional correlation spectroscopy (2D-COS).

The interaction of N,N-dimethyl formamide (DMF) and N,N-dimethyl acetamide (DMA) with methanol in solution mixtures was studied using Fourier transform infrared-attenuated total reflection (FT-IR/ATR) spectroscopy. The concentration-dependent FT-IR/ATR spectra of DMF/methanol and DMA/methanol mixtures were recorded in the wavenumber range 4000-650 cm(-1) to investigate wavenumber shifts as a consequence of hydrogen bonding interactions. In combination with two-dimensional correlation spectroscopy (2D-COS), the positional fluctuations observed in the ν(C=O) and ν(O-H) regions of DMF/DMA and methanol, respectively, have been discussed in terms of changing populations of differently hydrogen-bonded and interacting species of the same and different component molecules.

Modeling of isomeric structure of diphenyl urethane by FT-IR spectroscopy during synthesis from phenylisocyanate and phenol as an inverse kinetic problem.

Isomeric structure of diphenyl urethane during synthesis from phenylisocyanate and phenol has been investigated by modeling the reaction extent as an inverse kinetic problem, using FT-IR difference spectroscopy, to obtain structural information on the formation of the isomeric structure. The aim of this study was to determine the primary algebraic structures (an inverse problem), which describe the chemical reaction system in terms of spectroscopic observables. Moreover, a conventional description of the evolution of chemical species and of the change of moles of the observable species, as a function of time, was explored, defined in terms of the extent of reaction ξ and the reaction stoichiometries ν, based on the Jouguet-de Donder equation, for an invariant system in batch experiments.