Use of Multivariate Curve Resolution to Monitor an Esterification Reaction by Near‐Infrared Spectroscopy

Multivariate curve resolution–alternating least squares (MCR‐ALS) methodology was applied to near‐infrared (NIR) spectra with view to estimating the reaction profile for the esterification of a mixture of caprylic and capric acids with glycerol. The reaction was conducted in excess glycerol, so the major products were the monoglyceride and diglyceride; the triglyceride was obtained in considerably lower proportions. Esterification processes were performed in a laboratory‐scale reactor from which samples were withdrawn to record NIR spectra. Some samples were also analyzed by gas chromatography and acid‐base titration in order to determine the composition of the reaction mixture. Concentration and spectral profiles were obtained by using the MCR‐ALS algorithm. Subsequently, concentration values and the pure spectra of reagents and the triglyceride were used to refine the models. The spectra obtained were processed with MCR‐ALS in new esterification batches to obtain their concentration profiles.     

Applications of Near‐Infrared Spectroscopy in Refineries and Important Issues to Address

Abstract

This review primarily concerns NIR (near‐infrared) applications in refineries. Initially, this article reviews the fundamental aspects for analysis of hydrocarbon mixture by NIR spectroscopy, such as spectral sensitivity in various spectral regions, signal‐to‐noise ratio, and spectral resolution. Though there are applications of NIR to diverse petroleum products, this review subsequently focuses only on applications to four major products: gasoline, diesel, naphtha, and crude oil, which are the most interesting from a refiner's viewpoint. In each application, discussion of important issues to consider for proper and optimal NIR measurement is included. Finally, the issue of calibration transfer is discussed.     

Fourier‐Transform Near‐Infrared Spectroscopy as a Tool for Olive Fruit Classification and Quantitative Analysis

Abstract

The potential of diffuse reflectance near‐infrared spectroscopy combined with pattern recognition to discriminate between olives (Olea europaea L.) of different qualities has been tested. The sample set was formed of sound olive fruits and those showing the most common alterations of olives, which lead to decreased oil quality, namely freeze damages, harvest after falling on the ground, fermentation due to prolonged storage time, and olive tree diseases. Near‐infrared (NIR) spectra were recorded between 9900 and 4100 cm^?1. Preliminary studies of the data set structure were performed using hierarchical cluster analysis and principal component analysis. Discriminant analysis provided prediction abilities of 100% for sound, 79% for frostbite, 96% for ground, and 92% for fermented olives using a leave‐a‐fourth‐out cross‐validation procedure. Quantification of oil and water content in the olives was also approached by using partial least squares (PLS) regression. Results, in terms of predictive ability using a leave‐one‐out cross‐validation, were compared for calibration using the whole sample set and calibrations for the sound and damaged samples separately. Relative errors of prediction using all samples were 7.2% and 3.4% for oil content and humidity, respectively. Using only sound samples, relative errors of prediction of 3.8% and 2.8% for oil and water content, respectively, were obtained. Thus, better accuracy could be achieved when classification of the olive samples prior to quantitative analysis was performed. These results demonstrate the utility of NIR spectroscopy to differentiate olives of different qualities. Using NIR, a fast selection of sound olives in a quality‐orientated production facility becomes feasible.     

Near Infrared Spectroscopy of the Cretaceous Red Beds in Inner Mongolia DongshengmiaoSCIEI北大核心CSCD

Take the cores and surface weathered soil from the Cretaceous red beds in the western of Dongshengmiao mine of Inner Mongolia and analysis with near-infrared spectroscopy. The result shows that near-infrared spectroscopy can identify mineral quickly through the characteristic absorption peaks of each group. The Cretaceous red beds in the western of Dongshengmiao mine is argillaceous cementation, it is mainly composed of quartz, feldspar, montmorillonite, illite, chlorite, muscovite etc, the mineral composition is mainly affected by the upstream source area. The clay mineral like montmorillonite water swelling and uneven drying shrinkage expands the original crack and creates new cracks, reduces its strength, which is the mainly reason of its disintegration. According to the composition of clay mineral, we speculate its weathering process is mainly physical weathering, the climate during the weathering is cold and dry. The results can not only improve the geological feature of the mining area, but also show that the near-infrared spectroscopy technology can analyze the mineral composition of soil and rock effectively on the basis of Mineral spectroscopy, which demonstrates the feasibility of the near-infrared spectroscopy can analyze minerals in soil and rock quickly, that shows the feasibility in geology study, provides new ideas for the future research of soil and rock.     

Monitoring of Pictorial Surfaces by mid‐FTIR Reflectance Spectroscopy: Evaluation of the Performance of Innovative Colloidal Cleaning Agents

Abstract

This study reports the use of mid‐FTIR reflectance spectroscopy to evaluate the efficiency of an innovative method to remove aged polyacrylic resins from porous carbonate surfaces. Acrylic copolymers have been extensively used in recent decades as protectives and consolidants of frescoes. However, their aging produces both yellowing and serious degradation of painted layers, necessitating their removal. The evaluation of the performance of a method aimed to remove such aged polymers is often a crucial and critical problem. The innovative technique proposed here is based on the use of mid‐FTIR reflectance spectroscopy in optical fibers to check the reliability of an innovative colloidal cleaning agent, namely an oil‐in‐water microemulsion, constituted of a four‐component system consisting of water as the continuous phase, sodium dodecyl sulfate as the surfactant, 1‐pentanol as the cosurfactant, and p‐xylene as the dispersed phase. The efficacy of this innovative method has been tested first in the laboratory and then on the surface of a Renaissance fresco by Spinello Aretino in the Cappella Guasconi at San Francesco Cathedral (Arezzo, Italy). Through mid‐FTIR reflectance spectroscopic measurements performed in situ, the efficiency of the treatment has been proved, demonstrating that the nanotechnology approach represents a new, safe, and very efficient way of removing aged polymers from fresco surfaces.     

Information Potentialities of the Optical‐Capacitance Spectroscopy of Semiconductors

The opticalcapacitance spectroscopy method and the means for its implementation are described. The results of experimental investigations of semiconductors are compared with the known data obtained by other methods. The information potentialities and advantages of the opticalcapacitance spectroscopy are shown.     

Partial Least Squares Processing of Near‐Infrared Spectra for Discrimination and Quantification of Adulterated Olive Oils

Abstract

A new processing based on partial least squares (PLS) algorithm for the discrimination and determination of adulterants in pure olive oil using near‐infrared (NIR) spectroscopy has been introduced. The 280 adulterations of olive oil with corn oil (n=70), hazelnut oil (n=70), soya oil (n=70), and sunflower oil (n=70) were prepared, and their NIR spectra in the region 12,000–4550 cm^?1 were collected. The 70 spectra of each adulteration of olive oil were divided into two sets, 50 spectra for a calibration set and 20 spectra for a prediction set. The spectra of a total calibration set (n=200) were separated into individual adulterant calibration sets (n_i=50, i=corn, hazelnut, soya, sunflower) by using discriminant PLS (DPLS) analysis, and PLS calibration models for the quantification of adulterants with corn oil, hazelnut oil, soya oil, or sunflower oil were developed separately. A variety of wavelength ranges and data pretreatments were examined for obtaining optimal results for the discrimination and quantification objects. Four PLS models for differentiating the adulterant types were evaluated by classifying the NIR spectra of a total prediction set (n=80) into known adulterant types. Then, these known adulterant spectra were analyzed by the PLS calibration models developed for each type to determine the content of an adulterant in pure olive oil. The results of evaluation revealed that the processing reported in this article works excellently for the discrimination and quantification of the adulterations of olive oil.     

Quantitatively Determination of Available Phosphorus and Available Potassium in Soil by Near Infrared Spectroscopy Combining with Recursive Partial Least SquaresSCIEI北大核心CSCD

Soil available phosphorus (P) and available potassium (K) don't possess direct spectral response in the near infrared (NIR) region. They are predictable because of their correlation with spectrally active constituents (organic matter, carbonates, clays, water, etc.). Such correlation may of course differ between the soil sample sets. Therefore, the NIR calibration models with fixed structure are difficult to achieve good prediction performances for soil P and K. In this work, the method of recursive partial least squares (RPLS), which is able to update the model coefficients recursively during the prediction process, has been applied to improve the predictive abilities of calibration models. This work compared the performance of partial least squares regression (PLS), locally weighted PLS (LW-PLS), moving window LW-PLS (LW-PLS2) and RPLS for the measurement of soil P and K. The entire data set of 194 soil samples was split into calibration set and prediction set based on soil types. The calibration set was composed of 120 Anthrosols samples, while the prediction set included 29 Ferralsols samples, 23 Anthrosols samples and 22 Primarosols samples. The best prediction results were obtained by the RPLS model. The coefficient of determination (122) and residual prediction deviation (RPD) were respectively 0.61, 0.76 and 1.60, 2.05 for soil P and K. The results indicate that RPLS is able to learn the information from the latest modeling sample by recursively updating the model coefficients. The proposed method RPLS has the advantages of wider applicability and better performance for MR prediction of soil P and K compared with other methods in this work.     

Mid‐ and Near‐Infrared Spectroscopic Determination of Carbon in a Diverse Set of Soils from the Brazilian National Soil Collection

Abstract

Calibrations for soil carbon content measured by combustion (total carbon, TC) and chromate oxidation by a modified Walkley‐Black method (Walkley‐Black carbon, WBC) from the Brazilian National Soil Collection were made using Fourier‐transform near (1100 to 2500 nm; NIRS) and mid‐infrared diffuse reflectance (2,500 to 25,000 nm; DRIFTS) spectroscopy combined with partial least squares (PLS). Calibration sets of sample populations of different carbon ranges, soil taxonomic classes, and soil textural groups were established. These are for TC ranges between 0.4 to 555.0, 0.4 to 99.1, and 0.4 to 39.9 g kg^?1: for WBC 0.2 to 401.0, 0.2 to 66.0, and 0.2 to 66.0, and 0.2 to 30.0 g kg^?1: for soil taxonomic classes Ferralsols and Acrisols; and for soil textural groups very clayey, clayey, and medium textures were examined. Calibrations obtained for the largest TC and WBC ranges were better compared to the lower ones, but lower root mean squared deviation (RMSD) and relative difference (RD=RMSD/mean value) were found for the lower carbon ranges. Taxonomic soil class was not an adequate criterium for calibration set formation. Soil texture had effect on calibrations, especially using NIR, because of the particle size effect to which NIR was more sensitive than mid‐IR. In general, DRIFTS showed better performance than NIRS. NIRS only outperformed DRIFTS when used with calibration set fairly homogeneous in its particle size distribution. Results demonstrated that while calibrations can be developed using either DRIFTS or NIRS for even a very diverse set of soil samples, which will determine C over a wide range of concentrations inherent in such a diverse set, it is desirable to seperate sample populations by soil textural properties and choose the adequate spectral range (NIR or mid‐IR) based on the textural group, for calibration development to achieve more accurate results.     

Identification of Urinary Stone Components by X‐Ray Photoelectron Spectroscopy

Abstract

X‐ray photoelectron spectroscopy (XPS) has been used for the first time to study the composition of calcium oxalate (CaOxa) stones and uric acid stones. This technique allows for the identification and location of various inorganic and organic species at the same time. In CaOxa stones, there were less than 10% of phosphates. Sectional analyses of these stones indicated that the content of phosphorus in the stone center is higher than that in stone crust. In uric acid stones, CaOxa was rarely found. XPS is able to detect differences in chemical functionality. In uric acid stones, the binding energy (E _b) for nitrogen atoms were about 399.5 ± 0.2 eV, which are largely characteristic of organic nitrogens N (?3). In comparison, the E _b values of N (+5) in inorganic compounds are about 401 eV.     

Determination of the Heat of Adsorption and Desorption of a Volatile Organic Compound Under Dynamic Conditions Using Fourier‐Transform Infrared Spectroscopy

Quantitative Fourier‐transform infrared spectroscopic analysis was used for the determination of adsorption capacity of a model volatile organic compound (VOC) under dynamic conditions. The analytical method used also offers the possibility of distinguishing between reversible and irreversible adsorption as well as further detection of adsorbed VOC transformation. The obtained adsorbed amounts have been used for the determination of the heat of adsorption and the activation energy of desorption using, respectively, isosteric and temperature programmed desorption methods. The approach has been applied to explore the potential use of local clay as an adsorbent material for VOC pollutants.     

Characterization of Crystalline Phase‐Transformations in Theophylline by Time‐Domain Terahertz Spectroscopy

Time‐domain terahertz (THz) spectroscopy has been used to characterize polymorphic transformations in polycrystalline theophylline, a widely used pharmaceutical compound. On transformation, different intermolecular bonding arrangements arise owing to changes in the lattice structure of the molecular crystal, leading to distinct THz spectral signatures. Temperature‐dependent THz absorption measurements in anhydrous theophylline confirm that the observed vibrational modes originate from phonons within the crystal structure.     

Interpretation of Viscosity Behavior of a Polyelectrolyte in a Salt‐Free Polar Solvent by Ion‐Association

Abstract

On the basis of three hypothesis: (1) ion association according to the mass action law, (2) no interchain association due to the same sort of charges on the chains, and (3) chain expansion owing to intrachain Coulombic repulsive force, a theoretical equation was derived to describe the viscosity behavior of a polyelectrolyte in a salt‐free polar solvent. The resulting equation fits well with experimental viscosity behavior of a polyelectrolyte solution in polar solvents. With some approximations, the equation leads to the Fuoss empirical equation. The effects of molecular weight, the average distance of two neighboring ionizable groups along the polymer chain, and the nature of the solvent on the polyelectrolyte conformation are discussed.     

Calibration of Membrane Viscosity of the Reconstituted Vesicles by Measurement of the Rotational DIffusion of Bacteriorhodopsin

Membrane viscosity of the reconstituted vesicles was calibrated by rotational diffusion of bacteriorhodopin(BR) in dimyristoylphosphatidylcholine(DMPC) and egg phosphatidylcholine(PC) vesicles.Rotational diffusion of BR in the vesicles was measured by flash-induced absorption anisotropy decay.BR was,for the first time ,reconstituted successfully into DMPC and egg PC vesicles,From the measurement of flash-induced absorption anisotropy decay of BR,the value of rotational diffusion coefficient D was obtained from each curve fitting by a global fitting procedure and ,in turn,membrane viscosity η was estimated from D.The results have shown that membrane viscosity is temperature-dependent,It was decreased as temperature increased,but a transition occurred in the region of the respective phase transition of DMPC and egg PC,respectively,The decrease of η was fast near the phase transition for DMPC and egg PC.Few effects of lipid/BR ratio and glycerol or sucrose in suspension medium on membrane viscosity were found.     

Using Short Wave Visible–Near Infrared Reflectance Spectroscopy to Predict Soil Properties and Content

In this study, short wave visible–near infrared reflectance spectroscopy was evaluated for prediction of diverse soil properties related to four different soil series of several regions in Jiangxi, China. A total of 240 soil samples were collected for the calibration (n = 168) and prediction (n = 72) sets. The used wavelength range of short wave visible–near infrared reflectance spectroscopy is 325–1075 nm. Partial least squares regression and back propagation neural network were used to develop models for soil properties such as organic matter and extractable forms of calcium, magnesium, and potassium. Performance of these models was also compared and analyzed. The input of back propagation neural network was the first six principal components resulted from the principal component analysis and the optimal number of latent variables obtained from partial least squares regression. The overall results showed that the performance of partial least squares regression model was inferior to all back propagation neural network models. The best prediction was obtained with latent variables as input of back propagation neural network model for organic matter (determination coefficient = 0.84 and relative predictive determinant = 2.38), which was classified as very good model predictions. The prediction of calcium, magnesium, and potassium was classified as fair (determination coefficient = 0.56–0.68 and relative predictive determinant = 1.51–1.61), where quantitative predictions were considered possible. It is recommended to adopt latent variables as input for back propagation neural network model predicting soil properties with short wave visible–near infrared reflectance spectroscopy. In conclusion, short wave visible–near infrared reflectance spectroscopy was variably successful in estimating soil properties and showed potential for substituting laboratory analyses.     

Detection of Terahertz,Mid- and Near Infrared Radiation by a Multilayer Metal—Insulator Heterostructure

An analogy between the tunneling of quantum particles through a chain of barriers and the propagation of electromagnetic waves through a metamedium has allowed new methods for the fabrication of selective detectors of terahertz, mid-infrared, and near infrared radiation. The calculations have shown that a resonance metal-insulator heterostructure with one and two metal layers allows achieving nearly 100% absorption of radiation in a narrow frequency range. The use of a large number of metal layers makes it possible to detect ultrashort (including picosecond) field pulses with a broad spectrum.

     

Infrared Line Strengths and Pressure Broadening Coefficients in the ν12 Vibrational Band of Hydrazine Measured by Infrared Tunable Diode Laser Spectroscopy

Infrared line positions, linestrengths, and pressure-broadening coefficients are required to determine absolute trace gas concentrations from high-resolution absorption spectra. We have measured these values for the infrared absorption lines in the ν₁₂ band (antisymmetric wag) of hydrazine between 965.4 and 965.7 cm⁻¹ using a high-resolution tunable diode laser system with 0.0006 cm⁻¹ spectral resolution and an 18-m path length multiple pass absorption cell. A continuous flow of hydrazine diluted to 100-500 parts per million in nitrogen at pressures between 0.1 and 50 Torr was used to prevent decomposition in the sampling cell. The total integrated linestrength from 965.477 to 965.663 cm⁻¹ is (2.20±0.14)×10⁻²⁰ cm² molecule⁻¹ cm⁻¹. The strongest line in this region at 965.5557 cm⁻¹ has a strength of 2.8×10⁻²¹ cm² molecule⁻¹ cm⁻¹. The only isolated line in this region, at 965.4905 cm⁻¹, has a broadening coefficient by nitrogen of 0.11±0.01 cm⁻¹ atm⁻¹ at 295 K. These results are compared to the qualitative high resolution spectra determined by other researchers using FTIR spectroscopy, and have been used to construct a HITRAN-format line list that can be used both to spectroscopically distinguish hydrazine from other components and to determine its concentration in a complex gas phase mixture.     

Trace Analysis of Al on Silicon Surfaces by Ultra‐soft X‐Ray Emission Spectroscopy

It is shown that near normal incidence, low‐energy electron excitation of Al on silicon surfaces by ultra‐soft X‐Ray emission spectroscopy yielded limits of detectibility (LD) in the picogram region. This result on L band emission via electron excitation is fully competitive with photon excitation using K‐α lines via grazing incidence total reflection techniques (TXRF). Surprisingly, it was also found that normal incidence synchrotron photon excitation on the same sample yielded much higher values of LD than low‐energy electron excitation, undoubtedly due to the use of a poor transmission grating used in the entrance optics.     

Spectroscopy of the Forming Process of Quantum Dots Accompanied by the Thinning of Wetting Layer

A series of Cd0.44Zn0.56Se/ZnSe sandwich structures with different Cd0.44Zn0.56Se embedded layer thicknesses were fabricated by metal organic chemical vapor deposition. When the embedded layer thickness exceeded 3.0 nm, the photoluminescence spectra of the sample changed into the two-band structure from the one-band structure, and atomic force microscopy images indicate that Cd0.44Zn0.56Se quantum dots were formed. In the two-band photoluminescence spectrum, the band at the low energy side was attributed to be from quantum dots, and the high-energy one arose from the wetting layer. Thinning of the wetting layer with quantum dots forming was confirmed indirectly by the significant blue shift of the wetting-layer photoluminescence band compared to the photoluminescence band of the samples for which the Cd0.44Zn0.56Se layer thickness was less than 3.0nm. This thinning arose from mass migration during the Stranski-Krastanow growth of Cd0.44Zn0.56Se quantum dots.