Horizontal Attenuated Total Reflectance Research Articles

Evaluation of chemometric classification and regression models for the detection of syrup adulteration in honey

Honey is a highly desirable commodity hence a target of adulteration to increase its bulk. Spectroscopic methods and chemometrics offer a fast, easy, and simple approach to the detection of syrup adulterations in honey. The idiosyncrasies associated with different instrumental data suggest varying performance for each algorithm. The objective of this study was to evaluate the performance of five commonly used classification and regression algorithms for the detection of syrup adulteration in honey. The prediction performance of the classification and regression algorithms was evaluated using data obtained from Fourier-transform infrared spectrometer with a Horizontal Attenuated Total Reflectance (HATR) Accessory analysis of honey samples. Gradient boosted discriminant analysis (GBDA) and Support vector machines discriminant analysis (SVMDA) were able to differentiate between adulterated and pure honey samples with an external validation set prediction accuracies of 0.988 and 0.981, respectively. Application of feature selection method did not lead to improved prediction accuracies. Gradient boosted regression (GBR) initialized with a ridge regression predicted the percentage level of adulteration with a regression coefficient of 1.000. The RMSE for the optimal GBR was 2.183 and 0.018 for before and after feature selection with the partial least squares (PLS) algorithm, respectively. Ensemble methods are generally better for both classification and regression of honey using FTIR-HATR spectroscopic data.

Eucalyptus globulus and Salvia officinalis Extracts Mediated Green Synthesis of Silver Nanoparticles and Their Application as an Antioxidant and Antimicrobial Agent.

Silver nanoparticles (AgNPs) biosynthesized using plant extracts as reducing and capping agents show multiple possibilities for solving various biological problems. The aim of this study was to expand the boundaries of AgNPs using a novel low toxicity and production cost phytochemical method for the biosynthesis of nanoparticles from Eucalyptus globulus and Salvia officinalis aqueous leaf extracts. Biosynthesized AgNPs were characterized by various methods (ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared (FTIR) spectroscopy with horizontal attenuated total reflectance (HART), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS)). The determined antioxidative and antimicrobial activity of plant extracts was compared with the activity of the AgNPs. The UV-vis spectral analysis demonstrated the absorption peaks at 408 and 438 nm, which confirmed the synthesis of stable AgNPs from E. globulus and S. officinalis, respectively. FTIR-HART results suggested strong capping of phytochemicals on AgNPs. TEM results show mainly spherical-shaped AgNPs, whose size distribution depends on the plant leaf extract type; the smaller AgNPs were obtained with E. globulus extract (with size range of 17.5 ± 5.89 nm compared to 34.3 ± 7.76 nm from S. officinalis AgNPs). The in vitro antioxidant activity evaluated by radical scavenging assays and the reduction activity method clearly demonstrated that both the plant extracts and AgNPs showed prominent antioxidant properties. In addition, AgNPs show much stronger antimicrobial activity against broad spectrum of Gram-negative and Gram-positive bacteria strains than the plant extracts used for their synthesis.

Phosphorus–nitrogen compounds. Part 41. Ferrocenyl pendant-armed spirocyclopiperidinocyclotriphosphazatrienes: Langmuir–Blodgett thin films and biological activity studies

The Cl replacement reactions of N/N or N/O spirocyclic monoferrocenylcyclotriphosphazatrienes (1–5) with the piperidine resulted in the geminal- (6–10) and tetra-piperidinophosphazenes with monoferrocenyl pendant arm (11–15). The structures of all the new compounds were determined using spectroscopic techniques. The ultrathin Langmuir–Blodgett (LB) films of two compounds (3 and 12) were prepared. The characterization of the LB films using p-polarized grazing angle (GAIR) and horizontal attenuated total reflectance (HATR) techniques was carried out. The molecular and crystal structure of the compound 6 was examined using X-ray crystallography. In addition, the interactions between six compounds (6, 7, 11, 12, 14 and 15) and pBR322 plasmid DNA were investigated by agarose gel electrophoresis. SYNOPSIS The ultrathin Langmuir-Blodgett (LB) films of two of these compounds were prepared. Molecular and crystal structure of a representative example was determined. In addition, the interactions between several of these with pBR322 plasmid DNA were investigated by agarose gel electrophoresis.

Water Adsorption Isotherms on Fly Ash from Several Sources.

In this study, horizontal attenuated total reflection (HATR) Fourier-transform infrared (FT-IR) spectroscopy was combined with quartz crystal microbalance (QCM) gravimetry to investigate the adsorption isotherms of water on fly ash, a byproduct of coal combustion in power plants. Because of composition variability with the source region, water uptake was studied at room temperature as a function of relative humidity (RH) on fly ash from several regions: United States, India, The Netherlands, and Germany. The FT-IR spectra show water features growth as a function of RH, with water absorbing on the particle surface in both an ordered (ice-like) and a disordered (liquid-like) structure. The QCM data was modeled using the Brunauer, Emmett, and Teller (BET) adsorption isotherm model. The BET model was found to describe the data well over the entire range of RH, showing that water uptake on fly ash takes place mostly on the surface of the particle, even for poorly combusted samples. In addition, the source region and power-plant efficiency play important roles in the water uptake and ice nucleation (IN) ability of fly ash. The difference in the observed water uptake and IN behavior between the four samples and mullite (3Al2O3·2SiO2), the aluminosilicate main component of fly ash, is attributed to differences in composition and the density of OH binding sites on the surface of each sample. A discussion is presented on the RH required to reach monolayer coverage on each sample as well as a comparison between surface sites of fly ash samples and enthalpies of adsorption of water between the samples and mullite.

Spectroscopic and structural studies on lactose species in aqueous solution combining the HATR and Raman spectra with SCRF calculations

In this work, the α and β isomers, the α-lactose monohydrate and dihydrate and the dimeric species of lactose were studied from the spectroscopic point of view in gas and aqueous solution phases combining the infrared, Horizontal Attenuated Total Reflectance (HATR) and Raman spectra with the density functional theory (DFT) calculations. Aqueous saturated solutions of α-lactose monohydrate and solutions at different molar concentrations of α-lactose monohydrate in water were completely characterized by infrared, HATR and Raman spectroscopies. For all the species in solution, the solvent effects were studied using the solvation polarizable continuum (PCM) and solvation (SM) models and, then, their corresponding solvation energies were predicted. The vibrational spectra of those species in aqueous solution were completely assigned by employing the Scaled Quantum Mechanics Force Field (SQMFF) methodology and the self-consistent reaction field (SCRF) calculations. The stabilities of all those species were studied by using the natural bond orbital (NBO), and atoms in molecules (AIM) calculations.

Desorption electrospray ionization high-resolution mass spectrometry for the fast investigation of natural polysaccharide interactions with a model drug in controlled release systems.

The control of drug release involves gaining an understanding of the complex interaction networks among drug-excipients-matrix-biological fluids. Thus, novel analytical methods that will lead to a better understanding of these interaction networks are urgently required. Desorption electrospray ionization high-resolution mass spectrometry (DESI-HRMS) was used to evaluate the behaviour of four biocompatible polysaccharides (chondroitin sulfate, chitosan, sodium alginate and λ-carrageenan) in the release of atenolol (ATN) from drug tablets. An aqueous solution at three different pH values (pH 7.4, 4.5 and 1.2) was electrosprayed onto the tablets, allowing direct, fast, sensitive detection of atenolol as the protonated molecule in positive ion mode. Information about the desorption mechanism was obtained by analyzing the ATN [M+H](+) ion signal as a function of time. ATN-polymer interactions in the drug/polymer mixtures were also studied by Horizontal Attenuated Total Reflectance (HATR) Fourier transform infrared (FTIR) spectroscopy. The DESI-MS results revealed statistically different ATN desorption trends as a function of the polysaccharide investigated and the pH of the desorbing solution. Different release kinetics were ascribed to the drug-polymer interactions, and to the diffusion process of the drug through the hydrated polymer mesh. In particular, the alginate and λ-carrageenan matrices were able to sustain drug release from the tablet even for a highly soluble drug. The HATR results confirmed the presence of ATN-polymer interactions that, depending on the polymer-drug-solvent combination used, might affect ATN diffusion. These results suggest that DESI-MS has a potential role for the micro-environmental analysis of drug diffusion and surface distribution in polymeric matrices.

Structural and vibrational investigation on species derived from the cyclamic acid in aqueous solution by using HATR and Raman spectroscopies and SCRF calculations

In this study, aqueous solutions at different molar concentrations of sodium cyclamate in water were completely characterized by HATR (Horizontal Attenuated Total Reflectance) and Raman spectroscopies. The theoretical structures of cyclamate ion, the zwitterionic and neutral forms of the cyclamic acid and its dimer were optimized in gas and aqueous solution phases by using the hybrid B3LYP/6-31G* method. The solvent effects for the four species in aqueous solutions were simulated by using self-consistent reaction field (SCRF) calculations employing the integral equation formalism variant (IEFPCM) model. The complete assignments of the vibrational spectra of all the forms of cyclamic acid were performed taking into account the factor group analysis with the Scaled Quantum Mechanics Force Field (SQMFF) methodology. The existence of the zwitterionic and neutral forms of the cyclamic acid and its dimer in a solution of cyclamate in water is evidenced by characteristic bands in the HATR and Raman spectra. The dimerization of cyclamate in aqueous solution was previously reported by conductimetric method. The natural population analysis (NPA) and Merz–Kollman (MK) charges, molecular electrostatic potential (MEP), natural bond orbital (NBO) and atoms in molecules (AIM) calculations predict for all the species the principal donor and acceptor sites for the H bonds formation in aqueous solution. The SQM force fields for the cyclamate ion, the zwitterionic and neutral species of the cyclamic acid were obtained and their corresponding force constants in both phases were reported. Additionally, the solvation energies for those species were reported.

The Use of Fourier Transform Infrared Spectroscopy for Quantification of Adulteration in Virgin Walnut Oil

Currently, the authentication of virgin walnut oil (VWO) has become very important due to the possible adulteration of VWO with cheaper plant oils such as soybean oil (SO), puer tea seed oil (PO), and sunflower oil (SFO). Methods involving Fourier transform infrared (FT-IR) spectroscopy combined with chemometric techniques (partial least square) were developed for quantification of SO, PO, and SFO in VWO. IR spectra of oil samples were recorded at frequency regions of 4000–650 cm−1on horizontal attenuated total reflectance (HATR) attachment of FT-IR. PLS model correlates the actual and FT-IR estimated values of oil adulterants (SO, PO, and SFO) with coefficients of determination (R2) of 0.9958, 0.9925, and 0.9952, respectively. The obtained RMSEC values of SO, PO, and SFO in VWO are 1.35%, 1.85%, and 1.43% (v/v), respectively. The method, therefore, has potential as a rapid method for quantification of product adulteration.

Classification of Green Bristle Grass, Yellow Foxtail and Chinese Pennisetum Seeds via HATR-FT-IR Combined with Chemometrics

Fourier transform infrared (FT-IR) and horizontal attenuated total reflectance (HATR) technique are used to obtain the FT-IR spectra of the seed of green bristle grass (the seed fromSetaria viridis(L.) Beauv), yellow foxtail seed (the seed fromSetaria glauca(L.) Beauv), and the Chinese pennisetum seed (the seed fromSetaria faberiiHerrum). In order to extrude the difference among them, cluster analysis is considered to identify the three kinds of plant seeds. Because they belong to the sibling plant seeds, and have similar chemical components and close FT-IR spectra. The result of Cluster analysis is not satisfactory. The discrete wavelet transformation (DWT) and a support vector machine (SVM) were used for further study. The compression detail 3 and 4 in DWT are used to extract the feature vectors, which are used to train SVM. The trained SVM is used to classify seed of green bristle grass, yellow foxtail seed and Chinese pennisetum seed. The seed samples are collected from different places around the country. With 40 testing samples we could effectively identify the sibling plants, seed of green bristle grass, yellow foxtail seed and Chinese pennisetum seed by FT-IR with discrete wavelet feature extraction and SVM classification.

Water Adsorption on Clay Minerals As a Function of Relative Humidity: Application of BET and Freundlich Adsorption Models

Water adsorption on kaolinite, illite, and montmorillonite clays was studied as a function of relative humidity (RH) at room temperature (298 K) using horizontal attenuated total reflectance (HATR) Fourier transform infrared (FTIR) spectroscopy equipped with a flow cell. The water content as a function of RH was modeled using the Brunauer, Emmett, and Teller (BET) and Freundlich adsorption isotherm models to provide complementary multilayer adsorption analysis of water uptake on the clays. A detailed analysis of model fit integrity is reported. From the BET fit to the experimental data, the water content on each of the three clays at monolayer (ML) water coverage was determined and found to agree with previously reported gravimetric data. However, BET analysis failed to adequately describe adsorption phenomena at RH values greater than 80%, 50%, and 70% RH for kaolinite, illite, and montmorillonite clays, respectively. The Freundlich adsorption model was found to fit the data well over the entire range of RH values studied and revealed two distinct water adsorption regimes. Data obtained from the Freundlich model showed that montmorillonite has the highest water adsorption strength and highest adsorption capacity at RH values greater than 19% (i.e., above ML water adsorption) relative to the kaolinite and illite clays. The difference in the observed water adsorption behavior between the three clays was attributed to different water uptake mechanisms based on a distribution of available adsorption sites. It is suggested that different properties drive water adsorption under different adsorption regimes resulting in the broad variability of water uptake mechanisms.

Recognition Among Three Kinds of Pteridophyte Plants Based on Fourier Transform Infrared-Discrete Wavelet Feature Extraction and Artificial Neural Network Classification Method

Fourier transform infrared(FT-IR) and horizontal attenuated total reflectance(HATR) techniques were used to obtain the FT-IR of three kinds of pteridophyte plants(the root of Cyrtomium fortunei J.Sm,Dryopteris championii(Bench) C.Chr.apud Ching and Dryopteris varia(L.) O.Ktze.).The similar features of FT-IR among the root of Cyrtomium fortunei J.Sm,Dryopteris championii(Bench) C.Chr.apud Ching and Dryopteris varia(L.) O.Ktze.were extracted by discrete wavelet transform.The scale 4 and 5 were used to extract the feature vectors,which were used to train the artificial neural network(ANN).The trained neural network was used to classify the root of Cyrtomium fortunei J.Sm,Dryopteris championii(Bench) C.Chr.apud Ching and Dryopteris varia(L.) O.Ktze.,which were collected from different places.According to 240 prediction samples,we could effectively identify the root of Cyrtomium fortunei J.Sm,Dryopteris championii(Bench) C.Chr.apud Ching and Dryopteris varia(L.) O.Ktze.by FT-IR with discrete wavelet feature extraction and artificial neural network classification.

Molecular spectroscopic study for suggested mechanism of chrome tanned leather

Collagen represents the structural protein of the extracellular matrix, which gives strength of hides and/or skin under tanning process. Chrome tan is the most important tanning agent all over the world. The methods for production of leather evolved over several centuries as art and engineering with little understanding of the underlying science. The present work is devoted to suggest the most probable mechanistic action of chrome tan on hide proteins. First the affect of Cr upon hide protein is indicated by the studied mechanical properties. Then the spectroscopic characterization of the hide protein as well as chrome tanned leather was carried out with Horizontal Attenuated Total Reflection (HATR) FT-IR. The obtained results indicate how the chromium can attached with the active sites of collagen. Molecular modeling confirms that chromium can react with amino as well as carboxylate groups. Four schemes were obtained to describe the possible interactions of chrome tan with hide proteins.

Optical and spectroscopic studies on tannery wastes as a possible source of organic semiconductors

Tanning industry produces a large quantity of solid wastes which contain hide proteins in the form of protein shavings containing chromium salts. The chromium wastes are the main concern from an environmental stand point of view, because chrome wastes posses a significant disposal problem. The present work is devoted to investigate the possibility of utilizing these wastes as a source of organic semi-conductors as an alternative method instead of the conventional ones. The chemical characterization of these wastes was determined. In addition, the Horizontal Attenuated Total Reflection (HATR) FT-IR spectroscopic analysis and optical parameters were also carried out for chromated samples. The study showed that the chromated samples had suitable absorbance and transmittance in the wavelength range (500–850 nm). Presence of chromium salt in the collagen samples increases the absorbance which improves the optical properties of the studied samples and leads to decrease the optical energy gap. The obtained optical energy gap gives an impression that the environmentally hazardous chrome shavings wastes can be utilized as a possible source of natural organic semiconductors with direct and indirect energy gap. This work opens the door to use some hazardous wastes in the manufacture of electronic devices such as IR-detectors, solar cells and also as solar cell windows.

Analysis of chicken fat as adulterant in cod liver oil using Fourier transform infrared (FTIR) spectroscopy and chemometricsAnálisis de grasa de pollo como adulterante en aceite de hígado de bacalao usando espectroscopía infrarroja con transformada de Fourier (FTIR) y quimometría

Among three animal fats evaluated, chicken fat (CF) has close similarity in fatty acid profiles with cod liver oil (CLO), compared with mutton fat and beef fat; therefore, CF can be one of the potential adulterants in CLO. Fourier transform infrared (FTIR) spectra of CLO, CF, and their mixtures were measured on direct contact with horizontal attenuated total reflectance (HATR) in mid infrared region (4000–650 cm−1) at 32 scanning and 4 cm−1 resolution. The chemometrics of partial least square (PLS) and discriminant analysis (DA) were chosen for the quantification and classification of oil adulterant in CLO. The results showed that FTIR spectroscopy coupled with PLS calibration can predict the level of CF in CLO with coefficient of determination (R2) for the relationship between actual and FTIR predicted value of CF in CLO is 0.996. The root means square errors of calibration (RMSEC) and prediction (RMSEP) obtained using seven principal components (PCs) are 0.346 and 0.513, respectively. DA using the Coomanss plot can classify pure CLO and that adulterated with CF accurately. Besides, DA using 10 PCs can be successfully exploited for the classification of CLO and CLO adulterated with the mixture of animal fats. Entre tres grasas animales evaluadas, la grasa de pollo (CF) mostró una gran semejanza en perfiles de ácidos grasos con aceite de hígado de bacalao (CLO), comparado con grasa de cordero y grasa de buey; la grasa de pollo puede ser uno de los posibles adulterantes de aceite de hígado de bacalao. Espectros FTIR de aceite de hígado de bacalao, grasa de pollo y sus mezclas se midieron en contacto directo con la reflectancia total atenuada horizontal en la región media de infrarrojos (4000 – 650 cm−1) a 32 barridos y resolución de 4 cm−1. Las quimometrías de cuadrados mínimos parciales (PLS) y análisis discriminante (DA) se eligieron para la cuantificación y clasificación de aceite adulterante en aceite de hígado de bacalao. Los resultados mostraron que la espectroscopia FTIR asociada con la calibración de cuadrados mínimos parciales puede predecir el nivel de grasa de pollo en aceite de hígado de bacalao con coeficiente de determinación (R2) para la relación entre valores de reales y FTIR predichos de grasa de pollo en aceite de hígado de bacalao es 0,996. La raíz media cuadrada de errores estándar de calibración (RMSEC) y predicción (RMSEP) obtenidos usando 7 componentes principales (PCs) son 0,346 y 0,513, respectivamente. El análisis discriminante usando el gráfico de Coomans puede clasificar aceite de hígado de bacalao puro y aquél adulterado con CF de una forma precisa. Además, el análisis discriminante usando 10 componentes principales puede ser aprovechado con éxito para la clasificación de aceite de hígado de bacalao y aceite de hígado de bacalao adulterado con la mezcla de grasas animales.

The use of Fourier transform mid infrared (FT-MIR) spectroscopy for detection and quantification of adulteration in virgin coconut oil

Currently, the authentication of virgin coconut oil (VCO) has become very important due to the possible adulteration of VCO with cheaper plant oils such as corn (CO) and sunflower (SFO) oils. Methods involving Fourier transform mid infrared (FT-MIR) spectroscopy combined with chemometrics techniques (partial least square (PLS) and discriminant analysis (DA)) were developed for quantification and classification of CO and SFO in VCO. MIR spectra of oil samples were recorded at frequency regions of 4000–650cm−1 on horizontal attenuated total reflectance (HATR) attachment of FTIR. DA can successfully classify VCO and that adulterated with CO and SFO using 10 principal components. Furthermore, PLS model correlates the actual and FTIR estimated values of oil adulterants (CO and SFO) with coefficient of determination (R2) of 0.999.

Discrimination of Alicyclobacillus Strains Using Nitrocellulose Membrane Filter and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

Alicyclobacillus spp. are thermoacidophilic, spore-forming bacteria, some of which cause spoilage in pasteurized and heat-treated apple juice products through the production of guaiacol. It would be helpful if a rapid method to detect and discriminate Alicyclobacillus strains was available. A simple and rapid sample preparation method using nitrocellulose membrane filter (NMF) and a single reflection horizontal attenuated total reflection (HATR) accessory with Fourier transform infrared (FT-IR) was developed here. Fourier transform infrared (FT-IR) spectroscopy was used and tested on 8 Alicyclobacillus strains (KF, WAC, NWN-13501, NWN-12697, NWN-12654, NWN-10682, 1016, 1101). A linear discriminant analysis (LDA) was established to discriminate Alicyclobacillus strains. The sample preparation method could successfully separated strains into different groups by principal component analysis (PCA). High identification accuracy (95%) was achieved with the LDA model. The method developed in the paper can be used to discriminate different Alicyclobacillus strains from each other making it possible to easily determine whether the strain of Alicyclobacillus present is associated with juice spoilage.

Classification of Five Kinds of Moss Plants with the Use of Fourier Transform Infrared Spectroscopy and Chemometrics

Fourier transform infrared spectroscopy (FT-IR) with Horizontal Attenuated Total Reflectance (HATR) techniques is used to obtain the FT-IR spectra of five kinds of mosses, such asPtychomitrium dentatum(Mitt.) Jaeg.,Ptychomitrium polyphylloides(C. Muell.) Par.,Ptychomitrium sinense(Mitt.) Jaeg.,Macromitrium syntrichophyllumTher. Etp. Vard., andMacromitrium ferrieiCard. Sz Ther. Based on the comparison of the above mosses in the FT-IR spectra, the region ranging from 4000 to 650 cm−1was selected as the characteristic spectra for analysis. Principal component analysis (PCA) and cluster analysis are considered to identify the five moss species. Because they belong to the homogeneous plants, and have similar chemical components and close FT-IR spectroscopy, PCA and cluster analysis can only give a rough result of classification among the five moss species, Fourier self-deconvolution (FSD) and discrete wavelet transform (DWT) methods are used to enhance the differences between them. We use these methods for further study. Results show that it is an excellent method to use FT-IR spectroscopy combined with FSD and DWT to classify the different species in the same family. FT-IR spectroscopy combined with chemometrics, such as FSD and DWT, can be used as an effective tool in systematic research of bryophytes.

Classification of Five Kinds of Moss Plants with the Use of Fourier Transform Infrared Spectroscopy and Chemometrics

Fourier transform infrared spectroscopy (FT-IR) with Horizontal Attenuated Total Reflectance (HATR) techniques is used to obtain the FT-IR spectra of five kinds of mosses, such as Ptychomitrium dentatum (Mitt.) Jaeg., Ptychomitrium polyphylloides (C. Muell.) Par., Ptychomitrium sinense (Mitt.) Jaeg., Macromitrium syntrichophyllum Ther. Etp. Vard., and Macromitrium ferriei Card. Sz Ther. Based on the comparison of the above mosses in the FT-IR spectra, the region ranging from 4000 to 650 cm −1 was selected as the characteristic spectra for analysis. Principal component analysis (PCA) and cluster analysis are considered to identify the five moss species. Because they belong to the homogeneous plants, and have similar chemical components and close FT-IR spectroscopy, PCA and cluster analysis can only give a rough result of classification among the five moss species, Fourier self-deconvolution (FSD) and discrete wavelet transform (DWT) methods are used to enhance the differences between them. We use these methods for further study. Results show that it is an excellent method to use FT-IR spectroscopy combined with FSD and DWT to classify the different species in the same family. FT-IR spectroscopy combined with chemometrics, such as FSD and DWT, can be used as an effective tool in systematic research of bryophytes.

Synthesis and characterization of composite membrane by deposition of acrylic acid plasma polymer onto pre-treated polyethersulfone support

The plasma techniques were explored to deposit a layer of hydrophilic polymer on asymmetric porous membranes used as support material. Microporous membranes were synthesized by the phase inversion technique from polyethersulfone (PES) and submitted to a surface treatment with RF-plasma of non-polymerizable gas. Carbon dioxide (CO2) was selected to generate this plasma and to increase the surface energy. Further plasma treatment proceeded with acrylic acid (AA) in vapor phase as source for the permanent surface hydrophilic functionalization. The infrared spectra with horizontal attenuated total reflectance (HATR) show that the deposited plasma polymer provides a high concentration of carbonyl and hydroxyl groups. The hydrophilic polymer layer was evenly deposited, with good adhesion to the support, as was observed by electronic microscopy (SEM). The surface free energy (γS) was increased through plasma treatments and confirmed by the decrease of contact angle (θ) measurements and increase of adhesion work (Wa). The nitrogen permeability decreased 650 times; after that a dense thin film was deposited by plasma treatment during 40 min (at 5 W and 8 Pa). Final composite membranes show stability, high surface hydrophilicity, and a surface chemical nature very stable with time.

Application of Fourier transform infrared (FT-IR) spectroscopy combined with chemometrics for authentication of cod-liver oil

Some vegetable oils such as canola (CaO), corn (CO), soybean (SO), and walnut (WO) oils have similar color with cod liver oil (CLO), therefore, the presence of these oils was difficult to detect using naked eye. For this reason, Fourier transform infrared (FTIR) spectroscopy using horizontal attenuated total reflectance (HATR) as sampling accessory and in the combination with chemometrics was developed for detection and quantification of these vegetable oils as adulterants in CLO. The quantification of vegetable oils was carried out by using multivariate calibrations of partial least squares (PLS) and principle component regression (PCR), while the classification between pure CLO and CLOs adulterated with CaO, CO, SO, and WO was performed using discriminant analysis (DA). PLS with FTIR normal spectra was more suitable compared with PCR for quantification purposes with coefficient of determination (R2) higher than 0.99 and root mean square error of calibration (RMSEC) in the range of 0.04–0.82% (v/v). The PLS model was further used to predict the levels of these vegetable oils in independent samples for validation/prediction purpose. The root mean square error of prediction (RMSEP) values obtained were of 1.75% (v/v) (CaO), 1.39% (v/v) (CO), 1.35% (v/v) (SO), and 1.37% (v/v) (WO), respectively. The classification using DA revealed that the developed method can classify CLO and that mixed with these vegetable oils using 9 principal components.