Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy and chemometric techniques for the determination of adulteration in petrodiesel/biodiesel blends

We propose an analytical method based on fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy to detect the adulteration of petrodiesel and petrodiesel/palm biodiesel blends with African crude palm oil. The infrared spectral fingerprints from the sample analysis were used to perform principal components analysis (PCA) and to construct a prediction model using partial least squares (PLS) regression. The PCA results separated the samples into three groups, allowing identification of those subjected to adulteration with palm oil. The obtained model shows a good predictive capacity for determining the concentration of palm oil in petrodiesel/biodiesel blends. Advantages of the proposed method include cost-effectiveness and speed; it is also environmentally friendly.

Intra-population variation and geographic correlation in Canthon humectus hidalgoensis using FTIR-ATR spectroscopy

In some cases external morphology is not sufficient to discern between populations of a species, as occurs in the dung beetle Canthon humectus hidalgoensis Bates; and much less to determine phenotypic distances between them. FTIR-ATR spectroscopy show several advantages over other identification techniques (e.g. morphological, genetic, and cuticular hydrocarbons analysis) due to the non-invasive manner of the sample preparation, the relative speed of sample analysis and the low-cost of this technology. The infrared spectrum obtained is recognized to give a unique ‘fingerprint’ because vibrational spectra are specific and unique to the molecular nature of the sample. In our study, results showed that proteins, amino acids and aromatic ethers of insect exocuticle have promising discriminative power to discern between different populations of C. h. hidalgoensis. Furthermore, the correlation between geographic distances between populations and the chemical distances obtained by proteins + amino acids + aromatic ethers was statistically significant, showing that the spectral and spatial information available of the taxa together with appropriated chemometric methods may help to a better understanding of the identity, structure, dynamics and diversity of insect populations.

Analysis of biodiesel and frying vegetable oils by means of FTIR photoacoustic spectroscopy

Fourier Transform Infrared Photoacoustic Spectroscopy was used to determine the mid-infrared vibrational modes of biodiesel and vegetable oils. Our results indicate that this method can contribute significantly to the biodiesel wash process during the sample preparation. Besides, by analyzing the spectra of vegetable oils used to fry snacks we could to monitor the degradation in function of the fried time.

Efeito da variação da suavização espectral na robustez de modelos de calibração de metanol e teor alcoólico em aguardentes por FTIR-ATR

No presente estudo pretendeu-se compreender o efeito da variação do número de pontos da suavização espectral (ou filtro digital) no desenvolvimento de modelos de calibração por FTIR-ATR utilizando técnicas PLS-R para determinações rápidas do teor em metanol e do teor alcoólico em aguardentes. De acordo com o descrito em ANJOS et al. (2016) as zonas espectrais identificadas foram 1607-977 cm-1 e 3057-2864 + 1292-663 cm-1 respetivamente para o teor em metanol e teor alcoólico, com coeficientes de determinação superiores a 96,3 %. O valor de RPD apresenta qualidade suficiente para utilização em laboratório de controlo de qualidade. Foi avaliada a robustez dos modelos para 5, 9, 13, 17, 21 e 25 pontos de suavização para o pré-processamento usando a Primeira Derivada (1stDer), aplicando o algoritmo de Savitzky-Golay.

The relationship between charge density and polyelectrolyte brush profile using simultaneous neutron reflectivity and in situ attenuated total internal reflection FTIR

We report on a novel experimental study of a pH-responsive polyelectrolyte brush at the silicon/D2O interface. A poly[2-(diethylamino)ethyl methacrylate] brush was grown on a large silicon crystal which acted as both a substrate for a neutron reflectivity solid/liquid experiment but also as an FTIR-ATR spectroscopy crystal. This arrangement has allowed for both neutron reflectivities and FTIR spectroscopic information to be measured in parallel. The chosen polybase brush shows strong IR bands which can be assigned to the N-D+ stretch, D2O, and a carbonyl group. From such FTIR data, we are able to closely monitor the degree of protonation along the polymer chain as well as revealing information concerning the D2O concentration at the interface. The neutron reflectivity data allows us to determine the physical brush profile normal to the solid/liquid interface along with the corresponding degree of hydration. This combined approach makes it possible to quantify the charge on a polymer brush alongside the morphology adopted by the polymer chains. © 2013 American Chemical Society.

Síntese e caracterização de beads acrílicos preparados por polimerização em suspensão visando aplicação como excipiente farmacêutico para compressão direta

One of the difficulties reported for the suspension polymerization is control the size and granulometry of beads. The purpose of this work was to evaluate the use of cellulose nanowhiskers and mesoporous silica as stabilizers to reduce the size and the particle distribution. To monitor polymerization process was used FTIR-ATR spectroscopy. The morphology was analyzed by scanning electron microscopy. The particle size distribution was characterised using a CILAS granulometer. Thermal stability was studied by thermogravimetric analysis. The results indicated that cellulose nanowhiskers may provide stabilization and increase the thermal stability of the beads in contrast to mesoporous silica.

Evaluation of Postpolymerization as a Function of the Storage Time of Triethylene Glycol Dimethacrylate/2,2-Bis[4-(2-Hydroxy-3-Methacryloxy-Prop-1-Oxy)-Phenyl]-propane Bisphenyl-alpha-Glycidyl Ether Dimethacrylate Copolymers Used in Dental Resins by Differential Scanning Calorimetry and Dynamic Mechanical Analysis

The aim of this work was to evaluate the effect of the storage time on the thermal properties of triethylene glycol dimethacrylate/2,2-bis[4-(2-hydroxy-3-methacryloxy-prop-1-oxy)-phenyl]propane bisphenyl-alpha-glycidyl ether dimethacrylate (TB) copolymers used in formulations of dental resins after photopolymerization. The TB copolymers were prepared by photopolymerization with an Ultrablue IS light-emitting diode, stored in the dark for 160 days at 37 degrees C, and characterized with differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and Fourier transform infrared spectroscopy with attenuated total reflection. DSC curves indicated the presence of an exothermic peak, confirming that the reaction was not completed during the photopolymerization process. This exothermic peak became smaller as a function of the storage time and was shifted at higher temperatures. In DMA studies, a plot of the loss tangent versus the temperature initially showed the presence of two well-defined peaks. The presence of both peaks confirmed the presence of residual monomers that were not converted during the photopolymerization process. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 679-684, 2009

Exothermic Behavior, Degree of Conversion, and Viscoelastic Properties of Experimental and Commercially Available Hard Chairside Reline Resins

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Caracterização de materiais experimentais e comerciais para reembasamento imediato por meio de análise de propriedades físico-químicas e mecânicas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Magnetic Ionic Liquids Produced by the Dispersion of Magnetic Nanoparticles in 1-n-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2)

This paper reports on the advancement of magnetic ionic liquids (MILs) as stable dispersions of surface-modified gamma-Fe2O3, Fe3O4, and CoFe2O4 magnetic nanoparticles (MNPs) in a hydrophobic ionic liquid, 1-n-butyl 3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMI.NTf2). The MNPs were obtained via coprecipitation and were characterized using powder X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Fourier transform near-infrared (FT-NIR) spectroscopy, and magnetic measurements. The surface-modified MNPs (SM-MNPs) were obtained via the silanization of the MNPs with the aid of 1-butyl-3[3-(trimethoxysilyl)propyl]imidazolium chloride (BMSPI.Cl). The SM-MNPs were characterized by Raman spectroscopy and Fourier trail: form infrared attenuated total reflectance (FTIR-ATR) spectroscopy and by magnetic measurements. The FTIR-ATR spectra of the SM-MNPs exhibited characteristic absorptions of the imidazolium and those of the Fe-O-Si-C moieties, confirming the presence of BMSPI.Cl on the MNP surface. Thermogravimetric analysis (TGA) showed that the SM-MNPs were modified by at least one BMSPI.Cl monolayer. The MILs were characterized using Raman spectroscopy, differential scanning calorimetry (DSC), and magnetic measurements. The Raman and DSC results indicated an interaction between the SM-MNPs and the IL. This interaction promotes the formation of a supramolecular structure close to the MNP surface that mimics the IL structure and is responsible for the stability of the MIL. Magnetic measurements of the MILs indicated no hysteresis. Superparamagnetic behavior and a saturation magnetization of similar to 22 emu/g could be inferred from the magnetic measurements of a sample containing 50% w/w gamma-Fe2O3 SM-MNP/BMI-NTf2.

Adsorption of Sodium Dodecyl Sulfate on Ge Substrate: The Effect of a Low-Polarity Solvent

This paper describes the adsorption of sodium dodecyl sulfate (SDS) molecules in a low polar solvent on Ge substrate by using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and atomic force microscopy (AFM). The maximum SDS amount adsorbed is (5.0 +/- 0.3) x 10(14) molecules cm(-2) in CHCl3, while with the use of CCl4 as subphase the ability of SDS adsorbed is 48% lower. AFM images show that depositions are highly disordered over the interface, and it was possible to establish that the size of the SDS deposition is around 30-40 nm over the Ge surface. A complete description of the infrared spectroscopic bands for the head and tail groups in the SDS molecule is also provided.

Study of the biodegradation of a polymer derived from castor oil by scanning electron microscopy, thermogravimetry and infrared spectroscopy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

A New Method to Prepare Porous Silk Fibroin Membranes Suitable for Tissue Scaffolding Applications

A new method to prepare porous silk fibroin (SF) membranes without dialysis proposed. Silk fibers were degummed to remove sericin and the resultant fibroin was dissolved in a CaCl(2)-CH(3)CH(2)OH-H(2)O ternary solvent. Rather than undergoing dialysis, a fibroin salty solution was diluted in water and then submitted to a mechanical agitation that led to a phase separation through foam formation on the solution surface. This foam was continually collected and then compacted between plates to remove the excess of water. The membranes presented large pores with diameters of greater than 100 pm (as shown by scanning electron microscopy - SEM), porosity of 68% and water content of 91% w/w. X-ray diffraction (XRD) and infrared spectroscopy (FTIR-ATR) indicated that the membranes present SF in a beta-sheet structure even before the ethanol treatment. A typical elastic deformation profile and degradation under temperature were observed using calorimetric analysis (DSC), thermal gravimetric analysis (TGA) and mechanical tests. As indicated by the in vitro cytotoxicity tests, these membranes present potential for use as scaffolds. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 617-623, 2009