Synthesis,characterization and thermal behaviour of solid-state 3-methoxybenzoates of heavy trivalent lanthanides and yttrium(III)

Solid-state Ln(L)₃ compounds, where Ln stands for trivalent Tb, Dy, Ho, Er, Tm, Yb, Lu and Y, and L is 3-methoxybenzoate, have been synthesized. X-ray powder diffractometry, infrared spectroscopy, complexometry and elemental analysis were used to characterize the compounds. In order to study the thermal behaviour of these compounds simultaneous thermogravimetry and differential thermal analysis (TG-DTA) and differential scanning calorimetry (DSC) were used. The results provided information on the composition, dehydration, polymorphic transformation, thermal stability and thermal decomposition of the synthesized compounds.     

Thermoanalytical study of some anti-inflammatory analgesic agents

Thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC) as well as X-ray diffraction powder (DRX) patterns and Fourier transformed infrared spectroscopy (FTIR) were used to study ketoprofen, ibuprofen, and naproxen. The chemical or physical properties of the studied compounds were established and when possible by X-ray powder diffractometry and/or infrared spectroscopy were used. In this investigation, quantum chemical approach was used to determine the molecular structures using Becke three-parameter hybrid method and the Lee–Yang–Par (LYP) correlation functional. The performed molecular calculations in this work were done using the Gaussian 03 routine. Theoretical calculations help in interpretations of FTIR spectra supplying structural and physicochemical parameters.     

Crystal structures and phonon modes of Ba(Ca1/2W1/2)O3, Ba(Ca1/2Mo1/2)O3 and Ba(Sr1/2W1/2)O3 complex perovskites investigated by Raman scattering

This work investigates the crystal structures and phonon modes of Ba(Ca_1/2W_1/2)O₃, Ba(Ca_1/2Mo_1/2)O₃ and Ba(Sr_1/2W_1/2)O₃ perovskites by Raman spectroscopy. The samples were produced by conventional solid‐state processing at 1200 °C. X‐ray diffraction showed that single‐phase homogeneous materials were produced, which are cubic or pseudo‐cubic in symmetry. The existing controversies in the literature for these complex perovskites were investigated by comparing experimental Raman data with group‐theory analysis. Ceramics with Ca and W or Mo were found to be cubic, space group Fm3 m. For these materials, four Raman‐active bands were observed and the fitting parameters showed that the Ba(Ca_1/2Mo_1/2)O₃ ceramic presents bands at lower wavenumbers if compared with the Ba(Ca_1/2W_1/2)O₃ sample. For the Ba(Sr_1/2W_1/2)O₃ material, two hypotheses were investigated for monoclinic or triclinic structures. The experimental results showed 12 Raman‐active modes for this ceramic, which is in perfect agreement with the theoretical predictions for a monoclinic (I2/m) structure. Copyright © 2009 John Wiley & Sons, Ltd.     

Infrared spectroscopy and multivariate calibration to monitor stability quality parameters of biodiesel

This paper evaluates analytical methods based on near infrared (NIR) and middle infrared (MIR) spectroscopy and multivariate calibration to monitor the stability of biodiesel. There was a focus on three parameters: oxidative stability index, acid number and water content. Ethylic and methylic biodiesel from different feedstocks were used in experiments of accelerated aging, in order to take into account the wide variety of oilseeds and feedstocks available in Brazil. Partial least squares (PLS) and multiple linear regression (MLR) models were developed. Different pre-processing techniques and spectral variable/regions selection algorithms were evaluated. For MLR models, the successive projection algorithm (SPA) was employed. Interval PLS (iPLS) and selection of variables taking into account the significant regression coefficients were used for PLS models. Results showed that both near and middle infrared regions, and all variable selection methods tested were efficient for predicting these three important quality parameters of B100, the root mean squares error of prediction (RMSEP) values being comparable to the reproducibility of the corresponding standard method for each property investigated.     

Efficient solvent-free synthesis of thiazolidin-4-ones from phenylhydrazine and 2,4-dinitrophenylhydrazine

An efficient solvent-free synthesis of thiazolidinones from reaction of mercaptoacetic acid, aldehydes (benzaldehyde and valeraldehyde) or ketones (cyclopentanone and cyclohexanone), and hydrazines (phenylhydrazine and 2,4-dinitrophenylhydrazine) is reported. The compounds were generally characterized by spectroscopic techniques and specifically for 2-cyclohexanyl-3-(N-phenyl)-1,3-thiazolidin-4-one by X-ray crystallography.     

Insecticidal activity against Bemisia tabaci biotype B of peel essential oil of Citrus sinensis var. pear and Citrus aurantium cultivated in northeast Brazil

The fumigant action of peel essential oils of Citrus sinensis var. pear (pear orange = PO) and C. aurantium (bitter orange = BO) from the northeast of Brazil were evaluated against Bemisia tabaci biotype B and compared with eugenol as a positive control. The oil concentration in the PO at 8.5 microL/L of air caused 97% mortality, while the oil concentration of BO at 9.5 microL/L of air caused 99% mortality. However, the LC50 estimates for both oils (LC50 = 3.80 microL/L of air for PO and LC50 = 5.80 microL/L of air for BO) did not differ from each other, but they did when compared with eugenol (LC50 = 0.20 microL/L of air). Regarding their effects on oviposition, the Citrus oils showed concentration-response dependence, reducing the number of eggs as the concentration increased, which was not observed for eugenol. The minimum concentrations of the oils that caused a significant reduction in the egg lay were 3.5 and 7.0 microL/L of air for BO and PO, respectively. These results suggest that oils from PO and BO peels may be promising as models to develop new insecticides that might be applied into the integrated management of whiteflies.     

Solid-state compounds of 2-chlorobenzylidenepyruvate with some bivalent metal ions

Solid-state M-2-Cl-BP, where M stands for Mn, Fe, Co, Ni, Cu, Zn and Pb and 2-Cl-BP is 2-chlorobenzylidenepyruvate, have been synthesized. Thermogravimetry and derivative thermogravimetry (TG/DTG), simultaneous thermogravimetry and differential thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy, elemental analysis, and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration, thermal stability and thermal decomposition of the isolated compounds.     

Modified Particle Detachment Model for Colloidal Transport in Porous Media

Particle detachment from the rock during suspension transport in porous media was widely observed in laboratory corefloods and for flows in natural reservoirs. A new mathematical model for detachment of particles is based on mechanical equilibrium of a particle positioned on the internal cake or matrix surface in the pore space. The torque balance of drag, electrostatic, lifting and gravity forces, acting on the particle from the matrix and the moving fluid, is considered. The torque balance determines maximum retention concentration during the particle capture. The particle torque equilibrium is determined by the dimensionless ratio between the drag and normal forces acting on the particle. The maximum retention function of the dimensionless ratio (dislodging number) closes system of governing equations for colloid transport with particle release. One-dimensional problem of coreflooding by suspension accounting for limited particle retention, controlled by the torque sum, allows for exact solution under the assumptions of constant filtration coefficient and porosity. The explicit formulae permit the calculation of the model parameters (maximum retention concentration, filtration and formation damage coefficients) from the history of the pressure drop across the core during suspension injection. The values for maximum retention concentration, as obtained from two coreflood tests, have been matched with those calculated by the torque balance on the micro scale.     

High-throughput analysis by SP-LDI-MS for fast identification of adulterations in commercial balsamic vinegars

Balsamic vinegar (BV) is a typical and valuable Italian product, worldwide appreciated thanks to its characteristic flavors and potential health benefits. Several studies have been conducted to assess physicochemical and microbial compositions of BV, as well as its beneficial properties. Due to highly-disseminated claims of antioxidant, antihypertensive and antiglycemic properties, BV is a known target for frauds and adulterations. For that matter, product authentication, certifying its origin (region or country) and thus the processing conditions, is becoming a growing concern. Striving for fraud reduction as well as quality and safety assurance, reliable analytical strategies to rapidly evaluate BV quality are very interesting, also from an economical point of view. This work employs silica plate laser desorption/ionization mass spectrometry (SP-LDI-MS) for fast chemical profiling of commercial BV samples with protected geographical indication (PGI) and identification of its adulterated samples with low-priced vinegars, namely apple, alcohol and red/white wines.     

An improved photothermal gas analyser: Monitoring of simultaneous thermal diffusivity and thermal effusivity

In this paper we describe a new, simple and fast photothermal method for characterizing simultaneously the thermal diffusivity and thermal effusivity. The improved PTGA essentially combines a photoacoustic cell and a thermal wave pyroelectric cell enclosed in a single compact gas analyzer. The photo- acoustic cell is kept filled with nitrogen and sealed. The pyroelectric cell is also filled with nitrogen and after some warm up time, the nitrogen is exchanged to the gas of interest. It is shown that the analysis of the transient and saturation signals of both photoacoustic and pyroelectric cells are capable of measuring the thermal properties with an accuracy of 5%. The measurements were performed for hydrocarbons as ethane and propane, which are combustible gases. Knowing thermal diffusivity and effusivity, others important properties can be determinate: the thermal conductivity and the volumetric thermal capacity.