Thermoanalytical study of nimesulide and their recrystallization products obtained from solutions of several alcohols

Thermogravimetry, differential scanning calorimetry, and vibrational infrared spectroscopy were used to study nimesulide and its recrystallization products that were obtained from solutions of several alcohols. The thermoanalytical measurements were performed in both air and nitrogen atmospheres and the results suggest that, under the experimental conditions used in this paper, it was possible to obtain neither polymorphic nor pseudopolymorphic forms of this drug. In this investigation, quantum chemical approach methods were used to determine the molecular structures using the Becke three-parameter hybrid method and the Lee–Yang–Parr correlation functional. The performed molecular calculations were done with the Gaussian 09 routine and the theoretical calculation results were correlated with the experimental IR vibrational spectrum.     

The novel application of Fourier thermal analysis in foundry technologies

The process of casting in sand moulds is used for a large volume of castings manufactured in the world. Internal channels and complex geometries of these products are formed by the placement of cores within the mould cavity. Resin-bound sand mixtures are essential ingredients in engine component manufacturing. In this study, a state-of-the-art application of Fourier thermal analysis in foundry technologies is presented. Investigation of decomposition phenomena of resin-bound moulding materials during casting production is a brand new area to use the potential of thermal sciences. Temperature measurements in test samples of standard types of moulding mixtures were performed. The registered cooling curves were processed by a numerical iteration algorithm to determine the amount of heat absorbed during degradation of the moulding material. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) of sand mixtures were carried out to compare the results of the Fourier thermal analysis with TG and DTA curves.     

Burning of thermally thin polyethylene mixtures

The burning of polyethylene in the mixture with aluminium hydroxide, aluminium oxide, cellulose and Irganox 1010 has been examined by cone calorimeter under non-standard sizes of the sample. The time to ignition of pure polyethylene decreases with decreasing initial amount of polyethylene powder. The subtraction of the mass of water released from the total mass lost for polyethylene with aluminium hydroxide give the same values of effective heats of combustion as for pure polyethylene up to the load about 50 mass% of aluminium hydroxide. The mean heats of combustion determined from the cone calorimeter software are higher than those determined from the total oxygen consumed and mass lost multiplied by the factor 13.1. The additivity rule was found for effective heat of combustion and total smoke released for polyethylene with cellulose. The free radical scavenger Irganox 1010 does not show a significant effect on the flammability of polyethylene except for the increase of the total smoke released. The equation describing the heat release rate evolution in time has been proposed showing a good fit to the experimental runs.     

Solvent extraction with organophosphorus extractants in environmental samples: determination of cadmium(II) in natural water

In this work, Cd(II) extraction in natural waters by organophosphorus extractants as organic phase, as well as its back-extraction in an acidic media, has been studied. Cadmium extraction behavior at natural waters’ pH conditions (values in the range 7–8) was studied with two different extractants and co-ions, obtaining the highest extraction efficiency when using 0.1M Cyanex 272 in kerosene as organic phase and 0.1 M NO₃ ^? as co-ion. Once they were selected, the effect on the extraction efficiency of sample pH, buffer concentration, extraction time, Cyanex 272 concentration as well as back-extractant concentration, was studied. The presence of the main inorganic and organic ligands in the sample was also studied, observing that extraction efficiency was affected most significantly when chlorides were present, with a decrease of about 14%, proving negligible for the others. Under the selected conditions, spiked real samples were successfully analyzed.      

Determination of mercury species using thermal desorption analysis in AAS

Analytical aspects of the determination of inorganic mercury (Hg) species by thermal desorption followed by atomic absorption spectrometry (AAS) detection were investigated in this work. Characteristic Hg release curves of the following species were observed: Hg⁰, HgCl₂, HgO, HgSO₄, HgS, and the Hg bound to humic acids. Particular attention was dedicated to the thermal stability and change of bond of Hg⁰ in the following matrices: sand, kaolinite, granite, peat, power plant ash, and soil. The bond of elemental Hg in environmental materials was described on basis of this experiment. Contaminated soil samples from two locations in the Czech Republic were investigated by thermal desorption analysis. Afterwards, the contents of volatile and plant-available Hg in the studied samples were determined. The determination of Hg⁰ using the thermal method was related to the results of liquid sequential extraction. The development of Hg speciation and the stability of Hg were assessed on basis of the data obtained. Thus, the analytical procedure used is a suitable tool for the study of inorganic Hg species in contaminated soils.     

PHA-L lectin and carbohydrate relationship: conjugation with CdSe/CdS nanoparticles, radiolabeling and in vitro affinities on MCF-7 cells

This research aims to investigate the interaction between phytohemagglutinin-L (PHA-L) and sialic acid, which is abundant on the breast cancer cell (MCF-7) surface and displays monosaccharide characteristics, by experimental and computational methods. Experimentally, CdSe/CdS nanoparticles (QDs) were synthesized; PHA-L was conjugated with QDs and labeled with ¹²⁵I. Radiolabeling yield was found to be 97 ± 1.2 %. Afterwards, in vitro bioaffinities of radiolabeled PHA-L conjugated QDs have been investigated on MCF-7 cells and it has been observed that the cell incorporation increased with time. The results indicated that ¹²⁵I labeled QD-PHA-L conjugates represent significant affinity on MCF-7 cells. In the second step of the study, the crystal structure of carbohydrate interaction surface of PHA-L was extracted from the crystal structure of PHA-L. The interactions between this surface and sialic acid were calculated by computational tools. These calculations revealed specific interactions between PHA-L and sialic acid. Semi-empirical methods, PM3 and AM1, were used in these calculations. Significant outcomes have been obtained from the experimental and computational studies and these results demonstrated that PHA-L may be an effective agent for imagining MCF-7 cells.     

Sorption of cesium on composite sorbents based on nickel ferrocyanide

Composite sorbents based on potassium nickel ferrocyanide embedded in silica gel matrix were prepared and characterised by powdered X-ray diffraction analysis, IR spectra, Mössbauer spectra and electron microscopy. The sorbent exhibits very good efficiency for cesium uptake and radiation resistance. The sorption capacity for cesium ions is comparable with the capacity for the pure ferrocyanides.     

Optimisation and comparison of microwave-assisted extraction and Soxhlet extraction for the determination of polychlorinated biphenyls in soil samples using an experimental design approach

Optimisation of microwave-assisted extraction (MAE) for the extraction of polychlorinated biphenyls (PCBs) from soil samples has been accomplished using an experimental design approach. Variables studied have been: percentage of acetone (v/v) in an acetone:n-hexane mixture, solvent volume, extraction time, microwave power and pressure inside the extraction vessel. Five samples of a certified soil (CRM 481) have been extracted under the optimum conditions of the developed method and the results have been compared to those obtained by Soxhlet extraction. Good recoveries (>95%) have been obtained for all the PCBs studied. All extracts have been analysed by gas chromatography/mass spectrometry (GC/MS) and an optimum determination method for the electron impact mass spectrometric (EIMS) has also been developed.     

Spectrofluorimetric determination of cisatracurium and mivacurium in spiked human serum and pharmaceuticals

Spectrofluorimetric methods to determine cisatracurium and mivacurium are proposed and applied to the determination of both substances in human serum and to the determination of mivacurium in pharmaceuticals. The fluorimetric methods allow the determination of 5-500 ng ml(-1) of mivacurium in aqueous solutions and 5-500 ng ml(-1) of cisatracurium in water-acetonitrile solutions, both containing acetic acid-sodium acetate buffer (pH 5.5) with lambda(exc)=230 nm and lambda(em)=324 nm.     

Equilibrium studies of mercury(II) complexes with penicillamine

A solid-phase microextraction method coupled with a flame photometric detector was developed for the analysis of organophosphorus pesticides in water. Two kinds of fiber (100 mum polydimethyl siloxane (PDMS) and 85 mum polyacrylate (PA) fibers) were used and compared. Parameters that may affect the extraction, such as the duration of absorption and desorption, temperature of absorption, ionic strength, elutropic strength, and concentration of humic acid were investigated. Higher sensitivity and lower detection limits were achieved using a PA fiber than using a PDMS fiber. The detection limit is less than 0.3 mug l(-1) for most of the analytes, except for mevinphos (420 mug l(-1)). The precision is better than 9%.