On the acylation of 1,3-benzoxathiole systems

The acylation on 1,3-benzoxathiole systems, as well as the effect of the stoichiometry of the catalyst on the yields of ketones and of breaking products of the O C S bonds is here described.     

Optically active polymer carbon nanotube composite

A completely soluble optically active polyaniline-multiwalled carbon nanotube composite was investigated by spectroscopic and microscopic techniques. It was found that the polymer's optical activity was retained in the presence of carbon nanotubes. Solutions were found to be easily processable into thin films, which exhibited dendritic structures only in the presence of nanotubes.     

Residue analysis of organophosphorus pesticides in animal matrices by dual column capillary gas chromatography with nitrogen-phosphorus detection

Organophosphorus pesticides (OPPs) were determined in matrices of animal origin by dual column capillary gas chromatography using nitrogen-phosphorus detection (NPD). This method was tested on cow milk and on liver and muscle of wild boar. The isolation of these pesticides was performed by liquid partition followed by cleanup with solid phase cartridge (SPE C18), after extraction from the matrix. The analytes identification was obtained by comparing the retention times in two columns with different polarity. The quantification of each OPP was obtained using parathion-ethyl as internal standard. The method was developed in a UNI EN ISO 9001:2000 certified laboratory. The recovery, investigated by analyzing samples spiked at 5, 10 and 50 ppb, ranged from 59 to 117% in milk, from 60 to 81% in liver and from 68 to 76% in muscle. The limit of quantification (LOQ) and limit of detection (LOD) were, respectively, 5 and 1 ppb for each compound and allowed quantifying the residues below the legal limits.     

Reactivity of aryl- and heteroarylmalonates against ortho-dinucleophiles. Triaryl(heteroaryl)methane synthesis

Condensations of several aryl(heteroaryl)malonates 1 and ortho-dinucleophiles are studied as a possible synthetic approach to aryl(heteroaryl)bisheteroarylmethanes 2.     

Synthesis of novel tricyclic isoindole derivatives

Novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles were prepared from the thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in acetic anhydride. The structure of 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindole 6a was determined by X-ray crystallography.     

Capillary electrophoresis-mass spectrometry for the analysis of quaternary ammonium herbicides

Conditions for the simultaneous determination of the three herbicides paraquat, diquat and difenzoquat and the two plant growth regulators chlormequat and mepiquat by pressure-assisted capillary electrophoresis coupled to mass spectrometry (ion-trap) using electrospray as ionisation source have been established. A 200 mM formic acid-ammonium formate buffer solution at pH 3.0 with 50% of methanol was used as carrier electrolyte. Some capillary electrophoresis-mass spectrometry parameters such as sheath liquid and sheath gas flow-rates, sheath liquid composition, electrospray voltage andthe CE capillary position were optimised. The MS and MS-MS spectra of positive ions were studied in order to obtain structural information for the confirmation of the identity. The use of labelled standards allowed to confirm fragment ions assignation. The detection limits, based on a signal-to-noise ratio of 3:1, were between 0.5 and 2.5 mg l(-1) with hydrodynamic injection (10 s) and between 1 and 10 microg l(-1) with elecrokinetic injection (20 s, 10 kV) using standards in ultrapure water. Quality parameters such as linearity and run-to-run precision (n=6) were established. Quantitation was carried out using labelled standards. The method has been applied to the analysis of contaminated irrigation water and spiked mineral water samples.     

Role of surface oxygen groups in incorporation of nitrogen to activated carbons via ethylmethylamine adsorption

Coal origin and wood origin activated carbons were used in this study. To broaden the spectrum of surface features, the surface of the initial samples was modified using oxidation with nitric acid or impregnation with urea followed by heat treatment. Boehm and potentiometric titrations, thermal analysis, and sorption of nitrogen were used to characterize the pore structure and surface chemistry. Then adsorption of ethylmethylamine from aqueous solutions was carried out without controlling the pH of the carbon suspension. The isotherms were measured at 299 K and fitted to the Freundlich equation. The results showed that the amount of ethylmethylamine adsorbed on all carbons at a high concentration is dependent on the total number of surface groups whereas at low concentration it depends on the type of surface groups. The latter was observed exclusively for initial and oxidized carbons where acidic groups are present. The ethylmethylamine adsorption is mainly governed by dipole-dipole, hydrogen bonding, or specific acid-base interactions. Those interactions play a crucial role in incorporation of nitrogen to the carbon matrix at elevated temperatures.     

Determination of odour-causing volatile organic compounds in cork stoppers by multiple headspace solid-phase microextraction

Multiple headspace solid-phase microextraction (MHS-SPME) coupled with gas chromatography-mass spectrometry has been applied in order to determine 2,4,6-trichloroanisole (2,4,6-TCA), guaiacol, 1-octen-3-ol and 1-octen-3-one in three samples of cork stoppers. These compounds are responsible for cork taint in wine and can modify the organoleptic properties of bottled wine. Variables such as temperature, addition of water, extraction time, and amount of cork were studied. The extractions were performed with a 50/30 microm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre for 45 min at 100 degrees C using 20 mg of cork. For calibration, 50 microL of VOC aqueous solutions were used and the extraction were carried out for 45 min at 75 degrees C. The limits of detection of the method expressed as ng of VOC per g of cork were 0.3 for 2,4,6-TCA, 7.5 for guaiacol, 1.7 for 1-octen-3-one and 1.9 for 1-octen-3-ol. Relative standard deviation of replicate samples was less than 10%. Significant losses of analytes were observed when the samples were ground at room temperature. Finally, a recovery study was performed and the MHS-SPME results were validated using Soxhlet extraction results.     

Synthesis of 6-amino and 6-ethoxy-2(1H)-pyridone derivatives

An efficient route allowing the synthesis of 6-amino and 6-ethoxy-2(1H)-pyridone derivatives by reaction of ethyl cyanoacetimidate, ethyl ethoxycarbonylacetimidate and related acetamidines with diethyl ethoxymeth-ylenemalonate (EMME) is reported. The formation of dienamino derivatives as intermediates and their heterocyclization to the 2(1H)-pyridone derivatives is described.