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351.
2,4,6-trichloroanisole (TCA) is a microbial metabolite formed from chlorophenols through the activity of several natural fungal strains present on the cork oak bark. TCA is the primary compound responsible for the mousty/mould off-odour known as “cork taint” present in cork stoppers, wine, water and alcoholic beverages. Chromatographic and electrochemical methods are currently used for the determination of TCA, however its detection at low concentrations remains a technical challenge. The aim of this study was the development of a rapid novel biosensor system based on the Bioelectric Recognition Assay (BERA). The sensor measured the electric response of cultured membrane-engineered fibroblast cells suspended in an alginate gel matrix due to the change of their membrane potential in the presence of the analyte. Membrane-engineered cells were prepared by osmotic insertion of 0.5 μg/l of specific TCA antibodies into the membrane of the cells. The BERA-based sensor was able to detect TCA in a few minutes (3-5 min) at extremely low concentrations (10−1 ppt), thus demonstrating higher sensitivity than the human sensory threshold. In addition, the assay was quite selective against other haloanisoles and halophenols structurally related to or co-occurring with TCA. Finally the sensor was tested against real white wine samples from cork soaks. At this real test, the BERA sensor was able to detect TCA from cork soaks rapidly (3-5 min) at very low concentrations (1.02-12 ng/l), covering the whole range for the detection threshold for wines (1.4-10 ng/l). Therefore, this novel biosensor offers new perspectives for ultra-rapid, ultra-sensitive and low-cost monitoring of TCA presence in cork and wine and possibly also other food commodities.  相似文献   
352.
A one-step and in-situ sample preparation method used for quantifying chlorobenzene compounds in water samples has been developed, coupling microwave and headspace single-drop microextraction (MW-HS-SDME). The chlorobenzenes in water samples were extracted directly onto an ionic liquid single-drop in headspace mode under the aid of microwave radiation. For optimization, a Plackett-Burman screening design was initially used, followed by a mixed-level factorial design. The factors considered were: drop volume, aqueous sample volume, stirring speed, ionic strength, extraction time, ionic liquid type, microwave power and length of the Y-shaped glass-tube. The optimum experimental conditions found from this statistical evaluation were: a 5 μL microdrop of 1-hexyl-3-methylimidazolium hexafluorophosphate exposed for 20 min to the headspace of a 30 mL aqueous sample, irradiated by microwaves at 200 W and placed in a 50 mL spherical flask connected to a 25 cm Y-shaped glass-tube. Under the optimised experimental conditions, the response of a high performance liquid chromatographic system was found to be linear over the range studied and with correlation coefficients ranging between 0.9995 and 0.9999. The method showed a good level of repeatability, with relative standard deviations varying between 2.3 and 8.3% (n = 5). Detection limits were found in the low μg L−1 range varying between 0.016 and 0.039 μg L−1. Overall, the performance of the proposed method demonstrated the favourable effect of microwave sample irradiation upon HS-SDME. Finally, recovery studies from different types of environmental water samples revealed that matrix had little effect upon extraction.  相似文献   
353.
Chemoselective hydrogenation of double bonds in the presence of various functional groups occurred in high yields using water or toluene as solvent, and Pd nanoparticles as catalyst. Up to nine recyclings were achieved in water without decrease of the catalyst activity.  相似文献   
354.
The phosphorescence and fluorescence emitted by both the chromophores existing in raw PVC (allylic and ketoallylic structures and polyenes) and luminescent probes introduced by substitution of chlorine atoms have been used to study local features of the chain microstructure, namely the formation of blocky sequences during the nucleophilic substitution of chlorine atoms and the length and nature of the chain segments relaxing below Tg, i.e., the β relaxation. The comparison with results obtained by dynamic mechanical analysis of some of the copolymers has been carried out. Blocky sequences are found to exist and all isotactic sequences over a diad together with their heterotactic associated triads are found to participate in the β motions.  相似文献   
355.
Quinoline-2-carboxylic acid derivatives cap the N-terminal of several natural cyclic peptides with antitumoral activity. A new and convenient route for the preparation of 3-hydroxyquinoline-2-carboxylic acid is discussed. The preparation of the title compound is accomplished by a four-step procedure from 3-hydroxyquinoline via MOM protection of the hydroxyl group, followed by a 1,2-addition of methyllithium to the quinoline ring with concomitant oxidation, and, finally, a two-step oxidation procedure for the transformation of the methyl group to the carboxylic acid along with removal of the MOM group. Furthermore, different attempts to its preparation led to other interesting quinolines, such as 2-chloro-3-hydroxyquinoline-4-carboxylic acid and a protected 3,3′-dihydroxy-2,2′-biquinoline.  相似文献   
356.
The synthesis and spectroscopic characterization of NiII, CuII, PdII and AuIII complexes containing hydrazones derived from 6-amino-5-formyl-1,3-dimethyluracil and thiosemicarbazide, acetylhydrazine and nicotinic acid is reported. In all cases, the complexes appear to be monomeric and square planar, with three positions occupied by the N,N,Z-tridentate (Z = S or O) ligand, making two five- and six-membered chelate rings and the fourth position occupied by halide.  相似文献   
357.
A series of novel 7-indole substituted 2,4-diamino-5,8-dihydropyrido[2,3-d]pyrimidine analogous to the 2,4-diaminopteridine core were synthesized by the three-component one-pot cyclocondensation between 2,4,6-triaminopyrimidine, 3-(2-cyanoacetyl)indole and aromatic aldehydes. The reactions, which exhibited good performance, proceeded in EtOH using indium (III) chloride as catalyst under microwave irradiation, in short reaction times. On the basis of certain structural similarity of these compounds with known ligands of the D2 dopamine receptors (D2DR), the study of these compounds as possible ligands of dopamine D2 and D1 receptors was carried out. Three of them showed moderate affinity to D2-DR since the Ki D1/D2 ratio reached values of 40, 65 and 31 for compounds 4c, 4k and 4j, respectively. Finally, molecular modeling studies revealed stronger molecular interactions of such derivatives with the D2DR than with D1DR, what agrees with the experimental data, and gives an additional support to the observed selectivity to the D2DR.  相似文献   
358.
Agglomerated stoppers are manufactured from natural cork granules and adhesives. Esters, such as phthalates and adipates, are commonly used in adhesives at concentrations of typically 2-5%. Because of this, and regarding consumer safety, it is necessary to ensure that these compounds do not migrate into the beverage where the cork stopper is used. A reversed-phase high performance liquid chromatography method with tandem mass spectrometry detection is developed for the separation of nine phthalates into 12% ethanol, used as simulant of alcoholic beverages. The chromatographic separation was carried out with a Luna C18 (2) HSTcolumn (50 × 3.0 mm, 2.5 μm) with a gradient elution of water/methanol with 0.1% acetic acid at 300 μL min(-1). The method was validated for four selected phthalates: di-butylphthalate, di-isononylphthalate, di-isodecylphthalate, and butyl-benzyl phthalate, with recoveries ranging between 95% and 112% and intralaboratory precision (RSD) between 5 and 14%, depending on the phthalate. The lowest quantification limit, 0.15 mg kg(-1), was achieved for di-butylphthalate. Nevertheless, in all cases, the limits obtained guarantee the method utility if restriction limits set in Commission Regulation No 10/2011 for plastic materials are taken into account.  相似文献   
359.
360.
A bimetallic catalyst system has been developed that for the first time allows the decarboxylative cross‐coupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non‐coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic cross‐coupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho‐substituted or otherwise activated derivatives to a broad range of ortho‐, meta‐, and para‐substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10‐phenanthroline (10–15 mol %) and PdI2/phosphine (2–3 mol %) in NMP for 1–24 h, the other involving CuI/1,10‐phenanthroline (6–15 mol %) and PdBr2/Tol‐BINAP (2 mol %) in NMP using microwave heating for 5–10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non‐activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylative cross‐couplings are discussed.  相似文献   
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