Search results for "chemical analysis"
showing 10 items of 324 documents
Quadruply-bonded dimolybdenum compounds: Reactivity towards TCNE. Structural evidences for the 1-D polymer [Mo2(O2 CCF3)4(TCNE)]∞
2005
cited By 3; International audience; Reaction of [Mo2(O2CR)4] (R = CF 3, 1) with TCNE in toluene affords the new compound [Mo2(O2CCF3)4 (TCNE)·6H5CH3 (2). The structure of 2 is built on [Mo2(O2 CCF3)4] fragments having the usual paddlewheel structure of 1 (Mo-Mo 2.1117(8) Å) and TCNE units. Each polynitrile moiety acts as a bridging ligand between two Mo2 fragments (Mo-N 2.875(4) Å) affording 1-D polymeric chains crossing in the crystal; the toluene molecules occupy the cavities between the chains. 13C NMR, IR and electrochemical data clearly show that formation of 2 does not involve electron density transfer from dimolybdenum fragment to the TCNE unit, which remains in 2 in its neutral stat…
Polyaminocyclodextrin nanosponges: synthesis, characterization and pH-responsive sequestration abilities
2016
New pH-responsive nanosponges were obtained by reacting four different polyaminocyclodextrins with heptakis-(6-bromo)-(6-deoxy)-β-cyclodextrin. The materials obtained were characterized by various techniques (FT-IR, potentiometric titration, differential scanning calorimetry (DSC), porosimetry (BET), 13C{1H} CP-MAS NMR). Their adsorption abilities at different pH values were verified towards a suitable set of model guests, and seem mainly controlled by electrostatic interactions, as a function of the protonation/charge status of the polymer matrix. By contrast, data positively point out a lesser importance assumed by the induced-fit effect, important in affecting the formation of host–guest…
UV-patternable nanocomposite containing CdSe and PbS quantum dots as miniaturized luminescent chemo-sensors
2015
In this study, a novel multifunctional hybrid polymer-based luminescent material, particularly formulated for photolithography, was developed, fabricated and tested as a miniaturized chemosensor. This nanocomposites were formulated with either luminescent CdSe (for the visible) or PbS (for the near-IR) colloidal QDs embedded in a polyisoprene-based photoresist (PIP). We checked the sensing capability of the nanocomposite by exposing 1 cm2 CdSe nanocomposite patterns to vapours of some analyte solutions such as 2-mercaptoethanol (MET) and ethylenediamine (EDA). The transduction mechanism of the sensor is based on changes of the QD photoluminescence (PL) when molecules are adsorbed on the QD …
Influence of dissolved humic material and ionic strength on C8 extraction of pesticides from water
1995
A mixture of twelve intermediate polarity pesticides, mostly carbamate-type, have been chromatographied on an octadecyl-silica bonded-phase column using acetonitrile-water gradient mobile phase and UV detection. Pesticides were extracted from aqueous matrix by solid-phase extraction. The extraction system consisted of a glass microcolumn containing octyl-silica solidphase conditioned with methanol and water. The elution was by acetonitrile-dichloromethane (50:50). Studies of extraction factors like volume of sample, addition of 10% sodium chloride and presence of dissolved humic material are investigated.
Hydrolytic degradation of PLA/Posidonia Oceanica green composites: A simple model based on starting morpho-chemical properties
2021
Abstract In this work, we studied the degradability of PLA-based biocomposites containing Posidonia Oceanica flour at different loading levels and aspect ratios. Hydrolytic tests were carried out in neutral (pH = 7.4) and alkaline (pH = 10) environment. Time-dependent evolution of some key features, including residual mass and solution uptake, was monitored, and correlated with the changes observed in both morphology and chemical structure of the matrix. The results pointed out that biocomposites degraded much faster than neat PLA in both conditions, up to lose 70% of their initial weight after 1000 h immersion. A complex mechanism was unveiled, evidencing the crucial role of the fillers, c…
The PAH composition in limpets (Patella vulgate L.) from the coasts of Sicily (Italy)
2006
This article examines the presence, distribution, nature and sources of 19 Polycyclic Aromatic Hydrocarbons (PAH), in Patellae (patella vulgate L.) and seaweed (vulva) sampled in different stations of Sicilian coastal environments and analyzed for their polycyclic aromatic hydrocarbon (PAH) content. Analysis was performed by gas chromatography/mass spectrometry (GC/MS) with selected ion monitoring (SIM), after saponification of the sample and clean up of the extract. In the limpets the total concentration of polycyclic aromatic hydrocarbons ranged from 34 to 750 μg/Kg of dry matrix. The relative standard deviation (RSD) of the replicas on the concentrations of individual compounds ranged fr…
Polychlorinated Biphenyls in Sediments from Sicilian Coastal Area (Scoglitti) using Automated Soxhlet, GC-MS, and Principal Component Analysis
2014
A methodology for the PAHs and PCBs congener determination in sediment samples has been revised. We determined the distributions of PAHs and PCBs in the superficial sediments of the Scoglitti (Italy) coastal area to provide data for comparison with other marine systems and to hypothesize the sources. Extraction yield, for PCB, was never less than 60% in most cases, while for PAHs, utilizing perdeuterated surrogate standard (benz[a]anthracene-d12 and anthracene-d10) was never less than 72%. The total concentration of the 16 PAHs investigated, expressed as the sum of concentrations, PAHs, varied from 1–5087 μg/kg of dry matrix, while the PCBs ranged from detection limit to 36 μg/kg of dry mat…
Morphology of 1-alkyl-3-methylimidazolium hexafluorophosphate room temperature ionic liquids
2008
The structural organization in selected room temperature ionic liquids, namely (a) butyl-, (b) hexyl- and (c) octyl-3-methylimidazolium hexafluorophosphate, is investigated by means of X-ray diffraction. We find novel experimental evidences of the existence of a high degree of intermediate range order that is associated to nanoscale segregation of the alkyl chains into the charged matrix. The size of these structural heterogeneities depends linearly from the alkyl chain length. A similar behaviour had been observed in other systems, such as normal alcohols. The slope of such dependence provides hints on the nature of the structural organization of these segregated domains.
Infusion mass spectrometry as a fingerprint to characterize varnishes in oil pictorial artworks.
2007
Mass spectrometry methodology to characterize drying oil used as binding media and varnishes in pictorial artworks, prior to conservation or restoration treatment, is proposed. The analytical treatment requires prior basic hydrolysis of the samples to release the fatty acids : caprylic, pelargonic, capric, sebacic, azelaic, suberic, eicosanoic, lauric, mirystic, palmitic, linolenic, linoleic, oleic and stearic, followed by separation from the matrix by a hexane/water extraction. After removing the solvent, the remaining solid is dissolved in potassium hydroxide, propanol and methanol. The mixture is directly infused into a mass spectrometer without any previous derivatization or separation …
Transport of amino acids through liquid membranes supported on novel poly(vinylidenefluoride) porous flat-sheet matrix
1997
Flat-sheet membranes from poly(vinylidenefluoride) (PVDF) were prepared by the phase inversion process. LiCl was used as a modifying agent. The porosity, maximum pore size and LEPW (liquid entry pressure of water) were determined. Three types of these membranes were tested as a support for n-decanol supported liquid membranes (SLM). Transport of eight amino acids, selected to cover a wide variety of side chains, and of phenylalanine methyl ester through n-decanol SLM were studied. The ability of amino acids to permeates through these membranes depends on the type of flat-sheet PVDF used as a support. An increase in porosity and pore size of the microporous matrix resulted in an increase of …