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141.
In this paper we will show the results of our research on the direct simultaneous determination of multi-class pesticides and transformation products with different polarities and acid-base properties by applying an on-line trace enrichment coupled to the chromatographic system supplied with electrospray interface (SPE-LC-MS/MS method). The specific chromatographic separation allows the correct determination of almost fifty compounds (37 pesticides and 10 transformation products) using very low sample volume and very little sample handling. Recoveries between 70-120% were obtained for all compounds in drinking and groundwater, meanwhile in surface water 44 compounds were correctly quantified. Relative standard deviations lower than 15% were obtained for all compounds. Even at the lowest concentration level tested (25 ng L(-1)) 40 compounds presented satisfactory recoveries and repeatability. The use of methanol as organic modifier and the increase of injection volume are also studied. The applicability of the developed method to a monitoring programme is demonstrated by applying it to the analysis of hundreds of samples. 相似文献
142.
Javier Mazuela Alexander Paptchikhine Oscar Pàmies Pher G. Andersson Montserrat Diéguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(15):4567-4576
A library of readily available phosphite–oxazole/thiazole ligands ( L1 a – g – L7 a – g ) was applied in the Ir‐catalyzed asymmetric hydrogenation of several largely unfunctionalized E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (bridge length, the substituents in the heterocyclic ring and the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety), so that enantioselectivities could be maximized for each substrate as required. Enantioselectivities were therefore excellent (enantiomeric excess (ee) values up to >99 %) for a wide range of E‐ and Z‐trisubstituted and 1,1‐disubstituted terminal alkenes. The biaryl phosphite moiety was a very advantageous ligand component in terms of substrate versatility. 相似文献
143.
144.
Dicyclohexylcarbodiimide-promoted self-condensation of 2,3:4,5-di-O-isopropylidene-d-galactonic acid (3) led to the macrocyclic oligomeric cyclo[(2,3:4,5-di-O-isopropylidene-(1→6)-d-galactonate)2] (4) and cyclo[(2,3:4,5-di-O-isopropylidene-(1→6)-d-galactonate)3] (5), having, respectively, 14- and 21-membered rings. The macrocycles 4 and 5 were also synthesized by cyclization of the respective linear dimer 11 and trimer 14 ω-hydroxy acids precursors prepared by stepwise additions of 3. Compounds 4 and 5 are biomaterials that may be described as macrolactone-cyclodextrins. 相似文献
145.
André Romero da Silva Natalia Mayumi Inada Daniel Rettori Mariana Ozello Baratti Anibal Eugenio Vercesi Renato Atilio Jorge 《Journal of photochemistry and photobiology. B, Biology》2009,94(2):101-112
In(III)-meso-tetraphenylporphyrin (InTPP) was encapsulated into nanoparticles (smaller than 200 nm) of poly(d,l-lactide-co-glycolide) (PLGA) using the emulsification–evaporation technique. The photodynamic efficacy of InTPP-loaded nanoparticles and its cellular uptake was investigated with LNCaP prostate tumour cells, in comparison with the free InTPP. The effects of incubation time (1–3 h), drug concentration (1.8–7.7 μmol/L) and incident light dose (15–45 J/cm2) with both encapsulated and free InTPP were studied. The type of cell death induced by the photochemical process using both encapsulated and free InTPP was also investigated. Cell viability was reduced more significantly with increasing values of these effects for InTPP-loaded nanoparticles than with the free drug. The cellular death induced by both encapsulated and free InTPP was preponderantly apoptotic. Confocal laser scanning microscopy data showed that the InTPP-loaded nanoparticles, as well free InTPP, were localized in the cells, and always in the perinuclear region. Encapsulated InTPP was measured by the intensity of fluorescence intensity of cell extracts and was three times more internalized into the cells than was the free InTPP. Electron paramagnetic resonance experiments corroborated the participation of singlet oxygen in the photocytotoxic effect of nanoparticles loaded with InTPP. 相似文献
146.
Anne Guesdon Francesca Romero Sarria Christophe Tenailleau Bernard Raveau 《Solid State Sciences》2009,11(2):349-357
A new indium hydroxyphosphate containing silver, AgIn[PO3(OH)]2, has been synthesized using hydrothermal method. It crystallizes in the P21/c space group with the cell parameters a = 6.6400(2) Å, b = 14.6269(6) Å, c = 6.6616(4) Å, β = 95.681(5)°, V = 643.82(6) Å3, Z = 4. Its three-dimensional framework, built up of corner-sharing PO3(OH) tetrahedra and InO6 octahedra, presents intersecting tunnels running along <111> and [100] directions, in which the Ag+ cations are located. The presence of hydroxyl groups has been confirmed from IR spectroscopy studies and hydrogen atoms were located from the single crystal X-ray diffraction study. The structural relationships with the other compounds of general formula AIMIII[PO3(OH)]2 are analyzed. 相似文献
147.
Francisco Alcaide Garbiñe Álvarez Oscar Miguel María Jesús Lázaro Rafael Moliner Ana López-Cudero José Solla-Gullón Enrique Herrero Antonio Aldaz 《Electrochemistry communications》2009,11(5):1081-1084
Carbon nanofibers synthesized via the thermo catalytic decomposition of methane were investigated for the first time as an electrocatalyst support in PEMFC cathodes. Their textural and physical properties make them a highly efficient catalyst support for cathodic oxygen reduction in low temperature PEMFC. Tests performed in MEAs showed that Pt supported on carbon nanofibers exhibited an enhancement of ca. 94% in power density at 0.600 V, in comparison with a commercial catalyst supported on conventional carbon black, Pt/Vulcan XC-72R. 相似文献
148.
Isabel C. Henao Castañeda Carlos O. Della Védova Oscar E. Piro Nils Metzler-Nolte Jorge L. Jios 《Polyhedron》2010
Structural and conformational properties of S-benzyl ferrocenecarbothioate (I) and S-(2-methoxyphenyl) ferrocenecarbothioate (II) are analyzed using data obtained from X-ray diffraction, vibrational data and theoretical calculations. According to chemical quantum calculations, the synperiplanar and antiperiplanar forms are found as the first and second more stable conformations, respectively, for the title compounds. The geometric parameters and normal modes of vibration were calculated using a density functional theory method (B3LYP) and the 6-31+G∗∗ basis set for all atoms except for iron. For this atom the calculations were carried out with the Lanl2dz basis set. The calculated parameters are in good agreement with the corresponding X-ray diffraction values. The combined experimental and theoretical approach allows a consistent assignment for most of the fundamental modes. 相似文献
149.
150.
Dr. Raquel Andreu Dr. Santiago Franco Prof. Javier Garín Judith Romero Dr. Belén Villacampa Dr. María Jesús Blesa Dr. Jesús Orduna 《Chemphyschem》2012,13(13):3204-3209
Multichromophoric calix[4]arenes with two or four disperse red one (DR1) moieties linked to the lower rim have been synthesized. The second‐order nonlinear optical activity was measured by using the electric‐field‐induced second‐harmonic generation technique and there was a nearly linear increase of the μβ value with the number of chromophores in the molecule without affecting the charge‐transfer absorption wavelength. The effect that the number of DR1 units plays on the hyperpolarizability, the dipole moment, and the absorption maxima has been also studied by using quantum chemical calculations. It was found that it was necessary to synthesize multichromophores with distant chromophores to obtain large nonlinear optical responses. 相似文献