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31.
Centineo G Rodríguez-González P Blanco González E García Alonso JI Sanz-Medel A Font Cardona N Aranda Mares JL Ballester Nebot S 《Analytical and bioanalytical chemistry》2006,384(4):908-914
A standard GC-MS instrument with electron impact ionisation has been used to develop a fast, simple and reliable method for
the simultaneous determination of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in water samples. Isotope dilution
analysis (IDA) is used for the determination of species, taking advantage of a commercially available spike solution containing
a mixture of MBT, DBT and TBT enriched in 119Sn. Method detection limits for 100-mL samples were between 0.18 and 0.25 ng L−1 for the three butyltin compounds with typical RSD between 2 and 4% at levels between 100 and 10 ng L−1, respectively. Recovery of tin species in spiked samples (natural water, wastewater and seawater) was quantitative. The stability
of butyltin compounds in collected seawater samples was also studied. The addition of a 1% (v/v) glacial acetic acid preserved
tin species in the samples for at least 5 days at room temperature. The IDA method was finally implemented in a routine testing
laboratory and it was subsequently accredited by the Spanish National Accreditation Body according to the requirements of
UNE-EN ISO/IEC 17025. 相似文献
32.
Ignacio García Nuria Iturriza Hans Grande Julián González 《Journal of magnetism and magnetic materials》2010,322(13):1822-1827
The domain structure of a magnetostrictive Fe40Ni38Mo4B18 amorphous ribbon has been studied using magnetic force microscopy (MFM) at room temperature. First, the evolution of the magnetic domain patterns as a function of the annealing temperature has been investigated. In samples heat treated at 250 and 450 °C for 1 h, a transformation from 90° to 180° domain wall has been clearly observed, while the sample heat treated at 700 °C for 1 h showed a magnetic phase fixed by the crystalline anisotropy. Additionally, the evolution of the magnetic domain structure by applying a DC current was recorded by the MFM technique. For current annealed samples at 1 A for 1, 30 and 60 min, a transformation between different domain patterns has been observed. Finally, in samples treated by the current annealing method under simultaneous stress, an increase of the annealing time gives rise to a different magnetic structure arising from the development of transverse magnetic anisotropy. 相似文献
33.
[STRUCTURE: SEE TEXT] Cis-2,8-disubstituted oxocanes and the parent unsaturated precursors were prepared from the corresponding Co2(CO)6-cycloalkynic ethers. Key steps in such synthesis were the ether linkage formation by intermolecular Nicholas reaction, RCM of the suitable acyclic dienyl ether and montmorillonite K-10 induced isomerization of the complexed cycloalkyne. A short synthesis of (+)-cis-lauthisan taking advantage of the developed methodology is described. 相似文献
34.
Low coverage water adsorption on alkaline-earth oxides is studied by first principles methods and ab initio molecular dynamic simulations. On CaO and BaO(001), water dissociation is thermodynamically favored in contrast with the molecular adsorption found for MgO(001). On CaO(001), the barrier for water splitting is very small leading to a tight ion pair H-OH that exhibits a dynamic character with the hydroxyl group able to visit four equivalent adsorption sites while remaining attached to the proton. In contrast, ion pair separation is endothermic by 0.8 eV. These results are common to other basic surfaces such as BaO(001) and have important implications in the chemistry of partially hydroxylated oxide surfaces. 相似文献
35.
Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η5‐C5Me5)IrIII 下载免费PDF全文
Dr. Ana Zamorano Dr. Nuria Rendón Dr. Joaquín López‐Serrano Dr. José E. V. Valpuesta Dr. Eleuterio Álvarez Prof. Dr. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2576-2587
This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η5‐C5Me5)IrIII fragment. The new complexes have the chemical composition [Ir(Ap)(η5‐C5Me5)]+, exist in the form of two isomers ( 1+ and 2+ ) and were isolated as salts of the BArF? anion (BArF=B[3,5‐(CF3)2C6H3]4). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H2, the electrophilicity of the IrIII centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ2‐N,N′‐bidentate binding in 1+ and the unprecedented κ‐N,η3‐pseudo‐allyl‐coordination mode in isomers 2+ through activation of a benzylic C?H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H?H, C?H and N?H bonds, is catalysed by dihydrogen under homogeneous conditions. 相似文献
36.
Dr. Antonio Sánchez-Ruiz Dr. Julián Rodríguez-López Dr. Andrés Garzón-Ruiz Dr. Sonia B. Jiménez-Pulido Dr. Nuria A. Illán-Cabeza Dr. Amparo Navarro Dr. Joaquín C. García-Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13990-14001
Different molecular strategies have been carefully evaluated to produce solid-state luminescence enhancement (SLE) in compounds that show dark states in solution. A set of α-phenylstyrylarene derivatives with a butterfly shape have been designed and synthesised, for the first time, with the aim of improving the solid-state fluorescence emission of their parent styrylarene compounds. Although these butterfly molecules are not fluorescent in solution, one of them (1,2,4,5-tetra(α-phenylstyryl)benzene) exhibits a fluorescence quantum yield as high as 68 % in a drop-cast sample and 31 % in its crystalline form. In contrast, 1,3,5-tris(α-phenylstyryl)benzene and 4,6-bis(α-phenylstyryl)pyrimidine do not show SLE. A range of fluorescence spectroscopy experiments and DFT calculations were carried out to unravel the origin of different photophysical behaviour of these compounds in the solid state. The results indicate that a rational strategy to control the SLE effect in luminogens depends on a delicate balance between molecular properties and inter-/intramolecular interactions in the solid state. 相似文献
37.
Rodríguez-Calvillo Pablo Ferrer Nuria Cabrera José-María 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1393-1403
Journal of Thermal Analysis and Calorimetry - The thermal behavior of two copper alloys, with 0.2 and 0.5 mass % of Mg, was analyzed after severe plastic deformation processing by Equal Channel... 相似文献
38.
Determination of 3-MCPD by GC-MS/MS with PTV-LV injector used for a survey of Spanish foodstuffs 总被引:1,自引:0,他引:1
3-Monochloropropane-1,2-diol (3-MCPD) is the most common chemical contaminant of the group of chloropropanols. It can occur in foods and food ingredients at low levels as a result of processing, migration from packaging materials during storage and domestic cooking. A sensitive method for determination of 3-MCPD in foodstuffs using programmable temperature vaporization (PTV) with large-volume injection (LVI) gas chromatography (GC) with tandem mass spectrometry detection (MS/MS) has been developed and optimized. The optimization of the injection and detection parameters was carried out using statistical experimental design. A Plackett-Burman design was used to estimate the influence of resonance excitation voltage (REV), isolation time (IT), excitation time (ET), ion source temperature (IST), and electron energy (EE) on the analytical response in the ion trap mass spectrometer (ITMS). Only REV was found to have a statically significant effect. On the other hand, a central composite design was used to optimize the settings of injection temperature (T(inlet)), vaporization temperature (T(vap)), vaporization time (t(vap)) and flow (Flow). The optimized method has an instrumental limit of detection (signal-to-noise ratio 3:1) of 0.044 ng mL(-1). From Valencian, Spain, supermarkets 94 samples of foods were surveyed for 3-MCPD. Using the optimized method levels higher than the limit established for soy sauce by the European Union were found in some samples. The estimated daily intake of 3-MCPD throughout the investigated foodstuffs for adults and children was found about 0.005 and 0.01%, respectively, of the established provisional tolerable daily intake. 相似文献
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