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181.
Differentiation of certified brands of origins of Spanish white wines by HS-SPME-GC and chemometrics 总被引:1,自引:0,他引:1
Jurado JM Ballesteros O Alcázar A Pablos F Martín MJ Vilchez JL Navalón A 《Analytical and bioanalytical chemistry》2008,390(3):961-970
A headspace solid-phase microextraction gas-chromatographic (HS-SPME-GC) procedure was used to determine the composition of
the volatile fraction of white wine samples from several Spanish certified brands of origin (CBO). The compounds present were
previously identified by gas chromatography−mass spectrometry (GC−MS) and quantitative determinations were carried out by
GC-FID. Four CBO, Rueda, Ribeiro, Penedés, and Condado de Huelva, were studied. Rueda wines present the highest concentrations
of ethyl acetate (55.86−125.27 μg mL−1), isoamyl acetate (0.91−6.72 μg mL−1), hexyl acetate (0.09−0.81 μg g mL−1), and 2-phenethyl acetate (0.14−0.66 μg mL−1). Compounds such as ethyl hexanoate (0.88−2.15 μg mL−1) and ethyl decanoate (0.29−0.96 μg mL−1) appeared in higher concentration in Ribeiro, Rueda, and Penedés samples. According to the results obtained and by applying
pattern-recognition procedures differentiation of the considered CBO was attained. Principal-component analysis (PCA), linear
discriminant analysis (LDA), and multilayer perceptrons neural networks (MLP-NN) were used as chemometric tools for pattern-recognition
studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
182.
Bernardo Llano Juan José Montellano‐Ballesteros Eduardo Rivera‐Campo Ricardo Strausz 《Journal of Graph Theory》2008,57(4):344-352
An induced subgraph of a graph is called a derived subgraph of if contains no isolated vertices. An edge e of is said to be residual if e occurs in more than half of the derived subgraphs of . In this article, we prove that every simple graph with at least one edge contains a non‐residual edge. This was conjectured by El‐Zahar in 1997. © 2008 Wiley Periodicals, Inc. J Graph Theory 57: 344–352, 2008 相似文献
183.
Intense Ground‐State Charge‐Transfer Interactions in Low‐Bandgap,Panchromatic Phthalocyanine–Tetracyanobuta‐1,3‐diene Conjugates
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Michael Sekita Dr. Beatriz Ballesteros Prof. Dr. François Diederich Prof. Dr. Dirk M. Guldi Dr. Giovanni Bottari Prof. Dr. Tomás Torres 《Angewandte Chemie (International ed. in English)》2016,55(18):5560-5564
A cycloaddition–retroelectrocyclization reaction between tetracyanoethylene and two zinc phthalocyanines (ZnIIPcs) bearing one or four anilino‐substituted alkynes has been used to install a strong, electron‐accepting tetracyanobuta‐1,3‐diene (TCBD) between the electron‐rich ZnIIPc and aniline moieties. A combination of photophysical, electrochemical, and spectroelectrochemical investigations with the ZnIIPc‐TCBD‐aniline conjugates, which present panchromatic absorptions in the visible region extending all the way to the near infrared, show that the formal replacement of the triple bond by TCBD has a dramatic effect on their ground‐ and excited‐state features. In particular, the formation of extremely intense, ground‐state charge‐transfer interactions between ZnIIPc and the electron‐accepting TCBD were observed, something unprecedented not only in Pc chemistry but also in TCBD‐based porphyrinoid systems. 相似文献
184.
185.
Ballesteros B Torre Gde L Ehli C Rahman GM Agulló-Rueda F Guldi DM Torres T 《Journal of the American Chemical Society》2007,129(16):5061-5068
HiPco single-walled carbon nanotubes (SWNTs) have been sidewall-functionalized with phthalocyanine addends following two different approaches: a straightforward Prato reaction with N-octylglycine and a formyl-containing phthalocyanine, and a stepwise approach that involves a former Prato cycloaddition to the double bonds of SWNTs using p-formyl benzoic acid followed by esterification of the derivatized nanotubes with an appropriate phthalocyanine molecule. The two materials obtained by these routes comprise different carbon/Pc-addenda ratios, as evidenced by Raman, TGA, and photophysical studies. The occurrence of electron transfer from photoexcited phthalocyanines to the nanotube framework in these ZnPc-SWNT ensembles is observed in transient absorption experiments, which confirm the absorption of the one-electron oxidized ZnPc cation and the concomitant bleaching of the van Hove singularities typical from SWNTs. Charge-separation (i.e., 2.0 x 1010 s(-1)) and charge-recombination (i.e., 1.5 x 106 s(-1)) dynamics reveal a notable stabilization of the radical ion pair product in dimethylformamide. 相似文献
186.
Ballesteros B Garzón A Jiménez E Notario A Albaladejo J 《Physical chemistry chemical physics : PCCP》2007,9(10):1210-1218
A newly constructed chamber/Fourier transform infrared system was used to determine the relative rate coefficient, k(i), for the gas-phase reaction of Cl atoms with 2-butanol (k(1)), 2-methyl-2-butanol (k(2)), 3-methyl-2-butanol (k(3)), 2,3-dimethyl-2-butanol (k(4)) and 2-pentanol (k(5)). Experiments were performed at (298 +/- 2) K, in 740 Torr total pressure of synthetic air, and the measured rate coefficients were, in cm(3) molecule(-1) s(-1) units (+/-2sigma): k(1)=(1.32 +/- 0.14) x 10(-10), k(2)=(7.0 +/- 2.2) x 10(-11), k(3)=(1.17 +/- 0.14) x 10(-10), k(4)=(1.03 +/- 0.17) x 10(-10) and k(5)=(2.18 +/- 0.36) x 10(-10), respectively. Also, all the above rate coefficients (except for 2-pentanol) were investigated as a function of temperature (267-384 K) by pulsed laser photolysis-resonance fluorescence (PLP-RF). The obtained kinetic data were used to derive the Arrhenius expressions: k(1)(T)=(6.16 +/- 0.58) x 10(-11)exp[(174 +/- 58)/T], k(2)(T)=(2.48 +/- 0.17) x 10(-11)exp[(328 +/- 42)/T], k(3)(T)=(6.29 +/- 0.57) x 10(-11)exp[(192 +/- 56)/T], and k(4)(T)=(4.80 +/- 0.43) x 10(-11)exp[(221 +/- 56)/T](in units of cm(3) molecule(-1) s(-1) and +/-sigma). Results and mechanism are discussed and compared with the reported reactivity with OH radicals. Some atmospheric implications derived from this study are also reported. 相似文献
187.
188.
189.
Ballesteros LM Martín S Pera G Schauer PA Kay NJ López MC Low PJ Nichols RJ Cea P 《Langmuir : the ACS journal of surfaces and colloids》2011,27(7):3600-3610
Langmuir films have been fabricated from 4-[4'-(4'-thioacetyl-phenyleneethynylene)-phenyleneethynylene]-aniline (NOPES) after cleavage of the thioacetyl protecting group. Characterization by surface pressure vs area per molecule isotherms and Brewster angle microscopy reveal the formation of a high quality monolayer at the air-water interface. One layer Langmuir-Blodgett (LB) films were readily fabricated by the transfer of the NOPES Langmuir film onto solid substrates. X-ray photoelectron spectroscopy (XPS), surface polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and quartz crystal microbalance (QCM) experiments conclusively demonstrate the formation of one layer LB films in which the functional group associated with binding to the substrate can be tailored by the film transfer conditions. Using LB methods this molecule could be transferred to gold samples with either the amine or thiol group attached to the gold surface. The amine group is directly attached to the gold substrate (Au-NH(2)-OPE-SH) when the substrate is initially immersed in the subphase and withdrawn during the transfer process; in contrast, monomolecular films in which the thiolate group is attached to the gold substrate (Au-S-OPE-NH(2)) are obtained when the substrate is initially out of the subphase and immersed during the transfer process. The morphology of these films was analyzed by atomic force microscopy (AFM), showing the formation of homogeneous layers. Film homogeneity was confirmed by cyclic voltammetry, which revealed a large passivation of gold electrodes covered by NOPES monolayers. Electrical properties for both polar orientated junctions have been investigated by scanning tunnelling microscopy (STM), with both orientations featuring a nonrectifying behavior. 相似文献
190.
Santos L Martínez E Ballesteros B Sanchez J 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2000,56(10):1905-1915
The UV fluorescence excitation and dispersed fluorescence spectra of a jet-cooled m-methylaniline have been obtained for the S1<--S0 transition, in which some of the bands have been observed for the first time. The main spectral bands have been assigned by comparison with those of other relevant substituted benzenes. It was found that the spectra exhibit an important feature which is the internal rotation of the methyl group in the electronic ground and excited states. Ab initio calculations at MP2/6-31G* and CIS/6-31G* show that the optimized structure of m-methylaniline in the ground state is not planar with the amino group having sp3 hybridation-like character due to the existence of lone-paired electrons on the nitrogen atom. Upon electronic excitation, the C-N bond exhibits a partial double bond character, indicating an enhanced interaction between the ring and the NH2 group as in the case of aniline. 相似文献