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81.
Arias M Simó C Ortiz LT de Ios Mozos-Pascual M Barbas C Cifuentes A 《Electrophoresis》2005,26(12):2351-2359
Capillary zone electrophoresis with mass spectrometry (CE-MS) and UV detection (CE-UV) was applied to the quantitative determination of gamma-glutamyl-S-ethenyl-cysteine (GEC), a bioactive and unstable compound present in Vicia narbonensis L. seeds. This compound is responsible for, among other negative effects, palatability reduction and grain toxicity. In order to carry out the quantitative analysis of GEC, different conditions (such as composition, concentration and pH of the background electrolyte, and type and time of extraction) were studied. Also, adequate conditions for electrospray-mass spectrometry of this bioactive compound were investigated. The best extraction conditions of GEC from V. narbonensis L. seeds flour were obtained using ethanol-water (70:30 v/v) for 45 min. The use of a 20 m ammonium hydrogen carbonate at pH 7 provided adequate analytical conditions compatible with the unstable nature of GEC as well as with the requirements of CE-UV and CE-MS analysis. A comparative study was carried out between the different figures of merit of CE-UV and CE-MS for quantitative purposes. Both techniques provided similar limit of detection and can be applied with confidence within the same linear dynamic range. However, reproducibility and speed of analysis were better using CE-UV. The developed methods were readily applied to quantify GEC in seeds of 21 genotypes of V. narbonensis L. A good agreement between CE-MS and CE-UV results was observed corroborating the usefulness of both approaches for quantitative purposes. 相似文献
82.
The rhenium(V) monooxo complexes (hoz)2Re(O)Cl (1) and [(hoz)2Re(O)(OH2)][OTf] (2) have been synthesized and fully characterized (hoz = 2-(2'-hydroxyphenyl)-2-oxazoline). A single-crystal X-ray structure of 2 has been solved: space group = P1, a = 13.61(2) A, b = 14.76(2) A, c = 11.871(14) A, alpha = 93.69(4) degrees, beta = 99.43(4) degrees, gamma = 108.44(4) degrees, Z = 4; the structure was refined to final residuals R = 0.0455 and Rw = 0.1055. 1 and 2 catalyze oxygen atom transfer from aryl sulfoxides to alkyl sulfides and oxygen-scrambling between sulfoxides to yield sulfone and sulfide. Superior catalytic activity has been observed for 2 due to the availability of a coordination site on the rhenium. The active form of the catalyst is a dioxo rhenium(VII) intermediate, [Re(O)2(hoz)2]+ (3). In the presence of sulfide, 3 is rapidly reduced to [Re(O)(hoz)2]+ with sulfoxide as the sole organic product. The transition state is very sensitive to electronic influences. A Hammett correlation plot with para-substituted thioanisole derivatives gave a reaction constant rho of -4.6 +/- 0.4, in agreement with an electrophilic oxygen transfer from rhenium. The catalytic reaction features inhibition by sulfides at high concentrations. The equilibrium constants for sulfide binding to complex 2 (cause of inhibition), K2 (L x mol(-1)), were determined for a few sulfides: Me2S (22 +/- 3), Et2S (14 +/- 2), and tBu2S (8 +/- 2). Thermodynamic data, obtained from equilibrium measurements in solution, show that the S=O bond in alkyl sulfoxides is stronger than in aryl sulfoxides. The Re=O bond strength in 3 was estimated to be about 20 kcal x mol(-1). The high activity and oxygen electrophilicity of complex 3 are discussed and related to analogous molybdenum systems. 相似文献
83.
M. J. Arias P. Muñoz J. R. Moyano J. M. Ginés Cs. Novák 《Journal of Thermal Analysis and Calorimetry》1998,51(3):973-980
Techniques of DSC, TG/DTG, EGD and HSM were used to study and characterize the complex formation and state of dispersion after co-grinding of a 1:1 mixture of omeprazole (OME) and γ-cyclodextrin (γ-CD) under various conditions. The changed crystalline properties of the composites obtained by co-grinding suggested distinct types of interactions between the components, as a consequence of the variations in the grinding procedure. The experimental data clearly revealed that a true solid complex OME-γ-CD was obtained only by wetting the mixture of the components with phosphate buffer during the co-grinding. Other co-grinding procedures yielded only amorphous drug—CD mixtures or their combination with partial complexation. 相似文献
84.
Simultaneous spectrophotometric determination of diuretics by using multivariate calibration methods
The wavelength range and number of factors used in partial least-squares (PLS) calibration for the resolution of the dihydralazine (DHZ)-hydrochlorothiazide (HCT) binary mixture and the dihydralazine-hydrochlorothiazide-reserpine ternary mixture were optimized in terms of the relative standard error (R.S.E.) and relative mean standard error (R.M.S.E.). Under the optimum conditions thus established, synthetic mixtures of the analytes can be resolved with errors and relative standard deviations (R.S.D) less than 4.5 and 1.0%, respectively. The ensuing method, which was validated by comparison with high performance liquid chromatography (HPLC), also gives good results with real samples (pharmaceutical preparations). 相似文献
85.
J. M. Ginés M. J. Arias C. Novák P. J. Sánchez-Soto A. Ruiz-Conde E. Morillo 《Journal of Thermal Analysis and Calorimetry》1995,45(4):659-666
The formation of crystalline inclusion complex of triamterene with β-cyclodextrin (β-CD) was studied, evaluating the thermal behaviour and dispersion state of this drug in different types of binary systems. Spray-drying and co-grinding (oscillating mill) mixtures of triameterene with β-CD were prepared in 1∶1 molar ratio. The changes of crystalline properties of original (untreated) triamterene, β-CD, and composites obtained by co-grinding and spray-drying were investigated in comparison with those produced in simple physical mixtures. The thermal behaviour of the different samples was investigated using DTA. X-ray diffraction was applied as a complementary technique. The results have been explained by formation of amorphous drug particles on spray-drying samples and co-grinding or alternatively by means of a solid dispersion formation or a combination of these two. A contamination effect by grinding media was also observed as increasing grinding time. 相似文献
86.
Summary A simple method for quantitative determination of carbohydrates by reversed-phase, high-performance liquid chromatography
after pre-column derivatization and UV detection has been developed. Reducing sugars are condensed with 4-(3-methyl-5-oxo-2-pyrazolin-l-yl)
benzoic acid (PMPA) to yield UV adducts absorbing at 271 nm, which are resolved under typical reversed-phase conditions. After
derivatization, excess PMPA is easily removed from the reaction mixture by precipitation with mineral acids at pH<4. The influence
of experimental conditions on reaction yield, as well as chromatographic separation of derivatives, were investigated. The
quantitative performance was evaluated by means of a protocol comprising replicate measurements at several analyte levels.
The calibration curves obtained for 8 sugars showed excellent linearity over 10–5000 pmol. Limits of detection and quantification
for several monosaccharides were ca. 10 and 50 picomoles, respectively. Optimized conditions were successfully used for quantitative
determination of monosaccharides released after hydrolysis from fetuin, mucin, α1-acid glycoprotein, ovalbumin and transferrin. 相似文献
87.
88.
Ph3SiSH transforms amides to thioamides and Ph3SnOH performs the reverse process, with the concomitant formation of Ph3SiOH (or Ph3SiOSiPh3) and Ph3SnSSnPh3, respectively. The chemistry is a delightful illustration of the oxophilicity of silicon compared to the thiophilicity of tin and occurs under relatively mild conditions, and for amide to thioamide transformation requires no amide activation. The chemistry is in accord with available data for Si? (S)(O), Sn? (O)(S) and C?(O)(S) bond energies. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
89.
D. Baldomir V. Pardo S. Blanco-Canosa D.I. Khomskii A. Piñeiro J.E. Arias 《Journal of magnetism and magnetic materials》2009,321(7):679-681
Electronic structure calculations were performed for ZnV2O4, a material close to a metal-insulator transition. Structural optimization leads to the formation of V-V dimers along the off-plane chains. A strong spin-lattice coupling is expected close to the transition to itinerancy. No orbital ordering is observed in such a structure, and the experimentally found magnetic structure is naturally explained. 相似文献
90.
Areli A. Molina‐Paredes Víctor M. Jimnez‐Prez Jesús A. Lara‐Cern Ivana Moggio Eduardo Arias Rosa Santilln Mario Snchez Alma Saucedo‐Yaez Blanca M. Muoz‐Flores 《应用有机金属化学》2019,33(1)
Five novel organoboron complexes were synthesized in just 15 min via microware irradiation, by one pot multicomponent reactions between diverse aryl aldehydes with benzoylhydrazide, or 4‐nitrobenzoylhidrazine and diphenyl boronic acid, in a 1:1:1 ratio in benzene. The products were characterized by 1H, 13C, 11B NMR, UV, IR, spectroscopy and high‐resolution mass spectrometry (HRMS). The molecular structure was also determined by single‐crystal X‐ray diffraction for two complexes, which showed the tetra‐coordination of the boron atoms giving rise to distorted tetrahedral molecular geometry with a strong intermolecular C‐H···π interactions. In spite of the low quantum yields exhibited by the series in solution, some complexes stained uniformly the silk fibroins emitting enough fluorescence to allow its characterization by confocal microscopy. Boron as chelate center of the five complexes resulted not to be toxic for B16F10 cells, these compounds are appropriate for their used in medical applications. 相似文献