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991.
992.
Joseph J. Pesek Maria T. Matyska Milton T.W. Hearn Reinhard I. Boysen 《Journal of chromatography. A》2009,1216(7):1140-1146
The use of silica hydride-based stationary phases for the retention and analysis of nucleotides has been investigated. Both reversed-phase columns with a hydride surface underneath as well as those with an unmodified or a minimally modified hydride material were tested. With these systems, an aqueous normal-phase mode was used with high organic content mobile phases in combination with an additive to control pH for the retention of the hydrophilic nucleotides. Isocratic and gradient elution formats have been used to optimize separations for mixtures containing up to seven components. All conditions developed are suitable for methods that utilize mass spectrometry detection. 相似文献
993.
Vanessa Gisele Pasqualotto Severino Cristiane de Melo CazalMoacir Rossi Forim Maria Fátima das Graças Fernandes da SilvaEdson Rodrigues-Filho João Batista FernandesPaulo Cezar Vieira 《Journal of chromatography. A》2009,1216(19):4275-4281
High-speed counter-current chromatography (HSCCC) with a two-phase solvent system (hexane–ethanol–acetonitrile–water 10:8:1:1, v/v) was applied to examine the leaves of Hortia oreadica, which afforded the known limonoid guyanin (1), the alkaloids rutaecarpin (2) and dictamnine (6), the dihydrocinnamic acid derivatives methyl 5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran-6-propanoate (3), 5,8-dimethoxy-2,2-dimethyl-2H-1-benzopyran-6-propanoic acid (4), together with the new E-3,4-dimethoxy-α(3-hydroxy-4-carbomethoxyphenyl)cinnamic acid (5). The recovery of compounds 1–6 was determined by comparison with LC-atmospheric pressure chemical ionization MS/MS data: 66.2%, 93.1%, 102.5%, 101.2%, 99.0% and 84.9%, respectively. Compound 3 showed IC50 of 23.6 μM against Plasmodium falciparum and 15.6 μM against Trypanosoma brucei rhodesienses and was not toxic to KB cells (IC50 > 100 μM). 相似文献
994.
Maria A. Mendoza DeEtta K. Mills Hemant Lata Suman Chandra Mahmoud A. ElSohly Jose R. Almirall 《Analytical and bioanalytical chemistry》2009,393(2):719-726
Cannabis sativa is the most frequently used of all illicit drugs in the USA. Cannabis has been used throughout history for its stems in the
production of hemp fiber, seed for oil and food, and buds and leaves as a psychoactive drug. Short tandem repeats (STRs) were
chosen as molecular markers owing to their distinct advantages over other genetic methods. STRs are codominant, can be standardized
such that reproducibility between laboratories can be easily achieved, have a high discrimination power, and can be multiplexed.
In this study, six STR markers previously described for C. sativa were multiplexed into one reaction. The multiplex reaction was able to individualize 98 cannabis samples (14 hemp and 84 marijuana, authenticated as originating from 33 of the 50 states of the USA) and detect
29 alleles averaging 4.8 alleles per loci. The data did not relate the samples from the same state to each other. This is
the first study to report a single-reaction sixplex and apply it to the analysis of almost 100 cannabis samples of known geographic
origin.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
995.
Dalibor Hodko Maria Gamboa-Aldeco Oliver J. Murphy 《Journal of Solid State Electrochemistry》2009,13(7):1063-1075
A photopolymerization process that simultaneously deposits electronically conducting polymer films and incorporates nanophase
silver grains within the films, the silver grains having been formed in situ on irradiating cast, photopolymerizable formulations
containing silver salts, was developed. Polymer films produced from formulations containing large organic anions were very
flexible and strongly adherent to substrates. Polypyrrole films containing silver grains were characterized electronically
on measuring their electronic conductivities and electrochemically on recording their cyclic voltammetric profiles. Conductivities
were affected by the chemical identity and concentration of components added to photopolymerizable formulations. The best
photopolymerized films had a conductivity of the order of 1 S cm−1. Electronically conducting films derived from formulations consisting of a monomer, an electron acceptor/“dopant,” and a
photoinitiator were electrochemically active. They possessed long-term stability under extended electrode potential cycling
conditions, acceptable charge storage capacity, and the ability to oxidize or reduce redox couples in solution.
Paper submitted for inclusion in the special issue of the Journal of Solid State Electrochemistry honouring the 85th birthday
of Professor John O’M. Bockris. 相似文献
996.
Maria Brai Gaetano Gennaro Tiziano Schillaci Luigi Tranchina 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009,64(10):1119
The laser-induced breakdown spectroscopy (LIBS) is an applied physical technique that has shown in recent years its great potential for rapid qualitative analysis of materials. Thanks to the possibility to implement a portable instrument that perform LIBS analysis, this technique is revealed to be particularly useful for in situ analysis in the field of cultural heritages. The purpose of this work is to evaluate the potentiality of LIBS technique in the field of cultural heritages, with respect to the chemical characterization of complex matrix as calcareous and refractory materials for further quantitative analyses on cultural heritages. X-Ray Fluorescence (XRF) analyses were used as reference. Calibration curves of certified materials used as standards were obtained by XRF analyses. The LIBS measurements were performed with a new mobile instrument called Modì (Mobile Double pulse Instrument for LIBS Analysis). The XRF analyses were performed with a portable instrument ArtTAX. LIBS and XRF measurement were performed on both reference materials and samples (bricks and mortars) sampled in the ancient Greek–Roman Theatre of Taormina. Although LIBS measurements performed on reference materials have shown non linear response to concentrations, and so we were not able to obtain quantitative results, an integrated study of XRF and LIBS signals permitted us to distinguish among chemical features and degradation state of measured building materials. 相似文献
997.
Maria Lalia-Kantouri Christos D. Papadopoulos Antonios G. Hatzidimitriou Stavroula Skoulika 《Structural chemistry》2009,20(2):177-184
The reaction of Fe(III) with the substituted salicylaldehydes [X-saloH, where X = 3-OCH3 (L 1 ), 5-CH3 (L 2 ), 5-Cl (L 3 ), 5-NO2 (L 4 )] led to the formation of four new iron(III) hetero-heptanuclear complexes (Fe–Na) under the general formula [Fe2(X-salo)8Νa5] · 3OH · zH2Ο. The two different coordination modes of the ligand, as well as the geometry around the metal ions were deduced by X-ray structure analysis of compound 1, [Fe2(3-OCH3-salo)8Νa5] · 3OH · 8H2Ο. The complexes have also been characterized by physicochemical and spectroscopic (IR, UV–Vis, Mössbauer) methods. 相似文献
998.
Maria Grazia Sarpietro Sara Ottimo Maria Chiara Giuffrida Dorotea Micieli Francesco Castelli 《Thermochimica Acta》2009,495(1-2):149-154
The interaction of eicosapentaenoic acid, a polyunsaturated fatty acid belonging to the omega-3 class, with biomembrane models represented by multilamellar or unilamellar vesicles made of dimyristoylphosphatidylcholine was monitored by means of differential scanning calorimetry technique. The calorimetric analysis of vesicle prepared in the presence of increasing molar fraction of eicosapentaenoic acid was carried out to show its maximum interaction with biomembrane models evaluating the effects of eicosapentaenoic acid on the biomembrane models thermotropic parameters (transition temperature and enthalpy variation). Furthermore, in order to detect the influence of the presence of hydrophilic or lipophilic media on the entity of the compound absorption by the biomembrane models, kinetic experiments were carried out.The results indicate that eicosapentaenoic acid strongly interacts with the biomembrane models depressing the transition temperature and the enthalpy variation. Eicosapentaenoic acid is absorbed by the biomembrane models and the absorption is affected by the used medium; in fact a bigger absorption happens in the presence of a lipophilic medium. 相似文献
999.
Giovanna Gomez dAyala Emilia Di Pace Paola Laurienzo Diletta Pantalena Elvira Somma Maria Rossella Nobile 《European Polymer Journal》2009,45(11):3217-3229
Functionalization of polymers is a particular relevant approach in the field of biodegradable polymers, where modifications are often required to allow these materials to replace more conventional, not biodegradable polymers in a wider range of applications. This article will report on functionalization of poly(ε-caprolactone) with unsaturated monomers bearing either anhydride groups (PCL-g-(MA-GMA)) or tertiary amines (PCL-g-DMAEA), obtained through radical grafting in a Brabender mixer. Crystallization kinetics parameters have been determined with several techniques (rheology, optical microscopy and differential scanning calorimetry) and the results obtained are in good agreement. It was observed that the crystallization rate significantly increases in the case of the modified polymers. 相似文献
1000.
Jacyra V.D.S. Araújo Rafael V. Ferreira Maria I. Yoshida Vnya M.D. Pasa 《Solid State Sciences》2009,11(9):1673-1679
Metallic Zn nanowires have been synthesized by a new carbothermal reduction route in which ZnO and Eucalyptus sp. tar pitch were used as source materials. This simple practical procedure was capable of producing Zn nanowires in large quantities without reoxidation. This process was carried out in inert atmosphere, without vacuum or catalyst, at temperatures (800–900 °C) lower than those required in the carbothermal reduction of ZnO with graphite. A comparative study was performed using graphite that is traditionally used as a ZnO reducer, under the same experimental conditions, however, no reaction was observed. The new process involves the pyrolysis of biopitch to obtain a highly reactive coke and the reduction of ZnO with the release of Zn(v) for the growth of Zn(s) nanowires. The resulting Zn nanowires were characterized by X-ray diffractometry, energy-dispersive spectroscopy and scanning electron microscopy. Differential thermal analysis and thermogravimetric analysis coupled with infrared analysis techniques were used in an effort to understand the underlying mechanism and establish the best ratio biopitch/ZnO to be used. This paper presents the characterization of the as-synthesized nanowires and discusses the main reactions involved in their production. 相似文献