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41.
Geisamanda Pedrini Brandão Reinaldo Calixto de Campos Eustáquio Vinicius Ribeiro de Castro Honério Coutinho de Jesus 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
A procedure for the direct determination of Cu, Fe and V in petroleum samples by electrothermal atomic absorption spectrometry using a solid sampling accessory, without any sample pre-treatment or dilution, is proposed. A Pd + Triton X-100 solution was used as chemical modifier. The pyrolysis and atomization temperatures, as well as the Pd mass were defined by multivariate optimization. The other parameters of the temperature programs were defined by univariate optimization. The limits of detection at the optimized conditions were 10, 200 and 800 pg for Cu, Fe and V, respectively, for typical sample masses ranging from 0.10 to 3.00 mg. Method accuracy was confirmed by the analysis of oil certified reference materials as well as by comparison with independent methods. Aqueous calibration solutions were used and no statistically significant difference (analysis of variance) was observed between obtained and expected values. 相似文献
42.
Alcicla da Conceio Pereira Monteiro Ly Santabaia N. de Andrade Aderval S. Luna Reinaldo Calixto de Campos 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2103-2112
The present procedure is based on the sequential selective reduction of mercury(II) and methyl mercury using two gas–liquid separators in series. Cold vapor atomic absorption spectrometry was used for detection. Mercury(II) is reduced by a 0.01% m/v sodium tetrahydroborate solution and driven to the absorption cell in the first separator. The methyl mercury species is reduced by the same reductant but at a 0.3% m/v concentration, and in the presence of iron(III) chloride. Parameters such as argon flow rate, and the NaBH4 and dithiophosphoric acid diacyl ester concentrations were optimized. At the optimized conditions, and using aqueous standards for calibration, the corresponding limits of detection (3σb, n=10) were 400 and 600 ng l−1 for mercury(II) and methyl mercury, respectively. The sample throughput was 12 h−1. The procedure was used for the determination of methyl mercury in dogfish liver and dogfish muscle certified reference materials, and good concordance between found and certified values was observed. 相似文献
43.
[reaction: see text] Contrasting and interesting electrochemical behavior is observed in anodic oxidation of N-substituted p-toluenesulfinamides under controlled current conditions. For sulfinamides derived from secondary alkylamines and primary arylamines, the N-sulfinyl group is removed and the corresponding amines are formed; for sulfinamides derived from primary alkylamines, sulfur oxidation yields the corresponding sulfonamides in good yields. 相似文献
44.
Miguel E. Alonso Reinaldo Compagnone Wladimir Chitty 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):9-10
Abstract Recent studies on the fragmentation of some organic disulfides upon electron impact in a mass spectrometer have shown two main decomposition routes besides simple bond disconnection: skeletal rearrangements1–3 and proton transfer4. Transposition of the molecular components takes place via loss of one or two sulfur atoms while the carbon skeleton is preserved. Such molecular rearrangements are particularly noticeable in small molecules like dimethyl disulfide. Larger systems show a different fragmentation pattern in which proton transfer to give alkyl hydro-disulfides becomes predominant. The transfer of protons has been shown to proceed by way of intramolecular 1,2 and 1,3 hydrogen shifts from α and β carbons respectively by means of selective deuterium labbeling of diethyl disulfide.4 相似文献
45.
Jos Antonio Henao ngela Marcela Montao Leonor Y. Vargas‐Mndez Vladimir V. Kouznetsov Reinaldo Atencio 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):o228-o230
The title compound, C16H15N3, shows a hindrance effect between adjacent amino and methyl groups that leads to a structural distortion, which is reflected in the non‐planarity of the quinoline entity and in the bond angles and distances. The crystal packing consists of chains along the b axis sustained by an intermolecular hydrogen bond between the amino group and the N atom of the pyridyl ring. 相似文献
46.
47.
Roberta de Oliveira Ramos Alice Battistin Reinaldo Sim?es Gon?alves 《Journal of Solid State Electrochemistry》2012,16(2):747-752
This paper presents experimental evidence of the ability of alcoholic Mentha extracts to inhibit the corrosion of low-carbon steel in aqueous acid solutions. Alcoholic extracts of Mentha spicata L., Mentha x gentilis L., Mentha crispa L., Mentha piperita L., and Mentha x piperita L. were tested. The corrosion inhibition capability of these extracts was confirmed by means of weight loss experiments,
cyclic voltammetry, chronoamperometry, polarization curves, and electrochemical impedance spectroscopy. 相似文献
48.
49.
Juan C. López-Realpozo Reinaldo Rodríguez-Ramos Raúl Guinovart-Díaz Julián Bravo-Castillero J.A. Otero Federico J. Sabina F. Lebon Serge Dumont Igor Sevostianov 《International Journal of Solids and Structures》2014
In this contribution, effective elastic moduli are obtained by means of the asymptotic homogenization method, for oblique two-phase fibrous periodic composites with non-uniform imperfect contact conditions at the interface. This work is an extension of previous reported results, where only the perfect contact for elastic or piezoelectric composites under imperfect spring model was considered. The constituents of the composites exhibit transversely isotropic properties. A doubly periodic parallelogram array of cylindrical inclusions under longitudinal shear is considered. The behavior of the shear elastic coefficient for different geometry arrays related to the angle of the cell is studied. As validation of the present method, some numerical examples and comparisons with theoretical results verified that the present model is efficient for the analysis of composites with presence of imperfect interface and parallelogram cell. The effect of the non uniform imperfection on the shear effective property is observed. The present method can provide benchmark results for other numerical and approximate methods. 相似文献
50.
Macedo Jde S da Costa Júnior NB Almeida LE Vieira EF Cestari AR Gimenez Ide F Villarreal Carreño NL Barreto LS 《Journal of colloid and interface science》2006,298(2):515-522
Mesoporous activated carbon has been prepared from coconut coir dust as support for adsorption of some model dye molecules from aqueous solutions. The methylene blue (MB) and remazol yellow (RY) molecules were chosen for study of the adsorption capacity of cationic and anionic dyes onto prepared activated carbon. The adsorption kinetics was studied with the Lagergren first- and pseudo-second-order kinetic models as well as the intraparticle diffusion model. The results for both dyes suggested a multimechanism sorption process. The adsorption mechanisms in the systems dyes/AC follow pseudo-second-order kinetics with a significant contribution of intraparticle diffusion. The samples simultaneously present acidic and basic sites able to act as anchoring sites for basic and acidic dyes, respectively. Calorimetric studies reveal that dyes/AC interaction forces are correlated with the pH of the solution, which can be related to the charge distribution on the AC surface. These AC samples also exhibited very short equilibrium times for the adsorption of both dyes, which is an economically favorable requisite for the activated carbon described in this work, in addition to the local abundance of the raw material. 相似文献