https://repositorio.ufba.br/handle/ri/1995 2026-04-17T03:14:41Z 2026-04-17T03:14:41Z Borges, Aline Rocha Becker, Emilene M. François, Luciane L. Jesus, Alexandre de Valea, Maria Goreti R. Welz, Bernhard Dessuy, Morgana B. Andrade, Jailson Bittencourt de https://repositorio.ufba.br/handle/ri/17279 2022-08-26T14:02:39Z 2014-01-01T00:00:00Z

Investigation of spectral interferences in the determination of lead in fertilizers and limestone samples using high-resolution continuum source graphite furnace atomic absorption spectrometry Borges, Aline Rocha; Becker, Emilene M.; François, Luciane L.; Jesus, Alexandre de; Valea, Maria Goreti R.; Welz, Bernhard; Dessuy, Morgana B.; Andrade, Jailson Bittencourt de In the present work, spectral interferences on the determination of lead in fertilizer and limestone samples were investigated using high-resolution continuum source graphite furnace atomic absorption spectrometry at the main analytical lines: 217.001 and 283.306 nm. For these investigations, samples were introduced into the furnace as slurry together with a mixture of Pd and Mg as chemical modifier. Spectral interferences were observed for some samples at both analytical lines. In order to verify whether a wet digestion procedure would avoid these interferences, a reference method for wet digestion of fertilizers was employed as an alternative sample preparation procedure. However, the same interferences were also observed in the digested samples. In order to identify and eliminate the fine-structured background using a least-squares background correction, reference spectra were generated using the combination of different species. The use of the latter technique allowed the elimination of spectral interferences for most of the investigated samples, making possible the determination of lead in fertilizer and limestone samples free of interferences. The best results were found using a reference spectrum of NH4H2PO4 at 217.001 nm, and a mixture of H2SO4 + Ca and HNO3 + Ca at the 283.306 nm line. The accuracy of the method was evaluated using a certified reference material “Trace Elements in Multi-Nutrient Fertilizer”. Similar results were obtained using line source graphite furnace atomic absorption spectrometry with Zeeman-effect background correction, indicating that the latter technique was also capable to correct the spectral interferences, at least in part. Artigo de Periódico

2014-01-01T00:00:00Z Lopes, Paula Aparecida Lima Santos, Maurício Brandão Mascarenhas, Artur José Santos Silva, Luciana Almeida https://repositorio.ufba.br/handle/ri/17277 2022-08-26T14:03:06Z 2014-01-01T00:00:00Z

Synthesis of CdS nano-spheres by a simple and fast sonochemical method at room temperature Lopes, Paula Aparecida Lima; Santos, Maurício Brandão; Mascarenhas, Artur José Santos; Silva, Luciana Almeida Nano-spheres of hexagonal CdS were prepared by a sonochemical method using CdCl2 and Na2S2O3 as precursors, with different molar ratios of cadmium and sulfur in starting solutions, in ethylene glycol and cetyltrimethylammonium bromide (CTAB) as a surfactant. The XRD patterns for all samples presented the set of peaks characteristic of CdS in hexagonal phase. The crystallite size decreases as the sulfur content increased in the starting solution as a consequence of the quick release of sulfide ions trapped in the micelles formed by the CTAB surfactant, which controls the CdS nanoparticles growth. The diffuse reflectance spectroscopy (DRS) results have shown that it is possible to tune the emission of visible light of the CdS semiconductor changing only the starting Cd:S ratios in this synthesis procedure. Artigo de Periódico

2014-01-01T00:00:00Z Pereira, Éderson R. Welz, Bernhard Lopez, Alfredo H. D. Gois, Jefferson S. de Caramori, Giovanni Finoto Borges, Daniel L. G. Carasek, Eduardo Andrade, Jailson Bittencourt de https://repositorio.ufba.br/handle/ri/17274 2022-08-26T14:03:23Z 2014-01-01T00:00:00Z

Strontium mono-chloride — A new molecule for the determination of chlorine using high-resolution graphite furnace molecular absorption spectrometry and direct solid sample analysis Pereira, Éderson R.; Welz, Bernhard; Lopez, Alfredo H. D.; Gois, Jefferson S. de; Caramori, Giovanni Finoto; Borges, Daniel L. G.; Carasek, Eduardo; Andrade, Jailson Bittencourt de A new method has been developed for the determination of chlorine in biological reference materials using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) of the strontium mono-chloride (SrCl) molecule and direct solid sample analysis. The use of the SrCl molecule for high-temperature MAS was not described up to now in the literature. Preliminary time-dependent density functional theory calculations of the SrCl structure were carried out in order to obtain reasonable estimates of the absorption spectrum of the target molecule. The calculations, which were carried out at BHandHLyp/def2-QZVP level of theory, proved a very accurate and inexpensive way to get information about the spectrum of the SrCl molecule, which enabled us to perform the Cl determination with good sensitivity and specificity. The molecular absorption of the SrCl molecule has been measured using the wavelength at 635.862 nm, and zirconium and palladium have been evaluated as the chemical modifiers in order to increase the sensitivity of the gaseous SrCl molecule generated in the graphite furnace. The pyrolysis and vaporization temperatures were 600 °C and 2300 °C, respectively. Accuracy and precision of the method have been evaluated using biological certified reference materials of both animal and plant origins, showing good agreement with the informed and certified values. Limit of detection and characteristic mass were 1.0 and 2.2 ng, respectively. The results found using HR-CS GF MAS were in agreement (95% confidence level) compared to those obtained by electrothermal vaporization-inductively coupled plasma mass spectrometry. Artigo de Periódico

2014-01-01T00:00:00Z T. F, Grecco Saulo Ernesto, Urquieta González A. Patrício, Reyes Marcelo, Oportus Carmo, Rangel Maria do https://repositorio.ufba.br/handle/ri/17272 2022-08-26T14:03:44Z 2014-01-01T00:00:00Z

Influence of Temperature and Time of Seed Aging on the Properties of Beta Zeolite/MCM-41 Materials T. F, Grecco Saulo; Ernesto, Urquieta González A.; Patrício, Reyes; Marcelo, Oportus; Carmo, Rangel Maria do The diffusion restrictions of the reactants caused by the micropores limit the use of zeolites for processing heavy molecules. This demands the development of materials that combine the properties of zeolites and mesoporous materials. With this goal in mind, the influence of temperature and time of seed aging on the properties of beta zeolite/MCM-41 materials obtained by mesostructuration/ crystallization was studied in this work. It was noted that the most suitable conditions to obtain the crystalline microporous phase of beta zeolite and the MCM-41 mesoporous phase was 140 °C, during 24 h of seed aging. At the other temperatures (60 and 90 °C) poor crystallized solids and a lamellar phase of MCM-50 were produced. On the other hand, increasing time of aging seeds bigger crystals of crystalline beta zeolite and less organized mesoporous phases were obtained at 140 °C. Artigo de Periódico

2014-01-01T00:00:00Z