https://repositorio.ufba.br/handle/ri/1995 2026-05-17T07:07:47Z https://repositorio.ufba.br/handle/ri/17279 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 https://repositorio.ufba.br/handle/ri/17274 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 https://repositorio.ufba.br/handle/ri/17272 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 https://repositorio.ufba.br/handle/ri/17234 Slurry Sampling and HG AFS for the Determination of Total Arsenic in Rice Samples Santos, Walter Nei Lopes dos; Cavalcante, Dannuza D.; Macedo, Samuel Marques; Nogueira, Jéssica S.; Silva, Erik Galvão Paranhos da This paper proposes a procedure for the determination of total arsenic in rice using slurry sampling and hydride generation atomic fluorescence spectrometry (HG AFS). During optimization, water, hydrochloric acid, and nitric acid solutions were tested as extractor. Best results were found using 2.0 mol L−1 nitric acid solutions. The slurries are prepared using 200 mg of rice sample, 5.0 mL of nitric acid solution, and sonication for 30 min. Then, an aliquot of 5.0 mL of the slurry was taken and 3.0 mL of 1.5 mol L−1 hydrochloric acid solution and 1.5 mL of 10 % potassium iodide in 2 % ascorbic acid solution were added. After 30 min, the volume was completed up to 10 mL with ultra-pure water and arsenic quantified by HG AFS. In these experimental conditions, the method allows the determination of arsenic employing external calibration, with limits of detection and quantification of 1.1 and 3.3 ng g−1 and precision expressed as relative standard deviation (%RSD) varying between 5.9 and 1.3 % for arsenic concentration of 0.12 and 0.47 μg g−1. Accuracy was confirmed by analysis of the NIES standard reference material for rice flour, SRM 10b. This method was used to determine the arsenic content in 20 rice samples that were purchased at supermarkets in Salvador, Bahia, Brazil. The arsenic content for the three types of rice (white, parboiled, and brown) varied from 0.12 and 0.47 μg g−1. Some of the samples were also analyzed by HG AFS after complete mineralization in block digester employing a reflux system (cold finger). A statistical test showed that there was no significant difference between the results obtained using slurry sampling and those obtained after complete digestion of the sample. Artigo de Periódico 2013-01-01T00:00:00Z