RESUMO
Alongside the Brazil nut's role as an excellent source of vitamins, oil, fatty acids, lipids and nutrients, it is also recognized as a rich source of selenium. The pathway along which selenium and sulfur are metabolized in plants is theorized to be the same as that used for tellurium. Total tellurium content and its bioaccessibility are then evaluated by ICP-MS. Interferences and sample preparation are evaluated for the accurate determination of tellurium, and the accuracy determined through analysis of the certified reference material 1643e. A concentration of 4.02⯱â¯0.391â¯ngâ¯g-1 is obtained as an average concentration through external and internal calibrations. Through this reliable result, tellurium bioaccessibility in Brazil nuts is obtained via an in vitro validated unified bioaccessibility method. Values of 32% and 30% of total tellurium are available in the gastric and gastrointestinal fractions, respectively.
Assuntos
Nozes/química , Nozes/metabolismo , Telúrio/análise , Telúrio/metabolismo , Brasil , Espectrometria de MassasRESUMO
Internal standardization (IS) and dilute-and-shoot preparation of distilled alcoholic beverages were evaluated for the direct determination of Cu by high-resolution continuum source flame atomic absorption spectrometry. Among Bi, In, Sn and Te evaluated as internal standards, Bi and Te furnished best results. Calibration curves were built up by plotting A(Cu)/A(Bi) and A(Cu)/A(Te)versus Cu concentration (0.05-4.0 mg L(-1)) and linear correlation coefficients were 0.9994 and 0.9990, respectively. Contents of Cu in 22 commercial distilled beverages analyzed by the proposed method varied in the 0.029-3.608 mg L(-1) interval. These results were in agreement (paired t-test) at 95% confidence level with those obtained by line source FAAS using standard addition calibration. Recoveries improved from 77-83% (without IS) to 99-101% (with IS) intervals. The relative standard deviation (n=12) was 0.8-3.7% (IS-Bi), 0.4-4.4% (IS-Te), and 0.5-9.1% (without IS) and the limit of detection was ca. 5 µg L(-1) using Bi or Te.
Assuntos
Bebidas Alcoólicas/análise , Cobre/análise , Bebidas Alcoólicas/normas , Bismuto/análise , Calibragem , Etanol , Análise de Alimentos , Limite de Detecção , Padrões de Referência , Espectrofotometria Atômica , Telúrio/análiseRESUMO
In this work, the energy response functions of Si(Li), SDD and CdTe detectors were studied in the mammographic energy range through Monte Carlo simulation. The code was modified to take into account carrier transport effects and the finite detector energy resolution. The results obtained show that all detectors exhibit good energy response at low energies. The most important corrections for each detector were discussed, and the corrected mammographic x-ray spectra obtained with each one were compared. Results showed that all detectors provided similar corrected spectra, and, therefore, they could be used to accurate mammographic x-ray spectroscopy. Nevertheless, the SDD is particularly suitable for clinic mammographic x-ray spectroscopy due to the easier correction procedure and portability.
Assuntos
Compostos de Cádmio/análise , Lítio/análise , Mamografia/métodos , Silício/análise , Análise Espectral/métodos , Telúrio/análise , Raios XRESUMO
A fast, simple, and reliable chemical method for tellurite quantification is described. The procedure is based on the NaBH(4)-mediated reduction of TeO(3)(2-) followed by the spectrophotometric determination of elemental tellurium in solution. The method is highly reproducible, is stable at different pH values, and exhibits linearity over a broad range of tellurite concentrations.
Assuntos
Meios de Cultura/química , Espectrofotometria/métodos , Telúrio/análise , Oxirredução , Reprodutibilidade dos TestesRESUMO
Tellurites may be subdivided according to formula and structure. There are five groups based upon the formulae (a) A(XO3), (b) A(XO3).xH2O, (c) A2(XO3)3.xH2O, (d) A2(X2O5) and (e) A(X3O8). Raman spectroscopy has been used to study rajite and denningite, examples of group (d). Minerals of the tellurite group are porous zeolite-like materials. Raman bands for rajite observed at 740, and 676 and 667 cm(-1) are attributed to the nu1 (Te2O5)(2-) symmetric stretching mode and the nu3 (TeO3)(2-) antisymmetric stretching modes, respectively. A second rajite mineral sample provided a more complex Raman spectrum with Raman bands at 754 and 731 cm(-1) assigned to the nu1 (Te2O5)(2-) symmetric stretching modes and two bands at 652 and 603 cm(-1) are accounted for by the nu3 (Te2O5)(2-) antisymmetric stretching mode. The Raman spectrum of dennigite displays an intense band at 734 cm(-1) attributed to the nu1 (Te2O5)(2-) symmetric stretching mode with a second Raman band at 674 cm(-1) assigned to the nu3 (Te2O5)(2-) antisymmetric stretching mode. Raman bands for rajite, observed at (346, 370) and 438 cm(-1) are assigned to the (Te2O5)(2-)nu2 (A1) bending mode and nu4 (E) bending modes.
Assuntos
Minerais/química , Análise Espectral Raman/métodos , Telúrio/química , Cristalização , Geologia/instrumentação , Geologia/métodos , México , Minerais/análise , New Mexico , Óxidos/química , Espectrofotometria Infravermelho/métodos , Telúrio/análise , Zeolitas/análise , Zeolitas/química , Zinco/químicaRESUMO
A procedure for the determination of traces of total tellurium (Te) in garlic (Allium sativa) is described that combines hydride generation atomic absorption spectrometry with preconcentration of the analyte by coprecipitation. The samples, each spiked with lanthanum nitrate (20 mg/L), are introduced into an Amberlite XAD-4 resin and mixed with ammonium buffer (pH 9.1). Te is preconcentrated by coprecipitation with the generated lanthanum hydroxide precipitate. The precipitate is quantitatively collected in the resin, eluted with hydrochloric acid, and then transferred into the atomizer device. Considering a sample consumption of 25 mL, an enrichment factor of 10 was obtained. The detection limit (3sigma) was 0.03 microg/L, and the precision (relative standard deviation) was 3.5% (n = 10) at the 10 microg/L level. The calibration graph using the preconcentration system for Te was linear with a correlation coefficient of 0.9993. Satisfactory results were obtained for the analysis of Te in garlic samples.