Encontrados 11 documentos, a visualizar página 1 de 2
Multivariate optimization and validation of an analytical method for the determ...
Ferreira,Sérgio L. C.; Jesus,Robson M. de; Matos,Geraldo D.; Andrade,Jailson B. de; Bruns,Roy E.; Santos,Walter N. L. dos; Cavalcante,Danuza D.This work describes the optimization and validation of a direct method employing electrothermal atomic absorption spectrometry (ET AAS) for the determination of cadmium in wine. The optimization step was carried out using a two-level full factorial design, involving the followings factors: pyrolysis time (10 s) and temperature (600 ºC), atomization temperature (1300 ºC) and modifier mass (15 µg). Under the opti...
Implementação computacional do modelo carga-fluxo de carga-fluxo de dipolo para...
Gomes,Thiago C. F.; Silva Jr.,João Viçozo da; Vidal,Luciano N.; Vazquez,Pedro A. M.; Bruns,Roy E.The first computational implementation that automates the procedures involved in the calculation of infrared intensities using the charge-charge flux-dipole flux model is presented. The atomic charges and dipoles from the Quantum Theory of Atoms in Molecules (QTAIM) model was programmed for Morphy98, Gaussian98 and Gaussian03 programs outputs, but for the ChelpG parameters only the Gaussian programs are support...
Mineral composition of wheat flour consumed in Brazilian cities
Araujo,Rennan G. O.; Macedo,Samuel M.; Korn,Maria das Graças A.; Pimentel,Maria Fernanda; Bruns,Roy E.; Ferreira,Sergio L. C.In the present paper, the mineral composition of wheat flour consumed in Brazil was evaluated. In the sampling step 54 samples were collected in 15 cities, including principal Brazilian cities such as: São Paulo, Rio de Janeiro, Salvador, Porto Alegre, Recife and others. The elements determinate were: calcium, copper, magnesium, manganese, iron, phosphorus, potassium and zinc. The samples were digested using ni...
Hidrocarbonetos policíclicos aromáticos como traçadores da queima de cana-de-aç...
Magalhães,Dulce; Bruns,Roy E.; Vasconcellos,Pérola de CastroIn this study atmospheric particulates of PAHs were measured in Araraquara, Piracicaba and São Paulo in July 2003 (sugarcane harvest season in Araraquara and Piracicaba) and in Araraquara in March of 2003. The results were normalized to the total PAH concentrations. Comparison among the sites and principal component analysis (PCA) were used to investigate possible tracers of emission. Fluoranthene and pyrene co...
25 anos de quimiometria no Brasil
Barros Neto,Benício de; Scarminio,Ieda S.; Bruns,Roy E.Chemometric activities in Brazil are described according to three phases: before the existence of microcomputers in the 1970s, through the initial stages of microcomputer use in the 1980s and during the years of extensive microcomputer applications of the ´90s and into this century. Pioneering activities in both the university and industry are emphasized. Active research areas in chemometrics are cited includin...
Optimization of mobile phase for separation of carbohydrates in honey by high p...
Cano,Cristiane B.; Felsner,Maria L.; Bruns,Roy E.; Matos,Jivaldo R.; Almeida-Muradian,Lígia B.A mixture design was used to optimize the mobile phase composition for separation of carbohydrates in honey by High Performance Liquid Chromatography. Nine ternary acetronitrile, water and ethyl acetate mobile phases corresponding to a simplex centroid design with axial points were test to separate those carbohydrates most frequently encountered in honey samples. The results suggest that a special cubic model a...
Reducing the number of experiments in split-plot optimization designs
Bortoloti,João A.; Andrade,João Carlos de; Bruns,Roy E.Two experiment reduction procedures for split-plot designs are investigated using a data set containing 160 experiments, consisting of 80 duplicate results for the optimization of a water-acetone-N,N-dimethylformamide mixture with HCl, o-dianisidine and H2O2 reagent system for the analytical determination of Cr(VI). Stabilities of the model coefficients and ANOVA mean squares are used as quality criteria to jud...
Optimization of thermogravimetric analysis of ash content in honey
Felsner,Maria L.; Cano,Cristiane B.; Matos,Jivaldo R.; Almeida-Muradian,Lígia B. de; Bruns,Roy E.A factorial design to evaluate ash content in honey by thermogravimetry as well as to establish the optimum analysis conditions that produce ash values in agreement with those obtained by the official method (gravimetry) was executed. Heating rate and use of fiber glass paper effects were significant as was the interaction effect between them. Lower heating rates and the use of fiber glass fiber paper are recom...
The linear relationship between Koopmans' and hydrogen bond energies for some s...
Bruns,Roy E.; Haiduke,Roberto L. A.; Amaral,Antonia T. doRecently Galabov and Bobadova-Parvanova have shown that the energy of hydrogen bond formation calculated at the HF/6-31G(d,p) level is highly correlated with the molecular electrostatic potential at the acceptor site for a number of simple carbonyl compounds. Here it is shown that the electrostatic potential can be replaced by Koopmans' energy. The correlation between this energy and the hydrogen bond formation...
3D-WHIM pattern recognition study for bisamidines. A structure-property relatio...
Menezes,Fabiano A. S.; Montanari,Carlos A.; Bruns,Roy E.A proposed model for the interaction of bisamidine analogues with the B-DNA receptor is established by structure-property relationship studies derived from 3D-WHIM descriptor calculations. Three classes, each with relevant information about structural relationships, were determined by PCA and SIMCA analyses for molecular conformations described by 3D-WHIM descriptors for a set of 29 bisamidines with antileishma...
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