Planejamento fatorial aplicado à digestão de amostras de feijão assistida por radiação microondas

The use of factorial design was evaluated for optimization of focused-microwave-assisted digestion of bean samples. Calcium, Fe, Mg, Mn and Zn percentual recoveries were determined in digestates after focused-microwave-assisted digestion according to factorial design procedures. A cavity microwave digestion was carried out to certify the elemental compositions obtained. The accuracy was checked using a standard reference material, the NIST SRM 8433 - Corn Bran. Results are in agreement with certified values at the 95% confidence limit when the Student t-test was used. Volumes of nitric and sulfuric acid, temperature, and the interplay between HNO3 and H2SO4 initial volumes were significant variables according to P-values in the analysis of variance (ANOVA).

Azul de metileno imobilizado na celulose/TiO2 e SiO2/TiO2: propriedades eletroquímicas e planejamento fatorial

The electrochemical properties of methylene blue immobilized on cellulose/TiO2 and mixed oxide SiO2/TiO2 matrices were investigated by means of cyclic voltammetry. The electron mediator property of the methylene blue was optimized using a factorial design, consisting of four factors in two levels. The experimental observations and data analyses on the system indicate that the lowest peak separation occurs for Sil/TiOAM, 1.0 mol L-1 KCl solution and 20 mV s-1 scan rate, while values of current ratio closest to unity were found for Cel/TiOAM independent of electrolyte concentration, 0.2 or 1.0 mol L-1, and scan rate, 20 mV s-1 or 60 mV s-1.

Integração de técnicas analíticas e proposta de experimentos para cursos de graduação em análise instrumental: uso de espectrômetro de absorção atômica para medidas de absorção molecular

Simple experiments are proposed for measuring molecular absorption of chromate and dichromate ions using an atomic absorption spectrometer. The experiments can help undergraduate students in instrumental analysis courses understand important aspects involving conceptual and instrumental similarities and differences between frequently used analytical techniques. Hollow cathode lamps were selected with wavelengths in the region of molecular absorption of chromate and dichromate. Calibration curves were obtained and the linear dynamic range was evaluated. Results were compared with those obtained in a molecular absorption spectrometer. The molar absorptivities obtained were also compared.

Importância do metabolismo no planejamento de fármacos

It is widely recognized that pharmacokinetic optimization needs to be addressed early in drug discovery to reduce the high failure rate in bringing drugs to market. Poor absorption, too short duration of action due to high elimination rate, or the presence of active metabolites are examples of properties that can potentially lead to unsuccessful clinical programmes. Here I describe a brief overview of advantages and molecular strategies for improving metabolic and pharmacokinetic properties applied to the discovery of fluconazol, beta-blockers, ritonavir and ezetimibe and to the development of the prodrugs enalapril and bambuterol.

Planejamento estatístico de experimentos como uma ferramenta para otimização das condições de biossorção de Cu(II) em batelada utilizando-se casca de nozes pecã como biossorvente

In order to reduce the total number of experiments for achieving the highest amount of adsorbed Cu2+ (qmax) using pecan nutshells (Carya illinoensis) as biosorbent, a full 2(4) factorial design with two central points was carried out (mass of biosorbent- m, pH, initial metallic ion concentration- C0, time of contact- t). In order to continue the optimization of the system, a central composite surface analysis design with two factors and five central points was carried out. The maximum amount of Cu2+ taken up by the pecan nutshells was 20 mg g-1. These results were confirmed by determining a Cu2+ isotherm using the best conditions attained by the statistical design of experiments.

Terminologia para as técnicas analíticas de eletromigração em capilares

This is a contribution that presents a translation of the work "Terminology for Analytical Capillary Electromigration Techniques" by Riekkola and collaborators (Pure Appl. Chem., Vol. 76, No. 2, 443-451, 2004) from IUPAC© for the Portuguese Language. Additional terms that had not been defined in native Portuguese were included for the benefit of the local community. Additional notes were also included to clarify some important concepts and to highlight the differences between techniques.

Descrições de técnicas da química na produção de bens de acordo com os relatos dos naturalistas viajantes no Brasil colonial e imperial

European naturalists explored Brazil in long scientific expeditions and published accounts that make up a rich and still largely untapped historiographic source for the understanding of the history of chemistry. The production of indigo dye, the manufacture of limestone, extraction and purification of saltpeter and the production of salt are discussed. Lime was used to whitewash walls and, mixed with whale oil, as cement to glue stones in buildings of the colonial period. It was prepared by burning seashells in specifically designed ovens. Saltpeter was produced by reacting naturally occurring calcium and magnesium nitrate with potassium-rich wood ashes to yield KNO3. NaCl was obtained by evaporating seawater under the sun. Indigo, a native plant, was cultivated and processed to produce the renowned dye, which was exported to Europe.

Planejamento participativo no subprograma QEQ do PADCT

The development of the Brazilian chemistry sector, during the last 30 years, is nowadays being attributed to PADCT (Science and Technology Development Program). Since the seventies, the Government took notice of the importance of research in chemistry for the Brazilian economy, therefore creating PADCT to support chemistry and chemical engineering among other areas of science and technology. Planning and implementation of the second phase of this program represented a real joint strategic planning. Since then, academic research and human resources education have experienced significant improvements. However, in the chemical trade, the deficit continues to grow, in spite of an almost constant ratio between importation costs and export revenues. Continued investments for research in the area remain necessary.

Mapeamento das interações proteína-ligante através de técnicas de RMN de ¹H utilizando detecção do ligante

NMR is a valuable screening tool for the binding of ligands to proteins providing structural information on both protein and ligands and is thus largely applied to drug-discovery. Among the recent NMR techniques to probe weak binding protein-ligand complexes we have critically evaluated the advantages and disadvantages of STD (Saturation Transfer Difference), WaterLOGSY (Water Ligand Observation with Gradient Spectroscopy), NOE pumping and DOSY-NOESY (Diffusion-Ordered NOESY) using a mixture of BSA (bovine serum albumin) plus salicylic acid, caffeine, citric acid, adipic acid and D-glucose.

Emprego de planejamento fatorial no desenvolvimento de uma metodologia para extração de zinco de resíduos galvânicos

The plating process generates solid waste rich in heavy metals and aiming to reduce environmental impact of such waste, this work suggests a methodology for zinc reduction, through a 2(4) factorial planning, studying the influence of the following variables: acid concentration (15, 20 or 30% v/v), acid type (sulfuric or hydrochloric), acid volume (15, 20 or 25 mL) and extraction time (12, 24 or 36 h). Through this methodology it is possible to establish the optimal conditions (15 mL of a 30% hydrochloric acid concentration during 12 h) to get a 100% efficiency in zinc extraction.

Metodologias eletroanalíticas para a determinação de herbicidas triazínicos por voltametria de onda quadrada e técnicas de deconvolução

This work describes the development of electroanalytical methodologies for the determination of atrazine, ametrine and simazine by square wave voltammetry on a mercury electrode. For pure atrazine and pure ametrine, the detection limits (DL) were 3.7 and 4.3 µg L-1, respectively, while they increased to 4.8 and 6.5 µg L-1 in the presence of 3.0 x 10-6 mol L-1 of the other component (a mathematical deconvolution program was used in the mixture cases). The voltammetric response for simazine could not be separated from that of atrazine and measurements were carried out only in pure simazine solutions (DL: 7.5 µg L-1).

Cânfora: um bom modelo para ilustrar técnicas de RMN

The use of Nuclear Magnetic Resonance spectroscopy to establish the three-dimensional structures of molecules is an important component of modern Chemistry courses. The combination of techniques that can be used for this purpose is conveniently illustrated by their application to the camphor molecule. This paper presents applications of several techniques used in NMR spectral interpretation in an increasing order of complexity. The result of individual experiments is illustrated in order to familiarize the user with the way connectivity through bonds and through space is established from 1D/2D-NMR spectra and molecular stereochemistry is determined from different NMR experiments.

Otimização de metodologia para derivação de desoxinivalenol através de planejamento experimental

The objective of this work was to optimize the derivatization reaction for determining deoxynivalenol (DON) by gas chromatography employing an experimental planning procedure. The factors were: temperature, reaction time, catalyst and trifluoroacetic anhydride concentration. The relative peak areas were used to evaluated the effects. The best conditions for DON derivatization were 200 µL TFAA and 18 mg sodium bicarbonate for 6 min at 74 ºC for 7 to 21 µg of DON. Under these conditions, the detection limit was 1.4 µg of DON.

Biotecnología de la Reproducción Porcina: Estado actual y futuro de las técnicas de análisis seminal

Estat actual i futur de les tècniques d'anàlisi seminal

Efeito antagônico do ferro e do zinco em uma formulação de alimentação enteral utilizando planejamento de misturas da metodologia de superfície de resposta

Nutritional therapy with enteral diets became substantially specialized over the last years. This work's aim was to study the effect of the components of a formulation: fiber, calcium and medium-chain triglycerides for dialysability of minerals. Analysis of multiple variables was carried out using response surface methodology. The level curve showed an antagonic effect of interaction between iron and zinc. TCM was the variable responsible for characterizing competition between the two minerals in the formulation. More studies on foods are needed for knowing the effecs of minerals in formulations.