366 resultados para Concentração de mercado


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The participation of the students in the planning, execution and discussion of experimental results is important for the valuation of the role of them in the construction of the chemical knowledge implicited in the approach between education and research. This work relates either the construction of selective membrane electrodes for surfactants and its application in the potenciometric determination of the critical micellar concentration of the sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) surfactants. In adition it´s possible to discuss the potenciometric results in matching with the data valued for the tensiometric and condutimetric traditionally used in the physical-chemistry lessons.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Ultraviolet radiation is the major exogenous mediators of skin damage. To prevent such damage, sunscreen products are used. New research aims at both the elucidation of new sunscreen compounds, as well as new assets for supporting and synergistic action. In this article it is presented a systematic data of innovation for sunscreen and a discussion on prospects for partnership between universities and enterprises, where it is believed that the innovations in cosmetics, driven by the constant demand of the market in new products, may be a stimulus for the interactions between university and company in Brazil.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Capillary electrophoresis has become a well-established and routine-based separation technique. It is based on the differences between charged analyte mobility in aqueous or organic electrolytes. Its major limitation is the sensitivity due to small sample injection volumes and the narrow diameter of the capillaries, especially when UV detection is used. There are a number of ways to increase the concentration sensitivity. This report shows some on-line preconcentration strategies to perform it in free solution capillary electrophoresis that are based on manipulation of the analyte electrophoretic velocity during the sample introduction (stacking, field amplification and transient isotachophoresis).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The objective of this work was to obtain hydrolysates with different degrees of hydrolysis using Alcalase 2.4L® and to evaluate the effect of the enzyme [E] and substrate [S] concentration on the functional properties of the hydrolysates. It was obtained hydrolysates with hydrolysis degree values ranging from 12.2 to 43.7%. The values of solubility and water holding capacity were similar for the greater number of the hydrolysates with minimum values in the pH 5.0. The hydrolysis degree showed direct relationship with the solubility and indirect with the water holding capacity, oil holding capacity, emulsifying capacity and foaming capacity.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The present work purposes the preparation of a silica gel sorbent organically modified with 2-aminoethyl-3-aminobutylmethyldimethoxysilane (AAMDMS) and imprinted with Cu2+ ions by means surface imprinting technique and its use for selective on-line sorbent preconcentration of Cu2+ ions with further UV-VIS spectrophotometric determination by flow injection analysis. The Cu2+-imprinted silica gel, when compared with non imprinted silica gel and silica gel, showed from the binary mixture of Cu2+/Ni2+ relative selectivity coefficient (k') of 6.84 and 5.43 and 6.64 and 19.83 for the mixture Cu2+/Pb2+, thus demonstrating higher selectivity of Cu2+-imprinted silica gel towards Cu2+ ions. Under optimized condition, the on-line preconcentration method provided detection limit of 3.4 μg L-1 and linear range ranging from 30.0 up to 300.0 μg L-1 (r = 0.995). The accuracy of method was successfully assessed by analyzing different kind of spiked water samples with recovery values ranging from 92.2 up to 103.0%.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This work describes CE preconcentration strategies based on the effect of manipulation of the disperse/secondary velocity. Introduced by Terabe et al. in 1984, micellar electrokinetic chromatography is a powerful separation approach that increases the usage of electrokinetic phenomena for the separation of nonionic compounds. The main disadvantage of MEKC is the low concentration sensitivity associated with the limited optical path length for on-capillary photometric detection and the limited volume of sample solution that can be injected. This paper compiles on-line concentration strategies for neutral analytes by sample stacking and sweeping in micellar electrokinetic chromatography.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Speciation of metals in a synthetic freshwater was comparatively evaluated using Anodic Stripping Voltammetry, Diffusive Gradients in Thin Films and a Chemical Equilibrium Model. The labile fractions of Cu and Zn quantified by DGT were similar to the ones measured by ASV. The labile species of Cd and Pb could not be determined by both experimental methods due to the formation of inert complexes with organic ligands in the sample. Despite the differences among the methods, the speciation results obtained by the use of DGT and ASV agreed well with predictions made by the chemical equilibrium model.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

This paper evaluates the adsorption capacity of zirconocene-based silica materials in the pre-concentration of antimicrobians (tetracycline, sulfamethoxazole and trimethoprim) in aqueous medium. These materials were prepared by grafting the zirconocene onto silicas pre-treated at different temperatures. The retention capacity of these materials was evaluated by off line SPE and HPLC-UV and the proposed methodology was validated in ultrapure, tap and river water. The recovery for tetracycline was 72% (in the solid phase A) and, for sulfamethoxazole and trimethoprim was 68 and 95% in the commercial C18, respectively. The target antimicrobians were not detected in the Arroio Dilúvio (Porto Alegre - RS).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The clay mineral montmorillonite-K10 (MT), treated under acidic medium and saturated with potassium ions (MTK), was employed in sorption and desorption studies aiming the preconcentration of Cr(III) and the speciation analysis of chromium. The sorption process of Cr(III) was close to 100%, suggesting that MTK was a good material for Cr(III) preconcentration, although, the maximum recovery in HNO3 solution was near 89%. On the other hand, Cr(VI) practically was not retained in MTK, suggesting this material as an appropriate mineral phase to be used in speciation analysis of chromium in aqueous medium.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Several flavors and fragrances (F&F) companies hold the economic leadership in the market, although not always have also the leadership in patent applications. The ranking of technological production in the fragrance area still remains with industries while scientific knowledge is equally shared between industries and academia. Contextualizing Brazil in this scene, despite all scientific expertise gained over the years, brazilian technological park is still at the beginning of the production of technologies applied directly to the F&F industries. The dependence on foreign technologies is remarkable as indicated by the great trade deficit in this sector.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The DGT technique allows one to measure quantitatively free and labile metal species in aquatic systems. Nevertheless, for this approach, knowledge is required of the diffusion coefficients of the analytes in a diffusive layer. In this study, the diffusion coefficients of Hg(II), As(III), Mn(II), Mg(II), Cu(II), Cd(II) were determined in agarose gel and those of Ba(II), Cd(II), Cu(II), Mg(II), Mn(II) e Zn(II) in cellulose acetate membranes. These materials presented good performance and the reported results can be used as a data base for further DGT studies.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The present study proposes a method for cloud point preconcentration of copper ions at pH 2.0 based on complexes formed with [4,5-dimercapto-1,3-dithyol-2-thionate] and subsequent determination by flame atomic absorption spectrometry (FAAS). Under optimal analytical conditions, the method provided limits of detection of 0.84 and 0.45 µg L-1, by preconcentrating 12.0 and 24.0 mL of sample, respectively. The method was applied for copper determination in water samples, synthetic saliva, guarana powder, tea samples and soft drinks and the accuracy was assessed by analyzing the certified reference materials Dogfish Liver (DOLT-4) and Lobster Hepatopancreas (TORT-2).

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Difenoconazole residues in strawberry fruit cultivated in pots were estimated using the solid-liquid extraction with low temperature partition (SLE/LTP) method for sample preparation and gas chromatography with electron capture detection (GC/ECD) for analysis. The optimized method presented excellent recovery values from fortified samples and reproducibility (average recovery values ≥ 98%; CV values < 15%). Linearity of response was demonstrated (r = 0.995) with a detection limit of 9 µg kg-1. The method was successfully applied for the determination of difenoconazole residues in strawberries. Based on these results, the fungicide dissipates quickly, but the residual concentration increases after multiple applications.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

AbstractThe types of compounds used in the production of biomaterials, namely metals, ceramics, synthetic and natural polymers, as well as composite materials, are discussed in the present work, together with details of their application and evolution from biocompatible to bioactive, biodegradable, and biomimetic clinical products. The chemical structure, the three-dimensional structure, and the molecular organization of compounds frequently used in the manufacture of relevant classes of biomaterials are discussed, along with their advantages and some of their major limitations in specific clinical applications. The main chemical, physical, mechanical, and biological requirements of biomaterials categories are presented, as well as typical tissular responses to implanted biomaterials. Reasons for the recent economic growth of the biomaterials market segment are addressed, and the most successful biomaterial categories are discussed, emphasizing areas such as orthopedic and cardiovascular implants, regenerative medicine, tissue engineering, and controlled drug release devices. Finally, the need for the development of innovative and more accessible biomaterials, due to the expected increase in the number of elderly people and the growing trend of personalized medical procedures, is pointed out.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Foi avaliada a influência da temperatura (5, 15, 25 e 35 °C), da duração do período de molhamento (0, 3, 6, 12, 24, 48 e 72 h) e da concentração de inóculo (10¹, 10², 10(4), 10(6) e 10(8) esporos/ml) na incidência de podridões de pós-colheita em frutos de tomateiro (Lycopersicon esculentum) (cv. Santa Clara) causadas por Fusarium verticillioides, Geotrichum candidum e Rhizopus stolonifer. A temperatura influenciou significativamente (P=0,05) a incidência de podridões, ocorrendo maior incidência de lesões em frutos incubados a 25 °C. Não foi observado o desenvolvimento de podridão em frutos inoculados com F. verticillioides e incubados nas temperaturas de 5 e 35 °C, sendo nesta última verificada a menor incidência de podridões causadas por G. candidum e R. stolonifer. Nas temperaturas de 5, 15 e 25 °C, a incidência de podridões causadas por R. stolonifer variou entre 97,5 e 100%. A presença de água livre na superfície dos frutos de tomateiro foi desnecessária para a incidência de podridões causadas por F. verticillioides, G. candidum e R. stolonifer, embora os níveis de incidência tenham aumentado com o incremento no período de molhamento, exceto para R. stolonifer, que causou a incidência máxima de doença (100%), na ausência de molhamento. A incidência de podridões aumentou com o incremento na concentração de inóculo de 10¹ a 10(8) esporos/mL, atingindo o máximo (100%) na concentração de 10(4) esporos/ml para F. verticillioides e R. stolonifer, enquanto o mesmo nível foi atingido por G. candidum com 10(8) esporos/ml.