Propriedades e aplicações recentes das ciclodextrinas

Cyclodextrins (CDs) are cyclic oligosaccharides comprised of six or more glucose units connected by alpha-1,4 bonds. They have hydrophobic cavities with a hydrophilic exterior, and are versatile receptors for a variety of substrates. This ability allows them to be applied in many fields, as distinct as supramolecular chemistry, nanotechnology, pharmaceuticals, green chemistry, agrochemicals, analytical chemistry, toiletries, foods, and cosmetics. This review summarizes several aspects related to the physico-chemical properties of CDs and discusses their potential applications illustrated by recent examples. The prospects for their use in several areas are also described.

Análise dinâmico-mecânica: aplicações em filmes comestíveis

Edible films are thin materials based on biopolymers and food additives. The aim of this work is a review on the application of dynamic mechanical analysis in edible film technology. After a brief review of the linear visco-elasticity theory, a description of some practical aspects related to dynamic mechanical analysis, such as sample fixation and sample dehydration during analysis and types and modes of tests are presented. Thus, the use of temperature scanning analysis for glass transition and for plasticizer-biopolymer compatibility studies and frequency scanning tests, less common in edible film technology, are critically reviewed.

Efeito de microondas na estrutura cristalina e na atividade catalítica de argilas

The effect of microwave (MW) irradiation on the crystalline structure of two natural clays and one commercial clay, Montmorillonite K10, was analyzed comparing the X-ray diffraction, N2 isotherms, NMR-MAS of 27Al and 29Si spectra of the clays before and after MW irradiation. The preparation of dioxolane ketals of isatin was used to analyze the MW effect on the catalyst activation. The yields achieved using catalysts activated by MW irradiation were lower (2 to 5%) than the yields achieved using catalysts activated by heat in a conventional oven.

Microextração em fase líquida (LPME): fundamentos da técnica e aplicações na análise de fármacos em fluidos biológicos

The analysis of drugs and metabolites in biological fluids usually requires extraction procedures to achieve sample clean-up and analyte preconcentration. Commonly, extraction procedures are performed using liquid-liquid extraction or solid-phase extraction. Nevertheless, these extraction techniques are considered to be time-consuming and require a large amount of organic solvents. On this basis, microextraction techniques have been developed. Among them, liquid-phase microextraction has been standing out. This review describes the liquid-phase microextraction technique based on hollow fibers as a novel and promising alternative in sample preparation prior to chromatographic or electrophoretic analysis. The basic concepts related to this technique and its applicability in extraction of drugs are discussed.

Catalisadores contendo carbenos n-heterocíclicos como ligantes: propriedades, sínteses, aplicações e comparação com outros ligantes

N-heterocyclic carbenes (NHCs) have become of considerable importance in modern organometallic chemistry and homogeneous catalysis. There are several advantages in the use NHCs over their phosphorus analogues, which explains the enormous development of NHC ligands in the field of organometallic catalysis in the past few years. In this article, we present an overview of the importance of the catalysts containing NHC ligands, their synthesis, some pertinent synthetic applications, and a brief comparison with other catalysts.

Monoglicerídeos: produção por via enzimática e algumas aplicações

Monoglycerides (MAG) are non-ionic surfactants, widely used in the pharmaceutical, food and cosmetic industries. Although MAGs are manufactured on an industrial scale by chemical glycerolysis of oils and fats, new developments in lipase catalyzed synthesis have been studied as an alternative to the classical method seeking to use clean technology and green chemistry. In this work, different methods such as glycerolysis, selective hydrolysis of fats and oils, and esterification of fatty acids or transesterification of esters with glycerol are presented. The properties and applications of the monoglycerides are also included in this review.

Principais aplicações das microondas na produção e refino de petróleo

Microwave irradiation offers a clean, inexpensive, and convenient method of heating, which is an alternative way of introducing energy into chemical systems. In particular, applications of microwave irradiation technology for petroleum processing have been developed in the last twenty years. The main objective of this paper is to review the use of microwave irradiation technology as an alternative technique applied during petroleum refining and primary processing of petroleum fluids, presenting and discussing successful applications of this technology as a tool for petroleum emulsion separation and catalytic reactions normally found at hydrorefining plants.

Síntese de poliestireno sulfonado para aplicações no tratamento de água produzido a partir de copos e bandejas descartadas de poliestireno

In the present paper, the use of poly(styrene sulfonate) (PSS), produced from discarded polystyrene materials through heterogeneous and homogeneous processes, was investigated. The use of PSS for water treatment, using a kaolin suspension as wastewater model, reduced water turbidity for all the employed materials when compared to the blank analysis, without PSS. The most efficient polyelectrolyte was PSS cups obtained by homogeneous route. The same behavior was observed for real system. The homogeneous PSS cups showed a balance between a moderate molecular weight and high anionic character that improved flocks formation and water removal turbidity.

Cutinases fúngicas: propriedades e aplicações industriais

Cutinases (EC 3.1.1.74) are also known as cutin hidrolases. These enzymes share catalytic properties of lipases and esterases, presenting a unique feature of being active regardless the presence of an oil-water interface, making them interesting as biocatalysts in several industrial processes involving hydrolysis, esterification and trans-esterification reactions. They are also active in different reaction media, allowing their applications in different areas such as food industry, cosmetics, fine chemicals, pesticide and insecticide degradation, treatment and laundry of fiber textiles and polymer chemistry. The present review describes the characteristics, potential applications and new perspectives for these enzymes.

Eletrodo compósito à base de grafite-araldite®: aplicações didáticas

A composite electrode prepared by mixing a commercial epoxy resin Araldite® and graphite powder is proposed to be used in didactic experiments. The electrode is prepared by the students and applied in simple experiments to demonstrate the effect of the composite composition on the conductivity and the voltammetric response of the resulting electrode, as well as the response in relation to the scan rate dependence on mass transport. The possibility of using the composite electrode in quantitative analysis is also demonstrated.

Um novo procedimento de síntese da zeólita A empregando argilas naturais

This work proposes the synthesis of zeolite A by IZA standard proceedures starting from a natural clay. The clay was used in its natural form and after calcination at 900ºC. The resulting materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and porosity analysis by nitrogen adsorption. Results showed low surface area for Na-A zeolite in sodium form, but a higher one in CaA based on the nitrogen accessibility. The presence of cubic crystals for the A phase was observed in the SEM micrographies. The new procedure starting from natural clay favors the formation of sodalite while that using the calcinated clay gives A.

Reações de organocatálise com aminas quirais: aspectos mecanísticos e aplicações em síntese orgânica

The philosophy of organocatalysis is based on the utilization of organic compounds to catalyze organic transformations without the intervention of metals. This area has attracted much attention of the synthetic chemistry community on the last years, which can be confirmed by the explosion of published papers dealing with this subject. Phosphorus compounds, urea and thiourea derivatives, alkaloids, guanidine derivatives, for example, have already been used as organocatalysts. In this review we have focused on the use of chiral amines as organocatalyst. We have also chosen some outstanding examples to demonstrate the potentiality of this strategy in the synthesis of natural products and biologically active compounds.

Aplicações de fibras lignocelulósicas na química de polímeros e em compósitos

The use of lignocellulosic fibers and their constituents, as raw materials in the production of polymeric and composite materials, represent an exceptional opportunity of sustainable technological development. In the present report works that discuss promising alternatives of obtaining and use of materials such as cellulose, hemicellulose, lignin, cellulose nanocrystals and biocomposites were revised. The advance in the use of biomass can be, in a near future, capable of going beyond the application difficulties of these vast materials, especially in relation to the economical unviability, by the production of high performance polymeric and composite materials. This advance would represent a higher profitability to some areas of agrobusiness, especially the sector of biofuels, which produces elevated amounts of biomass waste.

Modificação química de argilas: desafios científicos e tecnológicos para obtenção de novos produtos com maior valor agregado

Chemical modification of clays is possible due to their ion-exchange and adsorption capacities, which allows the adjustment of the physicochemical properties of the surfaces of their layers. This modification makes possible the use of clays to produce a great number of new materials, which range from coarse applications such as oil based drilling fluids to refined applications such as pharmaceutical products. This article intends to expose where there is still space for research and investment aiming at the performance improvement of clay-based materials.

Cromatografia de afinidade por íons metálicos imobilizados (IMAC) de biomoléculas: aspectos fundamentais e aplicações tecnológicas

Immobilized Metal Ion Affinity Cromatography - IMAC - is a group-specific based adsorption applied to the purification and structure-function studies of proteins and nucleic acids. The adsorption is based on coordination between a metal ion chelated on the surface of a solid matrix and electron donor groups at the surface of the biomolecule. IMAC is a highly selective, low cost, and easily scaled-up technique being used in research and commercial operations. A separation process can be designed for a specific molecule by just selecting an appropriate metal ion, chelating agent, and operational conditions such as pH, ionic strength, and buffer type.