Scielo RSS <![CDATA[Química Nova]]> vol. 40 num. 1 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[PREPARAÇÃO DE NOVOS FILMES POLIMÉRICOS CONTENDO NANOEMULSÕES DO ÓLEO DE MELALEUCA, COPAÍBA E LIMÃO PARA APLICAÇÃO COMO BIOMATERIAL]]> The sodium alginate is a linear polymer used in industry and in medicine for many applications such as dressings for wounds, due to low toxicity and maintains a proper moist environment. The essential oils are materials that have antimicrobial activity and are active materials, which may be incorporated in polymeric films. This study has as objective the produce alginate films incorporated with nanoemulsions of melaleuca, copaiba and lemon oil and investigate water vapor permeability (WVP) analysis of the films, particle size and ζ-potential of nanoemulsions. Particle size analyzes showed formation of large and small particles nanoemulsion depending on the agitation speed used during production of nanoemulsions. Results of the WVP analyzes showed that the film with alginate 3 % w/v and nanoemulsions with little particle prepared with agitation speed of 15000 rpm showed better WVP. Produced films show good quality for a future application as dressings because it has good WVP. This is very interesting because the skin needs to breathe. <![CDATA[COMPETITION BETWEEN THE REACTION MEDIUM AND NANOSTRUCTURED ZnO IN THE PHOTOCATALYTIC DEGRADATION OF ANTHRACENE. TOWARD AN OPTIMAL PROCESS FOR POLYCYCLIC AROMATIC HYDROCARBONS REMEDIATION]]> Contamination with polycyclic aromatic hydrocarbons (PAHs) is considered an important health issue due to the toxicity of these compounds. Photocatalytic degradation of anthracene, a representative molecule of PAHs, using the high quantum yield semiconductor ZnO, has been reported. The solubility of anthracene in water makes necessary to use mixtures with organic solvents in fundamental degradation studies. It is well known that some organic solvents participate in the photochemical transformation of this molecule. In the PAHs photocatalysis, the competition between a semiconductor and solvents has not reported. Therefore, in this work, we decided to study the photocatalytic degradation of anthracene with two common reaction media and nanostructured ZnO. The semiconductor was obtained by a one pot method which consists in an alkaline hydrolysis of Zn(CH3COO)2·2H2O in ethanol. Nanoparticles size in colloidal dispersion was calculated using UV-Vis spectroscopy and High Resolution Transmission Electron Microcopy (HR-TEM). ZnO powder was isolated and characterized by X-ray diffraction to be used in photocatalytic experiments. Surface area determination and photocurrent spectroscopic experiments were also carried out. Linear sweep voltammetries under darkness and UV-Vis irradiation indicate a charge separation due to photoexcitation. Photocatalytic experiments in ethanol:water pH 12 (1:1) and acetone:water pH 12 (1:1), with and without ZnO was explored. The results demonstrated that ethanol:water and acetone:water promotes the photo-transformation of anthracene to 9,10-anthraquinone. Meanwhile, ZnO transformed anthracene to benzoic acid and to 9,10-anthraquinone in ethanol:water and acetone:water, respectively. A faster photochemical kinetic is observed when acetone was used as solvent in the presence and in the absence of ZnO. <![CDATA[UTILIZAÇÃO DE HEMICELULOSES CATIÔNICAS, OBTIDAS A PARTIR DO APROVEITAMENTO DA PALHA DE MILHO, ASSOCIADAS COM TANINO PARA O TRATAMENTO DE EFLUENTES DE LAVANDERIA INDUSTRIAL]]> The synthesis of cationic derivatives of hemicelluloses from corn husk was carried out by the reaction of hemicelluloses with 2,3-epoxypropyltrimethylammonium chloride (ETA) in aqueous sodium hydroxide. The characterization of the cationic derivatives was carried out by elemental analysis, Fourier Transformed Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TG/DTA). An important characteristic was the solubility in water of the produced derivatives. This characteristic was used to apply derivatives as auxiliary coagulation with tannin in wastewater treatment for industrial laundries. The results showed that the association of tannin and cationic hemicelluloses (3,200 mg L-1) is important because the turbidity removal was greater than 95% in all range of pH, including alkaline regions. Then it is unnecessary to adjust the pH before the coagulation step. <![CDATA[ON-LINE SOLID PHASE EXTRACTION COUPLED WITH LIQUID CHROMATOGRAPHY TANDEM MASS SPECTROMETRY FOR THE DETERMINATION OF CODEINE IN HUMAN PLASMA]]> A specific LC-MS/MS method was developed and validated for automated determination of codeine in human plasma, using on-line solid phase extraction (SPE) system coupled with positive ion electrospray ionization tandem mass spectrometry. The method allowed plasma direct injection onto cartridge without sample pre-treatment. Total analysis time per run was 3 min, allowing high-throughput for codeine determination. SPE on-line along a monolithic column (Chromolith Performance RP-18e, 100 mm x 4.6 mm) demonstrated to be highly effective in terms of backpressure, separation speed and peak asymmetry. Calibration curves range was linear 5.0-200 ng mL-1. Method showed an excellent intra-day and inter-day precision ranged from 2.34 to 7.25% (CV%) as well as great intra-day and inter-day accuracy, ranging from 97.64 to 110% (RE%). SPE-LC-MS/MS method provided selectivity, accuracy, precision, fastness and high-throughput to assess codeine pharmacokinetics in human plasma samples. <![CDATA[OTIMIZAÇÃO MULTIVARIADA DE METODOLOGIA PARA DIGESTÃO DE MICROPARTÍCULAS POLIMÉRICAS CARREADORAS DE CÁTIONS METÁLICOS]]> There are not reports in the literature of digestion processes of metallic cation carrier microparticles. Multivariate experimental designs were utilized to ensure an appropriate digestion for further analysis by atomic absorption spectroscopy. It was used a heater plate and the polimeric degradation was evaluated utilizing an analyzer of total organic carbon (TOC). For the total carbon (TC) content, the full factorial design 24 pointed the significance of sample volume (VAm), in relation to the variables acid volume (VAc), temperature (T) and digestion time (t). However, according to the normal distribution graph it was noted a possible significance of the T and t effects. The same was observed for TOC, including the VAm × VAc × T effect suggestive of complex behavior. In the central composite design all variables were again studied and the VAM was significant, promoting a TC decreasing at the lower evaluated level. By ANOVA a quadratic model without lack of fit was found, with the significant quadratic term. The best digestion condition was: 5.00 mL of sample, 10.00 mL of nitric acid, 60 ºC and 90 min. The multivariate optimization allowed an efficient digestion, with the initial carbon concentration of 4.60 mg L-1 decreased to 0.55 mg L-1. <![CDATA[DEGRADAÇÃO FOTOCATALÍTICA DE ATRAZINA NA PRESENÇA DE CATALISADORES NANOPARTICULADOS]]> Atrazine is a persistent herbicide and several studies have detected their presence in drinking water sources. In this work the atrazine photocatalytic degradation was investigated in aqueous solution using TiO2, ZnO and TiO2/ZnO catalysts. The catalysts were synthesized by Pechini's method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The process was monitored using absorption spectroscopy in ultraviolet and visible (UV-vis) region and high performance liquid chromatography (HPLC). The prepared catalysts were used in ultrafine powder form and its characterization showed nanometer order particle sizes. The atrazine absorbance decrease was observed after samples irradiation in catalysts presence and HPLC analysis showed a significant herbicide reduction and other compounds formation as degradation products. The ZnO catalyst use was more effective in atrazine molecule degradation compared to the other nanoparticles. <![CDATA[HS-SPME AS AN EFFICIENT TOOL FOR DISCRIMINATING CHEMOTYPES OF <em>Lippia alba</em> (Mill.) N. E. Brown]]> Lippia alba (Mill.) N. E. Brown (Verbenaceae) is a medicinal plant for which several biological activities are reported, such as sedative, anxiolytic, anti-ulcer, antifungal, antimicrobial, antioxidant, antispasmodic, anti-nociceptive and anti-inflammatory. It is characterized by the production of essential oils which have been used to classify the plant in different chemotypes. In the Northeast region of Brazil, the presence of three chemotypes are reported: myrcene-citral (chemotype I), limonene-citral (chemotype II) and carvone-limonene (chemotype III). In this work, headspace-solid phase microextraction (HS-SPME) was used on the analysis of the volatile organic compounds (VOCs) of three chemotypes of L. alba from the Northeast region of Brazil, and compared to the essential oils of the plants extracted by hydrodistillation. Volatile compounds from each chemotype were more effectively differentiated when extracted by HS-SPME than by hydrodistillation. <![CDATA[FE<sub>3</sub>O<sub>4</sub>@SIO<sub>2</sub>-OSO<sub>3</sub>H NANOCOMPOSITE AS AN EFFICIENT CATALYST FOR THE PREPARATION OF TRICARBOXAMIDES]]> In this research a highly efficient one-pot preparation of tricarboxamide derivatives via five-component reactions of isocyanides, aldehydes Meldrum's acid and 2equiv. of amines have been developed in the presence of Fe3O4@SiO2-OSO3H nanocomposite. Nano-Fe3O4 encapsulated-silica particles bearing sulfonic acid was readily recovered using an external magnet and could be reused several times without significant loss of reactivity. The catalyst was fully characterized by VSM, FT-IR, SEM, XRD, EDX and TEM analysis. <![CDATA[UM NOVO CONCEITO DE BRANQUEAMENTO DE POLPA <em>KRAFT</em> DE EUCALIPTO COM OZÔNIO EM MÉDIA CONSISTÊNCIA]]> The effect of hot acid hydrolysis (A-stage) pretreatment on the ozone (Z/E) performance at medium consistency was evaluated. An experimental plan was set up involving full optimization of A and Z/E stages for an oxygen delignified eucalypt kraft pulp. A-stage caused significant kappa and HexA drop, and the optimum condition for this stage being pH 3.0, 90 ºC, 120 minutes at 10% consistency. For A-stage pretreated pulp, the conditions for maximum Z/E-stage efficiency and selectivity were pH 2.5, 40 ºC, 5.0 kg O3 adt-1 pulp for the (Z/)-treatment and pH 10.5 for the alkaline extraction (E). The values of kappa drop per kilogram of ozone applied were 1.04 and 1.18 for A-stage pretreated and reference pulps, respectively. Since the A-stage pretreatment did not decrease the (Z/E)-stage efficiency to a large extent, such stages are complementary rather than competitive. The potential of the A-stage pretreatment to save bleaching chemicals is quite large given that pulp kappa number (brightness) after Z/E and AZ/E treatments were 5.5 (brightness 67.3% ISO) and 1.1 (brightness 72.6% ISO), respectively. The impact of the A-stage pretreatment on overall bleaching performance, comparing the sequences Z/EDP and AZ/EDP will be a matter of other publication on the subject. <![CDATA[OTIMIZAÇÃO DA SÍNTESE DE HIDROGÉIS NANOCOMPÓSITOS INTERCALADOS PARA POSSÍVEL APLICAÇÃO NA ÁREA MÉDICA]]> In this study, the hydrogel formulations based on polysaccharide sodium alginate were investigated for further development of intercalated nanocomposite hydrogels, for purposes of future applications in the areas of health as a carrier in drug delivery systems. Thus, the objective of the work dealt with in the optimization of hydrogels synthesis and obtaining nanostructured hydrogels with clay in an intercalated conformation. The optimization of the hydrogel synthesis was successful, and it is possible to define the materials and / or solutions to be used and concentrations of these solutions to the best formulations of hydrogels. The choice of the concentration of the polysaccharide, the type of crosslinking agent and nanofiller to continued development work, it was determined following criteria as the degree of swelling, and in some cases the physical properties, contributed to determine the best hydrogels. The development of intercalated nanocomposites hydrogel beads was confirmed by the X-ray diffraction technique, which thus could be used to observe evidence of effective incorporation or intercalation of the nanoclay in the hydrogel matrix. <![CDATA[DEVELOPMENT OF A SECOND TYPE ELECTRODE BASED ON THE SILVER/SILVER IBUPROFENATE PAIR FOR IBUPROFEN QUANTIFICATION IN PHARMACEUTICAL SAMPLES]]> Ibuprofen is a widely used pharmaceutical because of its therapeutic properties; it is considered a safe medicament, thus it does not require medical prescription to be sold. However, in order to ensure consumer's health it is indispensable that the pharmaceutical industry relies on analytic methods for its quantification. Potentiometry has proven to be a successful technique using second type electrodes, which in agreement with Nernst's equation can detect anions activity. On consideration of this, this research work presents the development of a second type electrode based on the silver/silver ibuprofenate pair. This involved modifying a pure silver wire using a sodium ibuprofenate solution, to obtain the redox pair. The following analytic parameters were obtained with the aid of the modified electrode: a sensitivity of -0.049 V decade [ibuprofenate]-1, 8 µmol L-1 for the detection limit and a quantification limit of 1.2 µmol L-1. The repeatability value in terms of the relative standard deviation was 5.9%. After performing an interferences analysis using some ions and excipients, it was corroborated that there were none, thus allowing appropriate quantification on a real sample. <![CDATA[BIOMATERIAIS PARA FORMULAÇÕES DE BASE NANOTECNOLÓGICA VISANDO TERAPIA GENÉTICA OCULAR]]> Gene therapy is a promising tool for the treatment of ocular diseases. Nevertheless, there are some import limitations, especially related to the ocular route and the characteristics of nucleic acids that must be overcome to ensure the success of the therapy. In this context, nanotechnology-based carriers such as nanoemulsions, nanoparticles, dendrimers and liposomes have risen as a promising vehicle for the protection of genetic material for vectoring the target cells. The success of such approach is closely related to the judicious selection of the biomaterial, where chemical structure and intermolecular interactions play a major role. So, this manuscript reviews some of the most important biomaterials, lipid and polymeric origin, employed in the manufacture of nanotechnologic carriers for ocular gene therapy involving interfering RNA (siRNA), antisense oligonucleotide (AS-ON) and plasmid DNA (pDNA). <![CDATA[POTENCIAL CATALÍTICO DE LIPASES LIGADAS AO MICÉLIO DE FUNGOS FILAMENTOSOS EM PROCESSOS DE BIOTRANSFORMAÇÃO]]> Over the past decades, mycelium-bound lipase of filamentous fungus has been extensively studied as an alternative biocatalyst in biotransformation processes. Mycelium-bound lipase can be used directly as suspended free cells or immobilized within biomass support particles as whole cells biocatalyst. In the latter, cells can be immobilized in situ or extra situ using different support materials avoiding the purification step. This represents an attractive, cost-effective technology to enhance chemical reaction efficiency. The present review covers the great versatility of mycelium-bound lipase to mediate biotransformation processes, given particular emphasis in its use as biocatalyst for biodiesel production. <![CDATA[EXTRACT OF <em>Punica granatum</em> L.: AN ALTERNATIVE TO BHT AS AN ANTIOXIDANT IN SEMISSOLID EMULSIFIED SYSTEMS]]> Pomegranate (Punica granatum L.) is a fruit which has important pharmacological activities and has been attracting attention due to its important antioxidant activity, a significant feature in relation to cosmetics. Formulations containing different concentrations of an ethanolic extract of pomegranate (0.1, 1.0 and 5.0%) (w/w) as an antioxidant agent showed that this is an interesting alternative for the use of natural products with biological activity. The stability and rheology of semissolid systems containing an extract of this plant were evaluated. Preliminary stability studies showed greater physico-chemical stability of the formulation, and thus it was used in an accelerated stability study, as well the quantification of total phenolic compounds and the determination of antioxidant activity. It was observed that different concentrations of the extract did not significantly influence the stability. Moreover, the formulation was found to have better stability when stored at room temperature than under heated or cooled conditions. Formulations containing 0.1 and 5.0% of extract showed more stable rheological behavior, due to the absence of a solid/liquid transition in the rheogram. Tests confirmed the high phenolic content and antioxidant activity, demonstrating the potential of this plant for use in cosmetology as an antioxidant. <![CDATA[DESENVOLVIMENTO PROFISSIONAL E COOPERAÇÃO INTERNACIONAL PARA PROFESSORES DE QUÍMICA: AVALIAÇÃO DA INTENÇÃO DE MUDANÇA PEDAGÓGICA APÓS FORMAÇÃO CONTINUADA NO PORTO, PORTUGAL]]> This article assesses the intention of chemistry teachers to integrate digital media in their classes. The evaluation was performed using a structured questionnaire after participation in two professional development actions. The formative sessions were designed with the aim of training the chemistry teachers for pedagogical integration of digital media in teaching chemistry in high school. The participants were 25 chemistry teachers from different regions of Brazil, who were participating in an international cooperation program for the professional development of teachers in Portugal. Data collection was conducted through questionnaires containing questions about the motivations for innovation in education, attitudes and beliefs in relation to the training actions and face the pedagogical integration of digital media in the chemistry discipline. The data analysis shows a remarkable behavioral intention of adopting the media which is positively correlated with the attitudes and perceptions of control and negatively with subjective norm. These results suggest that interventions focused on technical and pedagogical training centered on subject content are suitable for the professional development of teachers. <![CDATA[O PRÊMIO NOBEL DE QUÍMICA EM 2016: MÁQUINAS MOLECULARES]]> The Nobel Prize in Chemistry 2016 was granted to Jean-Pierre Sauvage, Sir James F. Stoddart and Bernard (Ben) L. Feringa. These scientists were responsible for the creation and development of molecular machines. The development of such systems represents a breakthrough in the field of supramolecular chemistry, nanotechnology and organic synthesis. This article aims to bring simple and objective information to the scientific community about the work of these three researchers.