Resumo em Inglês:

Micelles have aroused interest due to their ability to assist in the transport of poorly soluble drugs. In this study the mixture of copolymers F127/E45S8 in different proportions (F/ES 30/70, 50/50 and 70/30) was performed to improve the bioavailability of griseofulvin and quercetin. The results of cytotoxicity (MTT assay) revealed that the copolymers F127 and E45S8 had considerable biocompatibility and did not affect the metabolism of human neutrophils. The binary systems were also evaluated by critical micellar concentration (CMC) and thermoresponsive behavior. The CMC values were intermediate to those of the isolated copolymers. The systems maintained the thermoresponsive properties present in F127 making the systems interesting for subcutaneous administration. The systems presented small size, an average range in size from 17 to 38 nm, and the samples prepared with higher hydrophobic proportion presented more uniform sizes. Results suggest stability and the increasing of the nanosystems circulation time. The F/ES 30/70 system has polydispersity smaller than 0.1 and showed an increase of 129 times for quercetin solubility. Thus, it is possible to consider F127/E45S8 micelles as potential nanosystems for poorly soluble drug delivery.

Resumo em Inglês:

In this work, alkaline and nickel-metal hydride spent batteries were used as precursors of metals for the synthesis of polymetallic materials. These materials were synthesized via chemical reduction. Materials produced from nickel-metal hydride spent batteries (PM-NiMH) have a nanometric size, whereas the alkaline spent batteries (PM-Alk) have a micrometric size. PM-NiMH consists mainly of Ni, Co, and Cu and the PM-Alk consists mainly of Mn and Zn. The surface areas of PM-NiMH and PM-Alk were 82 m2 g-1 and 109 m2 g-1, respectively. The synthesized materials were applied in the removal of reactive blue dye 4 (RB4). Parameters such as initial pH of the system, dose of the materials, and initial concentration of the dye were optimized. For both materials, the removal capacity of RB4 was constant over a wide pH range of (4-10). The removal capacity increases with the decrease of the materials dose and increase of the dye concentration until saturation of the active sites. The RB4 removal by PM-NiMH occurs by adsorption and degradation processes, whereas PM-Alk occurs only by adsorptive processes. The RB4 removal process follows the Langmuir adsorption isotherm model with maximum removal capacities of 331 and 127 mg g-1 for PM-NiMH and PM-Alk, respectively.

Resumo em Inglês:

The contamination of water bodies by pesticide residues through direct flow, leaching and other methods has motivated the development of analytical methods for the determination of these compounds in water. A vortex-assisted liquid-liquid microextraction method followed by gas chromatography coupled to mass spectrometry for the determination of anilazine, linuron, prothiofos, and tebuconazole residues in water samples from the culture and processing of potatoes (Solanum tuberosum L.) was optimized. The complete factorial design and the central rotational compound design combined with the desirability function were used to evaluate and optimize the parameters of the method. The optimized conditions for extracting the pesticides were as follows: 316 µL of toluene, no sodium chloride addition, and a stirring time of 187 s. The method presented an enrichment factor of 142.4 times and good linearity, precision and accuracy, with limits of detection (LOD) of 0.005 - 0.007 mg L-1 and limits of quantification (LOQ) of 0.016 - 0.022 mg L-1. The co-extractives of the wastewater samples caused the suppression of the chromatographic response of linuron and prothiofos by 7.82 and 27.63%, respectively. The analyte concentrations in the wastewater samples from the industrial shing process, manual potato washing, and dam water were either lower than the LODs of the method or were absent.

Resumo em Inglês:

In recent years, estrogens have gained notable attention among emerging pollutants, increasingly leading to the need for less laborious analytical methods. Optical sensors are a promising technology for the determination of chemical contaminants in water, acting as an alternative screening method. The aim of this work was to evaluate the performance of poly(vinyl chloride) (PVC) as a sensing phase for the detection of 17β-estradiol in water using mid-infrared spectroscopy and chemometrics. The sensing phase was used for differentiation purposes with an accuracy of 80%, sensitivity of 100% and specificity of 71.4% based on soft independent modeling of class analogy (SIMCA). Satisfactory limits of detection (8.9x10-1 - 2.9 mg L-1), quantification (2.9 - 1.0x10 mg L-1), slope of the analytical curve (5.0x10-4 - 2.4x10-3 L mg-1) and determination coefficients (0.90 - 0.99) were obtained. Kinetically, a extraction time of around 30 min was estimated and in a regeneration study, it was possible to use the same phase after 4 cycles of use. Therefore, the results indicate that the PVC sensing phase is promising for the detection of 17β-estradiol in water by means of mid-infrared spectroscopy and chemometric methods.

Resumo em Inglês:

In previous work, the facile method to prepare perylene diimide radical anion salt by alkali treatment was reported. However, the effects of structure on synthetic process of perylene diimide radical anion salt, and the difference of response to Cu 2+ are not thoroughly understood. In this work, two bay-substituted perylene diimide derivatives radical anion salts have been synthesized and characterized in order to study the influence of the bay-substituted groups on the formation condition of the corresponding radical anion salt, and the sensitivity to Cu 2+. The result indicates that the perylene diimide with electron-donating groups (-O-Ph) at bay position was much easier to get the air-stable radical anion salts and had higher sensitivity to Cu 2+ compared to the perylene diimide with electron-withdrawing groups (-Br) at bay position.

Resumo em Inglês:

The aim of this study was to develop a chromatographic method for 4-NP determination in anaerobic batch reactors using low amount of organic solvents and also evaluate 4-NP degradation in the presence of different co-substrates. Chromatographic parameters was improved for stationary phase (C-8 column), mobile phase (acetonitrile/water solution 90:10, v:v), column temperature (40 ºC), eluent flow (0.8 mL min-1), injection volume (100 µL) and wavelengths in fluorescence detector (FLD) (λex=225 nm and λem=305 nm). Solid phase extraction (SPE) was performed for sample purification with smaller amount of solvents (methanol - 2 mL and ethanol - 1 mL) than previously reported. Reduction in reagent consumption was about 5.5 times for HPLC and about 19 times for SPE, according to previously reported. Method was validated according to the linearity (0.9951), selectivity and limits of detection and quantification were 15.7 µg L-1 and 55.6 µg L-1, respectively. The 4-NP removal in anaerobic batch reactors was higher than 50% (4-NP initial concentration of 398 µg L-1). Fumarate was a better co-substrate to favor methanogenesis in the presence of 4-NP, which provided higher organic matter removal, higher methane production speed and shorter start-up time for methane production.

Resumo em Inglês:

Corrosion is still one of the most serious and frequent problems in industries. The phenomena involved in the corrosion mechanism of Al-alloys may be explained by formation of galvanic cells between the metal matrix and heterogeneities, such as precipitates, intermetallic phases leading to potential differences and electrochemical reactions. In the cathodic sites, the main reactions are oxygen reduction reaction, in aerated neutral environments, and hydrogen evolution in acid media. This last type of reaction might also occur in neutral solutions inside pits (anodic region). In this study, the mechanism of hydrogen evolution during corrosion of the 2198-T8 Al-Cu-Li alloy exposed in a chloride solution was investigated. The mechanism was related to the presence of T1 phase (Al2CuLi), which is the main strengthening phase in this material. This phase is highly active and, when exposed to corrosive media, leads to severe localized corrosion (SLC). One of the main characteristics related to SLC is hydrogen gas evolution which was confirmed by gel visualization. In this study, the hydrogen evolution mechanism inside the SLC sites was studied by scanning electrochemical microscopy (SECM).

Resumo em Inglês:

Maytenus distichophylla is a medicinal species used in Northeast of Brazil. The hexane (HE), chloroform (CE), ethyl acetate (EAE) and methanol (ME) extracts and compounds from its roots were evaluated for their protective activity against Staphylococcus aureus and Candida albicans. The cytotoxicity for chronic myeloid leukemia (K562), acute monocytic leukemia (THP-1), and peripheral blood mononuclear cells of normal individuals (PBMC) cells was established by MTT method using etoposide as standard. The in vivo toxicity of samples was determined using Caenorhabditis elegans model. From HE and CE were isolated: friedelan-3-one (1), b-sitosterol (2), 3-oxo-olean-9(11),12-diene (3), a mixture of pristimerin (4) and 11a-hydroxylup-20(29)-en-3-one (5), 30-hydroxylup-20(29)-en-3-one (6), friedelane-3,7-dione (7), tingenone (8) and triacylglycerol (9). The structures of 1-9 were confirmed by spectral data. All samples reduced the viability of S. aureus and present no effect against C. albicans. The HE, CE, mixture of 4/5 and 8 reduced 75% of S. aureus viability. Cytotoxic effect for K562 and THP-1 cells was caused by compounds 1, 2 and 8. All samples displayed selectivity for leukemic cells and low toxicity to PBMC cells, suggesting their potential as anticancer agents. Extracts and compounds were non-toxic to L1 larvae of C. elegans. However, most of them reduced significantly young adult worm’s survival, being considered as potential nematicides.

Resumo em Inglês:

A rapid method has been developed for the determination of silver arsenite As(III), dimethylated arsenic DMA, monomethylated arsenic MMA, and arsenate As(V) in algae sample using liquid chromatography coupled with hydride generation atomic fluorescence spectrometry (LC-HG-AFS). Types, flow rate and pH of mobile phase were optimized. Under the optimal conditions, there were good linear relationships in the range of 0 -200 µg L-1 with correlation coefficients larger than 0.9995. The limits of detection and quantification of As(III), DMA, MMA, and As(V) were 0.005- 0.010 mg kg-1 and 0.019-0.034 mg kg-1, respectively. The recoveries at three spiked levels of 0.02, 0.5 and 1.0 mg kg-1 were in the range of 93-105 % with relative standard deviations (RSD, n=6) of 3.6%-6.2%. The proposed method was successfully applied in the determinaton of four arsenic species in algae sample. The developed method is simple, higher precision, stable data collection, and shorter separation time, and could be applied in the speciation and study of arsenic species in algae.

Resumo em Inglês:

The use of ethylenediaminetetraacetic acid disodium salt (Na2EDTA) as a chelating agent presents ideal characteristics to be used for the removal of lead from a contaminated site. Batch experiments together with a simple local equilibrium model were carried out to evaluate the role of EDTA as enhancing agent in electrokinetic remediation of a Pb-contaminated soil. According to preliminary results, Pb removal was close to 85% after 9 hours. Hence, electrokinetic experiments were designed implementing a pH control system at both electrode-compartments. From first experiments, no important Pb recovery was obtained probably due to the counteracting effect of the electroosmotic and electromigration movement of Pb-species. The use of an iron anode instead of a platinum anode involved the recovery of a high percentage of Pb (80%) at the cathode. These results were associated with the behavior of the iron as a sacrificial anode. Furthermore, the formation of Fe(EDTA)- hinders the formation of Pb(EDTA)2-, which entails the dissolution of the contaminant as Pb2+. Therefore, the Pb species are transported toward the cathode by electromigration and electroosmosis. Furthermore, the competition between the oxidation of iron and the water electrolysis entailed a lower consumption of NaOH to control pH value at the anode compartment.

Resumo em Inglês:

This review focuses on the use of functionalized carbon nanotubes (CNTs) on the development of preconcentration methods with substantial contributions on selectivity and sensitivity for metal ions determination. CNTs have been usually employed in the development of preconcentration/speciation coupled to spectroanalytical techniques for ions determination at trace levels in different kind of samples. With regard the electroanalytical ones, this material has been widely used in adsorptive voltammetry procedures. Despite intrinsic features of CNTs, they suffer from poor dispersion in aqueous medium and wettability, thus making them very useful for sorption of hydrophobic metallic complex, but few indicated for metallic ions. Thus, different syntheses strategies, purification and chemical and physical approaches for surface functionalization/modification have been reported for improving the applicability of CNTs for a wide range of analytes. Therefore, apart from the brief description of the main physical and chemical characteristics of the carbon nanotubes, this review report the critical evaluation of main applications of modified CNTs as solid phase and as electrodic material for metal ions determination in environmental samples, food and biological using spectroanalytical techniques such as flame and graphite furnace atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry and electroanalytical mainly the adsorptive voltammetric ones.

Resumo em Inglês:

Gold compounds engage an important place in the field of medicinal chemistry due to their therapeutic properties. Since the last four decades, Au(I) and Au(III) complexes have attracted the attention of researchers due to their anti-tumor proprieties and the different mechanisms of action they display in comparison to conventional anticancer platinum compounds. Au(I/III) complexes can inhibit the activity of enzymes containing thiols including thioredoxin reductase; nevertheless, the affinity for several therapeutic targets has been confirmed in recent years. The properties conferred by auxiliary ligands such as phosphines (PR3) and N-heterocyclic carbenes (NHCs) to gold complexes have been key to the development of more promising anticancer compounds. In the same way, it has happened with the inclusion of some multidentate ligands in Au(III) complexes, increasing their stability and selectivity for tumor cells. In this review, we discuss the anticancer effects of Au(I) complexes containing PR3 and NHCs ligands as well as Au(III) complexes containing multidentate ligands especially those that have high cytotoxicity and information on the mechanism of action, as well as attempts to target identification and validation.

Resumo em Inglês:

Mass spectrometry (MS) is a powerful and widespread technique but is inherently uncapable to differentiate species with same m/z ratio. For this reason, many classical approaches were developed based on differential fragmentation patterns in tandem MS. More recently, new techniques for isomer identification in MS were developed, and we highlight the photodissociation techniques that will be discussed in this review. This photodissociation techniques explore the selective activation of isomers to induce isomer specific dissociations in the gas-phase that depend on the spectroscopic features of the isomers. If tunable radiation sources are available, this selective activation may be monitored as a function of the radiation wavelength, allowing the acquisition of vibrational or UV-Vis spectra of the isolated ions, making it possible to evaluate different isomers, protomers and even conformers by MS. These photodissociation techniques are even more powerful when coupled to ion mobility techniques, that will be briefly discussed. Because these techniques enhance the fields and analytical applications where MS can be used, this review will discuss the classical MS methods for isomer differentiation that lead to the fundamentals of ion spectroscopy and selective ion activation, with emphasis on the vibrational ion spectroscopy.

Resumo em Inglês:

The beneficial effects of humic substances (HS) on crop development have been evidenced in the last decade, leading to the commercialization of HS products with fertilizing properties. Currently, three methods are frequently used for HS determination: method described in the manual of the Brazilian Ministry of Agriculture, Livestock and Supply (MAPA); method employed by the United States Humic Products Trade Association (HPTA) and method used for the determination of soil HS (“HS-Soil”). This study aimed to evaluate and compare the quantification of HS in commercial liquid fertilizers, by the mentioned methods. For HA-rich fertilizers the studied methodologies presented results close to the HA and FA contents informed in the labels. For products rich in FA, the methodologies that use dichromate to oxidize organic carbon overestimated the results of FA, taking as reference the HPTA method, that determines gravimetrically the purified FA and HA. The time of analysis varied between the methodologies studied, as well as the type and volume of the produced waste. Based on the chemical principle of HS determination of the method and the environmental impact of the waste generated, we propose that the most appropriate method for determination of HS in liquid fertilizers is that of HPTA.

Resumo em Inglês:

This article analyzes the abstracts accepted and presented at the Coordinated Sessions of the teaching area at the Annual Meetings of the Brazilian Chemical Society. The research is characterized as qualitative of bibliographic type, having as the source of information the abstracts book of the last 10 editions (2010-2019) of the event. Through the texts, were analyzed: the amount of abstracts; year of presentation; Brazilian geographic region; number of productions by Higher Education Institutions; academic background of the first authors; thematic focus of the abstracts; level of education discussed in the abstract; and chemical knowledge present in the productions. In all, 121 abstracts were analyzed. The results indicated non-continuous production from a temporal point of view in relation to the total of abstracts, the predominance of abstracts from the Southeast region, a parity between USP and UFG institutions about the total amount of texts, and a great diversity of thematic focus, showing new research trends and the decentralization of studies focused on Chemistry Teaching. We conclude that the area of Chemistry Teaching has much to be explored, since there are still issues that are little discussed by chemical educators.

Resumo em Inglês:

The Chemistry of organic compounds is present in many aspects of life on the planet. In addition to many substances in our body being organic compounds, the energy matrix is based on burning fossil fuels, the biodiesel industry is also linked to organic reactions as well as the pharmaceutical industry. However, Organic Reaction Mechanisms is considered one of the most difficult subjects of undergraduate courses in chemistry. In order to improve the teaching-learning process, it was planned to elaborate animations on mechanisms of organic reactions, using simple programs accessible to all operating systems. Better than two-dimensional representation, the three-dimensional animations represent more concretely a model, at a macroscopic level, of what occurs on a sub-atomic scale. This is a new initiative to motivate students to study the concepts related to the subject of Mechanisms in Organic Chemistry, through research, planning and elaboration of animations. As a result, videos of the main reactions worked out in chemistry undergraduate courses were made, making the study of Organic Reactions more enlightening and understandable and demonstrated the use of computational technologies in the teaching of Organic Chemistry. It is an innovative, accessible, motivating and applicable teaching strategy in chemical courses.

Resumo em Inglês:

Although the impacts of science discoveries are relevant to society, awareness of this intellectual output is still minimal. Much of this communicative failure between researchers and the general public lies in the disclosure, which contributes to the superficiality and misinterpretations of the content served. Strategies need to be found to improve science communication worldwide, promoting well-grounded content and accessible language to a non-specialist audience. This work aims to report writing strategies used in a course about public communication of science, offered to undergraduate chemistry students. The results showed that students fully achieved the task of writing popular science texts as a science journalist, emphasizing their ease and difficulties throughout the activity.

Resumo em Inglês:

A short experimental activity aimed at upper level undergraduate students or beginner researchers is presented to introduce the concepts of edge effects and hemispherical diffusion at ultramicroelectrodes. Students will perform simple cyclic voltammetry experiments varying the scan rate and using disk electrodes with different radii. They are then asked to interpret the results based on their previous knowledge. Simulations are also performed, which provide a clear visual interpretation of the underlying diffusion process and show the transition between linear and hemispherical diffusion regimes. The simulations are also presented as a tool to extend the study beyond the range of experimentally accessible conditions. The interplay between voltammetry experiments and simulations allows a natural comprehension of these concepts without the need of a previous rigorous theoretical introduction.

Resumo em Inglês:

During the last 150 years or more, society has witnessed many key scientific discoveries and inventions, which have dramatically improved not only our quality of life, but our lifespan. However, the motivation of scientists to provide scientific advances has generally not been the achievement of these goals, but mainly driven by research curiosity. Fundamental scientific studies, also known as basic science, have paved the way to a society of knowledge by means of continuously evolving education systems, and have led to applied science and technological breakthroughs changing the World. However, without basic science such life-changing advances would not happen, which is poorly understood by the society. Having this in mind, chemists and biochemists working in a chemistry network highlight here examples of how basic science has played a crucial role and led to major breakthroughs. In seven short stories, the authors describe cases and historical events where basic research discoveries have advanced science, and opened avenues for future achievements. Investment in basic science is crucial for a nation’s health and wealth. The support of scientists driven by curiosity ultimately can benefit the whole of society, not only in innovative products, but also in the improvement of the understanding of our own lives.

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Analytical validation has fundamental importance in the scope of Good Manufacturing Practice (GMP) for pharmaceutical products since it establishes scientific evidence that an analytical procedure provides reliable results. However, even with validation guidelines available it is very common to observe misunderstandings in the execution of validation and data interpretation. The misguided approaches of validation guidelines, allied with a disregard for the peculiarities of the analytical techniques, the nature of the sample, and the analytical purpose, have significantly contributed to oversights in analytical validation. This work aims to present a critical overview of the validation process in pharmaceutical analysis, addressing relevant aspects of various analytical performance parameters, their different means of accomplishment and limitations in face of the analytical techniques, the nature of the sample, and the analytical purpose. To help in the planning and execution of the validation process, some case studies are discussed, mainly in the area of high-performance liquid chromatography (HPLC).