Determinação voltamétrica por redissolução anódica de Cu(II) em águas residuárias empregando um eletrodo de pasta de carbono modificado com quitosana

The electrochemical applications of a CPE modified with chitosan for the determination of Cu(II) in wastewater samples using anodic stripping voltammetry are described. The best voltammetric response was observed for a paste containing 25% m/m of chitosan. A 0.10 mol L-1 NaNO3 solution (pH 6.5) as supporting electrolyte, a pre-concentration potential of -0.20 V, pre-concentration time of 270 s and a scan rate of 25 mV s-1 were selected. The calibration graph was linear in the Cu(II) concentration range from 2.0 x 10-7 to 7.4 x 10-6 mol L-1, with a detection limit of 8.3 x 10-8 mol L-1.

Sintesis de poliuretanos a partir de polioles obtenidos a partir del aceite de higuerilla modificado por transesterificación con pentaeritritol

Castor oil was reacted by transesterification with various percentages in mass of pentaerythritol to obtain different esters of pentaerythritol. Alternatively, glycerol was also used instead of pentaerythritol for the same reaction in order to establish comparative reference products. The products of the reactions were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy in order to detect and quantify (in terms of the molecular mass and structural information) the components of the products obtained. Analysis for hydroxyl value, acid value, viscosity and specific gravity were used to complete the characterization of the polyols obtained and also of the original castor oil. The polymer characterization was accomplished by tensile stress-strain tests, Shore A hardness, thermogravimetric analysis and chemical resistance to solvents.

Termoestabilidade de processos extrativos de Nasturtium officinale R. Br., brassicaceae por sistema Soxhlet modificado

This work had as objective verified the term-stability of the Soxhlet modified system with analytical and pharmacothecnical application in extractive processes of Nasturtium officinale. It has proven that the process is thermo-stable. The analysis with analytical have determined 3.606 mg g-1 in chlorogenic acid and 11.813 mg g-1 in rutin (extract 1:20 w/v) and with pharmacotecnical 3.427 mg g-1 in chlorogenic acid and 11.278 mg g-1 in rutin (extract 1:6 w/v). The income of the pharmacothecnical process was inferior to the analytical, suggesting that the pharmacothecnical process would need of at least the double of time in each extraction system.

Desenvolvimento de sistemas líquido-cristalinos empregando silicone fluido de co-polímero glicol e poliéter funcional siloxano

For the construction of the phase diagrams, the method of the aqueous titration was used. There were prepared 5 ternary diagrams, varying the surfactant and the oil phase. The liquid-crystalline phases were identified by polarized light microscopy. The formulations prepared with silicon glycol copolymer, polyether functional siloxane (PFS) and water (S1) and with diisopropyl adipate, PFS and water (S4) presented liquid-crystalline phases with lamellar arrangement. Moreover, after 15 days in hot oven (37 ºC), the formulations presented hexagonal arrangement, evidencing the influence of the temperature in the organization of the system.

Poliuretanos elastoméricos obtenidos a partir de aceite de ricino y almidón de yuca original y modificado con anhídrido propiónico: síntesis, propiedades fisicoquímicas y fisicomecánicas

Chemical modification of cassava starch was conducted through an acylation reaction by using pyridine and propionic anhydride to replace the functional groups of starch. Polyurethane elastomers were prepared using suspensions of the mixture obtained from castor oil and yucca starch that was modified by a propionic anhydride reaction. The suspensions were characterized by means of tests based on The Fourier Transform Infrared Spectroscopy and the Hydroxyl Index. The castor oil-AMP suspensions were used for the PU synthesis. The PUs were characterized by their physical-mechanical properties like tension- deformation and Shore A. hardness, thermal gravimetric analysis and swelling test. The density cross-linking of from swelling tests was determined by applying the Flory-Rehner equation.

Otimização e validação de método empregando quechers modificado e lc-esi-ms/ms para determinação de agrotóxicos em cebola

An evaluation of the pesticides extraction from onion using a modern sample preparation method (QuEChERS) and determination by liquid chromatography tandem mass spectrometry was carried out. All the calibration curves showed r>0.99. The recoveries ranged between 61.8 and 120.0% with relative standard deviation lower than 20% for all compounds. Due to the occurrence of matrix effect, the quantification was performed using matrix-matched calibration. The limits of quantification of the method were between 0.0005 and 0.05 mg kg-1. The method shows the advantages of not require the clean-up step and consume low volume of organic solvents, decreasing time, costs and residues.

Efeitos da história térmica nas propriedades do polímero pet: um experimento para ensino de análise térmica

Polyethilenetherephtalate (PET) is commonly used in manufacturing of beverage bottles representing a didactic appeal in thermal analysis education due to its presence in the student's day life. Additionally such polymer presents well defined thermal analytical curves and a well known thermal behavior. TGA curve is used to present the thermal stability. The thermal history effects in the thermal properties of a PET sample from a soft drink bottle are used to demonstrate the effect of different heating/cooling conditions on glass transition, melting, crystallization and crystalline degree using DSC curves.

Síntese, caracterização e estudo das propriedades magnéticas de um polímero de coordenação contendo cobalto(II) e cobre(II)

This work describes the synthesis and characterization of two new compounds with ligand opy (N-(2-pyridyl)oxamate): the copper(II) precursor [Me4N]2[Cu(opy)2].5H2O and CoII CuII coordination polymer {[CoCu(opy)2]}n×4nH2O. This latter compound was obtained by reaction of [Me4N]2[Cu(opy)2].5H2O and CoCl2.6H2O in water. The heterobimetallic CoII CuII chain was characterized by elemental analysis, IR spectroscopy, thermogravimetry and magnetic measurements. Magnetic characterization revealed typical behavior of one-dimensional (1D) ferrimagnetic chain as shown in the curves of temperature (T) dependence of magnetic susceptibility (χM), in the form of χMT versus T, and dependence of magnetization (M) with applied field (H).

Determinação de resíduos de agrotóxicos em leite bovino empregando método QuEChERS modificado e GC-MS/MS

Considering the possibility that pesticides used in cattle raising produce residues in milk and cause harm to public health, this study developed a multiresidue method for determination of pesticide residues in bovine milk, using a modified QuEChERS method for sample preparation, and quantification by GC-MS/MS. The method proved to be efficient, resulting in satisfactory recoveries in the range 71.1 to 117.4%, for 45 of the 48 compounds analyzed with RSD values < 17.3%. The method LOD and LOQ were3.0 and 10.0 µg L-1, respectively, except for cyfluthrin which showed 7.5 and 25.0 µg L-1.

Uso de diagrama V modificado como relatório em aulas teórico-práticas de química geral

In this article, we present data from a study in practical classes for General Chemistry. To this end, it was proposed to use a modified V diagram to replace traditional reporting. These reports consist of material commonly prepared in the subject, including introduction, materials and methods, results and discussion and conclusions. From the preparation of the modified V, the students were able to establish relationships between the theoretical and methodological aspects necessary for understanding the objects and events studied. Thus, student learning can be evaluated in light of the Theory of Meaningful Learning.

Poliuretanos obtenidos a partir de aceite de higuerilla modificado y poli-isocianatos de lisina: síntesis, propiedades mecánicas y térmicas y degradación in vitro

Biodegradable polyurethanes (PUR) were prepared from polyols derived from castor oil by transesterification of pentaerythritol-modified castor oil and lysine polyisocyanates (LDI and LTI). The polyurethanes obtained were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and dynamic mechanical thermal analysis (DMTA). The mechanical behavior of the polyurethanes was measured by Shore A hardness and tensile testing (stress-strain curves). The biodegradable nature of the material was determined by contact angle, water absorption tests, and in vitro degradation in PBS solution. This study aims to examine the effect of the structure and functionality of diisocyanate on the mechanical properties and in vitro degradation of the material. The results were compared with homologous materials obtained from isophorone diisocyanate (IPDI) used in previous works. The objective was to evaluate candidate materials that can be potentially used in tissue engineering.

Modificação do polímero condutor polianilina para uso como trocador catiônico

This article reports the use of polyaniline (PAni), chemically and electrochemically synthesized, for copper removal from aqueous solutions. PAni films were electrodeposited on reticulated vitreous carbon (RVC). In all cases, p-toluenesulfonate anion (PTS-) was used as the dopant to obtain cation exchange properties. RVC/PAni showed no expressive copper removal due to the small amount of polymer in the film. Chemically synthesized PAni-PTS- was obtained in its reduced form (leucoesmeraldine). PAni degraded at neutral pH but remained stable at low pH, showing a very high ion-exchange capacity, which is superior to those observed for commercial resins.

INVESTIGAÇÃO DO USO DE ELETRODO DE CARBONO VÍTREO MODIFICADO COM HEXACIANOFERRATO DE RUTÊNIO PARA DETECÇÃO DE PROCAÍNA

A glassy carbon electrode modified with ruthenium hexacyanoferrate (RuOHCF) was investigated as an electrocatalyst for the detection of procaine with the aim of quantification in pharmaceutical and forensic samples. The RuOHCF films were prepared by electrochemical deposition, and the parameters used in this process (concentration of RuCl3, K3Fe(CN)6, temperature, and number of cyclic voltammograms recorded in the modification step) were carefully optimized. Based on the optimal conditions achieved, the RuOHCF modified electrode allows the determination of procaine at 0.0 V with a detection limit of 11 nmol L-1using square wave voltammetry.

ANÁLISES FÍSICO-QUÍMICAS DE BIOFILMES DE SULFATO DE CONDROITOINA MODIFICADO

Numerous investigations are dedicated to the research and development of new polymer materials destined for innovation in pharmaceutical forms. The application of these technological resources has allowed the commercialization of new therapeutic systems for modified drug release. This investigation aimed to evaluate the association of modified chondroitin sulfate with an insoluble polymer, Eudragit® RS 30 D, widely available in the pharmaceutical market. Isolated films were prepared by the evaporation process using a Teflon® plate. The aqueous dispersions (4% m/v) of synthetic polymer received the addition of modified chondroitin sulfate at different ratios. The interactions of the polymer chains in the blends were physicochemically characterized by means of Fourier transform infrared spectroscopy, thermal analyses, differential scanning calorimetry, thermogravimetry and scanning electron microscopy combined with hydration and assays in alkaline pH. The results showed appropriate properties of the coating materials for solid oral forms intended for drug deliver in specific environments.