The present work focused on the screening process of different inorganic oxides and different temperatures for the epoxidation reaction of macaw palm vegetable oil without using solvent, a promising Brazilian biomass that can substitute other vegetable oils (e.g., soybean oil) in technological applications. This oil has an iodine value of 108.48 g of I2 per 100 g being categorized as a semi-dry oil. The epoxidized vegetable oil can be applied in manifold areas in polymer science. The epoxidation reaction here presented avoided organic solvents and organic acids and aimed to produce a greener route using metal oxides or niobium phosphate as a peroxide-activating catalyst. The experimental parameters were maintained as 10 mol% of catalyst loading and a time of 24 h; however, the temperature for some catalysts was changed to improve the epoxide conversion. Experiments were measured by proton nuclear magnetic resonance (1H NMR). Experiments using titanium oxide (TiO2) as a catalyst reached a conversion greater than 84.7%, while experiments using aluminium oxide (Al2O3) or lanthanum oxide (La2O3) achieved conversions of 22.6 and 30.1%, respectively. Furthermore, it was observed that both niobium compounds instantly react with hydrogen peroxide to form peroxy derivatives. solvent e.g., eg e (e.g. applications 10848 108 48 108.4 I semidry semi dry science peroxideactivating activating 1 mol 2 h however 1H H NMR. NMR . NMR) TiO2 TiO (TiO2 847 84 7 84.7% Al2O3 AlO Al O (Al2O3 La2O3 LaO La (La2O3 226 22 6 22. 301 30 30.1% respectively Furthermore derivatives e.g. (e.g 1084 4 108. (TiO 8 84.7 Al2O (Al2O La2O (La2O 3 30.1 e.g 84. 30.

A new composite based on acetylene black (AB) and vegetable derivative polyurethane (PU) was prepared and evaluated in the determination of bisphenol A (BPA) in water samples using a differential pulse voltammetric procedure (DPV). DPV pulse amplitude of 50 mV, 10 mV s-1 scan rate and 0.10 mol L-1 phosphate buffer were selected for the analytical studies. An analytical curve was obtained with linear range of 0.1-10 µmol L-1 BPA and a limit of detection of 14.1 nmol L-1. The proposed electrode was used without modifiers and with high sensitivity and low-cost preparation in the determination of BPA in both tap and artesian well waters spiked with 0.30 µmol L-1, with relative errors of 0.81 and 1.0% and recoveries of 102 and 105%, respectively. Interferences from oxytetracycline, furosemide, catechol, methyl viologen chloride and fenitrothion could be overcome by appropriate current measuring, while diclofenac did not interfere. AB (AB PU (PU (BPA DPV. . (DPV) 5 1 s1 s s- 010 0 0.1 L1 L L- studies 0.110 0110 0.1-1 141 14 14. L1. 1. lowcost low cost 030 30 0.3 L1, 1, 081 81 0.8 1.0 105 105% respectively oxytetracycline furosemide catechol measuring interfere (DPV 01 0. 110 0.11 011 0.1- 03 3 08 8 11

Composite films are an alternative in the replacement of synthetic polymers. These films can be prepared from polysaccharides and used to store various drugs to be applied in different areas. In addition, aminoethoxyvinylglycine (AVG) is an ethylene inhibitor that prolongs shelf life of food. For this reason, this research aimed to take advantage of the brown algae Macrocystis pyrifera and Lessonia trabeculata to extract sodium alginate and produce films composed of sodium alginate/kappa-carrageenan/iota-carrageenan, which were plasticized with glycerol and polyethylene glycol 400 and loaded with aminoethoxyvinylglycine. The extracted sodium alginate was characterized by 1H and 13C nuclear magnetic resonance (NMR), size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS), thermogravimetry (TG/DTG), Fourier transform infrared (FTIR), and X-ray diffraction (XRD); and the composite films were characterized by FTIR, XRD, TG/DTG, and scanning electron microscopy (SEM). Then, the drug release kinetics were investigated using Higuchi and Korsmeyer-Peppas kinetic models. The extracted alginates obtained were of low molecular weight, and the films showed desirable properties for AVG release. Furthermore, drug release profiles revealed that AVG release is governed by Fick’s Law, and this is favored at low temperatures. In summary, sodium alginate allows the preparation of composite films, which can replace synthetic polymers to be used in the loading and releasing of drugs. areas addition (AVG food reason alginate/kappacarrageenan/iotacarrageenan, alginatekappacarrageenaniotacarrageenan alginate/kappa carrageenan/iota carrageenan, kappa carrageenan iota alginate/kappa-carrageenan/iota-carrageenan 40 H C NMR, NMR , (NMR) multiangle multi angle SECMALS, SECMALS SEC MALS (SEC-MALS) TGDTG TG/DTG TG DTG (TG/DTG) FTIR (FTIR) Xray X ray XRD (XRD) SEM. SEM . (SEM) Then KorsmeyerPeppas Korsmeyer Peppas models weight Furthermore Ficks Fick s Law temperatures summary kappacarrageenan iotacarrageenan alginate/kappacarrageenan/iotacarrageenan alginatekappa carrageenaniota 4 (NMR (SEC-MALS (TG/DTG (FTIR (XRD (SEM

A graphite-polyurethane composite electrode (GPUE) was modified by electrodeposition of copper nanoparticles (CuNP) followed by electrochemical treatment in NaOH (GPUE-CuNP), in order to prepare an amperometric sensor for the determination of cysteine (Cys). Cyclic votammograms of Cys solutions at GPUE-CuNP allowed the description of a sequence of electrochemical reactions involving Cys oxidation and Cu/Cu+ equilibrium, generating a stable Cys-Cu+ complex. The presence of these nanoparticles was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) data. Hence, the developed device was then used as a Cys amperometric flow detector in a wall-jet system, after evaluation of flow injection parameters in an undescribed approach. In this system, a limit of detection (LOD) of 4.24 µmol L-1 was obtained with an analytical frequency of 36 determinations h-1. Intra-day and inter-day reproducibility and repeatability of the modified surface was evaluated. Then the GPUE-CuNP performance was investigated in the determination of Cys content in food supplements. Interference tests were carried out with pyridoxine, ascorbic acid, tryptophan and SO4 2- ions. The main interference was attributed to the interaction of some of these substances with copper oxides.

The use of spreadsheet softwares is not widespread in Chemical Education in Brazil as a computational education tool. By its turn the Qualitative Analytical Chemistry is considered a discipline with classical and non-flexible content. Thus in this work the spreadsheet software Excel® was evaluated as a teaching tool in a Qualitative Analytical Chemistry course for calculations of concentrations of the species in equilibrium in solutions of acids. After presenting the theory involved in such calculations the students were invited to elaborate the representation of the distribution of these species in a graphical form, using the spreadsheet software. Then the teaching team evaluated the resulting graphics regarding form and contents. The graphics with conceptual and/or formal errors were returned for correction, revealing significant improvement in the second presentation in all cases. The software showed to be motivating for the content of the discipline, improving the learning interest, while it was possible to prove that even in classical disciplines it is possible to introduce new technologies to help the teaching process.

Um eletrodo compósito sólido à base de grafite e resina poliuretana modificado com um complexo de base de Schiff do tipo tetradentada simétrica, N, N'-bis(salicilideno)etilenodiamino de cobre(II) ([Cu(II)Salen)]), foi avaliado como sensor bio-inspirado, usando dopamina (DA) como sonda eletroquímica. O comportamento voltamétrico do modificador [Cu(II)Salen] foi avaliado em eletrodo de pasta de carbono modificado e um mecanismo redox foi proposto. As potencialidades analíticas do eletrodo compósito à base de grafite e resina poliuretana (GPU) modificado com [Cu(II Salen] (MGPU) foram avaliadas usando DA. O eletrodo MGPU apresentou melhores resultados quando comparado ao GPU sem modificação, exibindo efeito eletrocatalítico, o que o caracteriza como sensor bio-inspirado. O eletrodo MGPU foi aplicado na determinação de DA em formulações farmacêuticas utilizando DPV e o resultado foi comparado àquele obtido com o método oficial (cromatografia líquida de alta eficiência, HPLC), descrito na farmacopeia americana, concordando em um nível de 95% de confiança de acordo com o teste t-student.

A solid composite electrode based on graphite and polyurethane resin modified with a copper(II) complex of the symmetrical tetradentate Schiff's base type, N, N'-ethylenebis(salicylideneiminato) copper(II) ([Cu(II)Salen]), was evaluated as a bio-inspired sensor using dopamine (DA) as a model analyte. The voltammetric behavior of the modifier [Cu(II)Salen] was investigated at a modified carbon paste electrode and a redox mechanism was proposed. The analytical potentialities of the composite electrode based on graphite and polyurethane resin (GPU) modified with [Cu(II)Salen] (MGPU) were evaluated using DA as probe. MGPU presents best results when compared with GPU without modification, with electrocatalytic effect, indicating that the electrode can be characterized as a bio-inspired sensor. The MGPU electrode was applied in the determination of DA in pharmaceutical formulation using DPV and the results were compared to those obtained with the official method (high performance liquid chromatography, HPLC) as described in US Pharmacopoeia, agreeing within 95% confidence level according to student's t-test.

Um seletivo método eletroquímico foi desenvolvido para determinação individual ou simultânea de paracetamol e cafeína em tampão fosfato pH 6,0, utilizando um eletrodo compósito impresso descartável à base de grafite e poliuretana (EIGPU), em Voltametria de Pulso Diferencial (DPV). Os picos de oxidação do paracetamol e cafeína aparecem em 0,3 V e 1,3 V (vs. pseudo-Ag/AgCl), respectivamente, mostrando a possibilidade de determinação simultânea de ambos analitos utilizando o EIGPU, além da determinação individual dos mesmos. A curva analítica da determinação simultânea mostrou uma resposta linear para as duas substâncias. O paracetamol apresentou uma região linear entre 1,00 - 40,0 µmol L-1 com limite de detecção de 0,84 µmol L-1 e a região linear da cafeína foi entre 4,00 - 200 µmol L-1, com limite de detecção de 1,6 µmol L-1. O método proposto foi aplicado na determinação simultânea de paracetamol e cafeína em três formulações farmacêuticas, com resultados que concordaram com HPLC ao nível de confiança de 95% (Teste t-Student).

A selective electrochemical method was developed for the individual or simultaneous determination of acetaminophen and caffeine in phosphate buffer pH 6.0 on graphite and polyurethane screen-printed composite electrode (EIGPU) using Differential Pulse Voltammetry (DPV). The oxidation peaks of acetaminophen and the caffeine appeared at 0.3 V and 1.3 V(vs. pseudo-Ag/AgCl), respectively, showing the possibility of simultaneous determination of both analytes, at the EIGPU, besides the individual determination. Analytical curves for the simultaneous determination showed a linear response for both compounds. The acetaminophen presented a linear region in the concentration range 1.00 - 40.0 µmol L-1 with detection limit of 0.84 µmol L-1, and the caffeine presented a linear region, in the concentration range 4.00 - 200 µmol L-1 with detection limit of 1.6 µmol L-1. The proposed method was applied in the simultaneous determination of acetaminophen and caffeine in three pharmaceutical formulations, with results similar to those obtained using a HPLC method, at 95% confidence level (Student t-Test).

A determinação de triptofano usando voltametria de varredura rápida com um ultramicroeletrodo de fibra de carbono (CF-UME) é descrita. O eletrodo CF-UME foi submetido a um pré-tratamento eletroquímico. Parâmetros tais como número de aquisição de ciclos, velocidade de varredura, intervalo de potencial e pré-tratamento eletroquímico da superfície foram otimizados. Sob condições ideais, três curvas analíticas foram obtidas para o triptofano (entre 30 e 300 µmol L-1) usando três diferentes CF-UME pré-tratados através de um procedimento de tratamento eletroquímico otimizado. Observou-se uma dependência na sensibilidade e concentração do triptofano com o raio do eletrodo, com limites de detecção entre 16,7 e 22,7 µmol L-1. O método foi aplicado na determinação de triptofano em amostras comerciais com erros entre -0,99 e +13,2% em relação a um método comparativo

Tryptophan determination using a fast-scan voltammetric method at carbon fiber ultramicroelectrodes (CF-UME) is described. CF-UME electrode was submitted to electrochemical pretreatment. Parameters such as number of acquisition cycles, scan rate, potential interval and electrochemical surface pretreatment were optimized. Under optimized conditions, three analytical curves were obtained for tryptophan (between 30 and 300 µmol L-1) using three different CF-UMEs pretreated by means of an optimized electrochemical treatment procedure. It was observed a dependence on the sensitivity and tryptophan concentration linear range with the radius of the electrode, with limits of detection between 16.7 and 22.7 µmol L-1. The method was applied in the determination of tryptophan in commercial samples, with errors between -0.99 and +13.2% in relation to a comparative method.

O eletrodo compósito grafite-poliuretana foi avaliado na determinação de tetraciclina (TC) em amostras de água natural. Utilizando voltametria de pulso diferencial (DPV), uma resposta linear foi observada no intervalo de 4,00-40,0 µmol L-1 com limite de detecção de 2,80 µmol L-1, sem necessidade de renovação da superfície entre medidas sucessivas. Durante determinação de tetraciclina em amostras de água, foram obtidas recuperações entre 92,6 e 100%. Os resultados para determinação de TC em amostras de água após a etapa de pré-concentração concordam com valor adicionado em um nível de confiança de 95% de acordo com o teste t-student.

A bare graphite-polyurethane composite was evaluated in the tetracycline (TC) determination in natural water samples. Using differential pulse voltammetry (DPV), a linear response was observed in the range of 4.00-40.0 µmol L-1 with limit of detection of 2.80 µmol L-1, without the need of surface renewing between successive runs. During the tetracycline determination in water samples, recoveries between 92.6 and 100% were found. The results for TC determination in water samples after a pre-concentration stage agreed with spiked value at a 95% confidence level according to student t-test.

A possibilidade de determinação eletroanalítica de cafeína com ultramicroeletrodo de fibra de carbono (CF-UME), utilizando voltametria de varredura rápida, foi avaliada. Os CF-UMEs foram submetidos a pré-tratamentos eletroquímicos. Parâmetros como o número de ciclos para cálculo da média, velocidade de varredura, intervalo de potencial e o tipo de pré-tratamento superficial foram otimizados. Sob condições otimizadas, foi possível alcançar intervalo linear de resposta entre 10,0 e 200 μmol L-1, obtendo limites de detecção de 3,33 μmol L-1. O método foi aplicado à determinação de cafeína em amostras comerciais de fármacos, com erros entre 1,0 e 3,5% em relação ao valor do rótulo e valores de adição e recuperação de 97-114%.

Caffeine determination using a fast-scan voltammetric procedure at a carbon fiber ultramicroelectrode (CF-UME) is described. The CF-UME was submitted to electrochemical pretreatment. Parameters such as number of acquisition cycles, scan rate, potential window, and the electrochemical surface pretreatment were optimized. Using the optimized conditions, it was possible to achieve a LDR from 10.0 up to 200 μmol L-1, with a LOD of 3.33 μmol L-1. The method has been applied in the determination of caffeine in commercial samples, with errors of 1.0-3.5% in relation to the label values and recoveries of 97-114% within the linear range.

The use of thermoanalytical data in sample preparation is described as a tool to catch the students' attention to some details that can simplify both the analysis and the analytical procedure. In this case, the thermal decomposition of eggshells was first investigated by thermogravimetry (TGA). Although the classical procedures suggest long exposure to high temperatures, the TGA data showed that the decomposition of organic matter takes place immediately when the sample is heated up to 800 °C under air atmosphere. After decomposition, the calcium content was determined by flame atomic emission photometry and compared with the results obtained using classical volumetric titration with EDTA.

Diversas estratégias para preparo de amostra, determinação e fracionamento, tais como espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite (GF AAS) e espectrometria de emissão óptica com plasma acoplado indutivamente com configuração axial (ICP OES), foram empregadas para o fracionamento de bário em Castanha-do-Pará. Esse alimento é amplamente apreciado tanto pelo valor nutricional, quanto pelo sabor agradável. A análise química de Castanha-do-Pará não é trivial devido à matriz complexa. O fracionamento de bário em Castanha-do-Pará foi estudado devido à toxicidade desse elemento e a correlação entre a forma química e a absorção. Os teores totais de bário nas amostras de Castanha-do-Pará variaram entre 860 e 2084 mg kg-1. Extrações sequenciais foram feitas com base na solubilidade em diferentes meios e composição química envolvendo lipídios, proteínas e compostos de baixa massa molecular (LMW). Teores mais elevados de bário foram determinados nas frações LMW e insolúvel em água que variaram entre 778-1606 e 551-1520 mg kg-1, respectivamente. Esses resultados indicaram a indisponibilidade de bário presente nesse alimento ao organismo humano. Baseando-se nos teores de bário e enxofre nas diferentes frações e em cálculos estequiométricos para as possíveis reações envolvidas pode-se inferir que bário se encontra principalmente na forma de BaSO4. Experimentos termogravimétricos também confirmaram essa suposição.

Several sample preparation strategies were employed for determination and fractionation of barium in Brazil nuts using measurements by graphite furnace atomic absorption spectrometry (GF AAS) and inductively coupled plasma optical emission spectrometry with axial view (ICP OES). This food is widely consumed because of its nutritional value and good taste. The chemical analysis of Brazil nuts is not trivial due to their complex matrix. The fractionation of barium in Brazil nuts was studied owing to the toxicity of this element and the strong correlation between chemical form and absorption. Total concentrations of barium varied from 860 to 2084 mg kg-1. Sequential extractions were performed based on solubility in different media and also according to lipids, proteins and low molecular weight fractions (LMW). The greatest contents of barium were determined in the LMW and in the water insoluble fractions with concentrations in the range 778 to 1606 and 551 to 1520 mg kg-1, respectively. Based on these results it can be inferred that Ba is not absorbed when Brazil nuts are ingested. Considering both the contents of barium and sulfur in different fractions and stoichiometric calculations it was also possible to assume that barium occurs mainly in the BaSO4 form. The presence of this chemical form was also confirmed by thermogravimetric measurements.

O uso de um eletrodo compósito à base de grafite de borracha de silicone (GSR) na determinação de rutina, (vitamina P), por voltametria de pulso diferencial, é descrito. Voltamogramas cíclicos da rutina apresentaram um par de picos de oxidação/redução no GSR em 0,411 e 0,390 V (vs. ECS), respectivamente, em solução tampão Britton-Robinson (B-R) pH 4,0. Em voltametria de pulso diferencial (DPV), após a otimização das condições, o pico de oxidação em 0,370 V (vs. ECS) foi usado na determinação quantitativa de rutina. Neste caso, um intervalo linear entre 5,0-50,0×10-8 mol L-1 foi observado com um limite de detecção de 1,8×10-8 mol L-1. Recuperações de 94 a 113% foram observadas. A superfície do eletrodo foi renovada por polimento, com uma repetibilidade de 1,09 ± 0,06 µA (n = 10) para a corrente de pico. A rutina foi determinada em uma formulação farmacêutica e os resultados concordaram com aqueles obtidos de um método oficial com 95% de confiança.

The possibility of using a graphite silicone-rubber composite electrode (GSR) in a differential pulse voltammetric(DPV) procedure for rutin (vitamin P) determination is described. Cyclic voltammograms of rutin presented a reversible pair of oxidation/reduction peaks respectively at 0.411 and 0.390 V (vs. SCE) at the GSR surface in Britton-Robinson(B-R) buffer solution pH 4.0. In DPV after optimization of conditions, an oxidation peak at 0.370 V (vs. SCE) was used to quantitative determination of rutin in B-R buffer solution pH 4.0. In this case a linear dynamic range of 5.0×10-8 to 50.0×10-8 mol L-1 was observed with a detection limit of 1.8×10-8 mol L-1 for the analyte. Recoveries from 94 to 113% were observed. The electrode surface was renewed by polishing after each determination, with a repeatability of 1.09 ± 0.06 µA (n = 10) peak current. Rutin was determined in a pharmaceutical formulation using the proposed electrode and the results agreed with those from an official method within 95% confidence level.

O desempenho do eletrodo de pasta de carbono (EPC) modificado com a sílica SBA-15 nanoestruturada organofuncionalizada com benzotiazol-2-tiol na determinação de íons Cd(II) em águas naturais é descrito, baseado no processo de DPASV. O Cd(II) apresentou um pico de oxidação por volta de -0,85 V (vs. ECS) em tampão fosfato (pH 3,0). Os melhores resultados obtidos foram com as seguintes condições otimizadas: amplitude de pulso 100 mV, 2 min de tempo de acumulação, velocidade de varredura 10 mV s-1 em solução tampão fosfato pH 3,0. Usando tais parâmetros observou-se uma resposta linear para o Cd(II) no intervalo de 1,00 a 10,0 <FONT FACE=Symbol>´</FONT> 10-6 mol L-1 com limite de detecção de 4,5 <FONT FACE=Symbol>´</FONT> 10-7 mol L-1. Cd(II) foi adicionado em amostras de águas naturais e determinado com recuperação média de 96,4% em concentrações da ordem de 10-6 mol L-1.

The performance of a carbon paste electrode (CPE) modified with SBA-15 nanostructured silica organofunctionalised with 2-benzothiazolethiol in the determination of Cd(II) ions in natural water is described, based in a DPASV procedure. The Cd(II) oxidation peak was observed around -0.85 V (vs. SCE) in phosphate buffer (pH 3.0). The best results were obtained under the following optimised conditions: 100 mV pulse amplitude, 2 min accumulation time, 10 mV s-1 scan rate in phosphate buffer pH 3.0. Using such parameters a linear dynamic range from 1.00 to 10.0 <FONT FACE=Symbol>´</FONT> 10-6 mol L-1 Cd(II) was observed with limit of detection 4.5 <FONT FACE=Symbol>´</FONT> 10-7 mol L-1. Cd(II) spiked in a natural water sample was determined with 96.4% mean recovery at µmol L-1 level. The results indicate that this electrode is sensitive for determination of Cd(II). Interference of some divalent cations were also evaluated.

Estudos termogravimétricos e calorimétricos exploratórios diferenciais de hexametilenoditiocarbamatos de níquel(II), cobre(II), zinco(II) e cádmio(II) foram realizados sob atmosferas dinâmicas de ar e nitrogênio, para avaliar as etapas e os produtos de decomposição térmica. Esses produtos, quando cristalinos, foram caracterizados por difratometria de raios X, sendo predominantemente constituídos por sulfetos e óxidos metálicos sob N2 e ar, respectivamente. Usando espectrofotometria na região do ultravioleta, também foram determinados o pKa = 3,6 ± 0,2 para o ácido hexametilenoditiocarbâmico em força iônica igual a 0,50 mol dm-3 (KCl) a 25,0 °C e os parâmetros cinéticos de decomposição em diferentes valores de pH (k lim = 2,21 x 10-2 s-1 e t½ lim = 156 s).

Thermogravimetric and differential scanning calorimetric investigation of the thermal behavior of nickel(II), copper(II), zinc(II) and cadmium(II) hexamethylenedithiocarbamates were performed under nitrogen and air atmospheres in order to investigate the steps and products of thermal decomposition. When obtained in a crystalline form, the decomposition products were identified by their X-ray diffraction patterns. Metal sulfides and oxides were the major residues under nitrogen and air atmospheres, respectively. Spectrophotometric measurements in the ultraviolet region were used to estimate the pKa = 3.6 ± 0.2 for the haxamethylenedithiocarbamic acid at 0.50 mol dm-3 ionic strength (KCl) at 25.0 °C and the kinetic parameters of decomposition at different pH values (k lim = 2.21 x 10-2 s-1 and t½ lim = 156 s).