Evaluation of oxidative stability, fatty acid profile and quality physico-chemical parameters of Brazil nut, coconut and Palm oils

The aim of this study was to assess the oxidative stability (OS) of oils Brazil nuts, coconut and palm, as well as determine the quality parameters: acid value (AV), humidity, ash content, and fatty acid profile (FA). According to the results the oils of Brazil nuts, coconut and palm oil showed AV of 2.02, 2.49 and 5.92 mg KOH g-1, humidity of 0.060, 0.101 and 0.040% and ash of 0.010, 0.005 and 0.009%, respectively. Considering FA, the Brazil nut oil showed greater amount of linoleic acid (38.61%) and oleic acid (31.95%) in its composition. While in coconut oil the major amounts were lauric acid (35.22%) and myristic (17.43%) and in the palm oil, oleic acid (48.30%) and palmitic (28.67%). The OS analysis showed that there is a relationship between the FA chemical composition of each oil and oxidative stability index (OSI) that relates to the resilience capacity to lipid degradation

Elaboração, Aplicação e Avaliação de uma HQ Sobre Conteúdo de História dos Modelos Atômicos para o Ensino de Química

This article reports the use of comics as an alternative methodology in the teaching learning process of atomic theory in the first level´s classrooms of high school. The proposed methodology was efficient in several aspects such as the breaking of routine and more approach in a relation student-teacher. With respect to learning due to the interest aroused by comics, there was a more careful reading of the content covered by students, thus developing the habit of reading and textual interpretation. DOI: http://dx.doi.org/10.17807/orbital.v7i1.52

Detecção do fungicida Thiram por meio da ativação eletroquímica de eletrodos impressos de carbono

O thiram (dissulfeto de tetrametiltiuram) é um fungicida que pertence ao grupo dos dimetilditiocarbamatos e fornece proteção durante a colheita, armazenamento e transporte de grãos. Sua determinação em amostras diversas pode ser realizada por várias técnicas analíticas, como cromatografia, espectrofotometria, voltametria, dentre outras. Na voltametria, vem se destacando o uso de eletrodos impressos (SPEs), principalmente, pelo fácil manuseio destes sensores, rapidez, robustez e reprodutibilidade nas análises; baixo custo e alta sensibilidade. No presente estudo, o efeito de vários parâmetros experimentais e instrumentais para a detecção voltamétrica de Thiram envolvendo seu processo de oxidação eletroquímica foi avaliado: como a modificação química e ativação eletroquímica de eletrodos impressos de carbono (SPEs), o pH do eletrólito de suporte e a frequência de aplicação do pulso em voltametria de onda quadrada. A ativação eletroquímica dos SPEs possibilitou melhores resultados para repetibilidade e estabilidade na detecção voltamétrica de Thiram. As melhores condições para a detecção do pico de oxidação do Thiram foram obtidas com voltametria de onda quadrada (VOQ) com frequência de pulso de 70 Hz em tampão Britton-Robinson (BR) de pH 8,00 usando eletrodo impresso de carbono modificado com nanotubos de parede múltipla (SPE-MWCNT) ativado eletroquimicamente. O método desenvolvido apresentou um limite de detecção (LOD) de 4,4 × 10-8 mol L−1, com um intervalo linear de reposta de 0,15 × 10−6 a 10,0 × 10−6 mol L−1, utilizando a VOQ.

Effect of the natural antioxidant eugenol on quality preservation of commercial biodiesels produced with soybean oil or waste frying oil during storage at different temperatures

The objetive of this study was to evaluate the eugenol antioxidant efficiency on the oxidation stability of commercial biodiesel synthesized from soybean oil (SB) and wast fring oil (ORB) by determining induction period (IP) and acid number (AN) during storage at 10 °C or in accelerated oxidation test at 85 °C. For the oxidation stability evaluation, the Rancimat method (EN 14112) and AN (ASTM D664) analyses were used. The initial studies showed that the antioxidants eugenol and TBHQ when added separately increased IP values for the two types of biodiesel analyzed. During the storage at 10 °C, the IP was reduced for all samples. However, the lowest reduction percentages were for samples containing eugenol (-2.07 and -11.30% for SB and ORB, respectively). In relation to AN, the samples with the antioxidant eugenol led a greater decrease of this index, with the 10000 mg kg-1 concentration being the most efficient in the conservation of biodiesel. In the accelerated oxidation test in oven at 85 °C, pure BS presented higher susceptibility to degradation than the sample containing 10000 mg kg-1 of eugenol. In both storage studies, the eugenol natural antioxidant efficiency in the control of oxidative degradation of biodiesel becomes evident

Síntese, caracterização e estudo das propriedades de um novo complexo mononuclear contendo quercetina e íon Ga(III)

Flavonoids are one of the most important compound groups applied as medicine given their antioxidant properties, but several intrinsic properties can be improved through structural modifications to their molecules. Here, the synthesis and characterization of a new gallium (III) complex with quercetin is described. Electrochemical properties, as well as antioxidant and cytotoxic activities, were investigated and compared to the free flavonoid molecule. The mononuclear complex obtained, [Ga(C15H9O7)3].2H2O.2CH3OH.CH3CH2OH, seems more active as a DPPH radical scavenger given its lower oxidation potential compared to quercetin. The new complex cytotoxic responses have shown to be more effective than those of the free flavonoid and of lapachol used as a control

Development of an Electrochemical Methodology for the Quantification of β-estradiol in Pharmaceutical Formulation

This paper describes a simple, inexpensive, highly sensitive, and efficient electrochemical method to determine Estradiol in pharmaceutical formulations. The oxidation reaction on the electrode surface was electrochemically characterized by cyclic voltammetry (CV) and square wave voltammetry (SWV). The investigation of Estradiol at carbon paste electrode revealed a non-reversible oxidation peak at +640 mV vs. Ag/AgCl, which was used for electrochemical detection of Estradiol. The operating parameters (pH, frequency, step potential, and amplitude) were optimized in relation to the peak current intensity, and a calibration curve was set up in a concentration range of 0.059 - 2.997 mg L-1, with a detection limit of 21.85 µg L-1. After calibration curve was plotted, the developed procedure was applied to determine Estradiol in parmacheutical formulation. These results show that the proposed method can be used for Estradiol quantification in pharmaceutical formulations with high sensitivity, specificity, stability, and reproducibility, and can be applied in analytical routines in laboratories of quality control analysis in drugs. DOI: http://dx.doi.org/10.17807/orbital.v11i4.1332</p