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- Author or Editor: I. Santos x
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Abstract
Optimal conditions for coupling sheep anti-T3 IgG to a solid phase are presented. We found that the optimal activation of microcrystalline cellulose was achieved with 0.15M 1,1
-carbonyldiimidazol (CDI) in acetone. We also found that using a 25 mg/cm3 anti-T3 IgG solution, in barbitone buffer 0.05M, pH 8.0, we could get a reasonable yield of coupling and a remaining solution of anti-T3 IgG (first supernatant) with a suitable concentration (
10 mg/cm3) for another coupling. The solid phase anti-T3 obtained in these two couplings present similar characteristics which make possible their use in a total T3 RIA.
Abstract
The thermogravimetric procedures applied to quality control of foods attain the global analysis of quality of the product, through the determination of quality parameters and the thermal stability of products. The kinetic parameters such as order of reaction, apparent activation energy, pre-exponential factors and the thermal decomposition rate constant were determined for the samples of corn and its derivatives by applying isothermal thermogravimetry, utilizing the Arrhenius law. This method presented excellent results as verified with the coherence and data adjustment. The rate constant values showed the expected performance from the chemical point of view.
Abstract
The babassu (Orbignya Phalerata Mart.) biodiesel has lauric esters as main constituents, resulting in high oxidative stability and low cloud and freezing points. In order to reduce these side effects, the saturated ethyl esters content was reduced by means of winterization process. The TMDSC and PDSC techniques were used to verify the thermal and oxidative stabilities of the ethyl babassu biodiesel. During the heating stage, the winterized solid phase of ethyl esters presented an endothermic transition associated to the solidification process. This behavior was not observed for the liquid winterized FAEE, confirming the efficiency of the winterization process.
Abstract
In this work, spinels with the general formula Zn2−xCoxTiO4 were synthesized by the polymeric precursor method and thermally treated at 1,000 °C. The powder precursors were characterized by TG/DTA. A decrease in the DTA peak temperature with the amount of zinc was observed. After the thermal treatment, the characterizations were performed by XRD, IR, colorimetry and UV/VIS spectroscopy. The XRD patterns of all the samples showed the presence of the spinel phase. Infrared spectroscopy showed the presence of ester complexes for Zn2TiO4 after thermal treatment at 500 °C, which disappeared after cobalt addition, indicating that organic material elimination was favored.
Abstract
Thermoanalytical, kinetic and rheological parameters of commercial edible oils were evaluated. The thermal decomposition of the oils occurred in three steps, due to polyunsaturated, monounsaturated and saturated fatty acids decomposition, respectively. According to the temperature of the beginning of the decomposition, the following stability order was observed: corn (A)>corn>sunflower (A)>rice>soybean>rapeseed (A)>olive>rapeseed>sunflower (A - artificial antioxidants). Kinetic parameters were obtained using Coats-Redfern and Madhusudanan methods and presented good correlation. According to the activation energy of the first thermal decomposition event, obtained of Coats-Redfern' method, the following stability order is proposed: sunflower>corn>rice>soybean>rapeseed>olive. In relation to rheological properties, a Newtonian behavior was observed and no degradation occurred in the temperature range studied.
Abstract
Biodiesel is a non-toxic biodegradable fuel that consists of alkyl esters produced from renewable sources, vegetal oils and animal fats, and low molecular mass alcohols, and it is a potential substitute for petroleum-derived diesel. Depending on the raw materials used, the amount of unsaturated fatty acids can vary in the biodiesel composition. Those substances are widely susceptible to oxidation processes, yielding polymeric compounds, which are harmful to the engines. Based on such difficulty, this work aims to evaluate the antioxidant activity of cashew nut shell liquid (cardanol), as additive for cotton biodiesel. The oxidative stability was investigated by the pressure differential scanning calorimetry (PDSC) and UV/Vis spectrophotometer techniques. The evaluated samples were: as-synthesized biodiesel — Bio T0, additivated and heated biodiesel — Bio A (800 ppm L−1 of hydrogenated cardanol, 150°C for 1 h), and a heated biodiesel — Bio B (150°C, 1 h). The oxidative induction time (OIT) analyses were carried out employing the constant volume operation mode (203 psi oxygen) at isothermal temperatures of 80, 85, 90, 100°C. The high pressure OIT (HPOIT) were: 7.6, 15.7, 22.7, 64.6, 124.0 min for Bio T0; 41.5, 77.0, 98.6, 106.6, 171.9 min for Bio A and 1.7, 8.2, 14.8, 28.3, 56.3 min for Bio B. The activation energy (E) values for oxidative processes were 150.0±1.6 (Bio T0), 583.8±1.5 (Bio A) and 140.6±0.1 kJ mol−1(Bio B). For all samples, the intensities of the band around 230 nm were proportional to the inverse of E, indicating small formation of hyper conjugated compounds. As observed, cardanol has improved approximately four times the cotton biodiesel oxidative stability, even after the heating process.
Abstract
The kinetics of thermal decomposition of solid In(S2CNR2)3 complexes, (R=CH3, C2H5, n-C3H7,i-C3H7, n-C4H9 and i-C4H9), has been studied using isothermal and non-isothermal thermogravimetry. Superimposed TG/DTG/DSC curves show that thermal decomposition reactions occur in the liquid phase, except for the In(S2CNMe2)3 and In(S2CNPri 2)3 compounds.
