Anderson Rodrigues Lima Caires

Oxidative Stability of Baru (Dipteryx alata Vogel) Oil Monitored by Fluorescence and Absorption Spectroscopy

Baru (Dipteryx alata Vogel) is a native fruit of the Brazilian savanna that provides a nutritive oil, which also has medicinal properties. Baru fruits were collected in central-western Brazil, and the oil was obtained by pressing the seeds. The Baru oil was heated at 110°C for 24 h, and its oxidative stability was investigated by using fluorescence and absorption spectroscopy. The data showed that both absorption and fluorescence were able to precisely monitor the oil degradation induced by the thermooxidative process. The results revealed a rapid growth of the primary compounds generation in the first 16 hours of degradation. Significant amounts of secondary compounds began to be generated after 14 hours.

Alternative binary blends and their synergistic effect on stability of soybean biodiesel

The primary antioxidant tert-butylhydroquinone (TBHQ) and an alternative additive, named 1,4-bis(ethylamino)-9,10-anthraquinone, were mixed to yield a potent blend able to be used in the field of biodiesel preservation. Physicochemical parameters such as peroxide value, total acid number, density and induction period were used to evaluate the effectiveness of the combination in stabilising soybean biodiesel during the accelerate storage period of degradation. The induction period values were also used to calculate the occurrence of synergistic effect, and it was observed a high percentage of synergism for the combined additives. The results showed that the presence of target alternative additive also enables lower the concentration of the primary antioxidant (TBHQ) in the blend. The cost-effective comparison was evaluated, and it was verified that the final cost of biodiesel can also be lowered, since the amount of additives (in the blend) required to meet the biodiesel specifications was reduced between 70 and 88%.

Fluorescence Spectroscopy as an Alternative Analytical Tool for Monitoring Biodiesel Oxidative Stability: Thermal Oxidation Effect on the Endogenous Chromophores and Fluorophores in Biodiesel

Thermal stability of biodiesel is an important quality factor and it must be precisely evaluated. Despite the existence of conventional methods, fast, accurate, and robust analytical procedures are needed and still being developed. In this study, soybean and canola biodiesels underwent degradation by heating the samples and a systematic dependence on the concentration of endogenous chromophores (conjugated dienes, trienes, and tetraenes) and fluorophores (conjugated tetraenes) was optically monitored. UV–Vis absorption and fluorescence spectra of biodiesel allowed to identify the molecules formed in the initial thermal degradation stage. Absorbance and fluorescence intensities systematically changed at thermal treatment over 100 °C. Therefore, monitoring of the degradation compounds allows to evaluate the biodiesel degradation and the evolution of the degradation compounds content. The results indicate that analytical methods based on UV–Vis absorption and fluorescence spectroscopy may be able to monitor the biodiesel degradation, providing basis for the development of simple, portable, and low-cost devices.

Fluorescence Spectroscopy Applied to Monitoring Biodiesel Degradation: Correlation with Acid Value and UV Absorption Analyses

The techniques used to monitor the quality of the biodiesel are intensely discussed in the literature, partly because of the different oil sources and their intrinsic physicochemical characteristics. This study aimed to monitor the thermal degradation of the fatty acid methyl esters of Sesamum indicum L. and Raphanus sativus L. biodiesels (SILB and RSLB, resp.). The results showed that both biodiesels present a high content of unsaturated fatty acids, ∼84% (SILB) and ∼90% (RSLB). The SILB had a high content of polyunsaturated linoleic fatty acid (18  :  2), about 49%, and the oleic monounsaturated (18  :  1), ∼34%. On the other hand, RSLB presented a considerable content of linolenic fatty acid (18  :  3), ∼11%. The biodiesel samples were thermal degraded at 110°C for 48 hours, and acid value, UV absorption, and fluorescence spectroscopy analysis were carried out. The results revealed that both absorption and fluorescence presented a correlation with acid value as a function of degradation time by monitoring absorptions at 232 and 270 nm as well as the emission at 424 nm. Although the obtained correlation is not completely linear, a direct correlation was observed in both cases, revealing that both properties can be potentially used for monitoring the biodiesel degradation.

Evaluation of Eosin-Methylene Blue as a Photosensitizer for Larval Control of Aedes aegypti by a Photodynamic Process

Aedes aegypti (Ae. aegypti) is a competent vector for transmitting important viral diseases such as yellow fever, dengue, chikungunya, and Zika. Several strategies have been applied to avoid Ae. aegypti proliferation by using environmental management, biological, and chemical approaches. However, the development of new methods for effective control of the insect vector population is still needed. Photodynamic control is an alternative way to control the vector population by using a physical approach based on the larval phototoxicity of a photosensitizer. In this context, the present study evaluated the use of eosin-methylene blue (EMB) as a new photosensitizer for photodynamic control of Ae. aegypti larval populations. The photodynamic assays were performed submitting Ae. aegypti third-instar larvae to different EMB concentrations (0.0, 0.5, 1.0, 5.0, 10.0, 50.0, and 100.0 µg mL−1) in combination of three different light doses (24.3, 48.6, and 97.2 J cm−2) under either white-light radiation from RGB LEDs or sunlight. The results demonstrated that EMB presented a rapid internalization into the larvae and was phototoxic. The photodynamic action induced 100% of larval mortality after about 40 min of sunlight irradiation even using low EMB concentration (0.5 µg mL−1). The findings reveal EMB as an effective photoactive compound to control larval populations of Ae. aegypti by photodynamic process induced by either sunlight or white-light from RGB LEDs.

Corrigendum to “Oxidative Stability of Baru (Dipteryx alata Vogel) Oil Monitored by Fluorescence and Absorption Spectroscopy”

Baru (Dipteryx alataVogel) is a native fruit of the Brazilian savanna that provides a nutritive oil, which also hasmedicinal properties. Baru fruits were collected in central-western Brazil, and the oil was obtained by pressing the seeds.The Baru oil was heated at 110C for 24 h, and its oxidative stability was investigated by using fluorescence and absorption spectroscopy. The data showed that both absorption and fluorescence were able to precisely monitor the oil degradation induced by the thermooxidative process.The results revealed a rapid growth of the primary compounds generation in the first 16 hours of degradation. Significant amounts of secondary compounds began to be generated after 14 hours.

Fluorescence Spectroscopy Applied to the Monitoring of the Production and Oxidative Degradation of Biodiesel

In this work we show that fluorescence spectroscopy is a powerful tool to monitor the production and the degradation process of biodiesel obtained from different oil sources.