Biodiesel derived from microalgae: advances and perspectives

Microalgae are a promising source of raw material for biodiesel production. This review discusses the latest developments related to the application of microalgae biomass for biodiesel production. Characterization of fatty acid of microalgae and comparisons with other sources of raw materials and processes are presented. Furthermore, technological perspectives and approaches for growing microalgae in photobioreactors, microalgal oil extraction techniques, and procedures for synthesizing biodiesel are reviewed

Introduction to celebrating Latin American talent in chemistry

In celebration of the excellence and breadth of Latin American research achievements across the chemical sciences, we are delighted to present an introduction to the themed collection, Celebrating Latin American talent in chemistry. [Image: see text

Aplicação de ondas ultrassônicas e seus efeitos nas propriedades tecnológicas de arroz germinado

O objetivo do trabalho foi aplicar ondas ultrassônicas em arroz, antes e depois do encharcamento, para avaliar a taxa de germinação, bem como a fraturabilidade e tempo de cocção dos grãos

Determinação de cloro e enxofre em farinhas de arroz.

O objetivo do estudo foi determinar as concentrações de cloro e enxofre em quatro variedades de arroz “integrais” e “comerciais” com diferentes colorações de pericarpo (parboilizado, branco polido, vermelho e negro) por meio da IC, após o preparo das amostras por MIC

Desenvolvimento de método analítico para a determinação de flúor em folhas de chás in natura

Com base nos resultados obtidos, pode-se concluir que o método desenvolvido foi eficiente para a determinação de flúor em chás. Os digeridos obtidos utilizando o método de MIC foram compatíveis com diferentes técnicas de determinação (ISE e IC), demonstrando a versatilidade deste método de preparo de amostra

Talanta

Texto completo: acesso restrito. p. 308–314The advantages and shortcomings of focused microwave-induced combustion (FMIC) for digestion of plant samples were studied. The effects of sample mass, absorbing solution, oxygen gas flow-rate, and time of reflux step on recoveries of major, minor and trace metals were systematically evaluated. Afterwards, Al, Ba, Ca, Co, Cr, Cu, Mg, Mn, Ni, Sr, V, and Zn were determined by inductively coupled plasma optical emission spectrometry (ICP OES) and by inductively coupled plasma mass spectrometry (ICP-MS). The main advantages of FMIC when compared to microwave-assisted wet digestion (MAWD) and focused-microwave-assisted wet digestion (FMAWD) are the possibility to digest larger masses of samples (up to 3 g) using shorter heating times and diluted nitric acid solution for absorbing all analytes. Using the selected experimental conditions for FMIC, residual carbon content was lower than 0.7% for all samples and relative standard deviation (RSD) varied from 1.5 to 14.1%. Certified reference materials (NIST 1515 apple leaves and NIST 1547 peach leaves) were used for checking accuracy and determined values for all metals were in agreement with certified values at a 95% confidence level. No statistical difference (ANOVA, 95% of confidence level) was observed for results obtained by FMIC, FMAWD, and MAWD. Limits of detection were lower when using FMIC in the range of 0.02–0.15 μg g−1 for ICP OES and 0.001–0.01 μg g−1 for ICP-MS, which were about 3 and 6 times lower than the values obtained by FMAWD and MAWD, respectively. It is important to point out that FMIC was a suitable sample preparation method for major, minor and trace metals by both determination techniques (ICP OES and ICP-MS). Additionally, since it allows lower LODs (because up to 3 g of sample can be digested) and diluted acid solutions are used (without any further dilution), the use of ICP-MS is not mandatory

Analytical Chemistry

p. 2155–2160A procedure for sample digestion based on focused microwave-induced combustion (FMIC) is proposed. This system was developed using a commercial focused microwave oven with a lab-made quartz sample holder and a modified glass vessel. Oxygen flow was used to start and support the combustion. A botanical sample was used to evaluate the operational conditions for further Al, Ba, Ca,Fe, Mg, Mn, Sr, and Zn determination by inductively coupled plasma optical emission spectrometry. Pelletized samples were positioned on the quartz holder, and 50 μL of 6 mol L-1 NH4NO3 solution was added as igniter. Combustion was completed in less than 2 min, and the temperature was higher than 950 °C. The use of a reflux step, the position of sample holder inside the vessel, sample mass, ignition and combustion time, oxygen flow rate, and condenser type were evaluated. Results were compared with those obtained by focused microwave-assisted wet digestion and by high pressure microwave-assisted wet digestion. Agreement of 95-103% was obtained for certified reference materials digested by FMIC (reflux step with 10 mL of 4 mol L-1 HNO3). With the proposed procedure, a complete sample decomposition (residual carbon content lower than 0.5%) was achieved with low consumption of reagents as only 10 mL of diluted nitric acid was necessary. Low relative standard deviation (lower than 3.8%) was observed and high amount of sample (up to 1500 mg) could be digested that allowed lower limits of detection

Bioaccumulation and oxidative stress parameters in silver catfish (Rhamdia quelen) exposed to different thorium concentrations

The objective of this study was to evaluate the effect of chronic thorium (Th) exposure on bioaccumulation, metabolism (through biochemical parameters of the muscle) and oxidative parameters (lipidic peroxidation levels and antioxidant enzymes in the gills and in the hepatic and muscular tissues) of silver catfish (Rhamdia quelen). Silver catfish juveniles were exposed to different waterborne Th levels (in lg L1 ): 0 (control), 25.3 ± 3.2, 80.6 ± 12.0, 242.4 ± 35.6, and 747.2 ± 59.1 for 30 d. The gills and skin were the organs that accumulated the highest Th levels. The increase in the waterborne Th concentration corresponded to a progressive increase in the Th levels in the gills and kidney. Chronic Th exposure causes alterations in the oxidative parameters of silver catfish gills, which are correlated with the Th accumulation in this organ. The levels of GST decreased in the gills of fish exposed to 747.2 lg L1 Th and SOD activity decreased in silver catfish exposed to 242.4 and 747.2 lg L1 Th. In addition, the increase in the LPO in the gills exposed to 242.4 and 747.2 lg L1 Th suggests that higher oxidative damage occurred in the gills. However, in the liver and muscle, these alterations occurred mainly in the lowest waterborne Th level. Metabolic intermediates in the muscle were altered by Th exposure, but no clear relationship was found.Fil: Kochhann, Daiani. Universidade Federal de Santa Maria.; BrasilFil: Pavanato, Maria A.. Universidade Federal de Santa Maria.; BrasilFil: Llesuy, Susana Francisca. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analítica y Fisicoquímica; ArgentinaFil: Correa, Lizelia M.. Universidade Federal de Santa Maria.; BrasilFil: Konzen Riffel, Ana P.. Universidade Federal de Santa Maria.; BrasilFil: Loro, Vania L.. Universidade Federal de Santa Maria.; BrasilFil: Mesko, Márcia F.. Universidade Estadual do Rio Grande do Sul ; Brasil. Universidade Federal de Santa Maria.; BrasilFil: Flores, Érico M.M.. Universidade Federal de Santa Maria.; BrasilFil: Dressler, Valderi L.. Universidade Federal de Santa Maria.; BrasilFil: Baldisserotto, Bernardo. Universidade Federal de Santa Maria.; Brasi