A simple, rapid and low cost reversed-phase dispersive liquid-liquid microextraction for the determination of Na, K, Ca and Mg in biodiesel.

In this work a method based on reversed-phase dispersive liquid-liquid microextraction (RP-DLLME) as sample preparation for the extraction and preconcentration of Na, K, Ca and Mg in biodiesel samples was developed. The analytes determination was performed by flame atomic absorption spectrometry (FAAS), operating in emission mode for Na and K and in absorption mode for Ca and Mg. The extraction/preconcentration step of the analytes was performed by using a mixture of dispersant and extractant solvents (isopropanol and HNO3, respectively) and the aqueous phase containing the analytes was separated by centrifugation. Some parameters such as sample mass, type and volume of dispersant and extractant solutions, HNO3 concentration (extraction solution), use of ultrasound, centrifugation time and temperature were evaluated. During the optimization of RP-DLLME, biodiesel samples were spiked with a multi-element biodiesel B100 (Conostan®) with final concentration of 1.0 µg g-1 of the analytes. Analytes determination was performed by FAAS using external calibration with aqueous reference solutions. The limits of quantification (LOQ) for Na, K, Ca and Mg were 0.04; 0.02; 0.05 and 0.08 µg kg respectively. The accuracy was evaluated by recovery tests, which ranged from 93.9% to 108.1%, with relative standard deviation lower than 3% for all analytes. Then, the proposed method was applied for analytes determination in five biodiesel samples produced from different raw materials. Comparing to conventional methods for elements determination in biodiesel (e.g., dilution with organic solvent, sample digestion, etc.), RP-DLLME combined to FAAS is simple, low cost, low reagents consumption and provides LOQs values significantly below compared to the limits established in the legislation for these elements in biodiesel.

Metabolismo e distribuição do flúor em ovinos jovens tratados cronicamente com fluoreto de sódio / Metabolism and distribution of fluor in lambs chronically treated with sodium fluoride

Este estudo teve por objetivo avaliar o metabolismo do flúor (F) em ovinos. Para tanto, utilizaram-se 12 animais, com cinco meses de idade, os quais receberam como dieta base 3 por cento do peso vivo de feno de alfafa e água ad libitum. Os animais foram divididos e constituíram um grupo Controle, que recebeu apenas sal iodado (5g de NaCl/animal + 0,2mg I/kg matéria seca) e, um grupo Tratado, que recebeu sal iodado adicionado de fluoreto de sódio (4,7mg F/kg de peso corporal). Esses sais foram administrados via sonda oro-esofágica, diariamente por um período de 150 dias. Para análise de F, coletaram-se amostras de sangue, urina e fezes e, ao fim do período experimental, após a eutanásia dos animais, coletou-se a glândula pineal e amostras de osso. Também nesta ocasião, coletou-se uma amostra de rim para exame histopatológico. Analisando-se os teores séricos, urinários e ósseos de F, verificou-se que foram significativamente superiores nos animais Tratados em relação aos Controles. Quanto ao F contido na glândula pineal, não houve diferença significativa entre os grupos. Na análise histológica do rim, não foram observadas alterações. Conclui-se que a administração crônica de flúor induz ao acúmulo desse elemento nos ossos, mesmo havendo um alto teor de cálcio na alimentação e esse acúmulo parece não ser nocivo aos animais. Em ovinos, a capacidade orgânica de acúmulo ósseo e excreção urinária do flúor é diferente de outras espécies animais.

The objective of the present study was to evaluate fluorine metabolism in growing lambs. Twelve 5-month-old male lambs maintained on alfalfa hay (3 percent BW) and non-fluorinated water ad libitum were used. Animals were allocated into Control, receiving 5g NaCl/animal/day + 0.2mg I/kg dry matter) and Treated group, receiving the same treatment plus sodium fluoride (4.7mg F/kg body weight). Mineral treatment was given by gavage, daily for 150 days. Blood, urine and fecal samples were collected during and the end of the experiment. At the end of treatment period animals were euthanized and kidney, pineal and bone samples were collected. Urine F was higher in treated animals throughout the experiment. Bone F levels were also increased in treated animals; pineal F content however, was not different between groups. Kidney histology revealed no differences. It is concluded that chronic F administration induces accumulation of the element in the skeleton. However such fact appears not to be detrimental to animals. Rates of F accumulation in bone and urine excretion obtained in other species can not be used in growing lambs.