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.

Fatty acid profile of lipid-rich food consumed in Paraguay

ABSTRACT The present study aims to establish the fatty acid profile of a variety of traditional foods consumed regularly in Paraguay. Thirty-two high-lipid content foods were evaluated by gas chromatography coupled with a flame ionization detector (GC-FID). Meat and dairy products were found to present high levels of saturated fatty acids, and this led to an increase in the atherogenicity and thrombogenicity indices of these products. Among the monounsaturated acids evaluated, oleic acid (18:1n-9c) was mainly found in olives (71.7%) and chipa (62.7%), which had been industrially prepared with the addition of oleic acid. Milk-based ice cream (5.1%) and chipa guazú (3.8%) presented the highest content of trans fatty acids. The n-6/n-3 fatty acids ratio obtained for the traditional sopa Paraguaya and empanada (fried pasty) was higher than 37:1; this can be attributed to the addition of soybean and corn oils in the preparation of these foods. The data evaluated and presented in this study can contribute toward the improvement of eating habits among the Paraguayan population, as well as help combat the risk factors commonly associated with bad eating habits and chronic health issues.

RESUMEN El presente estudio tuvo como objetivo establecer los perfiles de ácidos grasos de una variedad de alimentos tradicionales que se consumen regularmente en Paraguay. Se evaluaron treinta y dos alimentos con alto contenido de lípidos mediante cromatografía de gases acoplada a detector de ionización de llama (GC-FID). Los productos cárnicos y lácteos presentaron un elevado nivel de ácidos grasos saturados, aumentando los índices de aterogenicidad y trombogenicidad. Entre los monoinsaturados, el ácido oleico (18: 1n-9c) se encuentró principalmente en aceitunas (71,7%) y chipa (62,7%), este último preparado industrialmente por adición de ácido oleico. En cuanto al contenido de ácidos grasos trans, los valores más altos se encontraron en los helados a base de leche (5,1%) y chipa guazú (3,8%). Los valores de la relación n-6 / n-3 fueron superiores a 37:1 en sopa paraguaya y empanada (frita) debido a la adición de aceite de soja y maíz utilizado en la preparación de alimentos. Los datos evaluados y presentados en este estudio pueden contribuir a la mejora de los hábitos alimentarios de la población paraguaya, así como ayudar a combatir los factores de riesgo comúnmente asociados con los malos hábitos alimentarios y los problemas crónicos de salud.