ABSTRACT:Lead is one of the most dangerous contaminants which has been released to the environment during many years by anthropogenic activities. Adsorption of Pb 2+ on vermicompost was studied at 11°C, 30 °C and 50 °C by using Langmuir and Freundlich models, that adequately described the adsorption process, with maximum adsorption capacities were 116.3; 113.6 and 123.5 µg/g for each temperature. The differences in FTIR (Fourier Transform Infrared Spectrometer) spectra of vermicompost at pH 3,8 and pH 7.0 in the region from 1800 to 1300 cm -1 were interpreted on the basis of carboxyl acid ionization that reduce band intensity around 1725 cm -1 producing signals at 1550 cm -1 (υ a ) and 1390 cm -1 (υ a ) of carboxylate groups. Similar changes were detected at pH 3.8 when ionic lead was present suggesting that heavy metal complexation occurs throughout a cationic exchange reaction. Vermicompost was applied to a soil where white bean plants were planted. After irrigation with lead nitrate solutions the uptake of lead was reduced to 81 % in leaves and stem, while the reduction in the roots was around 50 %. The highest accumulation of lead was found in the roots and the translocations seems to be limited by the presence off vermicompost in the soil.
A flow injection analysis (FIA) methodology has been developed for the estimation of the radical scavenging activity (RSA) of edible oils as a measure of their antioxidant activity. The RSA determination was based on the inhibition of the luminol chemiluminescence (CL) induced by the Fenton's reagent in a microemuslion (n-hexane in water). At the optimum operational conditions, the RSA of gallic acid and buthylhydroxylanisol, usually employed as antioxidant in vegetable oils, as well as corn, sunflower, olive, soybean and sesame oils, were measured in terms of the IC 50 (the concentration required to reduce in 50% the CL emission measured in the absence of antioxidants in the organic phase). For this purpose, the percentage of the CL inhibition (%Inh) against the sample concentration was plotting. Virgin oils of sesame and olive showed the greatest RSA, which was associated to their elevated concentration of natural antioxidants, such as phenols, tocopherols and lignans. The refined soybean oil also has an important antioxidant activity due to the addition of synthetic antioxidants after the refining process, while the lower RSA activities were found in the refined corn and sunflower oils. The results of the proposed method showed good agreement with those obtained by the DPPH test, which suggests that it could be used as a complementary method for the evaluation of hydrophobic substances with antioxidant properties.
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