Abstract
Different calibration approaches and modifiers were tested for Cd, Pb and Tl determination in biodiesel by graphite furnace atomic absorption spectrometry (GF AAS). Microemulsions were prepared by mixing 2 g of biodiesel, 1 mL of a 10% (v/v) nitric acid aqueous solution and n-propanol to a 10 mL final volume. Pyrolysis temperatures of 600 °C for Cd and Tl with Pd as permanent modifier, and 800 °C for Pb with Ru as permanent modifier were used. Atomization temperatures were also optimized. Calibration solution prepared in aqueous medium did not correct non-spectral interferences, but matrix matching calibration using base oil led to accurate results with recoveries from 80 to 116%. The RSD values were lower than 8% for Cd and Pb and the LOD values were 0.5 ng g-1 for Cd, 6 ng g-1 for Pb and 1 ng g-1 for Tl. The obtained results using the analyte additions method or by matrix matching calibration were in agreement, confirming the accuracy of the proposed procedure. Organometallic standards were not required and different samples were analyzed.
Highlights
In recent years, biodiesel has been considered an important fuel, because of its advantages in relation to environmental pollution, and because itVol 21, No 4, 2010 the production and use of biodiesel from different raw materials.Biodiesel is mainly obtained by the alcoholic transesterification of vegetable oil or vegetable or animal fat, generally, in the presence of a catalyst.[6,7,8] It is produced from renewable biomass with a high potential for reduction of the emissions in the environment, being considered neutral in relation to carbon emission, since all carbon liberated in the combustion is captured by the plantations used in the production of the fuel.[9]
A mixture of 2% (v/v) biodiesel in diesel is already being commercialized and is expected to reach the 5% (v/v) fraction in 2013.12 According to Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP), resolution no 07 from 03/19/2008, biodiesel B100 is defined as the fuel composed of alkyl esters of long chain fatty acids, produced from vegetable oils or animal fat and biodiesel B2 is the commercial fuel mixture containing 98% (v/v) of diesel oil and 2% (v/v) of biodiesel B 100.13
Pd as permanent modifier produced a better defined peak shape. Considering this and the fact that the permanent modifier is more practical, since the modifier does not need to be pipetted into the tube before each determination, a Pd layer deposited on the graphite tube was selected as the permanent modifier for Cd
Summary
Biodiesel has been considered an important fuel, because of its advantages in relation to environmental pollution, and because itVol 21, No 4, 2010 the production and use of biodiesel from different raw materials.Biodiesel is mainly obtained by the alcoholic transesterification of vegetable oil or vegetable or animal fat, generally, in the presence of a catalyst.[6,7,8] It is produced from renewable biomass with a high potential for reduction of the emissions in the environment, being considered neutral in relation to carbon emission, since all carbon liberated in the combustion is captured by the plantations used in the production of the fuel.[9]. The analyte additions calibration curves were obtained from monoelemental stock solutions of the analytes by proper dilution in aqueous medium, as microemulsion with base mineral oil. The calibration standards microemulsions were prepared using 2.0 g of base oil, 1.0 mL of a 10% (v/v) acid nitric aqueous solution and n-propanol to a 10 mL final volume.
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