Electrothermal atomic absorption spectrometric method for the determination of vanadium in diesel and asphaltene prepared as detergentless microemulsions

A method based on electrothermal atomic absorption spectrometry for the determination of vanadium in diesel and asphalthene fractions is proposed. In order to avoid analyte losses observed at the microgram per liter range for metal traces in organic solutions, diesel samples were stabilized as detergentless microemulsions by mixing with propan-1-ol and nitric acid solution. The solid asphaltene oil fraction was separated and dissolved in dichloromethane before mixing these solution with propan-1-ol and nitric acid solution. Wall atomization as well as no modifier was used. For diesel, aqueous analytical solutions could be used for calibration. For asphaltene, calibration was performed with analytical solutions prepared at the dichloromethane+propan-1-ol+nitric acid medium, spiked with inorganic standard solution. Linear ranges up to 200 mug l(-1) were observed, as well as limit of detection of 5 mug l(-1) and 4 mug g(-1) for diesel and asphaltene, respectively. Good recoveries were obtained for V-cyclohexanebutyrates spiked diesel samples, as well as coherent results for the asphaltene fraction of the NIST 1634c (trace elements in fuel oil) certified reference material. (C) 2004 Elsevier B.V. All rights reserved.