Novel extraction induced by microemulsion breaking for Cu, Ni, Pb and V determination in ethanol-containing gasoline by graphite furnace atomic absorption spectrometry

摘要

This paper describes a detailed study on the determination of Cu, Ni, Pb, and V in ethanol-containing Brazilian commercial gasoline by graphite furnace atomic absorption spectrometry (GF AAS) after application of the novel extraction induced by microemulsion breaking (EIMB) for the extraction of analytes from the sample. EIMB is based on the formation and breaking of microemulsions with the sample and an extractant acid solution (typically HNO3 solution) in the presence of a dispersant agent (typically a short-chain alcohol). After microemulsion breaking, the following two phases are formed: (i) a top phase containing the remaining gasoline and (ii) a bottom phase containing the extracted metals in a medium composed of water, the dispersant agent, and ethanol, which was already present in the Brazilian gasoline. The bottom phase is collected and used for metal quantification by GF AAS. Several parameters that could affect the performance of the method were evaluated. Under optimized conditions, the microemulsion was prepared by mixing 4.6 mL of the sample with 0.35 mL of 1-propanol and 0.05 mL of a 3.5 mol L-1 HNO3 solution. The microemulsion was shaken for 5 min at 110 rpm to enhance the extraction and was then disrupted by the addition of 0.40 mL of a 3.5 mol L-1 HNO3 solution. The bottom phase formed under these conditions was taken for metal determination by GF AAS. The limits of detection of the method for Cu, Ni, Pb and were 0.7, 0.1, 0.8 and 1.6 mu g L-1, respectively. The method was applied in the analysis of five Brazilian gasoline samples, which presented concentrations of Cu, Ni, Pb, and V in the range of 7.1-63 mu g L-1, 1.6-2.8 mu g L-1, 5.3-9.7 mu g L-1, and 24-44 mu g L-1, respectively. Recovery tests were performed to assess the accuracy of the proposed method, with observed satisfactory recovery percentages of 87-116%.