Spectrochimica Acta Part B 59 (2004) 551–558 0584-8547/04/$ - see front matter  2004 Elsevier B.V. All rights reserved. doi:10.1016/j.sab.2003.12.025 Determination of Cd, Cu, Fe, Pb and Tl in gasoline as emulsion by electrothermal vaporization inductively coupled plasma mass spectrometry with analyte addition and isotope dilution calibration techniques  Tatiana D. Saint’Pierre , Lucia F. Dias , Sandra M. Maia , Adilson J. Curtius * a a,b c a, ´ Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC, Brazil a ´ Centro Federal de Educacao Tecnologica (CEFET), Ponta Grossa, PA, Brazil b ¸˜ ´ Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil c Received 13 October 2003; accepted 19 December 2003 Abstract The presence of some elements can be undesirable in gasoline, not only by the possibility of damage of the motor parts and poor performance of the fuel, but also because of the pollution caused by the release of toxic metals to the atmosphere by the combustion of the fuel. The gasoline sample preparation as emulsion is an adequate method for the sample introduction for sensitive analytical methods. In this work, external calibration with aqueous standards, analyte addition and isotope dilution calibration techniques were employed for the determination of Cd, Cu, Fe, Pb and Tl in gasoline by electrothermal vaporization inductively coupled plasma mass spectrometry. The concentrations of Cu and Fe were additionally determined by electrothermal atomic absorption spectrometry. The ETV program for the analytes in a gasoline sample emulsion was optimized and the determination was carried out without modifier at 400 8C pyrolysis and 1900 8C vaporization temperatures. In these conditions, the external calibration against aqueous standards could not be applied for the analysis of gasoline as emulsion, since the results of recovery tests were not acceptable. The determination by analyte addition or isotope dilution employing these conditions could be carried out for Cd, Cu, Pb and Tl, but not for Fe. The use of 10 mg Pd in solution as chemical modifier allowed the determination of all studied analytes together, at 800 8C pyrolysis and 2100 8C vaporization temperatures. The limits of detection for the analytes in gasoline, by analyte addition or by isotope dilution, were better than 5 mg l . The measured concentrations y1 for all analytes by analyte addition and by isotope dilution calibration techniques were mostly in agreement and the precision for both calibrations were also similar and adequate. Agreement was also found with concentration results for Fe and Cu obtained by ET AAS, without modifier.  2004 Elsevier B.V. All rights reserved. Keywords: Gasoline; Emulsion; Electrothermal vaporization inductively coupled plasma mass spectrometry; Isotope dilution; Analyte addition 1. Introduction The presence of some elements in fuels can damage the performance of the motor, by the decomposition of the fuel, formation of precipitates or by promoting the corrosion of motor parts w1,2x. Toxic elements in fuels  This paper was presented at the Colloquium Spectroscopicum Internationale XXXIII, held in Granada, Spain, 7–12 September 2003 and is published in the special issue of Spectrochimica Acta Part B, dedicated to that conference. *Corresponding author. Tel.: q55-48-3319219; fax: q55-48- 3319711. E-mail address: curtius@qmc.ufsc.br (A.J. Curtius). represent an important source of pollution, mainly in big cities and in the proximity of roads, even in low concentrations, since the consume of fuels is very high. Some elements occur in natural petrol and, conse- quently, in oils and gasoline. Others can be introduced through contact with refining and distilling equipment, storage and transportation. In addition, some elements can be added, normally in organic form, to improve some characteristics of the fuel. Since the combustion of fuels can release these elements to the atmosphere, it is very important to quantify their concentration, in order to control pollution levels w3x.