The development of a method for the determination of trace elements in fuel alcohol by ETV-ICP-MS using isotope dilution calibration

A method for the determination of Ag, Cd, Cu, Pb and Tl in fuel alcohol by isotope dilution electrothermal vaporization inductively coupled plasma mass spectrometry (ID ETV-ICP-MS) is proposed. The analytes were separated in two groups: Ag and Cu were determined without modifier and Cd, Pb and Tl with the use of Pd as chemical modifier. The employed ETV operational conditions were pyrolysis temperature of 800 degrees C for Cd, Pb and Tl and of 900 degrees C for Ag and Cu and vaporization temperature of 2400 degrees C for both groups. Seven common, one with additive and one anhydrous fuel ethanol samples were analyzed. The spiked and reference isotopes were, respectively, Ag-109 and Ag-107, Cd-112 and Cd-111, Cu-63 and Cu-65, Pb-206 and Pb-208 and Tl-203 and Tl-205. The added amounts of the enriched isotope material were the same for all samples: 4.6 ng of Ag-109, 5 ng of Cd-112, 21.1 ng of Cu-63, 9 ng of Pb-206 and 0.21 ng of Tl-203. The blank was bi-distilled ethanol, acidified with 0.3% (v/v) nitric acid, as the samples. The limits of detection (LODs) were calculated as three times the standard deviation of the concentrations in the blank (n = 10) and were, in mu g L-1, for Ag: 0.02, for Cd: 0.08, for Cu: 0.1, for Pb: 0.05 and for Tl: 0.001. The obtained concentrations in the samples were in agreement with those obtained by external calibration (EC), according to the paired t-test. The isotope dilution (ID) showed to be a robust, fast and simple calibration technique for the analysis of fuel ethanol. (c) 2005 Elsevier B.V. All rights reserved.