Evaluation of Ir and Pd(NO3)(2)/Mg(NO3)(2) as Modifiers for the Simultaneous Determination of Mn, Ni, Pb, and Sb in Fuel Ethanol by Graphite Furnace MS

Abstract

The mixture Pd(NO3)(2)/Mg(NO3)(2) and an Ir-coated platform co-injected with Pd(NO3)(2)/Mg(NO3)(2) were evaluated as modifiers for the direct and simultaneous determination of Mn, Ni, Pb, and Sb in fuel ethanol by graphite furnace atomic absorption spectrometry. For a 20-mu L diluted sample dispensed onto the platform of graphite tube in the presence of 5 mu g Pd and 3 mu g Mg, analytical curves in the 0 - 50.0 mu g L-1 range were built up resulting in linear correlation coefficients better than 0.99. The calculated characteristic masses were 6 pg Mn, 25 pg Ni, 67 pg Pb, and 50 pg Sb. The limits of detection CLOD) were 013 mu g L-1 Mn, 1.2 mu g L-1 Ni, 1.2 mu g L-1 Pb, and 0.10 mu g L-1 Sb.Accuracy was checked after the analysis of 10 commercial fuel ethanol samples. The results were in agreement at a 95% confidence level (paired Rest) with those obtained by inductively coupled plasma mass spectrometry. The recovery of Mn, Ni, Pb, and Sb in fuel ethanol samples was within the 97-104%, 86-116%, 83-119%, and 92-104% intervals, respectively, and the relative standard deviation (n = 12) was typically 4%, 7%, 6%, and 5%, respectively. The useful lifetime of the THGA atomizer was around 300 firings.