Direct Determination of Cd, Co, Cu, Fe, Mn, Na, Ni, Pb, and Zn in Ethanol Fuel by High-Resolution Continuum Source Flame Atomic Absorption Spectrometry

A method to determine nine elements (Cd, Co, Cu, Fe, Mn, Na, Ni, Pb, and Zn) in ethanol fuel using high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS) was developed. The proposed method consists of the direct analysis of samples, making use of inorganic standards for calibration and multi-element sequential determination. To evaluate the accuracy of the proposed method, the obtained results were compared to the results obtained by the following methods: (i) the standard method NBR 11331 for the determination of Cu and Fe in ethanol fuel by line source flame atomic absorption spectrometry (LS-FAAS), (ii) the standard method NBR 10422 for the determination of Na in ethanol fuel by flame photometry, and (iii) recovery tests for the other elements. Good accuracy was attained because the results obtained for Cu, Fe, and Na by the proposed method and the standard methods were not significantly different within a 95% level of confidence (Students t test) and the recovery tests for the other analytes ranged from 97 to 105%. Limits of detection of 0.006, 0.02, 0.001, 0.02, 0.003, 0.1, 0.04, 0.06, and 0.024 mg kg(-1) were obtained for Cd, Co, Cu, Fe, Mn, Na, Ni, Pb, and Zn, respectively. The relative standard deviations were in general lower than 3.0% for all analytes. The proposed method was shown to be an excellent alternative for the determination of metals in ethanol fuel, emphasizing multi-element sequential analysis, reducing the costs and analysis time, and, thus, can be recommended for routine analysis.