Simultaneous determination of Cu and Pb in fuel ethanol by graphite furnace AAS using tungsten permanent modifier with co-injection of Ir

Abstract

A method has been developed for the simultaneous determination of Cu and Pb in ethanol fuel by GF AAS using a transversely heated graphite atomizer (THGA) with W permanent modifier and co-injection of Ir. Pyrolysis and atomization temperature curves were established in fuel ethanol medium (1+1; v/v) containing 1.0% (v/v) HNO3 and spiked with 20μgL−1 Cu and Pb. For 20μL of diluted sample (10μL ethanol+10μL of 2.0 % (v/v) HNO3) dispensed into the graphite tube, analytical curves in the 5.0–25μgL−1 Cu and 10–50μgL−1 Pb ranges were established. The calculated characteristic masses were 18pg for Cu and 36pg for Pb. The limits of detection (LOD) based on integrated absorbance were 0.086μgL−1 and 2.47μgL−1 for Cu and Pb, respectively. The recoveries of the spiked samples varied from 93–103% (Cu) and 96–110% (Pb). The relative standard derivations (n=12) were ⩽0.5 Cu and ⩽0.7 Pb. Accuracy was checked for Cu and Pb determination in 10 samples purchased at local gas stations in Brazil. The found concentrations varied from 8.0 to 47μgL−1 Cu. All the analyzed samples presented Pb contents below the limit of detection of this method. These amounts are considered acceptable for the Brazilian regulatory agency for hydrated fuel ethanol.