Determination of trace metals in fuel alcohol by FAAS using Nb2O5-SiO2 as sorbent material in a flow injection on-line preconcentration system

This paper describes an on-line preconcentration system for the determination of copper(II), cadmium(II), cobalt(II), and zinc(II) in samples of fuel alcohol. The analytes were enriched in a minicolumn containing with silica gel chemically modified with niobium(V) oxide (Nb2O5-SiO2). The metals were desorbed from the minicolumn with a solution of nitric acid and determined on-line by flame atomic absorption spectrometry (FAAS). Enrichment factors for copper(II), cadmium(II), cobalt(II), and zinc(II) were 21.3, 23.1, 16.6, and 27.5, respectively, using a preconcentration time of 2 min. Detection limits for copper(II), cadmium(II), cobalt(II), and zinc(II) were 1.4, 0.2, 1.4, and 1.0 mug L-1, respectively. Method precision was evaluated by analyzing an alcoholic solution containing 30 mug L-1 of Cu(II), 15 mug L-1 of Cd(II), 45 mug L-1 of Co(II), and 15 mug L-1 of Zn(II), and their respective relative standard deviation (RSD) were 1.3%, 4.2%, 1.7%, and 1.7% (n = 7). The accuracy of the method was assessed by testing analyte recovery in the fuel alcohol samples.