Determination of Trace Metals in Fuel Alcohol by FAAS Using Nb2O5–SiO2as Sorbent Material in a Flow Injection On‐Line Preconcentration System

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Abstract
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 µg L−1, respectively. Method precision was evaluated by analyzing an alcoholic solution containing 30 µg L−1 of Cu(II), 15 µg L−1 of Cd(II), 45 µg L−1 of Co(II), and 15 µg 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.

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