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.
Acknowledgments
The authors thank Agencia Nacional de Petroleo (ANP) and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq, Project 460368/01‐0) for the financial support. Edson Luiz da Silva and Dilma Budziak have a research scholarship from CNPq.