Determination of Trace Metals in Fuel Alcohol by FAAS Using Nb₂O₅–SiO₂ as Sorbent Material in a Flow Injection On‐Line Preconcentration System

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.

Keywords:

• FAAS
• On‐line preconcentration
• Fuel alcohol
• Nb₂O₅–SiO₂

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.