Batch-injection stripping voltammetry of zinc at a gold electrode: application for fuel bioethanol analysis

• Anodic stripping voltammetry of Zn at gold electrode for fuel bioethanol analysis.
• Portable batch injection analysis coupled to anodic stripping voltammetry.
• Efficient gold electrode cleaning between measurements of Zn in fuel bioethanol.
• Adequate sensitivity, recovery values and no sample treatment required.
• On-site determination of metals on fuel bioethanol using mercury-free electrode.

This article reports for the first time the anodic stripping voltammetric (ASV) detection of Zn at a gold disk macroelectrode for the analysis of fuel bioethanol. The accurate determination of Zn at gold macroelectrodes was only possible with the aid of batch injection analysis (BIA) associated with ASV; this statement was proved by comparison with a conventional three-electrode system. The BIA system consisted of injections of bioethanol sample plugs (up to 1 mL) at 28.3 μL s−1 directly onto a working (gold disc) electrode immersed in 0.04 mol L−1 Britton-Robinson buffer (pH 7) solution through an electronic micropipette and the Zn deposition occurs simultaneously. The highest analytical response for Zn was obtained for a deposition time of 90 s, which indicated that Zn deposition also occurred from diffusion after the injection ended. The proposed method presented a low detection limit (5 μg L−1), a linear range between 25 and 250 μg L−1, and adequate recovery values (88–104%) for spiked samples, but no sample treatment was required. Such remarkable analytical features associated with the portability characteristics of BIA demonstrated the promising application of the proposed method for routine and on-site determination of metals in fuel bioethanol.

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