DOI: 10.1002/elan.201500619 Electrode Based on Nickel-containing SBA-15 for the Determination of Copper in Ethanol Biofuel Sakae Y. Neto, [a] Helmara D. C. ViØgas, [b] Joseany M. S. Almeida, [a] Eder T. G. Cavalheiro, [c] Antonio S. Araffljo, [d] Edmar P. Marques, [b] and AldalØa L. B. Marques* [a] 1 Introduction Among the inorganic contaminants present in the ethanol biofuel, one can highlight the metal ions. The main source of contamination of ethanol biofuel by metallic species are due to corrosive process taking place in the distillation columns, storage tanks and fuel stations [1].The presence of these species, even at low concentra- tions, can negatively affect engine performance and inten- sify the corrosive properties of ethanol biofuel [2] and bi- odiesel [3, 4]. The maximum contents of all of these contaminants are regulated by official standards. One of the critical param- eters indicated for quality control for the commercializa- tion of ethanol [5] is the presence of metals. The quantification of metals in biofuels is usually based on atomic absorption techniques [6], with direct sample analysis [7, 8], or in conjunction with pre-concentration techniques, in which the sample passes through a column packed with a complexing agent [9, 10] and is subsequent- ly eluted for analysis. On the other hand electrochemical techniques have also been successfully applied in the de- termination of metal trace in petroleum fuels [11, 12], and biofuels [13, 14]. Copper and iron determinations, according to the offi- cial procedures recommended by brazilian (ABNT NBR 11331-07), american (ASTM D1688-07) and european (BS EN 15488) norms, should be performed by atomic absorption spectrometry (AAS) [15–17]. However, low metal concentrations in organic matrixes require special analysis conditions [18]. According to the current Brazilian specification [19] (ABNT NBR 11331-07), the copper present in anhydrous ethanol fuel (density of 0.81 kg L 1 ) should not exceed to 0.07 mg kg 1 . This value corresponds to the molar concen- tration of 8.88  10 7 mol L 1 , which is the limit, set by the regulatory organ of fuel quality in Brazil (ANP). The literature presents recent reviews on analytical methods concerning the determination of metal ions in ethanol biofuel [20–23] including copper. Spectroscopic techniques such as atomic absorption spectrometry (AAS) [24–31], atomic emission spectroscopy with induc- tively coupled plasma (AES-ICP) [32], mass spectrometry with inductively coupled plasma (MS-ICP) [33–34], ultra- violet-visible spectrophotometry (UV-Vis) [35] and energy dispersive X-ray fluorescence (ED-XRF) [36] are among the used methods. Besides, other more recent de- velopments point the electrochemical techniques, includ- ing potentiometry [37] and stripping voltammetry [38–43] as potential alternative methods to determine metals in ethanol fuel. Takeuchi and co-authors [44] determined copper in eth- anol biofuel using a solid paraffin-based carbon paste electrode modified with 2-aminothiazoleorganofunction- alized silica by anodic stripping voltammetry, after 20 min of pre-concentration with limit of detection (LOD) of 2.0  10 9 mol L 1 in the linear concentration range of 7.5  10 9 to 1.010 6 mol L 1 . The same group demon- strated that a gold microelectrode can be successfully em- Abstract : A sensor based in a graphite–polyurethane composite electrode modified with the mesoporous nano- structured silica with hexagonal array of pores called Santa Barbara Amorphous type material (SBA-15) con- taining nickel was built. The presence of Ni, incorporated during the synthesis of SBA-15, resulted in an increase in sensitivity when compared to the other electrodes based on the unmodified SBA-15. A procedure was proposed for the determination of Cu 2 + in ethanol biofuel by square wave stripping voltammetry with linear response in concentration levels of 1.0  10 8 and 1.0  10 7 mol L 1 , resulting in a limit of detection of 1.83  10 10 mol L 1 and precision (RSD) of 2.09 %. Keywords: fuel ethanol · voltammetry · copper · NiSBA-15 [a] S. Y. Neto, J. M. S. Almeida, A. L. B. Marques Department of Chemical Technology, NEPE: LPQA/ LAPQAP-Federal University of Maranh¼o (UFMA), S¼o Luis, MA, Brazil *e-mail: aldalea.ufma@hotmail.com [b] H. D. C. ViØgas, E. P. Marques Department of Chemistry, NEPE: LPQA/LAPQAP-Federal University of Maranh¼o (UFMA), S¼o Luis, MA, Brazil [c] E. T. G. Cavalheiro S¼o Carlos Institute of Chemistry, University of S¼o Paulo, S¼o Carlos/SP, Brazil. [d] A. S. Araffljo Department of Analytical Chemistry, Federal University of Rio Grande do Norte (UFRN), Natal, Brazil. www.electroanalysis.wiley-vch.de # 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Electroanalysis 2016, 28, 1035 – 1043 1035 Full Paper