A new and simple strategy for the simultaneous determination of ethanol and methanol in fuel ethanol using cyclic voltammetry at a gold electrode is reported. A fuel ethanol aliquot was added into an electrochemical cell containing 0.5 mol L-1 NaOH and 0.1% (v/v) of methanol as the electrolyte and both analytes were determined using cyclic voltammetry. Ethanol was selectively detected at +0.19 V and both compounds were detected at +1.20 V. Current subtraction (using a correction factor) could be used for the selective determination of methanol. The limits of detection were estimated to be 0.028% and 0.045% (v/v) for ethanol and methanol, respectively. The proposed method presented similar results to those obtained by gas chromatography at a 95% confidence level. (C) 2012 Elsevier Ltd. All rights reserved.

The storage stability and corrosive character of soybean biodiesel stabilised with tert-butylhydroquinone (TBHQ) was investigated through static immersion corrosion tests. Coupons of carbon steel and galvanised steel were immersed in soybean biodiesel with and without TBHQ for 12 weeks. Measurements of total acid number, peroxide value, oxidation stability (Rancimat induction period), metal release, and TBHQ consumption at different stages of corrosion were performed. After 12 weeks of the static immersion test with both steels, the non-stabilised biodiesels presented induction times below the EN 14214 limit (6 h); these results were in agreement with increase in the peroxide values. Zinc release was only detected in the non-stabilised biodiesel exposed to galvanised steel, whilst iron was not detected in any biodiesel samples exposed to carbon steel. The absence of zinc in the TBHQ-doped biodiesel exposed to galvanised steel indicates that TBHQ may have acted as a corrosion inhibitor. Additionally, TBHQ was rapidly consumed in the first 3 days of experiments, providing evidence of its activity. For a storage period of up to 56 days, both galvanised and carbon steels were shown to be compatible with biodiesel even in the absence of an antioxidant. The presence of zinc (>2 mu g g(-1) after 28 days of immersion) due to corrosion did not promote biodiesel deterioration. (c) 2012 Elsevier Ltd. All rights reserved.