Determination of Methanol in Gasoline and Ethanol Fuels by High-Performance Liquid Chromatography

Gasoline and ethanol fuels have been adulterated with methanol in Brazil. Methanol is not permitted in concentrations greater than 0.5 vol% due its toxicity but its lower price stimulates the adulteration. A new approach for quantitative analysis of methanol in gasoline and ethanol fuels is reported employing high-performance liquid chromatography coupled with refractive index (RI) detector on C18 column (250 × 4.6 mm, 5 µm) using deionized water as mobile phase (0.6 mL min−1). The method showed good analytical performance in terms of linearity for methanol concentration ranging from 0.5 to 4.5 vol% (coefficient of determination (R2) = 0.999) and from 4.0 to 12.0 vol% (R2 = 0.998). The recoveries (accuracy) values ranged from 98.6 to 103.2%. The results indicated that the developed method is accurate and suitable for the determination of methanol in gasoline with ethanol and ethanol fuel as an alternative procedure to gas chromatography (GC)-based techniques.

巴西境内的汽油与乙醇燃料中存在甲醇掺假现象。由于甲醇具有毒性，其在燃料中的体积占比不得超过0.5 vol%，但甲醇售价更低，这使得掺假行为屡有发生。本文报道了一种可用于定量检测汽油与乙醇燃料中甲醇含量的新型分析方法：以去离子水作为流动相（流速0.6 mL·min⁻¹），采用配备示差折光检测器（refractive index, RI）的C18色谱柱（250 × 4.6 mm，5 µm）开展高效液相色谱法（high-performance liquid chromatography）分析。该方法在甲醇浓度0.5~4.5 vol%区间内的决定系数（coefficient of determination, R²）为0.999，在4.0~12.0 vol%区间内的R²为0.998，展现出良好的线性分析性能。其加标回收率（即准确度）范围为98.6%~103.2%。实验结果证实，所开发的方法准确度可靠，可作为基于气相色谱法（gas chromatography, GC）的检测技术的替代方案，用于含乙醇汽油与乙醇燃料中的甲醇含量测定。