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.

The aim of this paper was to use colorimetric assays for hydroxamic acid to quantify the biodiesel content in diesel and compare it with the traditional method (infrared spectroscopy, using the EN 14078 method). Samples were prepared from B2 to B10 with two kinds of diesel - S500 (red) and S50 (yellow) - to obtain two calibration curves. Through statistical methods it was shown that the slopes of the straight lines obtained for the different types of diesel were the same. Thus, the type of diesel did not influence the results of the colorimetric assay for hydroxamic acid. Real samples collected from gas stations were analyzed by both methods (colorimetry and EN 14078). By applying Student's t-test it was concluded that the methods could be considered statistically equivalent. Therefore, it was confirmed that the colorimetric assay for hydroxamic acid is suitable for detecting and quantifying the content of biodiesel in biodiesel/diesel blends and can also be easily adapted to field analyses.