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 present work aims at studying the preconcentration of Cu2+ ions by solid phase extraction using SiO2/Al2O3/TiO2 ternary oxide as adsorbent material. This methodology consists of the affinity of the analyte for the adsorbent material and its subsequent elution with the least amount of solvent. Subsequently, the aqueous phase containing the extracted analyte was collected and analyzed by square wave anodic stripping voltammetry (SW-ASV). For the applied solid phase extraction (SPE) methodology, a complete factorial design was carried out with 3 variables at 2 levels (pH, elution flow rate and analyte concentration) to optimize the extraction conditions. The results showed that at pH 9, the SiO2/Al2O3/TiO2 oxide presents excellent Cu2+ adsorption capacity with recovery values between 81.0 and 104% for this pH range. The limit of detection (LOD) and limit of quantification (LOQ) values were determined to be 1.71 and 5.64 µg L-1, respectively. The study of recovery for SPE method revealed results of 102 and 103%.

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.