Fuel Quality Monitoring by Color Detection

Abstract

The quality of automotive fuels-gasoline, diesel, biodiesel, and ethanol-is discussed in the light of their specifications in different countries and regions and in terms of their adulteration, which has such a prejudicial effect on the production chain, distribution chain, tax revenues, the environment, and end consumers. Different ways of adulterating automotive fuels are analyzed, as are the procedures for their detection. Several analytical methods for monitoring quality and detecting adulteration have been addressed in the literature, emphasizing the determination of properties such as density, distillation curve, octane rating, vapor pressure, etc., by means of physicochemical methods and chromatographic and spectrographic techniques, to the detriment of colorimetric methods. This chapter looks at colorimetric techniques designed for quality monitoring and the detection of adulteration in fuels, especially simple, quick, low-cost procedures with potential to be used in the field.

A Rapid and Versatile Method to Determine Methanol in Biofuels and Gasoline by Ambient Mass Spectrometry using a V-EASI Source

“…In this procedure, methanol is oxidized by potassium permanganate to formaldehyde, which reacts with the salt of chromotropic acid, resulting in a purple color, as measured by colorimetry; moreover, this method is subject to interferences and incomplete reactions, and although selective, it is not specific. 2 Methanol has similar properties to ethanol, such as color, odor, and density; for this reason, the most important techniques to analyze contaminated fuel (ethanol and gasoline) with methanol is from gas chromatography (CG) with a flame ionization detector (FID) and/or mass spectrometer (MS), producing methods that require a few minutes for each analysis. 12,15 In Brazil, the price of methanol is presently half the market price of ethanol and more slightly over a third that of gasoline, and it is not subject to taxes levied on the sale of fuels; for this reason, there have been several cases of ethanol fuel and gasoline adulteration with methanol discovered since 2010.…”

“…The main methods used for methanol detection presently are colorimetry, , cyclic voltammetry, , spectroscopy, − and gas chromatography coupled with mass spectrometry. , However, these techniques are usually time consuming and sometimes require accessories such as an automated liquid insertion system or headspace . Detection of methanol traces by colorimetric analysis has been performed using chromotropic acid to produce a colored complex.…”

“…Detection of methanol traces by colorimetric analysis has been performed using chromotropic acid to produce a colored complex. In this procedure, methanol is oxidized by potassium permanganate to formaldehyde, which reacts with the salt of chromotropic acid, resulting in a purple color, as measured by colorimetry; moreover, this method is subject to interferences and incomplete reactions, and although selective, it is not specific …”