Fingerprinting diesel and petrol fuels for adulteration in Sri Lanka

Abstract

Adulteration of petrol (gasoline) and diesel using petrochemical based products has often been reported in developing countries. This leads to the degradation of engine performances and fugitive emissions. Having similar chemical properties, the fuel and the adulterant cannot be distinguished easily leading to complications in identification and quantification of the adulterants. In this investigation, a synchronous fluorimetric analysis method was modified targeting to obtain the fingerprints for these fuels based on their polycyclic aromatic hydrocarbon (PAH) content. In a synchronous fluorescence scan, both the excitation and emission wavelengths are scanned keeping the wavelength difference at a fixed value. PAHs are a group of compounds with fused benzene ring systems, which are naturally present and/or formed during fuel processing that exhibit significant differences in their synchronous fluorescence scans. Simulated adulterated samples of petrol or diesel with kerosene, diluted in hexane, were prepared from the fuels collected from the petroleum refinery. These simulated fuel samples showed linear variations of the synchronous emission intensity with the level of kerosene in the fuel at specific wavelengths. This relation was utilized to investigate the level of adulteration for petrol and diesel available at different petrol stations. Diesel adulteration was found to be in the range of 0 to 35% while petrol adulteration was found to be in the range of 0 to 48% in Colombo and its suburbs.