INVESTIGATION OF LEADED PETROL AND DIESEL ADULTERATION IN SRI LANKA

Addition of adulterants to expensive consumer products is a common problem. Similarity of thephysical and lor chemical properties of the 'Consumerproduct to the adulterant is the biggestchallenge in the identification of the adulterant. However, the selection of a noticeable differenceof the adulterant to the consumer product can be utilized for the routine analysis of such anadulterant. The success of a routine analysis depends on several factors, which includedsimplicity, cost and the time for analysis.In Sri Lanka, both petrol and diesel are believed to be added with low cost petroleum-basedchemicals. The inclusion of cheaper adulterants increases with the ever-rising demand and costof the fuels. This research project was initiated to inv estigate a suitable procedure in identifyingthe petroleum-based adulterants in commercially avai lable petrol and diesel. Both these fuels arenot pure compounds and they contain different distillation fractions of crude oil. Hence, thechemical constituents in these two fuels are different but they have the similar chemicalcharacteristics. Ploycyclic aromatic hydrocarbons (PAH), a group of fluorescence activecompounds, are present in the petroleum base fuels. But, the PAH content in each of the fueltype varies with the boiling range of the fueSynchronous fluorescence scan (SFS) seems to be a promising technique in identifyingfluorescence active compounds in such samples, Unlike in conventional fluorescencespectroscopy, in SFS both the excitation and emission wavelengths are scanned keeping thedifference of the wavelengths to a constant value We have investigated the optimal SFSconditions for unadulterated kerosene, diesel and leaded petrol. Then the analysis were carriedout for the mixtures of leaded petrol + kerosene and diesel + kerosene at different levels.Positions of the SFS maxima and the fluorescence intensity of the leaded petrol and dieselshifted with the addition of kerosene .The magnitude of the shift and the change in fluorescenceintensity are indicatives of the added kerosene. Some of the petrol and diesel samples purchasedfrom different part of the country exhibited the characteristics of the fuel adulterants. There isstrong evidence that kerosene was used as an adulterant for some of these samples. Few of thesamples exhibit different SFS fingerprints which are not characteristic for diesel, kerosene orleaded petrol .We are investigating different analytical parameters that can be utilised inquantifying the level of adulterant in these fuels.