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Study On Techniques For Estimation Of Benzo(a)pyrene In Coal Tar Pitch

Rakesh K.Khandal, Sapana Kaushik, Rajesh K.Raina, Manjeet Aggarwal, Gurucharan L.Verma, Gopal Bhatia

Coal tar pitch is mainly a mixture of high molecular weight polycyclic aromatic hydrocarbons (PAHs), their alkyl derivatives and their heterocyclic analogs. Out of the numerous PAHs found in coal tar pitch, benzo[a]pyrene (B(a)P) is one of the most prominently reported carcinogens for humans. B(a)P is released into the atmosphere during processing of coal tar pitch for manufacturing various carbon products. In order to ensure their safe levels in the environment, maximum residual limits (MRLs) for various PAHs including B(a)P have been specified by regulatory authorities. To meet the prescribed requirements, it becomes necessary to characterize the coal tar pitch, especially with reference to B(a)P to ensure its application in an environmentally safe manner. In the present paper, the coal tar pitch from two different sources has been evaluated for B(a)P content using a sensitive, accurate, well developed and a validated method. Since coal tar pitch involves a complex matrix, certain components in the matrix are expected to cause interference during the analysis of B(a)P. To avoid interferences from the matrix it is necessary to selectively extract and isolate B(a)P using a suitable extraction technique before quantification. For this purpose, different extraction techniques were tried and the results were compared for the maximum recoveries of B(a)P from the coal tar pitch. The estimation of the extracted B(a)P was done using high performance liquid chromatography (HPLC). It was found that extraction in toluene using controlled soxhlet technique gave the best recoveries ranging between 87% and 95% with percent relative standard deviation(RSD) of 2.77%. Based on these studies, it is observed that the method developed can be used as a standard method for estimating B(a)P in coal tar pitch before approving the latter for application for various purposes.