Impacts of Extraction Methods and Solvent Systems in the Assessment of Toxic Organic Compounds in a Solid Matrix

Polycyclic Aromatic Hydrocarbons (PAHs) are among the listed persistent organic compounds (POP) which are pollutants of environmental concern due to their toxicity. This study evaluated soxhlet and ultrasonic extraction methods using a three-solvent system (acetone+dichloromethane+n-hexane) in order to compare the ability of the techniques to extract selected PAHs in raw coals collected from a coal mine in Okobo-Enjema, Nigeria. Then, binary solvent mixtures consisting of acetone+dichloromethane; dichloromethane+n-hexane; and acetone+n-hexane, were compared with the ternary solvent system for their ability to extract the target PAHs by soxhlet extraction method. The extracts were quantitatively analysed for sixteen PAHs using Gas Chromatography-Mass Spectrometer (GC-MS). Sonication extraction method extracted higher number of PAHs, required fewer amount of solvents, shorter time of extraction and less energy consumption compared to soxhlet extraction, which extracted higher amount of the target PAHs. The total amount of PAHs determined ranged from 0.02 mg/kg to 0.20 mg/kg in the various solvents' mixtures. The ternary mixture extracted larger quantities of the target toxic PAHs. This report will assist in the choice of analytical methods and solvent systems for environmental studies.