Characterization of polycyclic aromatic hydrocarbons created in lubricating oils

Used lubricating oils are major sources of polycyclic aromatic hydrocarbons (PAHs) in marine environments. This study presents an improved method for characterization PAHs in used lubricating oils. Recoveries of sixteen certified PAHs spiked into used lubricating oil indicated this method was more precise and efficient than those reported previously. Aromatic and aliphatic compounds in used lubricating oil were extracted by dimethylsulfoxide, then separated by a silica gel column using hexane and dichloromethane as solvents. Finally, gas chromatography-mass spectrometry was used in qualitative and quantitative analysis of various PAHs in oil samples. Sixteen certified PAHs and eighty-three other PAHs were identified and quantified using PAH standards and previously reported retention indices as references. The improved method was used to determine PAH profiles in lubricating oil samples collected from a gasoline-driven automobile after various driving distances. One hundred and eighty aromatic compounds, including ninety-nine PAHs, were identified by the gas chromatographic method. These results suggested that the new method was superior to methods described in previous studies. The concentrations of PAHs, including the comparatively toxic 5-ring PAHs, increased rapidly even after the automobile had only been driven for a short distance. 2- and 3-ring PAHs, most of them are alkylated, dominated the PAH profiles of the collected oil samples.