Determination of hydrocarbon types in petroleum and coal-derived products by thin-layer chromatography/densitometry

Different methodologies based on thin-layer chromatography (TLC)/densitomet ry were used to separate and quantitate hydrocarbon types in middle distill ates (gas oil), heavy distillates (lubricant) from petroleum, and coal-deri ved products. Thus, petroleum products were separated into saturates and ar omatics by development, using n-hexane (9 min) followed by dichloromethane (4.5 min), of silica gel plates impregnated with berberine sulfate. Detecti on of saturates and aromatics was performed by fluorescence scanning using 365 nm as the excitation wavelength, Alternative detection of aromatics can be performed on either silica gel or berberine-impregnated plates by using ultraviolet (UV) densitometry at 250 nm. On the other hand, polar coal-der ived products were separated into aromatics, polar compounds, and uneluted components by using silica gel plates and development with toluene (12 min) , followed by dichloromethane-methanol (95 + 5, v/v), with detection by UV densitometry at 250 nm, In all cases, external standard calibration was use d for quantitation, Results were validated by using standard methods or wel l-established techniques of the petrochemical industry. The potential usefu lness of TLC/densitometry is discussed.