"Resins" is a class of compounds believed to play an important role in the conversion processes of coal and coal-related materials into oils. Methods currently used to isolate this fraction, generally lack reproducibility and yield impure and strongly overlapping fractions which do not reflect the actual group-type distribution in the liquid fuel. A separation method based on liquid column chromatography was developed, which divides liquid fuels into eight distinct and minimally overlapping chemical classes: five non-polar (saturated, mono-, di-, tri-, and polynuclear aromatics), one intermediate polar (resins) and two polar (asphaltenes and asphaltols) fractions. Chemical characterization of "resins fractions," derived from two alternative fuels (coal-derived liquid and sugarcane bagasse), was achieved by first subjecting them to acid-base-neutral separation, followed by analysis of each subfraction by GC/MS. Identification of the eluted components was carried out utilizing a library search system, by comparing retention times (indices) of 150 model compounds believed to exist in liquid fuels, on two fused silica capillary columns (Carbowax 20 M and SE-54), and by mass spectral interpretation. GC/MS results indicate that "resins" are mainly composed of weakly acidic (phenols, indanols, naphthols), mildly basic (benzoquinolines, chloroanilines, etc.), neutral-nitrogen (indoles and carbazoles), and oxygen (carbonyl) compounds, and are free of hydrocarbons. / Ph. D.