A system for characterizing crude oil fractions includes a maltenes sample reservoir, a first solvent reservoir, a second solvent reservoir, and a third solvent reservoir. The system further includes a valve in fluid communication with the first solvent reservoir, the second solvent reservoir, and the third solvent reservoir and a pump in fluid communication with the valve. The system further includes a packed bed in fluid communication with the maltenes sample reservoir and the pump, a flowthrough cell in fluid communication with the packed bed, a spectrometer operably associated with the flowthrough cell, and a computer operably associated with the spectrometer. A method for characterizing crude oil fractions includes providing a maltene sample, eluting saturates, aromatics, and resins of the maltene sample, determining an optical density of each, and determining a concentration of each of the saturates, aromatics, and resins based upon optical densities over time for each.