An analytical technique designed to separate compounds, whereby a mobile phase (an inert carrier gas) passes through a capillary column containing an immobile stationary phase (a high molecular weight liquid). Various detectors, such as the flame ionization detector (FID), are used to measure the separated components. Gas chromatography analysis is performed on crude oils to separate the hydrocarbon compounds in the n-C4 to n-C42 carbon range. The compounds are separated based on their relative tendencies to partition into the stationary or mobile phases as they move through the column.