Biomarkers are primarily hydrocarbons which fall into two categories: saturated and aromatic compounds. Since many of these compounds chromatographically overlap, and sometimes have the same diagnostic ions (i.e., M/Z 231 for 4-methylsteranes and triaromatic steroidal hydrocarbons), the hydrocarbons are separated by Medium Pressure Liquid Chromatography (MPLC) into saturated (aliphatic) and aromatic fractions. These fractions are then analyzed by Gas Chromatography-Mass Spectrometry (GCMS) which allows each component to be better separated, identified, and quantitated. Qualitative and quantitative analysis is performed on crude oils and the saturate and aromatic fractions by injecting microliter volumes into a cool-on column injector. A capillary column is used to provide separation for hydrocarbon compounds in the n-C4 to n-C42 carbon range with detection by mass selective detector (MSD). GCMS can be used to determine sample properties such as source characteristics, depositional environment, and the extent to which biodegradation is present in the sample.