Medium pressure liquid chromatography (MPLC) is a quantitative method of analysis used to separate an extract into saturated hydrocarbons, aromatic hydrocarbons and polar materials. It utilises a pre-column containing thermally-deactivated silica and a main column of activated silica as the stationary phase (SP) with n-hexane serving as the mobile phase (MP). The sample is first deasphalted then passed through the deactivated silica pre-column and the main column. The aromatics are retained at the beginning of the main column while the saturates elute from the column and are collected. By then reversing the flow of hexane in the main column, the aromatics are eluted from the main column and collected. Resins (polar compounds) are adsorbed by the deactivated silica pre-column and subsequently eluted using a 50:50 mix of dichloromethane/methanol and collected. The saturate and aromatic fractions can then be analyzed bygas chromatography or gas chromatography-mass spectrometry.