In other cases, particularly in rock extracts, the sample may be contaminated. Plasticizers, for example, are common but are usually easy to recognize. [[:file:oiloil-and-oilsource-rock-correlations_fig8-19.png|Figure 15]] shows a gas chromatogram of saturated hydrocarbons from a source rock sample contaminated with bits of plastic. The largest peak is dioctylphthalate, derived from contact with the plastic. | In other cases, particularly in rock extracts, the sample may be contaminated. Plasticizers, for example, are common but are usually easy to recognize. [[:file:oiloil-and-oilsource-rock-correlations_fig8-19.png|Figure 15]] shows a gas chromatogram of saturated hydrocarbons from a source rock sample contaminated with bits of plastic. The largest peak is dioctylphthalate, derived from contact with the plastic. |