In other cases, particularly in rock extracts, the sample may be contaminated. Plasticizers, for example, are common but are usually easy to recognize. The figure below 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.
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[[file:oiloil-and-oilsource-rock-correlations_fig8-19.png|thumb|{{figure number|8-19}}See text for explanation.]]
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[[file:oiloil-and-oilsource-rock-correlations_fig8-19.png|left|thumb|{{figure number|15}}See text for explanation.]]
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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.