Changes

[[File:GCMS_closed.jpg|thumb|400px|GCMS closed|Gas chromatography mass spectrometer. Photo by [https://commons.wikimedia.org/wiki/User:Polimerek Polimerek].]]

[[File:GCMS_closed.jpg|thumb|400px|GCMS closed|Gas chromatography mass spectrometer. Photo by [https://commons.wikimedia.org/wiki/User:Polimerek Polimerek].]]

In [[gas chromatography]] the distributions of [[Wikipedia:Alkane#Linear_alkanes|''n''-alkanes]] and [[Wikipedia:Terpenoid|isoprenoids]] are usually most useful. Of particular significance for correlations are the wax content (C₂₃₊), the [[Wikipedia:Carbon Preference Index|carbon preference index (CPI)]]<ref name=ch08r3>Bray, E., E., Evans, E., D., 1961, Distribution of n-paraffins as a clue to recognition of source beds; ''Geochimica et Cosmochimica Acta'', vol. 22, p. 2–15., 10., 1016/0016-7037(61)90069-2</ref> and the [[pristane-phytane ratio]] (Pr/Ph). The following figures show gas chromatograms of the [[Wikipedia:Saturate, aromatic, resin and asphaltene|saturate fractions]] of several oils, illustrating the differences that can be observed in these compound classes as a result of differences in the source material.

In [[gas chromatography]] the distributions of [[Wikipedia:Alkane#Linear_alkanes|''n''-alkanes]] and [[Wikipedia:Terpenoid|isoprenoids]] are usually most useful. Of particular significance for correlations are the wax content (C₂₃₊), the [[Wikipedia:Carbon Preference Index|carbon preference index (CPI)]]<ref name=ch08r3>Bray, E. E., E. D. Evans, 1961, Distribution of n-paraffins as a clue to recognition of source beds; ''Geochimica et Cosmochimica Acta'', vol. 22, p. 2–15., 10., 1016/0016-7037(61)90069-2</ref> and the [[pristane-phytane ratio]] (Pr/Ph). The following figures show gas chromatograms of the [[Wikipedia:Saturate, aromatic, resin and asphaltene|saturate fractions]] of several oils, illustrating the differences that can be observed in these compound classes as a result of differences in the source material.

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