Changes

===Examples of problems with internal standards===

===Examples of problems with internal standards===

[[:file:oiloil-and-oilsource-rock-correlations_fig8-17.png|Figure 13]] shows gas chromatograms of the saturated hydrocarbons from two seep oils from Papua New Guinea. Both samples contain an internal standard that [http://www.thefreedictionary.com/elution elutes] just before ''n''-C₂₁. Because the left oil is [biodegradation|biodegraded]], the detector sensitivity was set very high to record the trace amounts of remaining [[Wikipedia:Alkane#Linear_alkanes|''n''-alkanes]]. Consequently, the internal standard peak is very tall. In contrast, the right oil (undegraded) shows a much smaller internal standard peak because the detector sensitivity was lower.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-17.png|Figure 13]] shows gas chromatograms of the saturated hydrocarbons from two seep oils from Papua New Guinea. Both samples contain an internal standard that [http://www.thefreedictionary.com/elution elutes] just before ''n''-C₂₁. Because the left oil is [[biodegradation|biodegraded]], the detector sensitivity was set very high to record the trace amounts of remaining [[Wikipedia:Alkane#Linear_alkanes|''n''-alkanes]]. Consequently, the internal standard peak is very tall. In contrast, the right oil (undegraded) shows a much smaller internal standard peak because the detector sensitivity was lower.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-18.png|Figure 14]] shows a gas chromatogram of the saturated hydrocarbons from the Lufa seep oil, another seep oil from Papua New Guinea. Because this work was carried out by a different laboratory than the analyses in the previous figure, the internal standard used here is different. This standard elutes just before ''n''-C₂₂. The pristane–''n''-C₁₇ ratio suggests that this oil is different from those in [[:file:oiloil-and-oilsource-rock-correlations_fig8-17.png|Figure 13]], a fact confirmed by other geochemical evidence.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-18.png|Figure 14]] shows a gas chromatogram of the saturated hydrocarbons from the Lufa seep oil, another seep oil from Papua New Guinea. Because this work was carried out by a different laboratory than the analyses in the previous figure, the internal standard used here is different. This standard elutes just before ''n''-C₂₂. The pristane–''n''-C₁₇ ratio suggests that this oil is different from those in [[:file:oiloil-and-oilsource-rock-correlations_fig8-17.png|Figure 13]], a fact confirmed by other geochemical evidence.