Changes

==Example of SIM==

==Example of SIM==

[[file:oiloil-and-oilsource-rock-correlations_fig8-21.png|thumb|{{figure number|1}}. Copyright: Unocal.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-21.png|thumb|{{figure number|1}}Three SIM mass chromatograms for a single oil sample. (top left) m/z 191 chromatogram; (bottom left) m/z 217 fragment in the mass spectrometer; (top right) m/z 218 fragment. Copyright: Unocal.]]

[[:file:oiloil-and-oilsource-rock-correlations_fig8-21.png|Figure 1]] shows three SIM mass chromatograms for a single oil sample. The top left chromatogram show the m/z 191 chromatogram, in which the only compounds are those having a fragment ion with a mass of 191 daltons. (The value m/z is the mass of the ion divided by its charge.) The bottom left chromatogram shows the compounds yielding an m/z 217 fragment in the mass spectrometer, while the top right chromatogram shows those compounds that give an m/z 218 fragment. The 217 and 218 mass chromatograms are very similar because both are derived mainly from steranes. The differences in relative intensity reflect the tendency of some types of steranes to give more 217 daughter ions and others to give more 218. These tendencies are due to structural differences among different families of steranes and are useful in themselves.

[[:file:oiloil-and-oilsource-rock-correlations_fig8-21.png|Figure 1]] shows three SIM mass chromatograms for a single oil sample. The top left chromatogram show the m/z 191 chromatogram, in which the only compounds are those having a fragment ion with a mass of 191 daltons. (The value m/z is the mass of the ion divided by its charge.) The bottom left chromatogram shows the compounds yielding an m/z 217 fragment in the mass spectrometer, while the top right chromatogram shows those compounds that give an m/z 218 fragment. The 217 and 218 mass chromatograms are very similar because both are derived mainly from steranes. The differences in relative intensity reflect the tendency of some types of steranes to give more 217 daughter ions and others to give more 218. These tendencies are due to structural differences among different families of steranes and are useful in themselves.