someone know or has any reference for explain me why polar columns (CarboWax e.g.)separate isomers like Linolenic acid(cis-trans ,doubble bond position isomers and others insaturates fatty acids) and Xylene(position isomers)?
thanks in advance
By Jason Ellis on Thursday, February 6, 2003 - 09:37 am:
I have two books that explain this well. Take a look at:
"A Practical Guide to the Care, Maintenance and Troubleshooting of Capillary GC Systems" by Dean Rood, Huthig GmbH, Heidelberg.
"Analytical Gas Chromatography", second edition, by Walter Jennings, et. al., Academic Press, New York, 1997.
Both have good basic discussions on stationary phase selectivity. The answer to your question has to do with dipole interactions between the analytes and the stationary phase -- stronger dipole interacting phases are capable of resolving compounds with smaller differences in dipole moment.
By Fabiano on Friday, February 7, 2003 - 02:56 am:
I will check this references .
Here we use CarboWax columns in C18:1 C18:2 C18:3 fatty acids methyl esthers separations ,but...
methyl esthers and xylene isomers are totally apolar compounds ,they donīt have dipole moment(maybe very low).
double bonds donīt contribute with polarity to any specie,at least without conjugation.
thatīs my doubt.