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lactic acid vs acetic acid retention times
Posted: Thu Nov 17, 2011 10:50 am
by siddana2005
in a partcicular GC method (FID column) What will be the RT relation between Lactic Acid and Acetic Acid i mean which will be higher and which will be lower. can any one please help me? what is the main property of a component that determines its RT?
Re: lactic acid vs acetic acid retention times
Posted: Thu Nov 17, 2011 11:13 am
by Peter Apps
I doubt that lactic acid will elute as a recognisable peak in GC. Retention depends on the partition of the compound between the stationary phase and the carrier gas. With non-polar phases higher molecular weight compounds elute later. With polar phases, compounds that have polar functional groups elute later than compounds with the same molecular weight but with no polar groups.
Peter
Re: lactic acid vs acetic acid retention times
Posted: Thu Nov 17, 2011 4:08 pm
by Consumer Products Guy
And lactic acid typically contains a significant amount of its self-ester. Even the "beloved" USP-NF assay in its monograph takes that into account.
Re: lactic acid vs acetic acid retention times
Posted: Thu Nov 17, 2011 6:30 pm
by chromatographer1
Theree is a chromatogram of lactic acid on Supelco's web site.
The lactone elutes more quickly and the dimer elutes later.
best wishes,
Rod