How to affect selectivity between achiral and racemate

[Mike H.]

I couldn't give an adequate description in the subject line., so I'll elaborate. I have resolved a racemic mixture using Chiralpak OJ-H column with 90:10 Hexane:IPA, 25°, 0.8ml/min as the conditions. I ran into a problem when trying to analyze the starting material using these conditions. The chemist are interested in yield as well as the racemates. The problem I'm having is that the starting material is very similar in structure to the racemates. The starting material is a ketone and the racemates have an OH group replacing the ketone.

Does anyone have any ideas about how to address selectivity issues in chiral chromatography when dealing with a racemate and an achiral compound? Is it even possible to do? Thanks.

[DR]

If playing w/ the % IPA does not allow you to separate the starting material from the products, you may well have to use a RP column to give starting material to racemates (%yield), then break down the yield figure with the chiral method.

[Mike H.]

There's definitely seems to be a learning with chiral methods. One of the major problems I've been dealing with is the difficulty of developing methods on the fly without a good background of the dominate mechanisms driving the separations. I've been having a hard time trying to find any information about this. Learning things through trial and error takes longer. I did get lucky here in that while I didn't find any parameters that affected the achiral compound, I did notice that the racemates were affected greatly by temperature. I increased the temp by 10° and pushed them away from problem analyte.