Chromatography Forum

Hi,
Every body, I am working with the analysis of (Ethyl 4,4-difluoroacetoacetate). I analyze it on CPSIL-8CB, the peak shape is good.
Now the problem is arises. It's raw material is EDFA(Ethyl difluoroacetate) and solvent is ethyl acetate. Both EDFA and Ethyl acetate is not separated on CPSIL-8CB column.(30 meter, 0.25mm ID and 1.0µm)
Another impurity EAA (EThyl acetoacetate) is separate with EDAAA but it's peak shape is not proper.
I also tried DB-5 column with 0.32mmID and 0.25µm with 30 meter length, but I did not get separation between EDFA and Ethyl acetate.
In DB-5 column with configuration of 25meter, 0.32mm ID and 0.52µm EAA peak breaks into keto enol form.
SO overall I still not understand which type of phase is very much suitable to separate all of above four (EDFAA, EAA, EDFA and Ethyl acetate)

Best regards

praveen

If you need different selectivity, use a 50% phenyl column like a Rxi-17Sil MS. The reaction you see is temperature dependent, so make sure that you have LOWEST elution temperatures:

Use THINNEST films;
Use 0.32mm and operate at HIGH FLOWRATE rate (use pressure programming)
Use slow temperature programs
Use shortest column that give you the desired separation

jaap de zeeuw, Restek corporation