[lenq86]

I have a mixture of molecules with phenol and tertiary amine as functional groups that I haven’t could separate by chromatography. I have tried silica gel, neutral alumina and kieselguhr as stationary phase. When this mixture elutes I never see spots, I always see a tailing (even in Kieselguhr). Tailing could appear due to high concentration, basicity or acidity of the compound, so I have tried mixtures with amines and acetic acid. Although the mixture elutes, I still see a tailing. Anybody could help me??

[Nescafe]

I have a mixture of molecules with phenol and tertiary amine as functional groups that I haven’t could separate by chromatography. I have tried silica gel, neutral alumina and kieselguhr as stationary phase. When this mixture elutes I never see spots, I always see a tailing (even in Kieselguhr). Tailing could appear due to high concentration, basicity or acidity of the compound, so I have tried mixtures with amines and acetic acid. Although the mixture elutes, I still see a tailing. Anybody could help me??

Have you tried a water based system? Something like DCM:MeOH:Water?

[Alberto_Kravina]

I had a similar problem some time ago, 20:1 DCM:MeOH with a hair of water (here your personal feelings and the alignment of Venus and Mars come into play  )did the job

[Dan]

here your personal feelings and the alignment of Venus and Mars come into play

Haha, I love those columns, they make you feel like a wizard.

[orgopete]

I think this is an example where an additional ion would help. This is what I think is happening. I think the amine-phenol is behaving as though it were a weakly bound compound and the streaking is caused by the breaking apart. This kind of behavior is common if decomposition is occurring on a column. A compound will streak because the actual component would be a mixture of the compound and its decomposition product. If the compound continues to decompose as it elutes, it continually streaks.

I suggest you use acetic acid or an amine in your elution solvent. In this way, you will be eluting the ammonium salt of your amine and your phenol as separate compounds. If acetic acid is present in your elution solvent, then separation of your amine or loss of a proton can be corrected by another molecule in the eluant.

[Dan]

You could also bind the amines to a strongly acidic ion exchange resin, then wash off the phenol, and then liberate the amines with triethylamine. That would at least separate the acidic components from the basic components, which you could then chromatograph on silica (separately) with triethylamine or AcOH doped eluents as appropriate. This does amount to 3 columns though, so if there is a quicker option I'd try that first.

[lenq86]

You could also bind the amines to a strongly acidic ion exchange resin, then wash off the phenol, and then liberate the amines with triethylamine. That would at least separate the acidic components from the basic components, which you could then chromatograph on silica (separately) with triethylamine or AcOH doped eluents as appropriate. This does amount to 3 columns though, so if there is a quicker option I'd try that first.

Hi!, thanks for yor answer, but I think I did not mean. I have the groups tertiary amine and phenol in the same molecules. I have  a mixture of aminomethylphenols. 

[Alberto_Kravina]

Hi!, thanks for yor answer, but I think I did not mean. I have the groups tertiary amine and phenol in the same molecules. I have  a mixture of aminomethylphenols. 

If you have an amine and a phenol in the same molecule maybe extracting it in an aqueous phase as Zwitterion could save you time...