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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Hachiko on March 18, 2020, 10:57:08 PM

Title: Column chromatography problem
Post by: Hachiko on March 18, 2020, 10:57:08 PM

Dear all,
My compound is low soluble so I need much polar solvent to dissolve it, when I runned column, I got the mixing. I think the reason is that my solution had low concentration and polar solvent make my sample all run together. I can't use dry loading because my compound can be soluble in solvent system. I try recrystallization but it's not good.
Could you share your opinion and experience when you handle with low solubility compound in column chromatography?

Title: Re: Column chromatography problem
Post by: phth on March 19, 2020, 04:02:02 AM

Change the stationary phase, i.e. maybe alumina will work over silica gel or C18 or ion-exchange. You could try more recrystallization solvents; get some small test tubes and a hot bath. Test more and TLC solvent systems. If your compounds are not crystallizing/forming a gel at room temperature then lower the temperature.

Title: Re: Column chromatography problem
Post by: Hachiko on March 19, 2020, 05:02:19 AM

Quote from: phth on March 19, 2020, 04:02:02 AM

Change the stationary phase, i.e. maybe alumina will work over silica gel or C18 or ion-exchange. You could try more recrystallization solvents; get some small test tubes and a hot bath. Test more and TLC solvent systems. If your compounds are not crystallizing/forming a gel at room temperature then lower the temperature.

Thank you for your suggestion.I will try different solvents for recryatallization.

Title: Re: Column chromatography problem
Post by: Babcock_Hall on March 19, 2020, 10:03:45 AM

We have also experienced similar problems.  Can you tell us what your solvent system is and what solvent you are using to dissolve the solute?

Title: Re: Column chromatography problem
Post by: kriggy on March 19, 2020, 03:39:56 PM

I dont understand, why you cant use dry loading?

Title: Re: Column chromatography problem
Post by: Hachiko on March 19, 2020, 10:52:37 PM

Quote from: Babcock_Hall on March 19, 2020, 10:03:45 AM

We have also experienced similar problems.  Can you tell us what your solvent system is and what solvent you are using to dissolve the solute?

I use DCM for dissolve and 4Hexane:1Ethyl acetate for mobile phase.

Title: Re: Column chromatography problem
Post by: Hachiko on March 19, 2020, 10:56:25 PM

Quote from: kriggy on March 19, 2020, 03:39:56 PM

I dont understand, why you cant use dry loading?

Oh,I may see my mistake here. I check the solvent system that I will use for mobile phase to dissolve my sample. My sample can be dissolved in this solvent system so I think dry loading is not good. So if I use dry loading and firstly run with hexane and increase the polarity slowly, will it be ok?

Title: Re: Column chromatography problem
Post by: kriggy on March 20, 2020, 02:55:31 AM

Yeah thats pretty much what I do all the time. I dissolve the sample in DCM, add silica, evaporate to dryness, add to collumn and use hexane:EtOAc as a mobile phase. TBH I dont even bother trying to dissolve my samples in mobile phases I use :D

Title: Re: Column chromatography problem
Post by: Hachiko on March 22, 2020, 01:26:17 AM

Quote from: kriggy on March 20, 2020, 02:55:31 AM

Yeah thats pretty much what I do all the time. I dissolve the sample in DCM, add silica, evaporate to dryness, add to collumn and use hexane:EtOAc as a mobile phase. TBH I dont even bother trying to dissolve my samples in mobile phases I use :D

thank you for sharing.