Column cracking due to trasition of non polar to polar solvent...
Yes. This is observed many times. So when you change mobile phase solvent from non polar to nonpolar:polar solvent, the change of polarity must be minimum. In other words, there should not be sudden change of mobile phase in column otherwise it will crack.
Gudluck
:)
Next time i will start with DCM and then move toward Ethylacetate...Thanks
With a table of increasing polarity can locate the solvent polarity index that is your solvent system and gradually increasing the solvent polarity with the available solvents in your lab. Here I leave a table:
http://macro.lsu.edu/howto/solvents/Polarity% 20index.htm
Best regards!
Cony
Can it be achievable the high purity of the compound using column chromatography? I am trying to isolate compounds from plant extracts, but the first trial was a poorer one. if I want to start with the basics what can be the strategies? I am following non polar to polar solvent transition but then the problem of cracking came. According to suggestions i will try a minimum change in solvent polarity. if anybody working in plant molecule purification, please help me out.
very useful information
I want to add if column has been cracked you have to run with the less polarity solvent by which one you have just started and take about 20 elutes you will find that slowly your stationary phase is settling again and then you can use half of the composition and run again column with increasing the polarity
i am sorry sandeep but i didn't get you. if I am changing the solvent from chloroform to chloroform (80): M€thanol (20), then what should be done? because when I change the solvent, in between column cracking start.
Piyush Chudasama. I wish to help you, give more information about what are you looking for? what plant? what kind of compounds want to isolate? preparative HPLC is a very good tool for the isolation of plant compounds but you need a large knowledge about your sample. Give some details about what are you looking for and I give you some recommendations.
Piyush ji
as i have told then again go to the previous solvent system and run column for time that all the solvent which you have added have came out then take just half means 9:1 ratio use
Cony Corrales
yes its good tool but costly and in general not in reach of scholars in UG and PG colleges
Piyush Chudasama please visit my blog and perform chemical test as given there
Dear colleauge
changing the chlorophorm with other solvents on Silica gel results in more cracks than the other ones. You would use hexane: ethyl acetate mixtures from less polarity to more polrity. besides you need to not let air comes in, by hitting gentlely the column during the packing, and not letting the column get died during the column running
good luck
What solvents are you using? I often see silica columns packed in hexane "outgas" when ethyl acetate is run throught the column. This seems to be because the ethyl acetate adsorbs on the silica (the column is often warm from the heat of adsorption where the ethyl acetate ismoving down the silica. This warm band moves down the column with the ethyl acetate solvent front). I also see this when using a hexane with dichloromethane
The two ways I avoid the issue are:
- a little bit of pressure. I use automated flash systems so they provide all the pressure I need
-If your chromatography permits, pack the column with 1 or 2% of the strong solvent. This lets the strong solvent adsorb on the column and you can run your gradient fine.
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