Here, the polymer pH is 1.5 and it might contain traces of chloroform and trifluoroacetic acid (TFA). So, How can I remove that traces TFA. Because I am going to use this polymer to conjugate a drug. The traces TFA and acidic condition are suitable to do EDC/NHS coupling reaction.
First, find out the molecular weight of your polymer. Then find a dialysis tubing that has a smaller MW cut off than the MW of your polymer. Put your polymer solution inside the dialysis tubing and seal it. Place in the appropriate buffer and do dialysis overnight with three changes of buffer. This dialysis tubing should be able to excrete the TFA from your polymer solution.
Also, make sure to put the set up on top of a magnetic stir plate and put a stir bar in your buffer. This will allow continuous movement and flow in and out of the dialysis tubing.
In addition to Zoraida P Aguilar 's answer. Make sure that the molar weight cut-off is much (we use half to one third of the polymers Mn) smaller than your polymer's Mn. Otherwise you'll loose too much polymer. Also, most dialysis membranes have to be used in aqueous solution, some in methanol.
You could use a rotary evaporator and use repeated addition of methanol to drag TFA out of your polymer.
Dear Prabu,
How are you, happy to see your interest here..
From your question, it seems that your polymer is soluble in chloroform, and probably not soluble in water. If it is true, dialysis in aqueous or methanol medium may not be helpful. Hence, the TFA can be removed by washing with diethyl ether repeatedly. If you still worry about TFA traces interfering the EDC/NHS reaction in next step, adding DMAP would be helpful to increase the basicity.
TFA is miscible in water. EDC/NHS are soluble in water. More than likely, the polymer is soluble in water. But, Prabhu knows what the solubility of the polymer is.
Dear Prof.. Zoraida P Aguilar and Erik Wegener...
Thank you for your valuable answer.
I bought a dendron which is commercially available. But It has some drawback to use it. Here, dendron is soluble in water but it may degrade over time in water.
So, I dissolved it in DMSO. Then I did NHS/EDC coupling reaction in water and DMSO (1:1).
I found more unbound drugs at the end... and then I realize that pH may affect this reaction.
Hi Prabhu,
Yes, I agree with you. So, try to store your polymer at various pH. Also, you may need to find the best buffer to keep it stable, Tris, PBS, HEPES, etc. Try to store it in different temperatures such as inside the refrigerator or outside, in the dark and in light to see which will slow down it's degradation.
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