Dextran have been used for determination the MWCO of UF membranes. Separation results of TOC tests for Dextran 150 KDa is like Dextran 70 KDa. And some sources suggested that if ultrafiltration membrane able to separate 90% dextran 450-600 kDa , MWCO of membrane is 150 KDa.
Is it because dextran molecules are devided into equal pieces so that 150 becomes two 75 and 450 becomes three 150?
Dear Foroogh,
Dextran is a complex branched glucan (polysaccharide made of many glucose molecules) composed of chains of varying lengths (from 3 to 2000 kilodaltons). Dextran is cleaved by acid catalyzed hydrolysis or by enzymatic hydrolysis.
https://en.wikipedia.org/wiki/Dextran
Generally, for the determination of MWCO of UF membranes a mixture of dextrans having a variety of molecular weights is used.
Regarding "Is it because dextran molecules are divided into equal pieces so that 150 becomes two 75 and 450 becomes three 150", the answer is no because the cleavage of dextrans can be accomplished only under the conditions described above (enzymatic or acid-catalyzed hydrolysis).
For the use of dextrans and other tracers to determine MWCO of HF/UF membranes, please see attached file.
Hoping this will be helpful,
Rafik
Dear Rafik
Thank you so much for your answer. I used of paper.
Best wishes for you.
Foroogh
Dear Foroogh,
if the membrane can separate 90% of dextran 450-600 kDa then that's pretty much the value of the MWCO, even though it shouldn't be determined merely based on one rejection experiment. General procedure is using dextran of different MW and plot the rejection over the MW and find the point where the rejection is 90%. Molecules with close MW may have a similar rejection.
Dextran solution (in water) is pretty stable for a few months. You can check with GPC to ensure its stability.
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