My drugs have molecular weights of ~350 g/mol and ~1200 g/mol respectively. I need to separate these drugs from the formulation containing both these drugs via nanofiltration or any other suitable method. Some research articles have used 10kDa MWCO membranes to filter drug A. Is that the correct? Which is the best MWCO to be used for both? Or any alternate method I could use?
Your question does not explain what are the drugs and if you need as an end product - the water or the drug, making answering more complex. If you need the drug but not the water you can try:
1. Solid Phase Extraction (SPE) such as on C18 column, ideally after adding salt to the water (~10% NaCl will do nicely) to improve extraction.
2. Two-phase extraction with polar water immiscible solvent (polar because assumingly your drugs are polar, or they would not be water soluble). Try one with low boiling point so you can dry it out after extraction.
3. Lyophilisation - dry the water out
Also see discussion here
https://www.researchgate.net/post/How_can_I_isolate_a_highly_polar_compound_from_an_aqueous_solution
Thank you for the replies. I need to separate flavonoids such as Quercetin from the nanoemulsion formulation to check the drug encapsulation efficiency. Some articles I referred to used Nanosep centrifuge tubes with 100 KD MWCO ultrafilter for separation of Quercetin fr the nanoemulsion formulation and the supernatant as well as the filtrate were analyzed by HPLC.
Can someone please explain why did they use a high cut-off filter for Quercetin (~350 g/mol)?
They use 100 kDa cutoff membranes because the 350 Da molecular weight is irrelevant in your system. You do not have a solution of Quercetin in water (and you could not as it is practically NOT WATER SOLUBLE; up to 60mg/L*) but rather you have an emulsion - meaning the Quercetin is not organized as micelles of much bigger size.
*https://pubchem.ncbi.nlm.nih.gov/compound/Quercetin
If you are removing the capsulated flavonoids you can extract the removing liquid with chloroform of MtBE, evaporate the solvent and quantify flavonoids in it.
Hello Ruchita;
I would just like to add to the thorough and accurate answer of Yoram Gerchman that the reason that the literature report uses a 100 kDa membrane (a larger MWCO than the ones used for rejecting standard size proteins, 30 kDa or lower) is because the size of the nanoemulsion droplets should be considerable large, above that range. So if you think that your nanoemulsion particles may be in the size range of the report, you may use ultrafiltration membranes with MWCO of 30, 10 or 5 kDa. However in practical applications, as you use membranes with MWCO which are closer to the size of the molecules you want to permeate, there is the risk that those molecules can be rejected by the membrane. So for instance, if you go down to the nanofiltration range (e.g. 1kDa) you may get rejection of your large MW drug molecule, which is not desirable. So you have to select the MWCO of the membrane according to the mean size of your nanoemulsion droplets. For carryng out ultrafiltration separations at a low scale you could simply use a microfiltration filter holder assembly for 47 mm membranes (Fusher Scientific No. 097531A)
Hope this helps. Regards,
Rogelio.
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