Centrifugation is not helping me as the particles are small and they are not settling.
I would first approach it by warming to the cloud point of the PEG which will be dependent on MW. At the cloud pt PEG becomes insoluble in water. This is the same for peg coploymers which you can find could points for in the literature between 20 - 100C.
once insoluble you may then be able to seperate by settling or filtration.
However if ther peg is there for stablity the whole system will coagulate and settle.
Alternative would be nanofiltration where the poresize of the membrane is chosen tgo remove peg buy not the nano partocles this would remove free peg but not that on the surface.
if you want to oxidise it then try ozone with potentially UV combined or hydrogen peroxide UV combine. this will break it down to a significant degree if not complelety
You can remove excess PEG by filtration through Centricon filter tubes (Amicon). They are available in different pore size tipically 100,000 is best for all perpose.
Do you plan to store your nanoparticles in suspension form? Because if you are going to store them as lyophilized particles, I'd just centrifuge the suspension. PEG will stay dissolved, and your nanoparticle pellet will be at the bottom. Give it a couple of washings and you're done.
Was that sentence about not centrifuging the particle there all along? I'm sorry for not noticing it.
Thank You all For your suggestions. I will try and let you know about the results. One more thing I would like to add that I am using PEG 200, which is liquid at room temperature. I am highly grateful to Tony for his thoughtful response. I request him, if he can suggest some measure regarding the removal of PEG 200, which stays in liquid form.
If the PEG is so low MW dialysis might work the best although it is unreliable for complete separation at higher MW. Then for sure centrifugation and/or column sephadex column separation is the most efficient. I am a bit surprised that the centrifugation does not work. What is your core material and how big is the core?
Hi Erik
Thanks for your reply. The mol wt of PEG is 200 and the core material is carbon particle of 4 nm.
This is of course very difficult to separate, since both size and density ratios can be similar for the particles and the dispersants. I would be ost interest to know in the end which method you find the best. I work only with inorganic cores.
Maybe by ultracentrifugation... if an excess of PEG really exists must be in solution, and after UC must stay there.
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