Hi, you can try density gradient centrifugation or size selective precipitation. Pls find an article for the same. Hope it helps.

Have you thought of membrane filters? There are filters with pore size 100nm or even 50nm, although the latter are only specified for air flow and not liquids.

e.g. https://www.millipore.com/catalogue/module/c153#1

Filed flow fractionation or chromatography can also be used. See for example: J. Anal. At. Spectrom., 2012,27, 1532-1539 (http://pubs.rsc.org/en/content/articlelanding/2012/JA/c2ja30069a#!divAbstract)

I have attempted to use membranes myself - limited success. Often the pore sizes are not exact and by diffusion alone the process is extremely slow, just imagine a 30nm NP trying to travel through a 5um (depth) pore? The same is true for dialysis membranes.

In my experience precipitation techniques and size-exclusion chromatography are OK methods for separation of mixed sized, sub 100nm NPs.

If you have any detection method for 10-30 nm particles you can use gel permation Chromatography columns or desalting colunms...

Thanks guys... I m leaning towards sephadex coumns.. may be a higher sephadex.. G75 or G100 may help better.

Sephadex-50 column seems to be an option.

1. Centrifuge and dry the particles.

2. Use filters with pore size 100nm or even 50nm

3. By shifting method , shake the powder sample and collect from the bottom.

Best Regards

You may try

column chromatography

or membrane filtration

or gel electrophoresis and dialysis techniques

What about gel filtration (Sephadex/Sepharose or controlled pore glass) with large pore sizes. This should work with mild buffers and the appropriate pore sizes.

There are a variety of methods for post preparation size separation of nanoparticles. The method of choice depends on the nature of the nanoparticles. Electrophoresis is only suitable for charged particles and the concentration of the gel must be low. All filtration techniques suffer from the disadvantage of pore blockage by larger

There are a variety of methods for post preparation size separation of nanoparticles. The method of choice depends on the nature of the nanoparticles. Electrophoresis is only suitable for charged particles and the concentration of the gel must be low. All filtration techniques suffer from the disadvantage of pore blockage by larger particles and hence the increased co-retention of smaller particles. Chromatographic technique can be used but the conditions have to be carefully selected and controlled. the literature is full of post separation techniques, The best method however is to control the size during preparation.

Another possibility is differential centrifugation - widely used method in biology. You need a high speed centrifuge and a routine method for determination of NPs size. You need to optimize the separation procedure by varying the centrifugation time and speed. Larger particles would get sedimented predominantly at lower speed and shorter centrifugation times. Of course, you will need to isolate at least few fractions of NPs and these fractions may need further fractionation to obtain NPs fraction with desired size distribution. Good luck!

I apologize for short answer as I'm entering via an iPad. As my expertise is rapid development of research into commercially-viable applied research or development my comments will succinct and can provide papers later depending on ur strategy.

In ur situation you have two commercially-viable approaches to consider top level:

1) chemical restriction and/or chemical physical separation then column nano separation (filtering) or nano pore electro separation (should not affect magnectic particles.

2) bulk nano emulsion mixing followed by chemical force sepration (basically electrical field stimulation within emulsion). Think creatiive micelles.

Cheap and effective nano particle sizing and pilot lot size distribution mapping for scale-up my choice is an IZON instrument from kiwi land and available in USA, UK and EU

I agree with Saeed Khan. Sephadex-50 column may be an option.

We do tangential flow filtration on a regular basis. I believe this works for your colloids. You can size select and concentrate them at the same time! Spectrum labs provide the whole unit as well as membrane filters of varying size range. Let me know if you need further details on this!

A simple calculation and using high speed centrifuge you can separate out particles in size range between 10-30 nm from larger sizes. For example with nearly 200000g(or 12000 rpm) you can sediment out particles larger than 10 nm.

Using high speed centrifugation, you can separate the particles with different size distribution.

Good luck!

I recommend you to use dialysis tubes (spectrum labs), which will permit the smaller to go outside the bags and the big ones will remain inside. Then you can lyophilize the small particles suspended/ dissolved in the solutions. Also chromotography is another solution and some gels can be used to filtrate your particles but then you will lose a lot of materials in case if you have low yield.

I tried and separated for my study 100 nm size particles and succeeded using a filter paper.

However yet to develop a system to do this at larger scale.

If I know the quantity and if filter paper use is not prohibited then I can help.

The quickest and easiest approach would be centrifugation! You could even add a buffer gradient to facilitate separation of different sized particles but it isn't always necessary and adds an additional purification step.

Dialysis similarly to filtration can work, but it can be very slow. 

Size exclusion chromatography could also work, but it is less successful when the particles are not so different, it worked well for me when separating 2nm and 200nm particles.

Electrophoresis will work too, not only because of size difference (I.e. Mobility) but also because of difference in surface area and consequently, ligands on the surface. Could take some optimising, but once you get it right, it should be a good approach! 

Can try filters of 0.45 micro meter

Dear Fatima,

You could use Nanofilter, you can fabricate it by electrospining device.

I hope the best for you

Mohammed

Try dialysis bag method

use dialysis and centrifugation

Centrifugation at high speed and for around 40-50 min. is also an option to separate nanoparticles

Centerfugiation