The current work I'm conducting includes an incubation process of small molecules with solid fractions. After the incubation, I usually centrifuge the solids down in a regular centrifuge and it takes quite some time to do that due to specific characteristics of the solids.
I understand that people use sucrose density gradient centrifugation to spin down proteins of different MWs. Is there such an approach for small molecules too, where the solution gets quickly separated into the supernatant ready for transfer while the solids end up at the bottom not being able to interfere with the solution?
It sounds like centrifugation works but is too slow. You might be able to speed it up by using ultracentrifugation, which uses higher g force than standard centrifuges.
Depending on the size of the solid particles, an alternative would be to use simple filtration through a 0.2 or 0.45 micron filter syringe filter for small volumes or vacuum filtration funnel for large volumes, or ultrafiltration using a centrifugal ultrafilter for small volumes or a pressure-driven stirred cell for large volumes. If you do this, you should pay attention to the possibility of loss of the small molecule due to adsorption on the filter. There are different types of filters that may differ in how much non-specific binding they allow.
Hello Wei Zhang,
May be I missunderstood your question, but if you only wants to seperate the solid from the solution, you dont need a gradiant or what ever. If the density of the solid is higher than the liquid it will seperate to the bottom, if it is lower on the surface. The speed of seperation depends on the avrage diameter and the difference of the density, the smaller the slower the seperation happens.
Regards
Andreas
Hi @ Andreas Pingel Keuth.
Thanks for your reply but probably I haven't made my question clear enough. I have always used regular centrifugation for 30 min for the precipitation of solids to the bottom but it doesn't work very well in ridding all the solids. And it is reflected in my instrumental analysis. Another issue caused by long centrifugation time is that it changes my sample composition.
What I need is speedy centrifugation that rids the solids completely, hence the question.
Hi, as I noted above, if the particles are to fine and/or the difference of the density between the solid and the liquid ist to small, it is difficult to remove all solids.
In some cases you can use a so called retention aid, but this will change your solution as well.
Filtration is no option? Syringe filters for example https://www.sigmaaldrich.com/catalog/product/sigma/cls431220?lang=de®ion=DE&cm_sp=Insite-_-caContent_prodMerch_gruCrossEntropy-_-prodMerch10-2
Hi,
quote:Another issue caused by long centrifugation time is that it changes my sample composition.quote
In this case I fear, is an ultracentrifugation worser to changes of sample composition.
If it is the small molecular fraction that you want possibly running the mix through sephadex gel filtration column might stop the solids at the top of the column allowing the soluble fraction to elute
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