# What type of centrifuge do I need?



## NobleMetalWorks (Jul 3, 2012)

I need to obtain a centrifuge, but I am not sure what type, I know nothing about centrifuges and have never used one.

I am planning on making quantities of silver nano spheres and I need a way to settle them out of solution. I thought ultra sound and vibration might work, but it doesn't seem like these are common methods of accumulating nano particles. I have read in several papers, the use of centrifuges to do so. I am not looking to re-event the wheel, I just simply want to get done what I need to do in the least expensive, easiest and less time consuming method possible. It seems that a centrifuge will satisfy all these requirements. But knowing nothing at all about centrifuges I am hoping someone here might help me.

I need something that can handle larger than test tube quantities, but I have no idea what type of lab glass I would need to accommodate a centrifuge of this type, nor the price involved, etc. I'm really not sure of anything other than a very basic understanding of how a centrifuge works.

Any help would be appreciated

Thank you

Scott


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## glondor (Jul 4, 2012)

would any of these work? http://merry-farm.com/ http://www.hoskin.ca/catalog/index.php?main_page=product_info&products_id=1500 http://www.arrayit.com/Products/Microarray_Instruments/Microplate_Centrifuge/microplate_centrifuge.html


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## MysticColby (Jul 5, 2012)

I've frequently wanted to use centrifuges to help settle metal powders in solution :lol:
I use all kinds of them at work. I'll go ahead and share everything I know.

There are a couple important parts about centrifuging: volume, g-force, and time. There is also fixed vs. swing out rotors, but those are usually dictated by your needs (swing out is nice, but isn't available at higher g's).
This formula will help: RCF = 0.000001118 x radius (mm) x RPM^2
RCF = Relative Centrifugal Force = g-forces produces
Each centrifuge usually has a set radius (distance from center to furthest point on container), and adjustable speed (RPM) and time.
I should point out that 1,000 g for 2 hours is NOT equivalent to 2,000 g for 1 hour. Maybe somewhere around 1,500 g for 1 hour? You can do it longer to make up for a small lack in g-force, but not a big one.

Oh yeah; one of the experiments I did at work involved colloidal gold (nano spheres of gold, 5-20 nm in diameter). These were the recommended centrifugations for separating these spheres from the solution (these are more than necessary to ensure you get everything):
5 nm = 45,000 g for 1 hour
10 nm = 25,000 g for 1 hour
15 nm = 15,000 g for 1 hour
20 nm = 8,000 g for 1 hour

As you can see, particle size matters. Any idea how big yours will be? I expect larger than these.
It also sounds like you're working with maybe 1 L of liquid?
I have never thought glass in a centrifuge was a good idea. I'm sure there are some glasses that can handle it, but we always use plastic (at higher speeds, we have specific bottles that can handle it. typically, faster = needs to be smaller). You really just need to have whatever your centrifuge fits.

I expect something like this is what you'll need: http://www.sorvallcentrifuge.co.uk/st16.html (4 x 400 ml bottles at 4,700 g)
or, for smaller size particles: http://www.thermoscientific.com/ecomm/servlet/productsdetail_11152_L11213_88611_12706028_-1 (4 x 180 ml bottles at 45,000 g)
Unfortunately, the higher the g-force and volume, the higher the cost.
Also, some centrifuges can do 45,000 g (for example) with max volume of 4 x 180 ml, but not necessarily together.

So, the first thing you need to do is figure out the volume size and necessary g-force.


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## gold4mike (Jul 5, 2012)

The collective wealth of knowledge on this forum never ceases to amaze me!


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