Centrifuge/rotor recommended g-force question

[Anonymous Modernist 3009]

I'm looking at a refrigerated high-capacity centrifuge which is rated for somewhat lower rpms:

10000 rpm

19800 g

for 6 ƒâ€”500ml

or

7000 rpm

11000 g

for 6 ƒâ€”1000ml

A number of other centrifuges are cheaper but only spin to 4000g at 3L.



What's the implications and adequacy for tasks such as creating pea butter or carrot butter? Are there certain separations that can''t be performed at lower Gs?

[Anonymous Modernist 393]

Although I can't say fo sure, from what I've learned there is a direct correlation between the # of g's and the time in which the sample needs to be processed.

Basically if you take what the book says 27,500g at 1 hour process time and you take your centrifuge (lets say the first one): 27,500g / 19,800g = 1.388 time scaling factor. This means that any of the recipes you work on would take 1.388x longer to process. So since the book calls a 1 hour processing time on every recipe (I used the recipe finder to check this) then it would take you 1.38 hours or a little over 1 hour and 20 minutes to do the same.

As I said, this information is what I could gather from other sources so I don't have a 100%definiteanswer, but hopefully that's a little bit more to go on than you had before.

[Anonymous Modernist 3603]

Theoretically speaking, anyseparationtask can be carried out at any force >0G, given an appropriate time. The greater the force however, the smaller the amount of time necessary. The amount of force supplied by thecentrifugeis a factor of both how fast the rotor spins (machine dependent) as well as the distrance and angle of the sample from the center of rotation (rotor dependent). When selecting a rotor, there is often times a factor that will be inscribed, by which to calculate the RCF (RelativeCentrifugalForce) imparted. Some of the specifications for spin force and time may be somewhatexaggerated (insurepelletforms, increase pellet density, etc), while others may be just enough. As such, the time it requires to spin at a lesser force may or may not need to be increased - you'll likely have toexperimentto see how much of a difference a decrease in force makes.

RCF Calculator:https://www.beckmancoulter.com/wsrportal/wsrportal.portal?_nfpb=true&_windowLabel=UCM_RENDERER&_urlType=render&wlpUCM_RENDERER_path=%2Fwsr%2Fresearch-and-discovery%2Fproducts-and-services%2Fcentrifugation%2Frotors%2Findex.htm&wlpUCM_RENDERER_t=3

[Anonymous Modernist 393]

Camhabib,

From what I know, not allseparationtasks can be carried out at any force greater than 0g, but most can be done at somewhere near 4,000g. A specific example is the task of making lime juice sweet throughseparationwould requires something like 48,000g's according to an article that I was reading. Again, please correct me if I am wrong

Joe

[Scott Heimendinger]

I'm using a refrigerated Beckman TJ-6, which only gives me about 1500 Gs. However, that is ample for every separation technique I've tried so far. Pea butter and corn butter, for example, work like a charm. However, they require longer spinning times due to the lower G forces - for example, I spin my pea butter for 3-4 hours.

Considering the great deal I got on my centrifuge, and the fact that it holds 2L, I've got no complaints :-)

[Anonymous Modernist 3603]

Joe, while you are correct that there are certain practical force minimums (aka you don't want to spin down for 20k hours), the point that I was trying to illustrate is that force alone is not enough to determineseparationresult - time must also be taken into account. This is mostanalogousto temperatures for foodsafetydiscussedin chapter 2. Temperature alone is of no use, time at that temperature must also be used. There do exist extreme specialcircumstances, mostly in the biological sciences, where you do need a higher force, but those are few and far between.

Seattle, and anyone else thinking about one, if I remember correctly, the TJ-6 is a swingbucketcentrifuge (vs a fixed angle). Be EXTREMELY careful with such models (don't mean to scare, just impact a healthyappreciation). As I'm sure you can imagine, should one of those buckets come loose, the result arecatastrophic, and potentially fatal. Tolerances are typically very high, adn defects can go undetectable by human eye; it's important to keep the machine well lubricated and cares for. Further, to achieve proper balance on a swingbucket, all buckets must be balanced witheach other, not just apposing sets - something that was told to me by a Beckman rep.

[Anonymous Modernist 10]

Jmwb said:

I'm looking at a refrigerated high-capacity centrifuge which is rated for somewhat lower rpms:

10000 rpm

19800 g

for 6 ƒâ€”500ml

or

7000 rpm

11000 g

for 6 ƒâ€”1000ml

A number of other centrifuges are cheaper but only spin to 4000g at 3L.

What's the implications and adequacy for tasks such as creating pea butter or carrot butter? Are there certain separations that can''t be performed at lower Gs?

Unfortunately, no, the cheaper ones won't give you a good yield. You want about 10k RPM at 90 to 120 minutes.