calamus - 1-8-2010 at 10:09
hi all
I'd like to know it is right or wrong ?
when i use centrifuge and a method state that centrifuge at 10000 rpm for 10 min. and the device i use maximum 6000 rpm so
i increase the time of separation to 20 min
is that right?
please i need someone to tell me
bbartlog - 1-8-2010 at 18:44
You want to know how many gees the centrifuge is putting on your material, not the RPM. Getting from RPM to acceleration requires knowing the distance
from the center to the sample, i.e. the radius. Even then I don't think there is a simple formula that will tell you whether doing a separation for
longer at some lower acceleration would work, or how much longer it should take.
A method that specifies centrifuging at 10K RPM should also say something about the device being used (otherwise the person who wrote it up is not
being very sensible).
calamus - 1-8-2010 at 23:48
thanks bbartlog for your interest
yes i'm not sensible in using the centrifuge
that is my first time i use it
and i only wanna separate a substance
and the method i use say that we use centrifuge at 10000 rpm
and when i tried to use the device i found it maximum speed 6000 rpm
and i do not know what can i do i say it may increase the time of centrifuge
and i do not know is right or it require me to do something else?
bquirky - 2-8-2010 at 00:02
is there any downside to leaving it in for ages ? like an hour or two ?
psychokinetic - 2-8-2010 at 02:43
There can be - and you still can't guarantee that it will work. Like bbartlog said - it's the Gs that count. The pressure exerted on the materials
force the heavier particles to the bottom - not enough pressure and it might not push through.
Perhaps your centrifuge has notation somewhere stating its RCF/Gs?
If not, Gs can be calculated by using RCF = 1.119*10^-5(RPM*2)r
Where RCF = relative centrifugal force or g, and r is the distance in centimetres from the centre of the rotor to the tube sockets.
Failing that,you could bust out a ruler and check out a conversion table: 6,000RPM @ 4cm r = 1610G
That said, a 6,000RPM spinner isn't going to get you very close to what 10,000RPM beast could do.
(10,000RPM @ r=15 =16770G 
)
calamus - 4-8-2010 at 00:47
thanks bquirky
psychokinetic, thanks for your help
i'll chick the device and i'll tell you
is there is any book or site i can relay on it calculation
conversion table and thanks for that equation
RCF = 1.119*10^-5(RPM*2)r
really you helped me
thanks again psychoinetic
[Edited on 4-8-2010 by calamus]
[Edited on 4-8-2010 by calamus]
psychokinetic - 4-8-2010 at 12:56
I was just working off the one in my lab manual, but after exercising my google muscle, I found a conversion site that asks for your centrifuge model,
therefore filling in the equation itself:
http://www.currentprotocols.com/tools/g-forcerpm-conversion-...
calamus - 6-8-2010 at 04:16
thanks psychokinetic
you are really helpful
thanks
I'll chick the device we r working as i did not find the catalog