Author Topic: RotoVap  (Read 2555 times)

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bbeeasheets

  • Guest
RotoVap
« on: August 31, 2004, 12:25:00 AM »
I would like to purchase a rotovap, but I know very little about them (except that it saves tons of annoying labor) First of all, when I look on labx most of them only come with a 100C water bath. Are rotovaps only designed to remove solvents with boiling points 100C and lower, ie if i wanted to recover 500mls of undecane from a reaction mix it would be of no use? Also, if I purchase a model that comes with a certain size glassware, am I essentially stuck with that size, or can I purchase larger and smaller sizes without buying the whole setup?

thanks!

TrypNballZium

  • Guest
,
« Reply #1 on: August 31, 2004, 01:06:00 AM »

bbeeasheets

  • Guest
rotovap
« Reply #2 on: August 31, 2004, 03:01:00 AM »
thanks, that helps alot. (i can see that the sample and recovery flasks are just standard rbfs right?) but will a rotovap remove solvents at greater than 100C? is it just dependant on the bath?

calcium

  • Guest
umm, vacuum, maybe?
« Reply #3 on: August 31, 2004, 03:34:00 AM »
umm, vacuum, maybe?

biffman

  • Guest
Vacuum is almost always used
« Reply #4 on: August 31, 2004, 03:33:00 PM »
With a rotovap a vacuum is almost always used (except when removing solvents that have a very low boiling point) thus solvents with boiling points of over 100 degrees can be stripped off at a temperature of less than 100 when the vacuum is applied.
  You are aware, I hope, that a rotovap is used just for the removing or stripping off of solvents from a mixture.  Although this is technically a distillation of course it does not mean that you use a rotovap when a procedure tells you to distill something.  In general it is not used to collect a product.  Perhaps this is why you are so concerned  about wanting to distill something over 100 degrees?  After doing lab work for over 10 years I have never come across a situation where I needed to use a rotovap at over 100 degrees.
  When you need to do a distillation you use a standard glassware distillation setup.   Although it would be possible to do it on a rotovap your losses would be very high since so much product would be retained on all the condenser coils and the large glass surface areas involved.  Not to mention that at higher temperatures the seals at the rotating connection would not last very long.
  Hope this helps.

java

  • Guest
Ref to RotoVap
« Reply #5 on: August 31, 2004, 07:50:00 PM »
I would suggest you buy some extra collar tubes, because if you have to order one it takes time and your project has to wait, as to my experience  tThe tube most often broke and failed most often. Also make sure to have extra plastic clamps to hold your flask, especially if there are acids in the solvent being distilled, because they have a tendency to break. Maybe use the wire ones to ensure you don't loose your flask and your goods.....java


biffman

  • Guest
Java gives good advice
« Reply #6 on: September 01, 2004, 06:55:00 PM »
If you haven't used a rotovap before, and you do acquire one, ALWAYS remember to use a clip (or clamp or whatever you call it) on the rotating flask. 
  As Java mentioned, a metal one (which usually comes with the rotovap) is always the best.
  In my experience I've seen many procedures go awry because the evaporating flask decided to separate itself from the works and immerse itself in the water bath (usually letting water in) only because someone forgot to put on the clip.
  If it happens to you once you won't let it happen again.
 (Just like leaving the stopcock open on a sep funnel when you pour in the goods. Aarrrghhh!).

armageddon

  • Guest
use an evaporation flask!
« Reply #7 on: September 11, 2004, 07:31:00 PM »
Standard RBFs are not suited for use with a rotovap. Reason: their glass joint isn't exactly centered, therefore they slowly damage the motor. Special evaporatory flasks don't only have centered necks but also a pear-like shape, allowing for greater surface and more even distribution of the liquid, and result in smoother evaporation, less noise and longer life of your precious (VERY helpful) machinery...

a