Sciencemadness Discussion Board

Buchi rotovapor el131

jamit - 4-10-2013 at 11:56

I just received a buchi rotovapor model el131. I think it's an old one. I have never owned one of these unit and so I'm wondering what can I do with it.

Now I'm missing some parts and will need to buy them but before investing on that I want to know what I can do with it in a home lab setting. Can some of you who have a rotovapor help fill in my lack of experience.

I' ve read wiki and other articles on the web and YouTube but they don't address its practicality for a home chemist. I know I can separate mixtures of solvents but what else can you do?

Can I distill nitric acid?
Is a rotovapor better at distilling then a regular RBF distillation set up?
What practical use is there with the rotovap in the home lab. I realize this is a very general question depending onus purpose... But I have it now and I want to know whether its worth investing in completing the whole rotovapor. Any suggestion or links will be appreciated.

DJF90 - 4-10-2013 at 12:28

A rotavap isn't for separating solvents. Thats what a fractionation setup is for.

Put simply, a rotavap is for the quick removal of solvents under reduced pressure, in order to isolate the dissolved substances, whether solids or oils. Clearly, if your gear is sufficiently volatile, you should excise caution that you don't have substantial losses due to vaporisation (use low boiling solvents that are easy to remove such as ether or pentanes or DCM) - the same applies if your gear is thermally unstable.

A rotavap is really for organic synthesis. After working up your reaction 90% of the time your desired product is in an organic solvent of some description (which has been washed with appropriate solutions, usually acid/base, water, then brine, and finally dried over a dessicant like Na2SO4 or MgSO4). Stripping the solvent off under reduced pressure then gives you the crude product, which can then be further purified by fractional distillation, sublimation or chromatography. If you go the route of chromatography, then you'll end up with your product dissolved in several fractions, which will be combined and the solvent again removed using the rotavap to isolate your purified material.

I used to have a Buchi Model M which is fucking ancient and microscale... Its currently being lent to a friend, but the point is this model had several auxillary pieces of glass available for it (see attachment). One of which was a Soxhlet extractor body, but there was also a fractionation set. I don't know if these were/are made commercially for the larger models, but I'm sure if you're friendly with a glassblower and have the cash, you could get one made.

I would not advise using this for distilling nitric acid, though there shouldn't be any reason it can't be. I suspect you'll cause the vacuum seal to perish at a faster-than-usual rate. I've heard they're not particularly fond of acetic acid either.

[Edited on 4-10-2013 by DJF90]

Attachment: Rotavapor_M.PDF (757kB)
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S.C. Wack - 4-10-2013 at 16:28

http://www.mybuchi.com/Training-Papers.16023.0.html

also on the page: "Purchase a Rotavapor R-3 for $1,995"
or a demo for $1,732.71
not that they'd ship one to me here

MrHomeScientist - 5-10-2013 at 08:51

I just recently got to set up and use an IKA RV-10 rotovap at work, and never having used one before I was amazed at how awesome it is. The advantages I've seen are 1) very efficient condensing of solvent, 2) gentle and even evaporation for fragile compounds, 3) pulling vacuum allows for lower temperature distillation (saving energy and time). I only tested it with water so far, but was amazed at how fast it works. I would love one at home for any procedure involving distillation. Should work fine for nitric distillation, as it's all ground glass. I'd be nervous about leaking fumes out onto my expensive rotovap though! You'd need to take extra care to not allow fumes to make it to your vacuum pump as well.

DJF90 - 6-10-2013 at 05:04

Quote: Originally posted by MrHomeScientist  
I just recently got to set up and use an IKA RV-10 rotovap at work...

...Should work fine for nitric distillation, as it's all ground glass.


Did you not see the polymer seal? A cursorary search reveals IKA sell replacements for £61.50...

I'll re-cap. Yes, you probably can use it to distil nitric acid. BUT, your seals probably won't last as long as they should. What's wrong with using proper glass to distil nitric acid? (or anything else for that matter).

[Edited on 6-10-2013 by DJF90]

MrHomeScientist - 7-10-2013 at 08:43

Of course you're right. For some reason I was under the impression the condenser connected directly to the vapor tube, but that's obviously not right. My seal is teflon, though, so I would think it would stand up pretty well.

I agree, though: just use a regular distillation setup for acid distillation and leave the rotovap for what it was intended, i.e. removing solvents.

jamit - 7-10-2013 at 09:32

The impression I get from DJF90, MrHomeScientist and S.C. Wack is that Rotovapor is for the most part, not a practical lab equipment for the home lab. I mean, how many of us are there that needs to remove solvents on a monthly or bimonthly basis? And even if you're really into organic chemistry is there a regular use for a rotovap?

Can someone direct me to some experiments or lab exercise I can do to learn more about the functionality and uses for the rotovap? Sorry if this is a newbie type of question, but I have a rotovap and if its not very useful, I'll sell it - it takes up a lot of space and there's no use in keeping it if I'm not going to use it very much.

DJF90 - 8-10-2013 at 02:30

I use a rotavap on a daily basis at work, and the one at home is used almost as often as I do any chemistry. My rotavap broke a couple times and I felt lost without it. It just shaves so much time off when doing org chem its a worthy investment if thats your field of interest.

jamit - 9-10-2013 at 00:58

I'm sorry if I'm sounding like a newbie... because I am, so far as using a rotovap is concerned. What kind of organic experiment can you do at home that would require a rotovap on a regular basis and therefore "worth the investment"? I really want to keep my rotovap el131 but in order to justify it I want to know what I can do with it... and what kinds of experiments are possible... please be as specific as possible or direct me to a link or articles, etc. thank you in advance!

DJF90 - 9-10-2013 at 01:31

As I said, 90%+ of organic experiments will require you to strip off solvent at some stage. You can of course get texts that discuss experiments where a rotavap is avoided (e.g. vogel). In these cases product is usually isolated by crystallisation from the reaction mixture or by distillation of a crude oil after aqueous workup)

Lambda-Eyde - 9-10-2013 at 22:56

Quote: Originally posted by jamit  
I'm sorry if I'm sounding like a newbie... because I am, so far as using a rotovap is concerned. What kind of organic experiment can you do at home that would require a rotovap on a regular basis and therefore "worth the investment"? I really want to keep my rotovap el131 but in order to justify it I want to know what I can do with it... and what kinds of experiments are possible... please be as specific as possible or direct me to a link or articles, etc. thank you in advance!

No organic experiments you can do at home require a rotavap, it is simply a (very) convenient apparatus for the quick, gentle and easy removal of solvents from a solution. Of course this can also be done with a conventional distillation apparatus but the rotavap simplifies and improves the process immensely. You don't have to assemble the apparatus (setting up stands, lubing joints, using keck clips, aligning the whole setup correctly and so on) as the rotavap is always assembled and just waiting for a flask to be connected, you don't clean it after each use, condensation is often much more efficient, you don't have to watch it all the time plus it's a lot faster due to the vacuum and rotation. You're essentially reducing the task of removing solvents from reaction mixtures from a separate distillation process that takes two hours to just putting a flask on the rotavap and forgetting about it for 20 minutes.

If you're not doing much synthetic organic chemistry (and don't plan to), I think you're better off selling your rotavap.

jamit - 10-10-2013 at 20:56

Thank you all for your input. One thing more... Can you direct me to some experiments I can do to learn about rotovap. Thanks.