I have a lot of NMR tubes and as a result I don't clean them very often and when I eventually decide to do something about it I'm faced with something like 30 dirty tubes. Now firstly if you work this way you have to soak the NMR tubes as soon as you are done with them. If you just let them evaporate to dryness you are in trouble. I normally just empty the tube and fill it to the lip with acetone and cap it. This way it wont dry out for months.When I was cleaning my tubes the other day I had three synthetic organic chemists from three different countries walk up to me and ask what I was doing. This was somewhat surprising so I've decided to share with you what I thought was common knowledge: The NMR Tube Cleaner. These things are commercially available (expensive) or you can have your glass blower make one at a reasonable price. You can see my set up on the picture above. This is how it works:
(1) take the cap of your NMR tube and attach it to its base
(2) stick the tube in the cleaner (see picture) so that the cap seals the opening at the top
(3) squirt solvent(s) into the solvent opening (see picture).
The system is under vacuum and the solvent gets sucked through a thin tube that goes to the bottom of the NMR tube. It is very effective and I usually do a combination of solvents to get rid of everything. Its smart to have a three way tap between the cleaner and the pump so that you can let air into the cleaner without having to turn the vacuum off all the time. There's an NMR tube entry at Wikipedia that also describes the NMR tube cleaner. D!
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15 comments:
Cool! Maaaaybe I'll make friends with the glassblower.
A lab where I used to work had a similar cuvette cleaner, which was also dead useful. Probably my favorite thing about it was that it was so easy to use that everyone cleaned the cuvettes when they were done.
We had one similar to that unit while I was in undergrad, and we have one at my work currently. They're great, but so incredibly fragile....I broke one once by accidently dropping the NMR tube in without a cap on the closed end. The little, delicate tube on the inside snapped off and then it was useless. If you're careful, they're great!
they are very fragile though - the inner glass capilary that goes inside the NMR tube breaks off by a shock easily. Our NMR guy bought a couple of tube cleaners from Wilmad and it hurts me to see now all of them ruined now by careless chemists.
I wash my tubes manualy, usually 4-5 at the same time, 6 double rinses acetone /DI water seems to suffice
Wow - but you need a lot of tubes before this is needed - but then I guees 30 tubes are actually a lot. I usually only uses 5-8 tubes, and then was them manually. First with the solvent that was used for the compound (excluding DMSO though) and then with acetone.
re henrik......
as long as you don't mix your (deutero)chloroform and acetone washings.
Everyone keeps telling me that the cleaner is very fragile. I have a feeling that people should just stop dropping it on the floor. I have worked in quite a few labs by now and only once did one break (Capillary tube snapped off). However, a quick trip to the glassblower and it was fully operational again the next day. Maybe some of the commercial ones are of poor quality? The Aldrich models I've used never broke. D!
now that you say you've never broken an Aldrich model NMR tube cleaner, I feel shameful that I've broken two of them within a year. stupid me.
Yeah, they are dead useful. We had one in undergra/grad school & amazingly it never broke. But then it only washed one tube at a time. Since then, I've graduated onto the kind that hold 5-tubes at a crack from ChemGlass (Wong Cleaner) & it kicks some serious butt. I normally go through more than 50+ tubes/mo. BTW- as an synthetic orgo chemist - I've never broken one.
There is a very cheap way to replace this glassware, even if it looks like less effective. But if you are use to break these NMR tube cleaners, it may be worthwhile to try it :
just put a long pasteur pipette through a septum that you adapt to you vaccuum flask. The thin part of the pipette must be out of the vacuum flask. Put your NMR sample on it and switch on your vacuum pump. The solvent is kept around the NMR tube thanks to the thin part of the septum and is aspired into the tube to the pipette.
I hope I am understandable, despite my english and the lack of schema. But I'm sure you'll find out what I mean.
"NMR tube cleaners are susceptible to breaking if a standard 5-mm, 7-in. NMR tube is dropped or pulled down the length of the cleaner. This often happens when one forgets to place a cap on the closed end of the NMR tube. An easy way to minimize this problem is to slide a short piece of plastic straw (ca. 1 inch) down the length of the inner tube. This prevents an NMR tube from dropping down onto the ring seal but still allows sufficient vacuum for solvent flushing."
Quted from: Aldrichimica Acta (1995) Vol. 28, No. 4, p. 94.
Another possibility is to make this cleaner from a long needle (instead of a capillary) and a polyethylene (betterteflonn) tube of a proper (as an outer tube).But I liked idea from adrien kaeser alot :)
I agree with Alexey. Glass cleaners are expensive and fragile and you can make one yourself easily from teflon tubing and a glass funnel. Example:
http://www.spectroscopynow.com/coi/cda/detail.cda?page=3&id=10170&type=EducationFeature&chId=5
Provided you have a glass blower glass NMR tube cleaners are cheap. Granted they break a lot easier than plastic would. However, I have worked in labs for more than 10 years and still haven't seen a broken one. I guess this is all down to how unlucky (clumsy, careless?)the user is. I have used some home made set ups in the past but they just aren't as nice and convenient as the glass ones. I have not used the particular set-up that you provided a link for. Thanks for the tip. I'm sure many readers will find that information very helpful. D!
You don't need anything so fancy. Just shove a glass capillary through a rubber septum and attach to vacuum. The solvent gets sucked up the tube just the same.
I just found your blog and I’ve found every article I’ve read very helpful. My problem is that I get lots of visitors, but very few comments!
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