Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: noone special on June 14, 2012, 04:50:30 AM
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hi all
do you have any idea for cleaning NMR tubes? for example any cleaning solution or any compound for cleaning them?
I have used H2SO4, HCl, acetone , CH2Cl2 (one by one and heating the last 2 solvents with shootgun) :'( but they can't clean well :'(.
do have any idea?
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hi all
do you have any idea for cleaning NMR tubes? for example any cleaning solution or any compound for cleaning them?
I have used H2SO4, HCl, acetone , CH2Cl2 (one by one and heating the last 2 solvents with shootgun) :'( but they can't clean well :'(.
do have any idea?
You used to be able to buy an NMR tube cleaner from Aldrich which was pretty effective.
I soaked mine in acetone then used the cleaner with acetone and ethanol and dried them in the oven.
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The tube cleaner is definitely a good idea. I rinse mine thoroughly with whatever solvent I used to take the NMR (hydrogenated version though, not deuterated), then with methanol, then acetone and allow it to air dry. After overnight drying, I have never seen an acetone peak in my spectrum. Of course, I can always get at least 1 mg of material for a sample; if you are working with smaller amounts or have very sensitive compounds, your mileage may vary. Drying in an oven is not recommended by the manufacturers - too many bent tubes have resulted from hot ovens, and those can damage the NMRs. If you absolutely have to use an oven, use a vacuum oven at lower temperature and be sure the tubes are stored absolutely flat in the oven.
A copy of Wilmad's instructions are here... http://nmr.uoguelph.ca/NMR%20Tube%20Cleaning.pdf (http://nmr.uoguelph.ca/NMR%20Tube%20Cleaning.pdf)
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The tube cleaner is definitely a good idea. I rinse mine thoroughly with whatever solvent I used to take the NMR (hydrogenated version though, not deuterated), then with methanol, then acetone and allow it to air dry. After overnight drying, I have never seen an acetone peak in my spectrum. Of course, I can always get at least 1 mg of material for a sample; if you are working with smaller amounts or have very sensitive compounds, your mileage may vary. Drying in an oven is not recommended by the manufacturers - too many bent tubes have resulted from hot ovens, and those can damage the NMRs. If you absolutely have to use an oven, use a vacuum oven at lower temperature and be sure the tubes are stored absolutely flat in the oven.
A copy of Wilmad's instructions are here... http://nmr.uoguelph.ca/NMR%20Tube%20Cleaning.pdf (http://nmr.uoguelph.ca/NMR%20Tube%20Cleaning.pdf)
Actually I should have said a vacuum oven with the temperature about 28°C at max. vacuum, sorry.
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One effective method is to place all the tube into a conical flask and fill the conical flask with water (change after each wash) and wash(adding the solvent into the tubes) the internal of the tube with 3 x methanol then 3 x acetone (each wash requires you to ultrasonicate for 10 mins). Therefore, the entire wash will takes 1 hour.
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I first wash with water, then methanol, then acetone, then DCM then I put them on the schlenk line and dry them under vacuum for 30 minutes. It works well for me
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I'm a novice interning at an institute and hence to prove how much of a novice I am, I wash it first with a solvent that is most compatible to the solvent in which NMR was carried out - say, chloroform if the solvent is CDCl3, or DMSO if the solvent is DMSO-d6 and so on... once. Then with water, and again with the solvent 4-5 times and then place it in the oven. This works for me... Or maybe I just haven't noticed the aftermath, if any :P
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I usually rinse with acetone , and then dry it immedietly with an air hose, then let 'em hangout somewhere dry. The problem with acetone is that it streaks on glass.
Frankly , i'd rather be doing science rather than dishwashing , so to me there is no point be outrageous.
DChloroform is pricey so I avoid washing it with that.
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Typically water and acetone washes will get them clean. for stubborn tubes that have stains/metal residues try this (BE CAREFUL!):
rubber band all the troublesome ones together and put them standing up in a big beaker or big dish (to catch the spewing I'll talk about in a second). Put a few drops of conc. nitric acid in them, and WITH A SQUIRT BOTTLE, quickly squirt ethanol in them and quickly cover them loosely with another beaker. The solution will begin to bubble, turn colors and shoot the mixture out of the tubes, kind of like a little cannon (which is why is good to have something under them that will catch the residue instead of your hood floor). Let them settle overnight and rinse them thoroughly with water in the morning. They will be squeaky clean. And if not, its not worth cleaning and toss it :P
Hope this helps.
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Typically water and acetone washes will get them clean. for stubborn tubes that have stains/metal residues try this (BE CAREFUL!):
rubber band all the troublesome ones together and put them standing up in a big beaker or big dish (to catch the spewing I'll talk about in a second). Put a few drops of conc. nitric acid in them, and WITH A SQUIRT BOTTLE, quickly squirt ethanol in them and quickly cover them loosely with another beaker. The solution will begin to bubble, turn colors and shoot the mixture out of the tubes, kind of like a little cannon (which is why is good to have something under them that will catch the residue instead of your hood floor). Let them settle overnight and rinse them thoroughly with water in the morning. They will be squeaky clean. And if not, its not worth cleaning and toss it :P
Hope this helps.
For stubborn stains we used pipe cleaners. I don't know if anyone smokes a pipe anymore but any tobacconists should have them.
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For stubborn stains we used pipe cleaners. I don't know if anyone smokes a pipe anymore but any tobacconists should have them.
And if you can't find a tobacconist, a lot of the large art stores carry them as well. For instance, http://www.michaels.com/on/demandware.store/Sites-Michaels-Site/default/Search-AdvancedSearch?cgid=entire&simplesearch=Search&q=pipe+cleaner (http://www.michaels.com/on/demandware.store/Sites-Michaels-Site/default/Search-AdvancedSearch?cgid=entire&simplesearch=Search&q=pipe+cleaner)
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… if not, its not worth cleaning and toss it!
Rinse with acetone (and/or methanol or water) and if needed, my method of choice.