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Wednesday, May 26, 2010

Retrieving Empty Spinners From Magnets

Despite my best efforts in teaching students how to properly use NMR spectrometers, invariably a new user will, on occasion, drop a sample spinner into a magnet without a sample. This is usually done in our undergraduate laboratory by inexperienced students who have finished collecting their data and feel a need to return the empty spinner to the magnet. The problem is that ejecting the empty spinner with the eject air is not possible as the air passes through the spinner. In the past I have removed empty rotors from magnets on Varian spectrometers by removing the upper barrel of the magnet. On Bruker spectrometers, I have removed the probe and inserted a semi-rigid NONMAGNETIC plastic hose in the bottom of the magnet and pushed the spinner to the top of the upper barrel where it can be removed by a helper. In either case, the entire operation took between 5 minutes (Varian) and 30 minutes (Bruker) depending on how much reshimming was required. To avoid this tedious chore, I had our machine shop make a plastic tool for empty rotor removal shown below.
This tool consists of a pole with a diameter slightly less than that of the spinner. On the end of the pole is a tapered prong with a diameter of 4 mm at the tip and 6 mm at the base. This tool is inserted in the top of the magnet and gently lowered until the prong gets wedged into the empty spinner. The spinner is removed with the tool. The entire operation takes less than 10 seconds and no reshimming is required.

6 comments:

Adolfo said...

It is also possible to eject them by simply increasing the air flow

Glenn Facey said...

Adolfo,

Thank you for your comment. The air flow is insufficient in our labs to ejct an empty spinner.

Glenn

Zeca said...

Adolfo,
I had the same problem with a Varian Mercury Plus 300 and it was impossible to eject the rotor even increasing the air flow

Bernie O'Hare said...

Try a wooden dowel rod with duct tape (sticky side out) wrapped around one end of the rod. It's worked for me in the past and hasn't left any residue in the bore or probe.

Sergey said...

Hello, Glenn.

We don't have a good machine shop in our institute, so guys from our lab built an alternative device. It consists of a wooden stick with a plastic tube glued to it's end. We used an empty tube from anti-flu pills (like this one http://www.farmshop.ru/imgprod/f02730_full.jpg). This tube ideally fits inside bruker spinners and allows to extract them easily without applying any extra force. Also, it doesn't require any machinery =) I can make some photos, if you like.

Sincerely,
Sergey.

Anonymous said...

Let me suggest simple way.
You can put on "Lift ON" button, wait some seconds and bend air hose (at the top of magnet, left side for Bruker) and wait 3-5 second for making pressure. Quickly straightening the hose,
the spinner will take off like bullet from air gun. Of course, you need some experience to catch it :-).
Best regards, Igor Ushakov