Last week, some of my peers and I had the privilege to see a real NMR spectrometer at the hospital in Siena. Because not everyone had the opportunity to see this truly fascinating machine, I will present a quick description about the machine and its different components.
First, the sample and an appropriate solvent are added to a tube made specifically for the NMR spectrometer. Then the tube is sealed and shaken. The tube is lowered into the machine at the probe head. Next, a superconductor generates the magnetic field. The magnetic field generated is quite strong (generally between 200 MHz and 900 MHz) and this is why we had to leave our credit cards in another room. Temperature control is a key issue for the superconductor, so the spectrometer has various components to monitor and control the temperature.
The next major component is the spectrometer cabinet. The role of the spectrometer cabinet is to provide three radiofrequency channels: the observe, the lock, and another channel for decoupling. These frequencies are controlled by the computer and are transmitted to the probe head (where the sample is located) and then after some amplification, they are transmitted back to the computer. The probe essentially delivers radiofrequency radiation to the sample and receives the signals from the sample.
Lastly, the computer collects the different frequencies and produces the data for us to analyze. Specifically, the computer has its own components to accumulate the NMR signal and process the NMR spectra. Also, these computers must have high computing speeds and high storage capabilities.
I have described the NMR spectrometer very briefly, but I recommend reading about the components and functions of the NMR in detail. It would be even better to see the actual machine and I am sure many of us will have the opportunity to see it in the future.
References:
media.wiley.com/product_data/excerpt/73/.../3527310673.pdf
http://www.varianinc.com/cgi-bin/nav?corp/businesses/nmr/components&cid=KOHOQNMIFIH
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Thank you for posting this.
ReplyDeleteI think it is important to point out that the magnetic field is being produced constantly. The magnet is carefully charged when the machine is installed, and the machine can never be moved. Daniela said that very bad things would happen if the magnet were “quenched” and the field died. So it is a good thing that the NMR machines are located in the Hospital which will have it’s own generator.
The magnet can be quenched when a large metal object interferes with the magnetic field. For example, if you walk by the instrument holding a wrench or pair of pliers, the magnet will pull the object towards the instrument. If you are not holding tightly, the magnet can pull the metal tool and it will fly across the room and hit the exterior of the instrument and quench the magnet. This is why you see painted marks on the floor and ropes blocking off the instrument. You cannot get too close to the magnet with objects that might quench the magnetic field.
ReplyDeletewell explanation. explain about interpretation of spectra peaks ,intensity and multiplicity and in hospital what is application of nmr which types of diagnosis made by this
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