Patent ID: 7449890

Claim:
An apparatus for performing a nuclear magnetic resonance measurement, the apparatus comprising: a magnet for applying a magnetic field to a sample; a nuclear magnetic resonance probe that is arranged in an area in which a magnetic field is generated by the magnet; a vessel that is equipped with the nuclear magnetic resonance probe and stores the sample; a transmitting/receiving system for transmitting an electromagnetic wave to the sample present in the vessel or receiving an electromagnetic wave from the nuclear magnetic resonance probe; sample tubing that forms a closed loop including the vessel; and a control section provided with a part of the sample tubing; wherein the control section includes: means for injecting a solution containing large molecules to be measured into the sample tubing; means for injecting a solution containing small molecules into the sample tubing; a liquid transfer pump for circularly transferring a solution present in the vessel and the sample tubing, which form the closed loop; a filter that allows the small molecules to be selectively discharged when pressure in the sample tubing is increased to a predetermined level or more by an operation of the liquid transfer pump; and means for monitoring the pressure in the sample tubing.