Question

Show an illustrative conceptual layout and design of a NMR spectrometer and how it operates

Answer 1

Nuclear magnetic resonance spectroscopy, commonly referred to as NMR, has become the preeminent technique for determining the structure of organic compounds. Of all the spectroscopic methods, it is the only one for which a complete analysis and interpretation of the entire spectrum is normally expected.

NMR spectrometers have now become very complex instruments capable of performing an almost limitless number of complicated experiments. Important parts of the spectrometer are not that complex to understand in outline, and it is certainly helpful when using the spectrometer to have some understanding of how it works. Spectrometer consists of the following components: a) An intense, homogeneous and stable magnetic field b) A probe which enables the coils used to excite and detect the signal to be placed close to the sample c) A high-power RF transmitter capable of delivering short pulses d) A sensitive receiver to amplify the NMR signals e) A digitizer to convert the NMR signals into a form which can be stored in computer memory f) A pulse programmer to produce precisely times pulses and delays g) A computer to control everything and to process the data.

Nuclear Magnetic Spectroscopy is based on the fact that when a population of magnetic nuclei is placed in an external magnetic field, the nuclei become aligned in a predictable and finite number of orientations.

Principle: Many nuclei have spin and all nuclei are electrically charged. If an external magnetic field is applied, an energy transfer is possible between the base energy to a higher energy level. The energy transfer takes place at a wavelength that corresponds to radio frequencies and when the spin returns to its base level, energy is emitted at the same frequency. The signal that matches this transfer is measured in many ways and processed to yield an NMR spectrum for the concerned nucleus.