Medical Biophysics 3505F Lecture Notes - Lecture 3: Phosphorus-31 Nuclear Magnetic Resonance, Larmor Precession, Fourier Analysis

• School: Western University
• Department: Medical Biophysics
• Course: Medical Biophysics 3505F
• Professor: Niel Gelman

Document Summary

Thus far, we have learned that the frequency of the nmr signal depends on the nuclear species (e. g. , 1h or 31p) and the magnetic field strength. However, if these were the only factors influencing the signal frequency then we would not be able to differentiate between signals coming from different chemical environments. For example, we would not be able to differentiate choline from creatine or lactate (all producing 1h signals). It turns out that there are slight differences between the frequencies of signals coming from these different chemical environments. These frequency differences are on the order of a few hz to a few hundred hz and are thus small compared to the larmor frequencies (10s to 100s of mhz). As explained in this slide the frequency differences arise from the fact that electrons near the nucleus tend to act as a. Shield , slightly reducing the magnetic field felt by the nucleus.