Achieving Better Sensitivity, Less Noise and Fewer Artifacts in NMR Spectra

Achieving Better Sensitivity, Less Noise and Fewer Artifacts in NMR Spectra 

Artifactual peaks are even more dangerous than noise since they may not always be immediately recognized and may lead to erroneous assignments. An important source of artifacts is instability in the steady-state condition, e.g. if the relaxation delay is set too short. A commonly encountered example is presented by peaks which occur at the double quantum frequencies in DQF-COSY spectra. For detailed treatments of aspects of noise and artifacts see [4, 5]. 

The sensitivity on the other hand is dictated by the spin density and the polarization (the relative population of a- and y3-states). The latter in turn depends on the energy separation of a- and y3-states, which increases concomitantly with field strength. Changing to a higher field will therefore not only increase spectral dispersion but also increase sensitivity because the polarization increases. The remarkable increase in resolution that is gained by going from 600 to 800 MHz is shown in Fig. 3.1. 

The gain in resolution is particularly clearly visible for the Q49/Q62 peak cluster. 

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