Chemical Sciences: A Manual for CSIR-UGC National Eligibility Test for Lectureship and JRF/Gradient enhanced NMR spectroscopy
Gradient enhanced NMR is a method for obtaining high resolution nuclear magnetic resonance spectra without the need for phase cycling. Gradient methodology is used extensively for two purposes, either rephasing (selection) or dephasing (elimination) of a particular magnetization transfer pathway. It includes the application of magnetic field gradient pulses to select specific coherences. By using actively shielded gradients, a gradient pulse is applied during the evolution period of the selected coherence to dephase the transverse magnetization and another gradient pulse refocuses the desired coherences remaining during the acquisition period.
- Significant reduction in measuring time
- Reduced T1 artifacts
- Elimination of phase cycling and difference methods
- Possibility for three and four-quantum editing
- The ability to detect resonances at the same chemical shift as a strong solvent resonance
- A need for field-frequency-lock blanking during long runs.
- Selection of transverse magnetization (Ix, Sx, Iy etc.):
(+)gradient 180°(x) (+)gradient
- Suppression of transverse magnetization (Ix, Sx, Iy etc.):
(+)gradient 180°(x) (-)gradient
- Ralph E. Hurd, Gradient-Enhanced Spectroscopy, Journal of magnetic resonance. 87, 422-428 (1990)