Comments- Lecture 1, page2
Exchange - Effect of exchange during periods of an NMR experiment
preparation period frequency labeling mixing period detection period
(1-5 sec) (100ms range) (0- 100ms range) (100ms - 2s)
a) in absence of saturation/solvent subtraction:
none line broadening in possibly line broadening
b) with solvent subtraction and labile, exchanging protons:
presat: exchange at any period reduces signal intensity!
significant signal signal reduction, and signal reduction line broadening
reduction line broadening in
watergate: applied directly before acquisition: waterg.
none line broadening in possibly sig.red. line broadening
this indirect domain (ms range)
but note: possible signal reduction of next scan, if water does not completely relax after watergate-filter during acquisition time (at) and preparation period of next scan (d1) !.
Watergate with selective excitation or non-excitation filters: these supression techniques leave the water along z = doesn’t need to relax = next scan will start with full intensity of labile protons .
These methods provide the highest intensity for labile, slowly exchanging protons!