Improved WATERGATE pulse sequences for solvent suppression in NMR spectroscopy

Modifications to the WATERGATE method for removing the solvent resonance from H-1 NMR spectra are presented. In the conventional WATERGATE, a pulse train with three pairs of symmetric pulses in the form 3 alpha-tau-9 alpha-tau-19 alpha-tau-19 alpha-tau-9 alpha-tau-3 alpha (designated here W3), where 26 alpha = 180 degrees, is used, while the improved versions use four and five pairs of symmetric pulses (designated here W4 and W5), respectively. The modified methods provide narrower noninversion regions and hence enhance the sensitivities of the peaks close to the water resonance. The inversion and suppression profiles of the pulse trains W3, W4, and W5 are compared theoretically and experimentally and good agreement is obtained. (C) 1998 Academic Press.