Doubly compensated multiplicity-edited HSQC experiments utilizing broadband inversion pulses

Abstract

We propose a family of doubly compensated multiplicity-edited heteronuclear single quantum coherence (HSQC) pulse sequences. The key difference between our proposed sequences and the compensation of refocusing inefficiency with synchronized inversion sweeps (CRISIS)-HSQC experiments they are based on is that the conventional rectangular 180° pulses on the proton channel in the latter have been replaced by the computer-optimized broadband inversion pulses (BIPs) with superior inversion performance as well as much improved tolerance to B1 field in homogeneity. Moreover, all adiabatic carbon 180° pulses during the INEPT and reverse-INEPT periods in the CRISIS-HSQC sequences have also been replaced with the much shorter BIPs, while the adiabatic sweeps during the heteronuclear spin echo for multiplicity editing are kept in place in order to maintain the advantage of the CRISIS feature of the original sequences, namely J-independent refocusing of the one-bond 1H- 13C coupling constants. These modifications have also been implemented to the preservation of equivalent pathways (PEP)-HSQC experiments. We demonstrate through a detailed comparison that replacing the proton 180° pulses with the BIPs provide additional sensitivity gain that can be mainly attributed to the improved tolerance to B1 field inhomogeneity of the BIPs. The proposed sequences can be easily adapted for 19F- 13C correlations. Copyright © 2008 John Wiley & Sons, Ltd.