Title :

Minimizing the t 1 -noise when using an indirect 1 H high-resolution detection of unlabeled samples

Author(s) :

Shen, Ming [Auteur]
Wegner, S. [Auteur]
Trebosc, Julien [Auteur]
Hu, Bingwen [Auteur]
Lafon, Olivier [Auteur]
Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181
Unité de Catalyse et Chimie du Solide - UMR 8181 [UCCS]
Amoureux, Jean-Paul [Auteur]

Journal title :

Solid State Nuclear Magnetic Resonance

Volume number :

87

Pages :

111-116

Publication date :

2017-10

HAL domain(s) :

Chimie/Chimie inorganique

English abstract : [en]

The most utilized through-space correlation 1H-{X} methods with proton indirect detection use two consecutive transfers, 1H → X and then X → 1H, with the evolution time t1 in the middle. When the X isotope is not 100% ...
Show more >The most utilized through-space correlation 1H-{X} methods with proton indirect detection use two consecutive transfers, 1H → X and then X → 1H, with the evolution time t1 in the middle. When the X isotope is not 100% naturally abundant (NA), only the signal of the protons close to these isotopes is modulated by the 1H-X dipolar interactions. This signal is theoretically disentangled with phase-cycling from the un-modulated one. However, this separation is never perfect and it may lead to t1-noise in case of isotopes with very small NA, such as 13C or even worse 15N. One way to reduce this t1-noise is to minimize, ‘purge’, during t1 the un-modulated 1H magnetization before trying to suppress it with phase-cycling. We analyze experimentally several sequences following the HORROR condition, which allow purging the 1H transverse magnetization. The comparison is made at three spinning speeds, including very fast ones for 1H resolution: 27.75, 55.5 and 111 kHz. We show (i) that the efficiency of this purging process increases with the spinning speed, and (ii) that the best recoupling sequences are the two simplest ones: XY and S1 = SR212. We then compare the S/N that can be achieved with the two most used 1H-{X} 2D methods, called D-HMQC and CP-CP. The only difference in between these two methods is that the transfers are done with either two π/2-pulses on X channel (D-HMQC), or two Cross-Polarization (CP) transfers (CP-CP). The first method, D-HMQC, is very robust and should be preferred when indirectly detecting nuclei with high NA. The second method, CP-CP, (i) requires experimental precautions to limit the t1-noise, and (ii) is difficult to use with quadrupolar nuclei because the two CP transfers are then not efficient nor robust. However, CP-CP is presently the best method to indirectly detect isotopes with small NA, such as 13C and 15N.Show less >

Language :

Anglais

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

ENSCL
CNRS
Centrale Lille
Univ. Artois
Université de Lille

Collections :

• Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181

Research team(s) :

RMN et matériaux inorganiques (RM2I)

Submission date :

2019-09-25T14:06:21Z