Improvement of conventional experiments by perfect echo
Fig. 1a) shows the spin echo pulse sequence that we usually use. The disadvantage of this pulse sequence is phase distortions due to J-modulation appear. These phase distortions make data analysis difficult. Fig. 1b) Fig 1 b) ※1 shows the perfect echo pulse sequence that suppresses the influence of J-modulation. Replacing the spin echo pulse sequence with the perfect echo pulse sequence in cleaner spectra free of phase distortions.
Fig. 1: Pulse sequences of spin echo a) and perfect echo b)
Examples of application.
The CPMG (Carr-Purcell-Meiboom-Gill) method is commonly used for T2 measurement. The PROJECT (Periodic Refocusing of J Evolution by Coherence Transfer) experiment applies the perfect echo approach to the loop parts. Fig. 2 show spectra collected with CPMG a) and PROJECT b) pulse sequences.
Next, the dpfgse (Double Pulseed Field Gradient Spin Echo) version of WATERGATE experiment is commonly used for water suppression. The experiment that combines the WATERGATE dpfgse and perfect echo is WATERGATE PE. Fig. 3 show spectra collected with WATERGATE dpfgse a) and WATERGATE PE b).
In both Fig. 2 and Fig. 3, the phase distortions are suppressed by the application of perfect echo.
Fig. 2: a) CPMG spectrum and b) PROJECT spectrum of α- cyclodextrin and glucose in D2O
Fig. 3: a) WATERGATE_dpfgse spectrum and b) WATERGATE_PE spectrum of 2mM sucrose and DSS-d6 in 90% H2O/10% D2O
- ※1 J. Magn. Reson., 84, 611-615 (1989)
- ※2 Chem. Commun., 48, 811–813 (2012)
- ※3 Chem. Commun., 49, 358-360 (2013)
- Please see the PDF file for the additional information.
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