A continuous phase-modulated approach to spatial encoding in ultrafast 2D NMR spectroscopy

Resolution and sensitivity aspects of ultrafast J-resolved 2D NMR spectra

“…However, the application of a short gradient can be useful to compensate for experimental errors or to set the echoes at the desired position. Tal et al [9] proposed another method leading to a continuous phase encoding, described in Fig. 1b.…”

“…Unfortunately, this method involves an amplitude modulation which is incompatible with phasemodulated techniques such as COSY [1] or J-resolved spectroscopy [8]. Different alternatives were then proposed [9][10][11] to obtain a phase-modulated encoding in order to circumvent these limitations.…”

“…This scheme was coupled to both Pelupessy's [11] and Tal's [9] excitation patterns. In this study, it appeared that the resolution along the k/m 1 axis was quite disappointing compared to conventional 2D spectra.…”

Improving resolution in single-scan 2D spectroscopy

“…This advantage can be achieved by replacing the usual incrementation of the t 1 -evolution interval by a spatial encoding of the phases across the sample, while decoding is performed with the help of alternating gradients applied during the detection period. The spatial encoding can be greatly improved by using adiabatic frequency-modulated pulses [7][8][9]. This new technique has been successfully combined with liquid chromatography [10] and with methods to increase the polarization of nuclear spins [11].…”

Optimization and practical implementation of ultrafast 2D NMR experiments

“…Moreover, it leads to the appearance of undesirable ''ghost peaks" 18 in the indirect domain. Consequently, this discrete excitation scheme was replaced by several continuous encoding patterns [19][20][21][22] relying on the combination of continuous frequency swept pulses applied during a bipolar gradient. The most efficient approach in terms of resolution and sensitivity is probably that proposed by Pelupessy ( Figure 1S, supplementary material), 20 where spatial encoding is carried out in a constant-time manner through the application of two chirp pulses concomitantly with a bipolar gradient pair (G e ).…”