The ge-2D RELAY experiment allows to obtain a multiple-step 2D RELAY spectrum with a single scan per t₁ increment provided that the S/N ratio is adequate. The main advantage of such approach is the large reduction in the total acquisition time compared with a conventional phase cycle 2D RELAY experiment. The RELAY experiment permits to correlate all protons resonances belonging to the same spin system via the stepwise propagation of the homonuclear J_HH coupling constants.

Easy implementation on any AVANCE spectrometer equipped with pulsed field gradients.

The gradient-enhanced version of the 2D RELAY experiment is easily made by incorporating two PFGs flanking the mixing process, the first during the variable evolution period and the second just prior to acquisition. When these gradients have the same duration and intensity, N-type data is selected in a single scan per t1 increment and, therefore, a magnitud-mode RELAY spectrum can be quickly recorded in a few minutes. As in conventional RELAY experiments, consecutive RELAY blocks can be added for step-by-step transfer magnetization through all spin system network

The ge-2D RELAY experiment is acquired an processed using the same experimental conditions as decsribed for its phase cycle version. The only difference is the presence of gradients. Thus, the user only need to define the strength, duration, shape of the gradients and the recovery delay. The experiment can be recorded in routine and automation modes using a single scan per increment t1 and minor changes are required if a predefined parameter set is available. The most important to modify in RELAY experiments is the fixed evolution period(s) to achieve antiphase magnetization (1/2*J(HH)).

More details on practical implementation of ge-2D RELAY experiments on AVANCE spectrometers can be found in

Tutorials: 2D homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments in H₂O

The magnitude-mode spectrum resulting of the gradient-enhanced RELAY version is a clean 2D map in which t1 noise has been efficiently reduced. As in the conventional RELAY spectrum, cross-peaks correlate chemical shifts between J-coupled spins. Three main peaks can be present:

Diagonal or autocorrelated peaks.

Off-diagonal or cross-peaks. These peaks reveal direct or relayed J-connectivities. A preliminary COSY spectrum can be helpful to differentiate them.

Axial peaks (appearing a F1=0) that are efficiently removed by using a two-step phase cycle.

Related experiments:

2D homonuclear experiments

2D gradient-based homonuclear experiments