1H chemical shift evolution followed by a 1H-X INEPT

Multidimensional NMR experiments must be specifically designed in order to reduce the number of pulses and the length of total experiment time to avoid sensitivity losses due to rf field inhomogeneities and T₂ relaxation effects. A widely used building block is one consisting of two following sequential steps:

• Variable ¹H chemical shift evolution t₁ period with refocusing of the heteronuclear ¹J_HS coupling constant.
• Fixed ¹H evolution period  of heteronuclear ¹J_HS coupling constant.

This approach allows to label magnetization with ¹H chemical shift in the w₁ dimension of a nD experiment and, in addition, to prepare anti-phase magnetization by a subsequent transfer step. It is possible to design a concatenated approach in which one of the two 180º X pulses is avoided and the overall duration of the sequence is minimized.
 

Examples showing this building block:

Easy implementation on AVANCE spectrometers.

The most standard way to implement such an approach is:
 

Original	Concatenated
...  d0 (p4 ph1):f2 d0 d4 (p2 ph2) (p4 ph3):f2 d4 ...	...  d4 d0 (p4 ph1):f2 d0 (p2 ph2) d4 ...

in which:

• d4 is the evolution delay optimized to 1/(4*J_XH) (in seconds).
• d0 is the incremented delay (in seconds).
• p2 is the 180º ¹H  pulse (in microseconds) applied at a power level pl1 from the f1 channel.
• p4 is the 180º X pulse (in microseconds) applied at a power level pl2 from the f2 channel.
• All phases may be specified at the end of pulse program.