The refocused INEPT block is a simple extension of the INEPT block in which antiphase X magnetization (I_zS_y) is allowed to evolve during a second heteronuclear spin echo after the last 90º pulses in order to achieve in-phase X magnetization (S_x) with respect to ¹J_CH or combined with other elements to achieve anti-phase X magnetization with respect to a third nucleus.

Similarly as described for the INEPT block, sensitivity improvements can also be obtained from an equivalent DEPT block from which in-phase X magnetization is also obtained.

Easy implementation on AVANCE spectrometers.

The refocusing delay (d3) must be optimized according to X multiplicity:

•  1/(6*¹J_XH)  XH, XH₂, XH₃ positive
• 1/(4*¹J_XH)  XH only
• 1/(3*¹J_XH)  XH, XH₃ positive, XH₂ negative.

For further details about implementation of 1D INEPT and 1D DEPT experiments in AVANCE spectrometers see, for instance:

• Tutorial: 1D INEPT experiment
• Tutorial: 1D DEPT experiment.

The standard way to implement the refocused INEPT block in a pulse program is:

... (p3 ph1):f2 d4 (p4 ph2):f2 (p2 ph5) d4 (p3 ph3):f2 (p1 ph6) d3 (p4 ph4):f2 (p2 ph7) d3 ...

in which:

p1 and p2 are the 90º and 180º X pulse (in microseconds) applied at a power level pl1 from the f1 channel

p3 and p4 are the 90º and 180º ¹H pulse (in microseconds) applied at a power level pl2 from the f2 channel

d4 and d3 must be optimized with respect to ¹J_XH

All phases are specified at the end of pulse program.

Analog blocks using several different commands can be used in inverse detected experiments in which the ¹H and X channels are exchanged. Thus, for ¹H-¹³C inverse detected experiments we have:

... (p1 ph1) d4 (p2 ph2) (p4 ph4):f2 d4 (p1 ph3) (p3 ph5):f2 d3 (p2 ph2) (p4 ph4):f2 d3 ...

The refocused INEPT block is used as a preparation period in some NMR experiments, optionally combined with water flip-back and/or purgued gradients:
  Also see Selective 1D INEPT experiment