Sample: 80% CHCl₃ in acetone-d₆

Record a conventional ¹H spectrum.

Record a ¹H-coupled ¹³C spectrum.

The calibration of the selective 90º ¹H pulse via the decoupler channel is performed using the standard ¹³C parameters (the pulse program is decp90sp) and the procedure is very similar to the 90º ¹H pulse decouple pulse calibration. The corresponding doublet ¹³C resonance of the CHCl₃ signal is analized in a  ¹H-coupled ¹³C spectrum as a function of the pulse length. 

The initial values are:

• p1=90º ¹³C observe pulse at high power level pl1
• d2=1/(2*¹J_CH) (2.36 ms optimized for 212 Hz)
• ns=1
• It is very important to use a long recycle delay, usually d1=5*T₁(¹³C) (d1=20 s).
• o1 and o2 are set on-resonance of the selected ¹³C and ¹H resonances, respectively.
• The following selective ¹H pulse parameters must be defined: duration (p13), power level (sp2) and shape (spnam2).

Start acquisition with rga and zg using an initial minimum value of p13=0us. Repeat the experiment varying the p13 value.

Use standard ¹³C processing parameters (efp with lb=2). After proper phasing, the first spectrum shows an up-down doublet. When p13 is increased, the signal intensity of this antiphase signal is decreased until a nul point is achieved (this is the selective 90º ¹H decoupler pulse). When p13 reachs 180º degree, an antiphase ¹³C resonance in a reverse down-up mode is obtained.

This pulse can also be calibrated using the SPT experiment.