Sample: ASTM sample (60% benzene/40% p-dioxane)

Record a conventional ¹H spectrum.

Record a ¹H-coupled ¹³C spectrum.

The calibration of the low-power 90º ¹H pulse via the decoupler channel is performed using the standard ¹³C parameters (the pulse program is decp90). 

The initial values are p1=90º ¹³C observe pulse at high power level pl1, d2=1/(2*J_CH) and ns=1. It is very important to use a long recycle delay, usually d1=5*T1(¹³C) (d1=60 s).

o1 and o2 are set on-resonance of the selected ¹³C and ¹H resonances, respectively.

using an initial value of p3=0us at low power level pl2. A typical antiphase pattern is observed.

Repeat the experiment increasing the value of p3.

In practice, p3 can be fixed to 80 usec and the user varies the power level pl2 until a nul point is achieved (this is the low-power 90º ¹H decoupler pulse).

Use standard ¹³C processing parameters (efp with lb=3.5). After proper phasing, the first spectrum shows an antiphase triplet with the two outer lines in phase and the center line in opposite phase. When p3 is increased, the signal intensity of this triplet signal is decreased until a nul point is achieved (this is the 90º ¹H decoupler pulse).

PLOT