Sample: 10% CHCl₃ in [D₆]acetone; do not use a degassed and sealed sample, since that would make the relaxation time of the CHCl₃ protons exceedingly long.

The probe-head should be tuned to the sample. Load standard ¹H parameters, record a normal ¹H NMR spectrum and note the offset of CHCl₃. Determine exactly the 90° pulse-duration according to Experiment 2.1. The experiment compares the inversion property of a normal 180° pulse with that of a composite one. Therefore you have to perform two experiments a and b according to the two pulse schemes shown above. You have to set:

transmitter attenuation [3 dB]
td	64 k
sw	80 ppm
o1	10 kHz towards higher frequencies from the resonance of the CHCl₃ signal
p2, p3, p4	90° ¹H transmitter pulse
p1	180° ¹H transmitter pulse
d1	30 s
d2	10 ms
rg	receiver gain for correct ADC input
ns	2

5. Processing

Use standard 1D processing (see Exp. 3.1) applying an exponential window with a line-broadening factor lb = 1 Hz. Adjust the phase of the CHCl₃ signal to be negative.

6. Result

The figure shows the results obtained on an AMX-500 spectrometer in a 5 mm multinuclear probe-head. In a the signal after inversion by a normal 180° pulse is given, in b the same signal is shown, but inverted by the composite pulse, leading to nearly fourfold greater intensity.

Normal and composite inversion comparison