Sample: 10% CHCl₃ in Acetone-d₆

Insert the sample (ij).

Choose the solvent deuterium signal with the lock command

Tune and match the probehead (wobb or atma if required).

Optimize the shim procedure (read an optimized shim file with the rsh command or performs a gradshim if required).

Record a conventional ¹H spectrum.

The calibration of the 90º pulse via the transmitter channel is performed using the standard ¹H parameter set (the pulse program is set to pulprog zg). A ¹H spectrum is repeated varying the pulse width (p1 at power level pl1) until maximum and null points are found. 

It is very important to use a long recycle delay, usually d1=5*T₁(¹H) (d1=30 s).

On the other hand, we select a specific resonance to be monitored as a function of the pulse length.  From this resonance we define the phase correction (using the phase subroutine) and the plot region (using the DefPlot button) to be monitored.

o1 is set on-resonance of the selected signal.

It is usually recommended to use a pl1 value giving a 90º observe proton pulse around 30-35 usec (for instance, pl1 can be set about 15dB).

Start acquisition executing the AU paropt program. Answer the questions as follows:
 
             Enter parameter to modify:             p1
             Enter initial parameter value:        15
             Enter parameter increment:             2
             Enter # of experiments:                  16
 
In this case, paropt automatically acquires 16 spectra while incrementing the parameter p1 from 15 usec to 47 usec.

Each spectra is automatically processed with the defined lb value (usually lb=1) and for each value of p1, only the spectral region defined above is plotted. All spectra appear side-by-side in the corresponding procno 999. The first maximum value must be the 90º proton pulse. However, more carefully calibration is performed when you get nul the signal. At this point, the pulse would correspond to a 180º pulse. Further nulling must occur at 360º.
 
 

Use the TOPSPIN plot editor (xwinplot)

In all TOCSY-like applications, the spin-lock is performed by applying MLEV, WALTZ or DIPSI pulse trains. The basic element of such mixing times is a 90 degree pulse (set to p6) at a given low power level (pl4). In some cases, the 60 (p5)or 180 (p7) pulses are also required.

To have a theoretical 90º 1H pulse value at a given power level, the pulse length is doubled each 6 dB and multiplied by 10 each 20 dB.  Also see 90º ¹H observe pulse calibration (high power level).