Calibrating the chemical shift of a peak does not influence the carrier frequency O1 (or SFO1 = BF1+O1). SFO1 is were you have the carrier. For a simple presat you want the carrier (O1) on the water. You could also do off resonance presat, then you do not have to have the carrier in the solvent but for a simple bruker zgpr O1 is on the solvent/water.
If you want to get fancy, you can optimize your spectrum in the gs mode slightly changing O1 interactively (just a few Hz). But in your case (organic solvent) this is probably overkill
Thank you for the suggestion Markus. I donot use organic solvent. I am sorry for the confusion. I use 90% water to record proton spectra of DNA samples and my reference compound is TSP. we take 4.7 as O1P for room temperature.. but we perform experiments at 278 and 283K too. I run Zg30 and take the O1 value by selecting the tip of water peak and enter it in Zgpr (I just give edc of my old Zgpr file instead of copying and changing pulse program of the same Zg30 file).
we have a 500MHz bruker machine. we try gs mode too at times.
my doubt is when I calibrate the TMS peak from 0.2 to zero, and then click on the tip of water peak for O1 value will there be variation of 100Hz in the O1 value while copying from zg30 or will the O1 value be same as in the acquisition parameter irrespective of the variation in water peak position upon calibrating TSP peak?
Ok.. just take the O1 value you get from zg to zg30 and use that for your preset. You have to be on resonance for zgpr to work. you can always reference later. But one thing confuses me you are using TMS in a water sample? Why nor DSS?
If you are looking at DNA you might also be interested in zgpgw5. To look at at weak base pair it is best to use a 11 pulse sequence, presat and gradient based experiments (while giving nice spectra) generally make you loose these peaks. IF you set up a 11 properly (use of gs for P0 and Phcor2 ) you get RG values that are better than you obtain for zgpr.
[modify the p11 bruker >> p0 ph2:r adjust phcor2 in the gs mode you only need a tiny correction, the idea is to minimize the fid]
good luck
DSS will be better for you, as it does not (as far as I know) temperature dependence. Calibrating pulses/O1 for water with zg30 is a bit odd, as you want your calibrations to run with the "perfect" 90H pulse... therefore ZG is much better option. Usually setting O1P to 4.7 and then fine tune in gs mode is the best way to proceed.
The referencing of the spectrum is better to do only for analysis and not while acquiring, as you will need to modify your carrier according to the actual SR value.
I don't want to get in the middle of the argument about possibly better water suppresion methods for this application but I would like to outline the correct procedure to optimize O1 of presat experiments.
• Create a new data set and setup the experiment parameters (e.g. “rpar zgpr all” and “getprosol”).
• Make sure you have good shim and your probe is properly tuned and matched.
• Make sure the pulse parameters are set correctly. Use a B1 of 50Hz for the CW .
• For the O1 optimization I usually work with a D1 of 5s.
• Start “gs”
• Optimize O1 to an accuracy of 0.1Hz - Go for the minimum FID area.
Make sure to wait at least four scans to see the result before making further changes.
Save the new O1.
• Start experiment with zg.