Hi,

yes, I observed such a behaviour before. I guess you are shimming on the lock signal of the solvent? This is the reason why your solvent signal is perfect. But I noticed that the perfect shimming parameters for the solvent not necessarily are the perfect parameters for your solute. In many cases they coincide, but sometimes they don't.

So I recommend that you shim while observing the signals of the solute in the spectrum instead of using the lock signal. On a Bruker machine you would use the "gs" mode to continuously acquire spectra. For this to work good, well, you should use a small d1 time and maybe a small acquisition time, so that your spectrum is updated rapidly. I found that with repetition times of <1s it is relatively easy to shim that way, as you have a more or less direct response.

Hi,

yes, I observed such a behaviour before. I guess you are shimming on the lock signal of the solvent? This is the reason why your solvent signal is perfect. But I noticed that the perfect shimming parameters for the solvent not necessarily are the perfect parameters for your solute. In many cases they coincide, but sometimes they don't.

So I recommend that you shim while observing the signals of the solute in the spectrum instead of using the lock signal. On a Bruker machine you would use the "gs" mode to continuously acquire spectra. For this to work well, you should use a small d1 time and maybe a small acquisition time, so that your spectrum is updated rapidly. I found that with repetition times of <1s it is relatively easy to shim that way, as you have a more or less direct response.