Dear AMMRL,
Have any of you encountered gradient shimming problems in D2O? What was the solution? How long do you let a sample equilibrate for best line shape results? Is an air supply temperature controller necessary (the air supply temperature is 20C)?
I have a Varian Mercury Plus 400 with a Nalorac 5mm PFG Indirect Probe. At the completion of installation of the probe it met all the specifications for line width beautifully (very impressive resolution numbers, none of the samples in D2O). However, when I began running my samples, all of which are in D2O, I discovered that the HDO peak was perfect (one peak, very narrow) but the other peaks were jagged and broad. Leaving the sample in the magnet for several minutes and then gradient shimming improved the line shape greatly so it was supposed that a thermal gradient was present. The installation engineers that have come to my lab have replaced the probe 3 times. The 2nd probe was tested at Varian's lab and found to work without problems. In order to get good results I must leave the sample in the magnet a minimum of 3 minutes before gradient shimming, have the room temperature set to 25C, have the variable temperature set to 25C.
Have any of you experienced this issue? Is this normal? I want to minimize my sample to sample times as much as possible; I do several samples per day, but resolution is extremely important to me since I am doing quantitation.
Thank you for your help.
Best regards,
Pat Hays
Received on Fri Aug 15 2003 - 08:13:07 MST