I have a question for the group-maybe someone else has seen this problem and
knows how to cure it. We have a Unity 500 with a 5mm bbprobe. Sometimes
we have trouble with the deuterium lock signal only when the H1 decoupler is
turned on and only on samples containing organo-metallic compounds with a
positive charge and an anion-say BF4-. This problem occurs in solvents with
relatively low boiling points, eg, acetone or methylene chloride. If the
decoupler is turned on then the lock signal decreases by about 60% and returns
to normal if its turned off. I assume some type of local heating occurs
causing eddy currents in the sample causing the lock to drop. Standard
organic compounds don't have this problem. Has anyone else seen this
phenomenon and cured the problem?
Thanks in advance.
Tom
Tom Nakashima
Chemistry Department
University of Alberta
Edmonton Alberta
Canada T6G 2G2
e-mail address:
vnmr1@ultranmr.chem.ualberta.ca