Thanks to everyone for their feedback regarding the iron dust from the HVAC
system, its effect on my NMR and my NMR tubes.
MR Resources was out yesterday. A good bit of very fine black powder was
cleaned off of the magnet with duct tape and moist towels. The probe tube
and bore tubes were removed and cleaned. Before cleaning, the line shape on
our 13C sensitivity standard (dioxane in deuterobenzene) was about 10ppm
wide, with a huge tail on the downfield side, which would not shim away.
After cleaning, the lineshape is symmetrical and far narrower. Spectra look
much better.
The ducts will be cleaned sometime in the next couple of weeks. Although
we've been assured that no more dust will enter the NMR room (yeah, right),
we'll recheck lineshape after that, then likely have MR out again to do a
full blown to spec tuning. I want to be sure things are back to pre-dust
standards. Being the end of the semester on a 4/4 load, I simply don't
have the time to deal with it!
I got lots of suggestions for tube washing/throwing tubes away. Many
suggested that nitric acid was a bad idea, because that would just make the
iron soluble and harder to see. The consensus was to wash with acetone and
deionized water, and possibly even EDTA. I'll have one of the undergraduate
lab aides work on that next week.
So things seem to have all worked out. I was very calmed by the number of
"oh, that happened to us!" comments.
The only "detail" that remains is that an air handler was turned off to
prevent any more iron blowing around until the ducts are cleaned. Our
department offices have no heat until the ducts are finished. But at
least the NMR works again.
Janet Asper
University of Mary Washington
Received on Sat Nov 13 2010 - 09:40:21 MST