Fri Apr 14, 2017 1:29 pm by GregBehbehani
Hi Mike,
I would second Mike Leipold's request for more information. I would also suggest that if you have any of that sample left, that you try diluting some of it 100- or 1000-fold in both water and nitric acid and then you can run it in solution mode and record all of the surrounding channels and their -16 channels.
I think Laurence's suggestion of Lu177 contrast agent is a great idea, but this should be primarily Lu177 and decay to Hf177, though this agent probably contains some 175 as well (if this is the case you would have an even bigger, unmeasured, signal on 177).
In any case, understanding the complete mass spectrum and whether it is present in solution (present when sample is diluted in H2O) or in the cells (present when the sample is diluted in nitric acid) will be the key to figuring out where this came from. Natural Lu is pretty rare and should have ~2% Lu176 so you should be able to readily detect that pattern. If you see a fairly even distribution of 175 and 177 that would strongly favor the idea of Lu-177 dotatate. If you just see 175 then you probably have contamination from one of your reagents (which could be in one of your pipettes). No matter how bright the signal is, you should be able to find a dilution that you can safely run. I would strongly suggest that you do try to track this down so that you don't have this coming up again (even if you have to go dig your sample tube out of the trash).
Good luck,
Greg