In my last entry, a New Zealand internet rabble rouser made a blatant attempt to hijack a fluffy politics of science thread with some nitty-gritty technical analytical questions. Then this afternoon, somebody from the Earth Environment group at the Australian National University read my entire 2007 archives. EE is the research unit responsible for running the ANU’s ICPMS lab, so it is conceivable that they were looking for some analytical alkali porn.
So, ladies and gentlemen, here is your open thread. Ask you questions about getting laser ICMPS systems to work in a reproducible and reliable manner. Background issues, interferences, sample-laser coupling, you name it. If I know, I’ll answer. Of course, I haven’t worked in a laser lab for 7 months, but it never hurts to stretch out the gray matter a bit, just for nostalgia’s sake.
OK, so I stepped in the doo-doo. Not as much as what I did over on Dot Earth. Oops, there I go again, mixing threads.
ReplyDeleteBTW, thanks for the comments on the high m/e 48 background. It may turn out to be SO+ degassing from new flexible tubing - haven't got the right diameter nylon tubing yet. In delayed response to your question, we have an Agilent 7500 CS. I'm planning to test out the collision cell on our instrument with a bit of He. We already flush the sample cell solely with He, then add Ar downstream, so I don't see how a little more He will hurt. What the collison cell does to the nasty mix we send into it is another matter...
The instruments are housed in the Chemistry Department here. The chemists are constantly amazed at us geochemists trying to measure 30 something elements in a material with the whole periodic table as potential interferences.
Have you talked to the Tasmanians? I think they were screwing around with their collision cell last year. My guess is that you will get all sorts of funky matrix effects appearing, but I haven't had a play with one yet. If you are extracting softly, though, you shouldn't even ionize the He, as long as your total acceleration is less than 25eV. And even if it does, I doubt there will be much dimer formation. If there is, though, I'd look for the appearance of a 104 peak running moly, or a 97 peak in a Nb rich phase like rutile.
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