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My apologies in advance for the very "beginner" nature of my question : ) We are interested in examining a carbon spectrum of a perfluorinated molecular, so of course, we need to do a 19F decoupled spectrum. I am trying to work out the best way to run a 13C{19F} on our Bruker Avance 400 in instrument. I am normally quite ok switching from our usual probe (BBO-H-D-0.5-Z) to the one we have available for 19F (TBI 400SB H/F-BB-D-0.5-Z) to run our routine 19F. ( I must normally switch the appropriate cables from the back of our preamplifier unit to run my standard 19F). The variety of advice I have received has confused me a bit. I was told that if I lacked a 1H/19F preamplifying unit, that I would have to connect the 1H preampliying cable directly to the probe..... I am most definitely beyond my depth and learning as a I go.....any advice would be greatly appreciated! |
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I can only talk to a couple issues here, and not all. You are on the right track that you have to switch probes, and the TBI looks to be capable. Note that with that probe your 13C sensitivity will almost certainly not be very good compared to the BBO. So the first question is how long a 13C{1H} takes on the BBO; if it takes a long time, just be aware that it may take 4 to 10 times longer on TBI (just a guess). And non-19F-bonded carbons will show very low in intensity compared to the 19F-carbons due to lack of NOEs. Another significant problem with 13C{19F} experiments is covering the 19F decoupling. If the range of 19F shifts is small (< 30 ppm) then it won't be too bad. But if it's 100ppm or so, then special techniques would be required to cover the bandwidth. Easier often to do decoupling then of just selected fluorines, by setting O2 to specific regions. I'm uncertain about issues with the preamp unit. You will in any event have to make sure the edasp is setup correctly to match the hardware configuration. Bruker might have some advice there, and I suggest you try the Bruker Center for help (see the support page online). Good luck, Charlie |
