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I'm using a Bruker 300 NMR, equipped with a BBO probe, to do Boron 11 NMR. But I got no signal no matter what pulse length or scan width I set, I don't know whether it's related with the borosilicate tubes I use, or should I use quartz ones. Could someone here give me some advice? Thank you!

asked Aug 20 '11 at 16:12

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Chemuri
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Hi Chemuri, Check that the probe is tuned properly to 11B. You will see a background (broader peak) with borosilicate tubes--useful in knowing that everything is working--and it can be advantageous to switch to quartz tubes for samples at lower concentration, or samples with broader 11B signals that can look like the tube background. But independent of the tubes, you should see 11B is everything is setup properly. Something wrong with the probe tuning is the mostly problem.

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answered Aug 21 '11 at 03:34

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Charlie Fry
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run a T1IR array and you'll clearly see an evolving peak (or manifold) - the fat borate signal will have a dramatically different T1 from the boric acid. If you don't see that in a T1, then something is wrong elsewhere. Do you have the correct 1/4-? cable in? I've made that mistake 50 times.

Like the fellow above said, whack it with a short pulse delay (~50-75ms) and just make your life easier by making a boric acid standard in quartz - throw away the Pyrex - eliminating a variable. If you don't know how to blow a standard, I can describe it in detail. You really only need O2, house gas (or what have you) and a torch with a broad (r ? 0.75-1cm), dual-peak head that can handle both oxygen and your hydrocarbon gas of choice.

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answered Aug 27 '11 at 18:47

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Thank you for answering my question. I can tune it to B11's frequency, using either atma or atmm, do you mean there's something wrong with the probehead? Should I use a blank tube to test it?

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answered Aug 21 '11 at 05:16

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Chemuri
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Hello Chemuri, please use comments to follow up, here we use answer space just for the answers. Best, Evgeny. - Evgeny Fadeev (Aug 21 '11 at 17:10)

If the probe will tune correctly, then the probe is likely OK. Perhaps the spectrometer is not on the correct frequency. Double-check the spectrometer setup to be sure the transmitter frequency is correct for 11B by comparing to the 13C or 1H frequency using the gyromagnetic ratio. - Jerry Hirschinger (Aug 13 '13 at 08:27)

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Both borosilicate tubes and borosilicate probe coil inserts can give 11B background signals which could mask the signal you're trying to observe. You might try to take a spectrum of an empty tube, then apply baseline correction to flatten out the borosilicate background, then run it with your sample and apply the same correction.

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answered Aug 22 '11 at 06:21

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Hi Chemuri. You normally see a background for the tubes but also a background from the glass inserts in the probe. These are very broad so don't expect anything looking too like a normal peak. When you say that you don't see a signal, what do you see? If your phase is a long way out, it may appear that all you have is a wavy baseline.

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answered Aug 23 '11 at 10:18

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John Hollerton
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Hi Chemuri,

What sample are you using to set up? I would try something like boric acid to start with, should give a single peak around 20ppm, reasonably sharp (<100Hz). Something like >10mM concentration should be enough to see a reasonable signal, I guess. This would be a good sample to calibrate a pulse on.

As others have indicated, you should see the background signal quite easily - if you see just a flat spectrum then there is probably something else wrong! If you start from the standard B11ZG parameter set, then the acquisition time is rather long (1 second) - I would use an acquisition time of 50 ms at most (the lines will be quite broad, even with boric acid they will decay into the noise within 50msec, and less time for the background signal). With the standard parameters the background signal may take a few scans to show up. Try efp with lb=500Hz and see if anything pops up!

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answered Aug 25 '11 at 04:16

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Pete Gierth
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The one problem that I have had with 11B is that because of its (relatively) high frequency it is right at the end of the tuning range of many BB probes. This makes the tuning controls VERY sensitive and I have found a very gentle touch is required.

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answered Aug 30 '11 at 04:15

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David Stephenson
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Hello Chemuri

Assuming your BBO probe can tune to the appropriate frequency, I recommend as a test & calibration sample a solution of BF3.etherate (use it neat, with the spectrometer lock and lock sweep switched off). You can use a borosilicate tube (although quartz is better) and the pulse length and power level for either 13C or 31P (on the same probe) as a starting point for pulse & power calibration with the B11ZG parameter set. The neat BF3.etherate solution will give you a sharp singlet at roughly 0 ppm from a single pulse.

Caution with the BF3.etherate solution - it is both toxic and corrosive; read the MSDS.

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answered Aug 05 '13 at 11:46

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Craig Grimmer
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  1. copy the CORTAB of 13C and change the name of 11B
  2. add the info into the probe (edhead)
  3. ATMM find out the right frequency of 11B, and save
  4. Set the wide SW and choose appropriate O1P
  5. no need do topshim
  6. turn the lock and sweep off
  7. > rga > zg
  8. Then will see the peak
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answered Aug 27 '13 at 19:59

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Sarah
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updated Aug 27 '13 at 20:03

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