At the risk of this being a bit of a digression, we are just recovering
from the after-shock of a group of enterprising users employing neat DCl
(deutero version of 37% Hydrochloric Acid), with our Prodigy probe (without
our knowledge, of course). The molarity turns out to be about 12.0 M and
Bruker manuals puts an upper limit of 100 mM ionic concentration for
cryoprobes.
For older systems, notwithstanding the excessive RF heating that can be
generated in the sample space of the probe, poor impedance matching also
will lead to reflecting most of the power you apply in your pulses, back to
the power amplifier, which is bad for the Amp i.e. can damage it.
Rajan
On Tue, Jun 24, 2025 at 10:14 AM Vander Velde, David via groups.io wrote:
> Yes, assuming that's the 1H match control on your system (it's channel 6
> on mine). High ionic strength samples drive the match towards its minimum
> value, and once you reach that in a particular probe, you're out of luck
> with getting the sample properly matched.
>
> Setting aside the question of whether it's necessary or advisable to
> prepare a sample like that, you can still get some kind of 1H spectrum by
> skipping probe tuning, taking some big hit on sensitivity. Some experiments
> are not going to work or not advisable, like 13C with 1H decoupling - you'd
> get high reflected power back from a mismatched probe, and the normal
> decoupling parameters will fail.
> ------------------------------
> *From:* main_at_ammrl.groups.io on behalf of Stephen Nolte via groups.io
> *Sent:* Tuesday, June 24, 2025 8:13 AM
> *To:* main <main_at_ammrl.groups.io>
> *Subject:* [AMMRL] New Error on Varian 400MR
>
> Hi all,
>
> Summer research students elicited a new intermittent error this week on
> our Varian 400MR failed - rf signal too weak on tune chan#5.
>
> Can this be related to high levels of ionic salts in the sample?
>
> Thanks!
>
> _______________________________
>
> Stephen Nolte | Chemistry Technician
> Millersville University
> 717-871-7413
>
>
-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#2451): https://urldefense.com/v3/__https://ammrl.groups=
.io/g/main/message/2451__;!!PvDODwlR4mBZyAb0!QHAf35MEWsmvLrukC0vyzGLrDW_Vjh=
iqiaa0tCEodR09OR1LSNTavxsBMyGDJpYeAWznGQ_Iu7pNQ3KyHFmUcZkc$
Mute This Topic: https://urldefense.com/v3/__https://groups.io/mt/113809292=
/7559972__;!!PvDODwlR4mBZyAb0!QHAf35MEWsmvLrukC0vyzGLrDW_Vjhiqiaa0tCEodR09O=
R1LSNTavxsBMyGDJpYeAWznGQ_Iu7pNQ3KyHKHYkqKk$
Group Owner: main+owner_at_ammrl.groups.io
-=-=-=-=-=-=-=-=-=-=-=-
Received on Tue Jun 24 2025 - 13:33:06 MST