Hi Emily,
Your sample (90% H2O) will have a very broad line at 600 MHz because of
"radiation damping". Try a "pure" D2O sample which should show a HDO
signal. It should have a linewidth appropriate for the shimming.
George Gray
Retired from Varian/Agilent
On 6/7/2025 2:03 PM, Shin, Ronald via groups.io wrote:
>
> Emily,
>
> This is from the good folks in Farmington, CT:
>
> https://health.uconn.edu/structural-biology/wp-content/uploads/sites/177/2017/10/Resetting_lock_freq_vnmrj.pdf
>
> I’d start by putting in an easy standard, such as one of your
> lineshape samples (99% d-acetone, 1% protonated chloroform), since
> this will have a very strong lock signal.
>
> Change the frequency downward in conservative increments, until you
> can see that strong lock signal (not a weak one like the sidebands),
> and try to get it to the middle of your numerical field.
>
> For Bruker spectrometers, the ‘cf’ command should access something
> similar where you can change the base frequency of the spectrometer.
>
> Ronald Shin
>
> University of Alabama at Birmingham
> O’Neal Comprehensive Cancer Center
> Central Alabama High Field Nuclear Magnetic Resonance Facility
>
> *From:*main_at_ammrl.groups.io On Behalf Of Emily Crull via groups.io
> *Sent:* Friday, June 6, 2025 11:44 AM
> *To:* main_at_ammrl.groups.io
> *Subject:* [AMMRL] Checking and editing magnet's base frequency on VNMRJ4 #agilent #varian #VarianAgilent
>
> Hi all,
>
> I'm working on a Unity Inova 600 MHz NMR. Recently, the console went
> offline due to a power issue. It has since come back online and we
> still have a magnet. However, it is experiencing a new problem.
>
> When acquiring a 1H spectra of our D2O standard (90% H2O, 10% D2O),
> the H2O peak is extremely broad (presumably due to poor shims) and
> appears at roughly 4.6 ppm. In addition to this, I cannot get a strong
> lock signal, even after sweeping all of the z0 range and phasing it.
> According to people who have been at WVU longer than I, it has had
> problems finding z0 automatically for years.
>
> I have the instructions for changing the lock frequency, but am
> wondering if we are also seeing the effects of magnet drift. *Is there
> a way to check the magnetic field and if necessary correct it in VNMRJ4?*
>
> Best,
>
> Emily
>
>
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Received on Sun Jun 08 2025 - 07:09:49 MST