Hi,
besides what George & Ronald correctly said, some remarks:
- try to insert a D2O sample (like "2/4 Hz H2O in 99% D2O or Autotest) and
click "Auto Lock"/Findz0. If a signal is found and you see a message "z0 set
to xyz" where xyz is a number not larger than maybe 25000 then the field
didn't change (which shouldn't happen anyway due to a power failure that
the magnet has no knowledge of…). If your water line appears at
4.6 ppm it doesn't look like your magnet has drifted much (if at all).
- check on the "Start - Shim" panel if your shims have been correctly loaded.
If in doubt or if many shims show a value of zero then likely the shims are
wrong and you should try to click "Load default shims" on the Shim panel or
load any known good shimset (open vnmrsys/shims via file browser, select
"show all files")
- after any power failure you should check the lock phase: Insert a D2O sample,
auto lock it, click "Lock Scan" and see if you can optimize the lock signal by
changing the lock phase on the Lock panel (usually in steps of 10 degrees is
enough)
- the 90/10 H2O/D2O sample is mostly used to run 3D gradshim (from Tools -
Standard Calibration Experiments) if the last time a good base shim was too
long ago.
It is otherwise natural that at only 10% D2O this sample gives only a low to
moderate lock signal (select "D2O-10%" as solvent before clicking "Auto Lock")
Cheers
Bert
> Am 08.06.2025 um 15:22 schrieb george gray via groups.io:
>
> 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.i=
>> Sent: Friday, June 6, 2025 11:44 AM
>> To: main_at_ammrl.groups.io <mailto: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?
>>0
>> Best,
>> Emily
>
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Received on Mon Jun 09 2025 - 14:05:42 MST