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Bruker 800:  Cryogenic probe (CPTCI)

Basic Workflow

Updated 3/24/2023

The cryogenic probe has outstanding sensitivity on both proton and carbon-13 channels. However, it uses much lower pulse powers than room-temperature probes and requires continuous cooling by the Cryoplatform. Please, follow instructions below to safely operate the Cryoprobe.

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Step 1: Verify status of the Cryoprobe

1. First, walk around the 800 and check status of the Cryoplatform (supplies Cryoprobe with ultra-cold helium gas). You should see a steady green light: "Cold".
   
   
   
   
   
   
   If you see any other button lit or flashing: Cryoplatform has some trouble and Cryoprobe will not work. Contact NMR staff immediately!   
   
   
   
   
   
2. Next, log into workstation, start Topspin, and type edhead on a command line. The dialog window appears:
   
   
   
   You should see the line with 5 mm CPTCI... highlighted.
   
   If a different line is highlighted - the instrument has a room-temperature probe, not the cryoprobe that you expect. Contact NMR staff!

   
   

   To quit this dialog, click Exit and Close in a subsequent window with spectrometer wiring.

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3. Go to Manage: Spectrometer: CryoProbe Control to launch CryoPanel
   
   
4. In the Main tab, and scroll the lists of messages and errors to the bottom (the top may have old errors shown):
   
   
   
   If you see .... Cryoprobe cold. All systems normal. , you can proceed with your experiments.
   If the message is different - contact NMR staff!
   
   
5. Note and record in your notebook the idle value of NMR coil heater . It should be about 27-29% when the cryoprobe coils are appropriately cooled. You will be checking this value when you run HSQC, H2BC, TOCSY, and ROESY experiments to make sure it never reduces below 15%.
   

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Step 2. Set the sample temperature

 


      IMPORTANT NOTE:

    Never turn OFF Probe Heater on the Cryoprobe! Temperature control must ALWAYS be on! 






1. Type edte
   
   EDTE screen appears
   
   
   

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2. Turn around in your seat and check visually if the orange light on the BCU-5 cooler is lit (beige box behind the staircase).
   
            
   
   
   
   
   

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3. Set EDTE Target temp according to the following calibration:
   
   

"Target temp." setting	Actual temperature in a sample
	K	Deg C
302	298.2	25.0
297	293.2	20.0
295	291.2	18.0
290	286.2	13.0
283	279.0	5.8
278	274.3	2.1





1. The Gas Flow field always remains at 670 lph
   
   
2. To change temperature, use steps of a maximum of 10-degrees and wait 3 min after each step.
   
   
3. If your target temperature is more than 5 degrees from the initial temperature: wait at least 10 min after reaching the target and before you proceed to shimming

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Step 3. Insert your sample, load shims, and lock

NOTE 1: The instrument is equipped with the SampleCase sample changer. You must review these guidelines before your proceed:  SampleCase training 

NOTE 2: Only blue spinners may be used on a cryoprobe!    

1. Turn off lock and rotation:
   • ro off
   • lock off
     

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For regular NMR tubes shorter than 9 inches: use the carousel of the changer

1. Place your sample in the SampleCase changer carousel
2. Insert your sample in the magnet: 
   sx N  (N - position number in the carousel)
   

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For J. Young tubes and other tubes longer than 9 inches: bypass SampleCase

If you need to do this: contact NMR staff for additional training!

Follow the Manual Insertion guidelines with these modifications:

• find the blue gas valve on top of the magnet near the bore (opposite side to the rail)
  
  
• Do NOT turn off VTU after you finished your experiments   
  

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After your sample is inserted

1. Load a standard shim set:
   
   
1. type rsh
   
   
2. select a standard shimset: Cryoprobe_CPTCI
   
   
3. click Read
   
   
2. Type lock and select your lock solvent
   
   NOTE: If lock fails: stop. Shimming will NOT work without a lock. Load standard shim set and try locking again.
   If still does not work:
1. reinsert the standard sample from position 1
2. load standard shim set
3. try to lock.

If the standard locked successfully but your sample did not -- the problem is with your sample: either you don't have lock solvent, or lock solvent is not what you think or its concentration is too low.   Check your sample preparation protocol.

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Step 4. Create a new experiment

1. Copy an experiment you want to run from a previous experiment, setup file, or a parameter set.
   
   
2. REQUIRED: type getprosol on a Topspin command line.
   
   NOTE: This step is required because you must adjust all pulses and powers to the requirements of the Cryoprobe. The getprosol command reads the current probe parameter table and updates parameters in your experiment.
   
        If you skip getprosol, you may damage the Cryoprobe!   
   
   


     NOTE: If your experiment uses a non-Bruker pulse program, which someone wrote,
               you must contact NMR staff to set it up properly for the Cryoprobe!



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Step 5. Tuning

1. You must be inside the experiment that you intend to run!
   Type atma and watch for wobble curves and final message "ATMA ... finished.. OK" in a status bar.

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2. If you missed atma screens showing the curves, you may issue wobb and to check the tuning status of the probe:
   
   
   
   The dip of the resonance must be at or close to the red line.

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3. If your experiment uses several nuclei: click the "staircase" button to switch to next nucleus
   
   
   
   
   
4. To exit wobb, click STOP button.
   

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Step 6. Shimming

1. Start rotation to help achieve better shimming. Type ro on

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2. Verify that you have good lock signal: relatively low noise:
   
   
   
   REMEMBER: Shimming works on lock signal. If you lock signal is poor, shimming may fail. 

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3. Initiate shimming procedure with Topshim:
   
   
   1. for a normal 5 mm tube: type topshim_cryoprobe
      
      
   2. for a Shigemi tube: type topshim_cryoprobe_shigemi
      
      NOTE: You may want to save your shigemi-specific shimset to help you shim quicker in your future runs. Type wsh and give a new file name like [your_initials]_cryoprobe_shigemi. For example, I will use EK_cryoprobe_shigemi for the shimset I optimized for a shigemi tube with the cryoprobe. Next time, I will load this shim set instead of a standard shims in when loading initial shims.

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4. After Topshim has finished, it will pop up a window with shimming results:
   
   
   
   Pay attention to:
   
   
   1. initial B0 stdDev - this is the measured deviation of magnetic field along the length of the sample that exists prior to shimming;
      
      
   2. final B0 stdDev - same measure after shimming.
      
      

   Normal value of initial B0 stdDev for a good tube right after insertion is several Hz.
   Successful shimming should bring final B0 stdDev to below 1 Hz.

   Troubleshooting:

1. If you see initial B0 stdDev > 25 Hz -- initial homogeneity is very bad. Did you load the standard shimset before shimming?
   Topshim may still be able to fix it. If you see 100 Hz or more -- there is some trouble with your tube. Try to shim but it may not succeed.
   
   
2. Before you conclude that the spectrometer shimming system does not work, reinsert the standard sample in position 1 and issue:
   - rsh Cryoprobe_CPTCI
   - lock cdcl3
   - topshim_cryoprobe
   
   If you get good shimming result on the standard sample, the issue is in your tube.
   
   If the standard cannot shim as well - this is a problem with  the spectrometer.
   
   Either way, contact NMR staff for help.
   
   
   
   
5. If you plan to continue with 1D experiments, leave the sample spinning. Otherwise, turn off the rotation: ro off

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Step 7. Adjust Parameters

1. Adjust parameters of your experiment as needed.

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2. In proton-detecting experiments, calibrate the proton pulses: issue pulsecal

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3. Perform receiver gain adjustement: issue rga

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4. Check experiment time: issue expt
   
   NOTE: Make sure your spectrometer booking is sufficiently long to accommodate duration of the experiment! Extend your booking as needed if possible. If - not (for example, a maintenance period is scheduled right after you), contact the NMR staff to see if more time may be negotiated.
   

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Step 8. Start Experiment.

1. type zg
   
   
   • NOTE: When your experiment uses long pulses or decoupling (namely, HSQC, H2BC, TOCSY, CPMG, T2 or ROESY ), you should monitor status of the cryogenic coils during the experiment.
     
     - Open Cryopanel (Manage: Spectrometer: CryoProbe Control)
     
     
     
     - observe the values of NMR coil heater for several minutes after your experiment started:
     
     

• A "healthy" range for NMR coil heater is above 20%.

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• If it drops below 20% but above 15%, you may continue but should let NMR staff know -- we may need to see if the experiment performed well.

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• If it drops below 15%, you data may be no good: let NMR staff know -- we will adjust your parameters.

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• If it drops lower to 5%, the Cryoplatform will force emergency warmup of the cryoprobe. If this happens, you will see red messages indicating trouble (like in the example below).
  
  Stop your experiment and inform NMR staff immediately.
  
  
  
  

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Step 9. Finishing your work

1. Check your current NMR coil heater value and record in your notebook.
   
   
2. Re-insert the standard sample and lock on CDCl3
   1. lock off
   2. ro off
   3. sx 1
   4. lock cdcl3
      
      
3. Wait till the system locks on the standard.
   
   
4. Place your spinner in a rack (do not touch the spinner!)
   
   
5. Remove any wipes or paper towels you used to trash.
   
   Thank you for keeping NMR lab clean!

 

 

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