How do I run a ¹H NMR?

Running a ¹H NMR is similar for every manufacturer because every NMR instrument operates using the same principles.  The first step (after inserting the sample) is to tune the probe, followed by shimming the sample, then establishing the parameters and data file and finally running the experiment.  This how-to will try to cover as many possible “gotchas” as possible so you can avoid errors and pitfalls and successfully getting your ¹H NMR. Running a ¹H NMR in SpinStudioJ consists of the following steps:

1. Change sample either manually or using the sample changer.
2. Tune probe using Smart Tune and Match (STM) Tool. or selecting “Tuning and Matching” from the Acquire menu.  Select the Automatic radio button.  If running the same nuclei (e.g. ¹H and ¹³C ), don’t select the checkbox “Initialize Actuators”.  (If you are running ¹H and 31P for example and the previous samples was ¹H and ¹³C , it is a good idea to check the “Initialize Actuators” checkbox.) Always run ¹H tuning first by selecting it from the drop-down. Click the “Start” button, the tuning will take a few second, but you should see the tuning curve converge on the vertical red frequency marker indicating the probe is tuned.  Next change the nucleus to ¹³C via the drop-down menu and click “Start”.  The frequency scale will change to reflect the ¹³C frequency and you should see the tuning curve converge on the red frequency marker.  Here’s an example:

   

3. Shim the field using the Smart Shimming tool by selecting it from the toolbar or from the Acquire Menu, Shim, Smart Shimming option. Select the checkbox “Show Workspace” and “Autolock” then click Start.

   

   Clicking “Start” will being the shimming process.  Click the tab over the data area “gradshim1d.nmr” and you can see the acquisition of the gradient shimming profiles. Once the gradient shimming is complete, the system will then Autolock on the sample, adjusting the Z0 shim so the field is set on resonance for the lock solvent and the lock parameters (Power, Gain, Phase) are optimized.  The sample is now ready to acquire data.  Next step is to select the experiment and set the parameters.
4. Select the tab in the Tools area, “NMR Data Navigator”, to start a new experiment, either
   1. Right click and select New Experiment

      

   2. Alternatively, users can create a new experiment from the “Acquire” menu, then “New Experiment” and “New from template”. (Note: it is permissible to use parameters from an existing workspace where the parameters can be “cloned” or “copied” from an existing dataset by selecting the option “Current Node Parameters” instead of using the Template option.  Take in using the Current Node Parameters option to make sure the current workspace isn’t the gradshim1d.nmr workspace.  If this is the case, you aren’t copying parameters useful to run a ¹H experiments, but rather the gradient shim parameters which uses the 2H or lock channel.)
   3. Another window will appear along with a sidebar on the workspace from which to select all of the “methods” to record a spectrum.  Each method has both acquisition and processing parameters, so the method is start to finish protocol for each experiment. For a routine method, select PROTON1 where the sample is not dilute.  For samples which are dilute (< 1 mg) select PROTON16.

      

      The user will then be prompted to select the location of the data file and the file name which is

      

      The Dir designation is the list of eligible directories for where to place the data and Exp Name is the name of the file.  Characters, spaces and numbers are permitted but symbols are not suggested.  In the Title, all characters, numbers, and symbols are permitted.  Users can change any and all parameters found in the Parameters tab just above the command history area.  Selecting the Sequence tab, users can visually confirm the pulse sequence and pulse sequence parameters such as the delay (D1) time, pulse time (P1) and acquisition time.  Other parameters can either be changed by clicking the Parameter tab or entering parameters in the command line with an equal sign and the value of the new parameter.  For example if the user had a dilute sample and had chosen the PROTON16 protocol, the user might want to extend the recycle delay d1 by typing d1=10 to increase the delay to 10 seconds.
   4. The next step is to type GO in the command line window or by clicking the Go button in the toolbar . Once the GO command is issued, the user can see the progress of the experiment for a multi-scan experiment by selecting the “Acqu” tab just above the command history in the row of tabs for the current workspace, OR select FID/Spec to see the acquired data once the acquisition is complete.
   5. Processing the data is accomplished by performing a windowed Fourier transform using the “wft” command in the command line, followed by automatic phasing using the “aph” command.