Corrected DOSY Calibration for 500-3
Since 500-3’s installation in February of 2023, we have been using a factory calibration setting for its pulsed field gradient strength, 5.35 G/mm. A recent calibration performed using Bruker instructions indicates the accurate value is 5.07 G/mm. 500-3 is the preferred instrument for DOSY, and the others have not been individually calibrated.
The new calibration number was implemented on June 4, 2025, and DOSY data processed on the instrument from that date onward will be slightly more accurate. There is no action for you to take in future data collection or processing. A procedure for correcting previously-acquired DOSY data is described below. This calibration should probably have been done when the new console was installed, but recent probing into DOSY details showed it still required an on-site determination.
This change is not major, and only affects the accuracy, not the precision of your results. To illustrate, here is a pair of diffusion curves obtained for a carvone signal taken with the old and new calibrations:
With old calibration
(5.35 G/mm):
Diffusion curve for carvone in CDCl3, showing data points and fit curve, resulting in D = 2.244 e-9 m^2/sec , calculated using the OLD gradient calibration value, 5.35 G/mm (the “factory setting”)
•
With new/corrected calibration
(5.07 G/mm):
Diffusion curve for carvone in CDCl3, showing data points and fit curve, resulting in D = 2.488 e-9 m^2/sec , calculated using the NEW gradient calibration value, 5.07 G/mm (measured using the recommended Bruker procedure with a sample of 99.98% D2O)
Note that these curves represent the same dataset, but used different calibrations when calculating the diffusion constant.
FIXING PREVIOUSLY-ACQUIRED DATA:
To recalculate diffusion constants obtained from spectra acquired between February 2023 and June 4, 2025, you are advised to reprocess the data using the command “dosy restore” to reset the difflist values. Personally, I suggest returning to 500-3 to accomplish this.
- Open your 2D DOSY dataset.
- Use “xf2” to redo the Fourier transform in F2 only.
- Re-phase the spectrum if necessary
- Use “abs2” to correct the baseline in F2 only.
- Re-reference the spectrum if necessary.
- In the command line, type “dosy restore“
- THEN, type “setdiffparm” to convert your GPZ6 gradient schedule to physically meaningful units
- From here, proceed as normal: either open up Dynamics center, process with “dosy2d” , or fit the curves in the T1/T2 analysis” tool
Further DOSY Tips and Insights
For more information about diffusion measurement by NMR and 2D DOSY spectroscopy, you would do well to watch the recorded training webinars by Dr. Nicole Kruse, Bruker’s diffusion expert application scientist.
“Introduction to DOSY and Diffusion NMR Methods”:
https://event.on24.com/eventRegistration/EventLobbyServlet?target=reg20.jsp&eventid=2380203&sessionid=1&key=DE0DECAE6357F281D2A6961C67DB8659&groupId=1121475&sourcepage=register
NOTE:
– On the linked pages, you need to scroll to find the webinar you want
– You will need to register for the webinar, as it is considered a Bruker training session, but it is free.