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Hello All

Does anyone have any ideas on why the S/N would increase and then degrade during an HMBC-style experiment? If I process as I acquire, the S/N is best at about 3/4 through the experiment. At the end, the signals are still visible but the S/N has decreased. Both the instrument and the pulse sequence/pulse program appear to be working correctly (tested with other samples).

Thank-you in advance.

asked Jul 25 '13 at 23:56

Craig's gravatar image


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Hi Craig,

maybe your acquisition time in the indirect dimension is too long? Did you check how long the signal survives in this dimension? If the last slices of the 2D experiment only consist of noise because your signal has decayed, you will of course increase the amount of noise in your spectrum as the amount of signal (the first slices) is getting smaller in comparison with the amount of noise (the last slices) that you acquire.

So if this is the case, you can safely decrease the acquisition time in the indirect dimension (td in F1) and you will so reduce your experiment time drastically. If you want to "rescue" the already acquired experiments, you can reduce the effective td value (on Bruker: set "tdeff" for the indirect dimension to 3/4 of your initially set td) and reprocess the spectrum.


answered Jul 26 '13 at 01:17

Pascal%20Fricke's gravatar image

Pascal Fricke

Hi Pascal That makes all the difference to the spectrum; thank-you very much. Craig. - Craig (Jul 29 '13 at 00:35)

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Good to see you got this sorted out. I thought I would suggest a reference for you to read so you have a greater understanding of what is happening here:



answered Aug 02 '13 at 08:42

Scott%20Robson's gravatar image

Scott Robson

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