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Monday, November 26, 2007

HMQC Responses in HMBC Data

Despite the built in low pass J filters written into the HMBC pulse sequences, the much larger one-bond 1H - 13C coupling responses are not fully suppressed. These one-bond HMQC responses show up as a pair of responses in the acquisition domain separated by the one-bond 1H - 13C coupling. The responses are doubled since 13C decoupling is not typically used in HMBC sequences. An example of these artifacts is shown below.

5 comments:

Anonymous said...

How to avoid such artefacts?

Glenn Facey said...

Anonymous,

To the best of my knowledge, there is no way to fully suppress these on-bond correlations aside from using various "low pass filters" written into the pulse programs.

Glenn

Anonymous said...

Why is decoupling not employed for HMBC? The resulting crosspeaks are 'split' into quadrants, and S/N is insufferable. In HSQC, decoupling is employed, and the crosspeaks are nice and round. Can I turn the decoupler on for HMBC to get harvest more S/N per scan?

Glenn Facey said...

Anonymous,
You can certainly decouple 13C if you wish but then the HMQC artifacts will also collapse and it may be difficult to distinguish HMBC from HMQC responses.

Glenn

Craig said...

Anonymous,

On this topic, here are two articles that you may find informative:

Concepts in Magnetic Resonance A, 2012, 40, 101-127 (A comprehensive discussion of HMBC pulse sequences, part 1: The classical HMBC)

Concepts in Magnetic Resonance A, 2012, 40, 146-169 (A comprehensive discussion of HMBC pulse sequences. part 2: Some useful variants)

Craig.