Anti-diagonal artefact in DQF COSY (Varian dqcosy.c)

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Hi I have the following problem in dqfcosy - have pretty strong antidiagonal.

I've run the same experiment before on other samples and did not have this problem, could you suggest anything? Is there any other pulse sequence in the Varian toolchest superior to this one?

... but probably something is just wrong with my setup, it is a really simple sequence though and I thought it would be hard to screw up :). Or is it normal and I just have low S/N?

edit: I've figured out that in this case I had receiver overflow. To test that go to the .fid directory of the experiment and inspect file called log.

image illustrating antidiagonal artefact in dqfcosy nmr experiment

asked Jan 21 '10 at 14:49

Evgeny Fadeev
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updated Jan 23 '10 at 12:09

Acquisition problem or processing problem? Do you get the same effect if you process with VnmrJ? - Kirk Marat (Jan 22 '10 at 06:46)

DOH. It was receiver overflow. I'll post the update a bit later. - Evgeny Fadeev (Jan 22 '10 at 09:07)

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Answering this one myself - I had receiver overflow on many increments, but not on the first one, so I did not notice this at startup.

It should be possible to test for this problem ahead of time by setting d2 delay to something other than 0. When d2 is not 0 at the beginning of the experiment you will be effectively "jumping" into the middle of the 2D experiment so that it would be possible to immediately inspect fids that are normally recorded in the middle of the acquisition.

File called log within the varian data .fid directory contains console log messages which can be inspected with a UNIX command like more log or looked at in some text editor.

link

answered Feb 26 '10 at 08:31

Evgeny Fadeev
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updated Feb 26 '10 at 08:32

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varian ×35
pulse-sequence ×22
liquids-nmr ×5
dqf-cosy ×1

Asked: Jan 21 '10 at 14:49

Seen: 1,941 times

Last updated: Feb 26 '10 at 08:32

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