They could be acoustic side bands caused by noisy VT air flow
in the coil/sample area of the probe. Basically, the probe is acting
like a flute, but the pitch is a little off for modern orchestral playing.
Try varying the VT air flow rate. We had this problem on an early Nalorac
triple resonace probe, (which they subsequently corrected). Supposedly
this problem has also been seen on certain Varian probes.
--Mike
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Michael Strain strain@mango.uoregon.edu
Institute of Molecular Biology desk/voice-mail: 541-346-4605
and Department of Chemistry lab: 541-346-4036
University of Oregon FAX: 541-346-5891
Eugene, OR 97403
NMR instrument rooms: 600MHz, 6-5161; 500MHz, 6-4621; 300MHz, 6-4616
-----------------------------------------------------------------------
note new "541" area code .... the old "503" will work for a while
On Thu, 20 Jun 1996, Lawrence Byrnes wrote:
> 20 June 1996, Thursday, 1215 EDT
>
> Dear NMR folks,
>
> Doing 200 MHz 1H NMR on following sample:
>
> 160 mg heparin sodium in 1 ml D20 with 0.75% TSPA
>
> Observe out of phase peaks of low intensity, symmetrical about the water peak
> and offset by ca. 436 Hz. Look like quad image peaks but are not. Persist
> when spectrometer frequency and spectral window are changed. Both low and
> high field peaks have same out of phase orientation. High field peak is
> three times intensity of low field peak. Any ideas concerning origin of
> these peaks?
>
> Will be away 21-25 June, returning 26 June. Will collect and repost any
> useful information.
>
> Thank you,
>
> Best regards,
>
> Lawrence
>
>
> --------------------------------------------------------
> Numare Spectralab, Inc.,
> 10 Summit Avenue, Unit 6, P.O. Box 96,
> Berkeley Heights, NJ, 07922-0096,
> Telephone 908-665-0066
> Telefax 908-464-4192
>
> Name: Lawrence Byrnes
> E-mail: numare@cnj.digex.net (Lawrence Byrnes)
> www: http://www.cnj.digex.net/~numare/index.html
> --------------------------------------------------------
>
>