Testing the Lower Limits of a CapNMR Probe...

Ask for this Customer Poster from SMASH 2008 in Sante Fe, NM

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Testing the Lower Limits of a CapNMR Probe on an Older Spectrometer

W F Reynolds1, T Burrow1, D McNally1 and R G Enriquez2
   1. Dept. of Chemistry, University of Toronto, Toronto, Canada
   2. Instituto de Quimica, U.N.A.M., Mexico City, Mexico

We have investigated the minimum amount of sample of a typical natural product (300 molecular weight) needed to obtain a complete set of usable NMR spectra in 24 hours using a Protasis CapNMR probe on a 15 year old spectrometer. High quality 1H COSY, T-ROESY, TOCSY and HSQC spectra and 13C and HMBC spectra which were adequate for structure determination were obtained in 24 hours using 120 μg of kauadienoic acid in 20 μL of CDCL3 with robot-controlled injection. This amount could be significantly further reduced by a combination of direct sample injection, use of a state of the art spectrometer and elimination of the 13C spectrum since the combination of HSQC and HMBC gave the same information as the 13C spectrum.

Advantages of CapNMR (from poster):

1. Comparable sensitivity to a 5 mm cryoprobe on a mass basis
2. Significantly lower capital & operating costs than cryoprobe
3. Changing probes is comparable to normal probes & much faster and easier than cryoprobes
4. Minimal reshimming is required when changing samples
5. Very short 90°pulse widths at relatively low power (i.e. 13C 90°pulse width = 3.0 ms)
6. Robot hardware seems rugged & reliable
7. Double-tuned coil means no compromise on 13C sensitivity

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